Houston, we have a slight (BMS) problem and... are now Off-Grid!

[@williamhustonrn6160]

Andy, since you have that spare QUCC BMS board from the failed relay, you can wire that board in parallel to the same relay, it would give you twice the balance capability with the same relayed shared for disconnect.

[@philbrooke-little7082]

The problem trying to balance at low voltage is that the charge curve is too flat until you Get into the ‘knee’ region. The cells don’t differ enough, despite being at different states Of charge, to activate the balance circuit. I use the same cells and I expected, on such inexpensive cells, that there would be some imbalance so I used a separate capacitative active balancer that works throughout the charge cycle and can balance at upto 5A if the imbalance is high. It has been running Now for 6 months with all cells staying within a few millivolts. My system has a self designed hybrid BMS so there is lead acid in the system that takes over if the lithium cut out however I also have a diode across the relay which allows for discharge when the relay is open. This would be an issue without the lead acid as there would be no low voltage disconnect but the lead acid gives loads of time for the gradual decline to be noticed. Also, with purely inverter based loads, the inverter low voltage cutoff can be used as protection. The hybrid idea was to give the best of both worlds so simplicity of charging using the uncomplicated lead acid profiles But giving the charge and cycle efficiency of lithium. I’ve found that the complexity of all the Victron gubbins can just tie you in logistical knots over what is in essence a fairly simple system. I do monitor everything using a pi and I can control all sorts of things but the basis of the system is simplicity hardwired into it. Yes it uses a microcontroller in the BMS but it is one you can adjust And program in something that approximates to English rather than proprietary gobbledygook.

[@paulbarrette2557]

I agree with your statement about being in the 'flat' part of the curve. 1 mv different may represent a large amount of imbalance from a capacity perspective. I was fully in agreement with his strategy here until this 'sh*t' happened with the BMS. I am reconsidering my position here and I think he needs to balance at a higher voltage (in the elbow of the curve) where 1 mv represents less of a capacity delta.

[@uhjyuff2095]

I like the idea of putting lead batteries in parallel with the lithium batteries so much. It can keep the electronics happy while the lithium finishes its super long balancing cycle!

[@OffGridGarageAustralia]

Yeah, well, I have to rethink my position here, I guess... 🤔

[@fransstroetmann3423]

@@OffGridGarageAustralia Or a supercapacitor

[@redstorm6767]

Ya, I use this same exact BMS, and I think it works great. I certainly have not experienced the switching on and off. Irrespective of the BMS though, I do think the you guys are right about trying to balance at too low of a voltage. I also use an active 2A balancer with my setup, however I was forced into that after my battery source on Alibaba sent me used cells.

[@1981dasimpson]

Victron need to make a bms so the systems can be more integrated together

[@ingmarmaul4464]

What about adding a Smart Battery Protect for charge and discharge. Or at least discharge so that the discharge is still possible even with charge disabled through the BMS.

[@OffGridGarageAustralia]

Apparently it is somehow possible and the BMS can talk to the Victron system. The QUCC BMS has a RS485 interface but I don't know how to connect and if the solar charger need a special firmware then so they know there is data from the BMS coming?

[@1981dasimpson]

@@OffGridGarageAustralia I would of thought it would do it like cambus system

[@sreekumarUSA]

062021/2320h PST 🇺🇸. @ David, you are absolutely correct. Thank you. I’m surprised, as to why, VICTRON Holland has refrained from producing their own BMS. I wrote to them a while ago and the response was tepid. One Country in the East mass produces BMS that VICTRON can’t compete, may be the first reason? I’m looking forward to VICTRON BMS in the near future. Until then stay safe and 73s…

[@michaelbouckley4455]

@@1981dasimpson Canbus

[@svtosca3371]

Andy, I think by balancing at 3.35 volts you are setting your bms up to fail. It just cannot see enough difference in volts to properly gauge soc. You might even turn your bms balancer into a randomizer. I think you should balance at least at 3.5 or maybe even 3.6 volts. See also default Victron lion settings that absorb to allow balancing.

[@OffGridGarageAustralia]

Yep, my testing failed. But good to see for me (and learn) this does not work due to the flat curve. I'll go a bit higher and see when I can make it work 😃

[@ai4px]

Really enjoy your ramblings. These are exactly the same problems that I’m having with my system. I let my batteries sit for about three weeks while I was waiting on a part and when I charged the batteries again I had all sales strong and one weak. I’m really enjoying watching you live the same problems that I’m living

[@trevilights]

I am getting accustomed to watch a daily video of you. If you do not post something it feels like something is missing from my day 😕.

[@OffGridGarageAustralia]

Hahaha, the daily battery soap, right!? I better hurry up then...

[@newton833]

try turning off the charge balance option: it will allow the balancing when the battery is not charging. which means you can leave it balancing overnight, and in the morning the solar will charge it again until the limit

[@MichaelEricMenk]

According Victron, you should set the reset voltage to 0.8V under absorbtion voltage (0.2V for 12V), 5% tail current for 5 minutes.

[@OffGridGarageAustralia]

Are these the standard settings?

[@MichaelEricMenk]

@@OffGridGarageAustralia these are the recommendation by Victron for LiFePo4 battery when charging with solar.

[@zjzozn]

BMS = Beer Management Systems 👍

[@wearemilesfromnowhere4630]

I concur about the BMS meaning. When I drink a bit too much, I float...then it's hard to balance.

[@wearemilesfromnowhere4630]

I tend to panic as well when this has happened to me. I go and check my batteries manually then with the same meter, check all other voltages from the different mudules such as the shunt and check those against the apps. Often it is as you say, needs to have a wider spread on the settings so you don't get that relay cycling. Eliminating variables. Good video Andy!

[@OffGridGarageAustralia]

Thanks. It's a lot to understand and link together to make this all works. I'm on 98% again so will do some more testing tonight with the manual charger, see if I can trip it again and just discharge this one cell.

[@ai4px]

The battery management system stops balancing when it considers it is in storage mode. Daily BMS does this also it will not balance in storage mode. It only balances in charge or discharge mode

[@b.morris2816]

I have an active balancer cabled but not connected. I have it so I can plug it in quickly if a condition like this occurs. Backup!

[@OffGridGarageAustralia]

Hmmmmm.... have you tested it?

[@carlbradley148]

I have concerns of how much balancing your BMS is doing. I believe your open balance voltage is too low in the curve. Balancing too low is causing issues. Try bumping it up to 3.4.

[@fidelreino]

I keep learning a lot and FREE !!! Thank you Sigo aprendiendo mucho y GRATIS!!! gracias

[@defjamsgreen]

You might can try discharging the high charged cell manually until the voltage gets back down to match the other cells voltage . Then the BMS may keep the cells balanced . It’s worth a try .

[@ai4px]

I used a car headlight on the high cells and a lab bench top power supply on the low ones.

[@defjamsgreen]

@@ai4px IF ANDY COULD ONLY SEE AND TRY OUT BOTH OUR REMEDY REPLY . NO BMS IS PERFECT WHEN MOST OF THE CELLS ARE OUT OF BALANCE .

[@junkerzn7312]

This isn't really surprising. You can't top-balance LiFePO4 at that voltage (as I said in my comment on the previous video). You might actually be unbalancing the cells instead, in fact, so now current acceptance is all over the place. You are giving the balancer parameters that it can't possibly work properly with. There are lots of reasons why it doesn't work at that voltage. In this case what you are seeing is probably related to massively different current acceptance at that voltage. Basically the voltage ramp for cells at different SOCs is going to behave very differently at 3.35V - 3.375V than they would at 3.50V-3.55V. So differently that the balancing circuit has an impossible job. -Matt

[@danfitzpatrick4112]

I have to agree, the balancing has them "Middle" balanced per se. I have an active balancer that never balances until my cells are over .5 deviation. I hadn't used my batteries for a month or two and they work fine. They stay at around .001 unless under a big load or charge then they may go to.3 to.5v. I would also check the cell 14 terminals as well. Could have a loose connection.

[@OffGridGarageAustralia]

I'm testing and exploring... so, 3.55V with a 2h absorption time still makes sense to allow balancing. The standard settings of the LFP profile...

[@danfitzpatrick4112]

I mis spoke that would be .03 -.05 my balance happens at .05 deviation. I ran maximum of 3.6kw (house power with 3 ton AC on) yesterday and batteries were in those specs. Max DC current through batteries was about 70 amps

[@danfitzpatrick4112]

@@OffGridGarageAustralia I'm looking forward to your findings!

[@junkerzn7312]

@@OffGridGarageAustralia It would be interesting to research just how much balancing is needed in the long-term. LiFePO4 maintains its balance quite well over long time periods, so theoretically even just giving the system a mere ~30 minutes a day in balancing time ought to be plenty. -Matt

[@JR-kk6ce]

LOL! It reminds me of the Three Mile Nuclear Plant accident. So many things were going wrong at the same time with so many alarms going off, that the technicians did not know what to do.

[@teardowndan5364]

In a more highly integrated system, the PPT voltage would get adjusted to limit charging current to balance current once a cell reaches its maximum voltage instead of causing a battery disconnect.

[@stuartsmith945]

I'm running a 4S2P system in my caravan using a single Daly BMS set to commence balance at 3.2v.I also have a capacitive energy transfer active balancer that can balance at 10A, but at very small voltage differences, it doesn't balance at high currents. It is balancing all the time. I have never top balanced the cells, but slowly incremented the charge voltage over a period of days, allowing the balancers to achieve less than 10mV differential at each increment. It has been running for about a month. The worst differential I have seen is 6mV and that was after storms where the caravan was running the house at night and being charged by generator during the day. Typically running 20 to 40A discharges and 60A charges. We were discharging around 250Ah each night. I went with 35mm2 wire busbars as they allow some flex. The solid busbars dont allow any movement, but with the possibility for the cells to bulge when charged, I felt this was a better solution. I do have my cells lightly clamped to minimise movement. Mostly I see differentials of up to 2mV, but mostly it sits at 0.000V. I have set my maximum charge voltage on my 2 Smartsolar controllers to 14.05V and the Smartshunt to synchronise at 14.0V. This has been working very well for me. So far I am very happy with the performance of the system.

[@naijawindandsolar]

I really love your intro music. Also your style of presentation is so authentic

[@OffGridGarageAustralia]

Thank you so much!!

[@firpofutbol]

I have an ELECTRODACUS and I think it has a number of benefits over your BMS. First, it has 4 disconnect ports, each can be configured in a different way, such as to disconnect chargers or disconnect loads independently. This function works with any device that has remote on/off functionality, including Victron MPPTs and inverters. It also works with any device that has a simple on/off switch. Eliminates the issue you questioned in the video as to why it cuts off load side when only charge side should be cut. Next, many have pointed out that your BMS parameters may be the issue. Electrodacus' lithium profile is as follows. End of charge = 3.48v. Overvoltage = 3.5. Overvoltage lock = 3.7v. Overvoltage recovery = 3.35v. Cell balance max = 3.55v. Maybe this will help? Lastly, it only monitors current via shunt but no current passes through the BMS itself. Probably conducive to less failures. It doesn't have a phone app but does have WiFi to monitor from the phone via the browser. It also has a screen built in. I'm thinking a BMS like this might be better way to go since the charge profiles are built in and and you can control loads and chargers independently.

[@tonmilly]

Hi Andy and the community, Tony From UK wales here. I've just seen the video and I Must say although not good news for you I'm quite pleased! You see I have been in a similar position with my system through my project and was keen to see yours work so well (up to now) But now you have run into this situation with single cell overvoltage (although I see your cell 7 was climbing fast too!) It seems maybe (as my suspicions for my system ) be due to 'Normal' cell operation. Through my issues I have suspected my cells may be mismatched and have placed a work around of lowering the max charge voltage to a lower point of the charge curve 54V (16* 3.75vper cell) although the capacity is lower than should be I still get 95% capacity and run the cells further down the charge curve easing cell degradation at the same time. Maybe now I have seen your cells behave in a similar manner it may point to us both running the cells to close to the 'end of the flat' part of the charge curve. i.e. the high cell taking the BMS out may only be a fraction higher than the other cells but flying out of control high because it reaches full state of charge first (one cell has to be first I guess due to us not living in a perfect world?) I also have 2 battery's on the same inverter as you are going to but did run into the same overvoltage issue. I have a 16s Lifepo4 (150AH) battery and 14s lipo Battery (170AH) in parallel (cant wait for comments about that!!!) and running at 54V well now for over 6 months and have swapped out BMS to 'seplos' system boards communicating to my grid tie system through my sofar ME3000sp. Balancing starts at 3.3V Per cell and runs constantly, this seems to keep the cells in check. I look forward to seeing how your system evolves, your doing a fantastic job. Enjoy the beers. Tony

[@OffGridGarageAustralia]

Thanks for sharing Tony, awesome!

[@Josh-b3c]

You'll need to do something to balance that cell out either manually discharge it with the resistor to get it more in line with the others or temporarily lower your peak charging voltage until the BMS can get that cell more in line

[@OffGridGarageAustralia]

Yeah, I don't think the BMS is able to fix that. Not in my lifetime 😂 0.2V balance current just don't cut it...

[@LogicMomentum]

Food for thought. I have similar situation with my cells and overvoltage. I’m using a BMS with separate charging and discharging relays. I have the charging relay situated on Solar positive input going into the charge controller and the discharging relay on the main battery positive. Works well when overvoltage occurs as it literally just “Turns off the sun” but keeps everything connected to the battery including inverter, charge controllers etc. Anyway, love your progress!

[@michaelbouckley4455]

Surely you don’t mean that “turning off the sun” leaves the SCC connected?

[@MrSummitville]

A Dual Port BMS ...

[@LogicMomentum]

@@michaelbouckley4455 Yes, you put the relay on input side of the SCC… That way the output connection to the battery is still connected.

[@OffGridGarageAustralia]

So you turn off your solar but leave the SCC connected...

[@LogicMomentum]

@@OffGridGarageAustralia Correct! By putting the charging relay between solar panels and the controller, it'll stop the charging from the sun while everything still functions without power cycling. You still have your discharging relay on the battery positive to protect it from discharging normally. It works great this way, but keep in mind that you're only protected when charging from the sun which is all I do. If you were to ever plug into the grid to charge or some other way, you would need to monitor and use another way to protect the battery from overvoltage during those times.

[@kuhrd]

A few thoughts I had while watching your last 2 videos. I am not a battery expert by any means but I have been on the same journey for several years. I balance my cells at 3.440-3.550v and I have the BMS set to disconnect charging at 3.550v and it won't kick back in until 3.450v where it floats. I also have the BMS set to balance within 0.001mV. My BMSs are all MOSFET-based so they can enable and disable charge and discharge separately. I keep the solar charge controller about 0.5v above the cutoff for the BMS. Originally LiFePO4 chemistries were charged to 4.2v just like many other lithium chemistries. Over time they discovered that the high charge voltage was not necessary unless you needed a very fast charge and this improved cycle life quite a bit. Once you are much below 3.65-3.7 (the current recognized 100% fast charge voltage for LiFePO4) the gains in cycle life are not really worth the added cycles because you are now well below the area where degradation due to high voltage causing the capacity loss is happening faster than calendar aging. The calendar life of LiFePO4 is around 15 years so if you did one full cycle per day for 15 years (15x365.25=5,478.75) you are just under 5,500 cycles. What you are running into now appears to be that one or more of your cells has drifted way out of balance (possibly by 10's of Ah) and at the rate of up to 200mA balance current, it is going to take a long while possibly days at full charge to get the cells back into balance. The flat discharge curve hides imbalance very well. This doesn't damage the cells but it means you may have temporarily lost some capacity with the imbalance. The main reason I bring my cells up over 3.450v is to ensure they are all fully charged and in balance with each other by the BMS. This doesn't happen every day but it happens most days as long as we have some sun. No real degradation is happening with the cells at this voltage especially since they are being partially cycled each day. As you know the voltage rises quickly after the cell reaches full charge and the current begins to taper off. This is where it would b nice if more BMSs had the ability to keep charging when the charge current reaches 0.1-0.2A. and instead could actively shuttle the current around the full cells by way of active balancing and only stop charge when all cells reach the same set voltage rather than relying on resistive shunting of excess charge through resistors.

[@MrShaneo369]

Andy you need a BMS that is non relay, so that voltage can flow out of the battery bank , and not allow charging

[@OffGridGarageAustralia]

Or I just need to top balance the battery correctly and leave the balancer turned off so it stays balanced. 😉

[@henvan8737]

Its a very interesting topic, what voltage should the charge be set at. I have a PYLONTECH battery system and I have been considering changing the perimeters after watching your videos. But Pylontech sets the cell voltage at 3.546 volts. Its a 15S battery system so the maximum pack voltage is 53.2v and float voltage is 53.2v. The Pylontech BMS also has a cutout voltage relay for an over / under voltage situation, (Which has never occurred) The BMS can charge and discharge independently as you are wanting but still have the battery voltage available for the inverter. Maybe your new BMS system will allow this to occur, keep up the great work. Henny

[@OffGridGarageAustralia]

Thanks, Henny. I'll keep experimenting and learning.

[@dama054]

If you use an active balance it gives you the ability to balance when the cells drift by a certain amount so you can allow a small drift or larger drift

[@OffGridGarageAustralia]

Yeah, I know...

[@dama054]

@@OffGridGarageAustralia it might just be worth fitting one as a bit of a backup

[@jeffhenley9851]

Love your Chanel. I am so happy to see you getting a BMS with out a relay.

[@OffGridGarageAustralia]

Hahaha, but it works well! It protects the battery from overcharging. 😬

[@NathanKrick]

I don't know if you have heard of or watched any of Jehu Garcia's content (JAG35). He uses mostly 18650 cells to power electric vehicles and build powerwalls. One of the more interesting things that he has done is design a PCB based 18650 system for powerwalls or portable power banks. His design is to place many PCBs in parallel, with each PCB containing (7) 18650 cells in series for a ~24V system (each PCB is 24V in parallel with other PCBs). Each of the 7 Li-ion cells needs to connect to a BMS, of course, but it does not use a BMS for each PCB, rather a single 7S BMS is used for the entire system (or multiple BMSes in parallel if you want a higher max amperage). So, as you add modules in parallel, there are PCB traces that link the individual cells in parallel to individual cells in other PCBs (all cell 1's in all PCBs are linked in parallel by a PCB trace to the BMS). This design has a side effect of keeping all the individual cells balanced since they are attached in parallel with each other as well as the entire 24V until being attached in parallel to other units. I know that doesn't apply to your current battery design since you are doing single cells in series rather than parallel cells in series, but perhaps it is something to consider as a different design as you start adding additional battery boxes/shelves. Rather than doing an individual BMS for each 48V battery, you instead connect the 48V batteries in parallel and also connect each cell in parallel with the other cells (all cell 1s in parallel, all cell 2s in parallel, etc). This would combine several cells in parallel from a BMS perspective, making it less likely that a single cell will cause high voltage problems like you are seeing currently since the voltage of all the parallel cells would have to be high.

[@OffGridGarageAustralia]

Thank you. Yeah, I'm watching Jehu's videos since he started his channel. I know about his PCB setup for 18650 cells. I recently made two video about this: kzbin.info/www/bejne/sISwmnVqlNCJj8k and kzbin.info/www/bejne/nKLVYqF_ncaKgNk

[@dtec30]

that would be quite the feat something I haven't mastered yet and it may be quite a while if ever (balancing while floating) the big question is what to do with your arms leave them level or flap them furiously lol cheers andy

[@distincampbell9463]

Add an active balancer to the mix... Will help with the low low voltage you charge to.

[@paddyhaig101]

I swear, this was better than watching the horse races. I totally enjoyed this video.

[@OffGridGarageAustralia]

Thank you very much!

[@daskasspatzle2396]

So you need a BFS - a Battery Fire-wood System ;-) For the second battery scenario, if the BMS switches off the first battery, the second one will get all the current at once, and it is more likely to have higher voltages on these cells as well. Thanks for sharing your experience :-)

[@OffGridGarageAustralia]

Well, then I need a 3. and 4. battery so it does not matter if one fails 😃

[@themobilecraftsman5533]

Andy, this is EXACTLY what happens to my set of 200ah lifepo4s, and I don’t think another BMS will make much difference. My set is perfectly balanced until charging around 3.4v. This is where one cell starts increases faster than the others forcing a shut off at ~3.65v, but the others are still ~3.48v. I figure the resistance is different in this cell (or maybe a point of swelling triggers an internal short...???) But, I knew this would be likely since these are definitely not grade A cells. Active Balancing? This will be my next attempt to remedy the rogue cell (even though you ruled this out). I think people are finding balancers inadequate or even a hinder to the BMS process in some forums/comments. Maybe it’s because most of them max out at 1amp at most, and even the 2.1amp seems to fall short. I’m looking at the 5 amp hoping it will transfer energy fast enough to let the other cells charge more without having to balance at lower voltages. One thing I just read is that these balancers gradually increase the balancing current the bigger the delta or difference between cells. So, you’re never getting the full power of the balancer until until the cell has probably gone too far out. AND, it seems the balancers only transfer from one cell to only one of its neighbors. So, maybe a strategic order of high/low cells next to each other may help the balancing act...???

[@john_in_phoenix]

Top balance, and stop trying to get the cells above 3.4v. The capacity above 3.4v is really between 2 and 5 amp hours on the Eve 280AH cells. About 2%.

[@themobilecraftsman5533]

Yep, I top balanced and have derated charging to 14v (3.5) and float at 13.6v (3.4) for a while now. Maybe I will lower the charging profile even more (13.8v Blk/Abs; 13.6v Flt) because I still get a shutdown jolt to my inverter once in a while charging to 14v. I might still get a balancer for experiment sake, but you are right about 3.4v is still above 90% SOC (92% -99% depending on sources). Like Andy said “It just feels like I don’t have control of the system,” and eliminating shutdowns will sure remedy that feeling. Thanks for the input.

[@john_in_phoenix]

@@themobilecraftsman5533 I've tested extensively, 3.4v with maintaining that until amps drop to 1, equals 98%. With a good top balance, 3.4v can be attained easily. I have tested a LOT with the EBC-A40L (one cell at a time) and 32+ tests say 98% for me. When assembled in packs where the cells are properly top balanced, you can get this easily.

[@robsouto4998]

I hope you've got an REC Si BMS on its way to you from Slovenia, they're expensive but they're proper bits of kit, you can easily add a CANbus HAT to your RPi and hook the bms to the Raspi so the BMS can dictate the charge current and voltage to the MPPTs so it can keep the cells balanced. Love that your channel shows the bits you do that don't work as well as what does, keep up the hard work 💪

[@ai4px]

If you are thinking your next BMS should be chargery, Please think again. I had many troubles with their DCC contactors, and the cell voltages jump all around through erroneous readings.

[@OffGridGarageAustralia]

It's not a chargery and it's not a Daly and it's not a DIYBMS and not Batrium...

[@farqend]

Andy could you set the relay reconnect delay to something like 5-10 minutes after an overvoltage. Slow down the off/on cycling of the relay

[@steve82608]

If you regularly charge to above the "knee" of the charge curve, you might want to add an active balancer. They do work.

[@stephsoltesz6731]

Victron Forum user questions discussion: Tail Current = End Amps. Per EVE Docs XXXah X 0.05 = EndAmps/TailCurrent. 280AH * 0.05 = 14A 4.2 Standard Charge The standard charge means charging the cell with charge current 0.5CA and constant voltage 3.65V at (25±2)℃, 0.05C cut off

[@plonkster]

If you have a high cell like that, lower your charge voltage until the high cell sits somewhere between 3.55V and 3.65V. Run the system like that for a week. The balancer will slowly pull the other cells up over time. Monitor the maximum cell voltage and move your charge voltage up by a 100mV every few days, until the entire pack is top-balanced. Some BMSes can do this voltage adjustment automatically and communicate it to the inverter using CAN-bms. OrionBMS as far as I know, also REC-BMS. The latest version firmware of the BYD Premium LV as well.

[@wolfgangjansen3628]

One of the reasons to have a split DC bus with one lithium pack, solar chargers on the charge side, inverter on the load side. IIRC Victron can connect to CANBUS J1939, but only via their GX.

[@jws3925]

Andy, I have come to appreciate and learn a lot from your experiments. I wish I had the capital to purchase all the "toys" you receive in the mail seemingly daily! Although I am gaining a lot of knowledge from your experiments I hope there are not many individuals who are just thinking about or getting started with solar.. This is because if one was a newbie the impression of solar I would get from your videos is that a solar/battery system requires CONSTANT tinkering and repeated component upgrades or replacements. If I had found you when I was just beginning to think about solar at our remote cabin I would have surely abandon the idea. I almost think there should be a warning on your channel something like "warning, this site not suitable for beginners." Luckily for me I watched KZbin videos of individuals setting up a system in a more simplistic approach which left me with the feeling that "I can do this." Yes, your system will EVENTUALLY (I think) be more efficient and sophisticated but a system does not need to be as complex as yours to functionally work. Our cabin system has been working fine now for 7 years. In that time there has been huge advances in solar and battery technology. Your site has given me many ideas on how to upgrade our system and someday I will do so. However, for a system to be functional, especially on a smaller scale than yours, it does not have to be constantly tinkered with or changed. Use some good quality components and let the system run until there is a problem. We have had only one minor problem in 7 years with our system.

[@OffGridGarageAustralia]

Thank you John. That's a very good point and I should highlight this in one of the next videos. You only need a few things to get started and can (not must) upgrade later on. As you said, this is just me, I'm so hungry for more information, experiments and exploration, that I constantly try out new stuff, settings and installations. I should mention this more often.

[@jwcolby54]

, this is why you need ewo shunts. One for charging and one for discharging. This allows control over the two sides independently

[@helmo5663]

Hi Andy, you made such good videos where we could see that a much lower cell voltage is also sufficient to fully charge the battery. At 3650mV you are in the steep curve. That a cell "goes up" is quite normal. I have set my maximum acceptable cell voltage to 3375mV. Important now the release voltage (of the charge access) not too close to this value. I'm still experimenting a bit there, but currently it seems to work quite well with a value of 3350mV. At such low values, there is no voltage drift of the cells. And the BMS doesn't switch back and forth between overvoltage and release too quickly. The battery still gets full because I only charge at about 0.05C to 0.1C, and the individual cells are almost 98% charged at about 3360mV. And starting from 3375mV that corresponds to a maximum of 54000mV battery voltage. This is then your values to which your system has to "orient itself". Just try And if the BMS switches off the battery input 3-5 times on a sunny day, so what? A cell drift is not to be seen there in this case.

[@jasondevine6014]

This is why I switch off the panels with the BMS. Glad you replaced the BMS! But yes not good situation with relays clicking. This is a settings problem of balance voltage vs float voltage. Not enough time balancing.

[@OffGridGarageAustralia]

The balance current is just not eneough to mkae a difference. Just for the ske of trying... I should test out a balancer. Just testing, not keeping it ;)

[@BobHannent]

I like the fully integrated solar hybrid inverters like the ones from MPP Solar in Taiwan. I know you said "no equaliser" but what about an active balancer? There are some active 1A, 2A, 5A and even 10A Bluetooth equipped equalisers from "JK" and they have a capacitor which helps I believe. The 2A balancer might be worth a try?

[@bishwagit]

I think, active balancer will solve this balancing problem. Hi Andy, will you give a try with a active balancer?

[@rendark419]

Hab hier einen aktiven Balacer von Aliexpress. Soll mit max 2A laufen. Funktionier hier in meinem 24V System ohne Probleme. Lade und Endlade Werte: 3.0-3.5 Volt! Hast du die Zelle mal mit dem Multimeter gemessen?

[@peterpetersen6024]

The problem is the high capacity of the cells. If you want to balance at higher voltages, you need to do it with higher current, then the "little" BMS can handle. And speaking of Wh, it's a question if the method of just "unloading" and burning the energy over a resistor of the high cell is clever with these high capacity cells. I think an "active" BMS of 2A is nessessary, which can pump the energy from the highest cell to the lowest, instead of just burning it.

[@OffGridGarageAustralia]

You have red my mind... it's on its way...

[@peterpetersen6024]

@@OffGridGarageAustralia I'm curious. ;-)

[@danporter9363]

Hey Andy I'm sorry to have in trouble with your BMS I can see your frustration maybe if you plug your modem into your blue Eddie you can keep power going to it so it doesn't have to reboot each time

[@OffGridGarageAustralia]

Just little things along the way, I need to better understand and learn. We'll get there eventually.

[@Mr.X3D]

I’ve commented on this issue before, there’s no way a bms can keep up at such a huge* bank. What happened here is that the top balance have been destroyed by the bms since it have balanced at the flat part of the resistance curve. Also consider the fact that you have a tolerance for the bms voltage readings. I doubt it is calibrated within a millivolt. If you stay within the voltage spec for the cells (2.5v-3.65v), you will get around 3000 cycles within 80% of capacity retention. Isn’t that enough? I mean, the storage technology will have advanced a LOT when you reach that point and cheaper and better storage solutions will most likely be available. 🤞 I’m glad you shared this experience though! (And also came to the conclusion that a relay-based BMS just don’t work in a real world application as yours) *(huge from the bms balancer perspective)

[@wenhaowong5549]

i have this situation also, my battery bank is 16s 202ah and when i charge the battery at 56v 100a, one of the cell will go crazy high like yours.

[@awesomusmaximus3766]

Did you factor your balancer current consumption into your charge parameters it will consume roughly 3.2 A if the balancer current is 200milliamps per cell

[@vaneay]

What about using an active balancer to transfer exxess energy from highest cell to other cells ?

[@justdoityourself7134]

This exact same thing happened to my with my 16 cell pack ( Same cells as yours ) this last weekend. It was a little worse than your situation as my JDB BMS with stock settings got confused and started charging a single cell past 3.65. The overcurrent protection started cycling every 2 seconds in stead of staying enabled. Resulting in it continuing past the 3.65 limit. Luckily I was there to see it and stop it. It is very disconcerting not being able to trust the BMS. These types of systems have to be watched constantly.

[@OffGridGarageAustralia]

Yeah, I'm still not sure, why it does not fall back to the voltage recovery voltage of 3.55V as it should. As long as the cell is higher than that it should stay turned off right? I don't like that!

[@justdoityourself7134]

@@OffGridGarageAustralia that is what I had expected: wait for two seconds AND the voltage to return to 3.55. I observed that it only waited 2 seconds. Well at 40 amps of charge coming into the bank that would've resulted in a run away for that single cell. A huge failure no matter how you slice it. I'm left to wonder if I configured something incorrectly ( using stock lifepo4 settings ), my unit is bad, or the programming in the BMS is fatally over rated 😒

[@grahamwinn979]

Would a very small amps. Flash lamp bulb or high resistance across that cell cure the problem for now or will the same fault happen on another cell. Till a solution is hopefully found.

[@Sylvan_dB]

Your battery still needs a good top balance.

[@OffGridGarageAustralia]

It was all top balanced the last time it was full... there was no issues

[@Sylvan_dB]

@@OffGridGarageAustralia Either it was not top balanced or it has become unbalanced. Those are the only options. Maybe the other comments are correct that balancing too early in the knee is unbalancing the cells? But ISTR it wasn't really top balanced, especially after the individual cell bleeds, etc. Starting with a full battery, rewire to connect every cell in parallel and charge to 3.6v and hold them until current drops effectively to 0a (no more than 1% of the capacity, and I hold mine to 0.1%). They have to be well past the knee in the charge curve and held there until all cells have quit accepting more charge. Only then are they top balanced. After that if you take them off charge but leave them all parallel they should drop fairly quickly to under 3.5v but then the decline slows. Six weeks after removing the charger my latest pack (20 cells in parallel right now) is still over 3.4v. The last 3 weeks it was at 3.47v but a day or two ago when I checked it was 3.46v. While in daily use they should NOT become unbalanced unless discharged too deeply. But I've never had a balancer trying to balance below 3.5v before.

[@gregs8672]

Bad cell? Thanks for sharing. Want to know what you come up with?!

[@OffGridGarageAustralia]

Yeah, me too. I don't thing it's a bad cell as it performes well under high output.

[@notyoung]

Shadetree engineering answer: Get a 5 ohm, 100 watt resistor and some alligator/crocodile clips to add to the bad cell long enough to bring the voltage in line. That resistor will draw 0.7 amp from the cell to drop the voltage enough to let the battery's charge reach 55 volts - just while you're waiting for the replacement cell(s). Unless the BMS itself (or the balance wiring - You did check the wiring?) has a problem, the most likely answer is a bad cell. A given BMS can only handle XX mA/A in balance current but the problem with that cell is greater than the BMS can manage. What is the maximum balance current of the installed BMS? A new BMS could only manage that cell if it has a high enough balance current rating. As someone else mentioned - does the BMS even do balancing in the flat part of the curve?

[@OffGridGarageAustralia]

I really don't want to manually balance single cells again. The BMS can balance at any set voltage but only with 0.2A max. The capacity is far too high that it could make a difference.

[@BajanAlan]

My cells also stick together in the middle and vary at the high end

[@MrSummitville]

The middle voltage is very flat and the ends are not ...

[@Monthy999999]

Maybe you should do a test with Batrium BMS, it works really well.

[@John-gm8ty]

and costs a LOT

[@OffGridGarageAustralia]

That's an expensive test...

[@alanhauser117]

@@OffGridGarageAustralia its worth it Andy I have 96 CALB 100A and its working great and also I also run the system at 54V max talk with Maxine at Batrium and see if they will set you up with the system I'm sure they will I run my shop on this solar system its my covid project lol

[@OffGridGarageAustralia]

@@alanhauser117 don't they need additional equipment like disconnect relays and stuff as there is no safety build in by default?

[@alanhauser117]

@@OffGridGarageAustralia Yes but the BMS can tell the relays when to shut off and back on again it a really nice setup Contact Batrium Can you send me your contact info

[@wrndlabs]

Set your bulk charge voltage lower by 10% to allow the bms range to balance in. If your bulk voltage is more than the balance topside voltage for all the cells then you will always have the bms disconnect when the batteries are getting close to 100% SOC. Set you cell balance to 3.55V and your cell disconnect to 3.8V (lifepo4 can handle 4.2V, most people don't know this) and set your bulk charge to 3.5V x 16cells. Get an active bms, most passive bms's have very little balance current and thus takes forever to balance. Some advice from a battery charger manufacturer.

[@peterrock2838]

No regrets with MOSFETs

[@andreblanchard8315]

To do what you want the BMS needs to be able to bypass the full output of the charging sources or the BMS needs to talk to the charge controllers and tell them to back the current down to something it can handle.

[@dankarau2307]

Time for an Electrodocus BMS!

[@kuhrd]

Last I checked Electrodacus was only messing around with 24v. At this point 48V is the sweetspot for DIY to keep wire and component costs down and provide plenty of expandaility for the future.

[@OffGridGarageAustralia]

I would love to test it but he's still building me one for 48V... 😃

[@chrisjsmith61]

@@OffGridGarageAustralia I love my Electrodacus, I only have it set up for 12v. I am only a novice and still learning. I like the fact that it will turn off either charging or discharging seperately

[@wiedapp]

Maybe the balancing current is too small. I know you did a video on why you didn't add a supplemental active balancer. But in this situation you might consider these again. On AliExpress you can get some with up to 5A balancing current. That should be enough to pull overcharged cells down fast enough. Your battery consists of different batches after all. Watched till the end...ups...

[@OffGridGarageAustralia]

Yeah, I'm close to pulling the trigger. Actually wanted to wait for the new BMS to come in and see if this works better. As you said, the 0.2A balance current is just too slow for these large cells.

[@williamsouthwick6117]

Check balance wire on # 14 to ensure a good connection. If you don't have a good connection #14 can't shed enough power to balance!

[@OffGridGarageAustralia]

Shouldn't it be flagged under high output as well if it is a bad connecton?

[@williamsouthwick6117]

@@OffGridGarageAustralia It is only flagged if there is no connection and the BMS would then shut the bank down. Aside from a balance wire, it could also be a failed MOSFET. Just because the App indicates the balance MOSFET has been triggered the cell voltage rise is an indication it may not be working. If the signal is coming from the gate voltage rather than the drain on the MOSFET it would give you a false confirmation of balancing even if it was not working!

[@keyem4504]

I don't understand why the BMS keeps reconnecting the battery. Shouldn't it wait until it reaches 3.55V?

[@uhjyuff2095]

I don't think Lifepo4 cells can maintain 3.65v without constant charging, so the cell drops voltage instantly when the charging stops.

[@OffGridGarageAustralia]

Yes, it should wait until the cell drops to 3.55V. That's what got me off as well. The QUCC BMS does not seem to work well. Whatever I try, it does never what I'm trying to achieve.

[@edwardvanhazendonk]

Andy, thanks for sharing, I hope you don't get these headaches anymore in the future. Maybe you are a bit to high in the voltage curve. But as always talking from the other side of the world will show things upside down. I hope you don't charge above 90%. And another question, is the balancing resistance high enough to cover the decrease the power high enough going into the cell?

[@edwardvanhazendonk]

Another remark is your relay is switching very often, maybe a longer delay suits the discharge of the cell better, but you'll be longer isolated. Also don't wear out your relay.

[@henvan8737]

Have you actually measured the cell voltage at the battery. Do you have a higher resistance connection at the terminal?

[@OffGridGarageAustralia]

I don't think it's that as the charge current was very small. Internal resistance was OK and inline with all other cells. A high discharge does nto flag this cell, so I doubt it is resistance at the terminals. But I'll check again.

[@wayne8113]

Thanks Andy

[@houseofancients]

did you order a bms that has canbus/rs485 ? that way your bms can tell your charge controllers to simply stop charging. there's a few brands that support that, pylontech/seplos, but also a diy project by stewart pittaway called diybms

[@andrewradford3953]

Batrium also support Victron. Good to know a few others, as I'm about to start researching a bms for my gen 1 Leaf cells and Victron Easysolar.

[@OffGridGarageAustralia]

Well, this one has a RS485 interface as well.... Just don't know how to connect this to the rest and control the SCC through that.

[@houseofancients]

www.victronenergy.com/live/battery_compatibility:pylontech_phantom

[@houseofancients]

this might be of interest for you new bms too : diysolarforum.com/threads/victron-venusos-driver-for-serial-connected-bms-available-ltt-power-jbd-battery-overkill-solar-smart-bms.17847/

[@lexicase5642]

I wish I had seen this video before buying the qucc bms last night, literally watched I think all of your videos now and then I see this one from 3 weeks ago saying you now don’t like the bms I’ve just bought and I see exactly why🤦‍♀️ maybe I should have offered to buy your qucc bms. Actually… that’s not a bad idea as I might need a spare 😆 get in touch if you want to part with it

[@OffGridGarageAustralia]

I've got two QUCC BMSs now. I repaired the broken one but haven't tested it yet. Got the same 200A relay as the newer versions.

[@cfeigel]

This must be how the guys at Chernobyl felt when the alarms started going off!

[@OffGridGarageAustralia]

Hahahaha! We should not laugh 😶

[@SenatorPerry]

You order all kinds of nifty devices. Despite what you said, I would really love to see if the 5a active balancer would solve this... I mean, even if you just tried it. :-) And let us know it doesn't work. You can get a parallel split for your BMS balance leads and leave the port open for testing.

[@hermanjordaan2719]

I have used an active balancer with a new pack of cells. They do work well over time, especially with the first charge cycle to get all the cells well balanced. The active balancers only using resistors are essentially useless, but the ones using capacitors are a go to. The alternative is to manually balance the cells by charging/discharging or getting a power supply and charging all the cells individually, but that takes days to do...

[@SkypowerwithKarl]

I am absolutely satisfied with my capacitive type active equalizer/ balancers both 4S and 16S. I’ve heard of issues with the resistive types but can’t speak from experience with those.

[@OffGridGarageAustralia]

Hearing you...

[@SkypowerwithKarl]

@@OffGridGarageAustralia There’s one more thing to check. When a BMS is balancing, it puts a resistive load on the high cell(s) than it stops looks at the voltage than repeats as needed. A bad crimp at the terminal balance lead can do weird things. It can give an accurate voltage when reading but it has resistance on balance load. Crimp the crap out of it. Check the balance connector too. Give it jiggle.

[@evelbsstudio]

Did you ever get the QUCC BMS working with raspberry pi? Would be great to share this

[@OffGridGarageAustralia]

I never tried...

[@rcinfla9017]

As you approach full charge the voltage on cells will diverge when the cells balance is not exactly equal. The highest state of charge cell will shoot up first. The BMS may be screwing up on balancing when you lowered the balance start voltage because you are getting close to the flat portion of battery voltage curve. The voltage readings on cells have to be very accurate and not taken at differing points in time as the load or charge current changes will impact the cells' voltage readings. Many cheap BMS's just average the cell readings over time to account for charge and discharge current impact. This is not good enough when you get near the flatter portion of battery curve. A good active balancer that is designed to operate in mid-state of charge snap shots a simultaneous voltage reading on all cells so the voltages are taken on the exact same charge or discharge current. On the smart shunt 100% reset, it might not be resetting because the charge current taper off is due to lack of available solar power and not actually the battery state of charge current taper off.

[@OffGridGarageAustralia]

Great explanation, thank you.

[@davidrobertson1980]

Hmmmm swapped batttery with another to isolate BMS issue and not battery/BMS?

[@gepettoautomobile]

On my opinion the BMS must have two relay. One to disconect the load in case you get minimal voltage but the charge controler remains connected. And the second relay to disconect the charge controler, in this situation, and let the load connected. Maybe the "secret" BMS will have this features.

[@551moley]

That makes good sense, the shunt has a relay output control that you can operate with various parameters, I don't know about the Phenix inverter but my multiplus also has a programmable relay connection.

[@MrSummitville]

@ionel popa - It is called a Dual Port BMS. Unfortunately, he has a Single / Common Port BMS = Yuk ...

[@michaelbouckley4455]

@@MrSummitville AKA Separate Port

[@dtec30]

got a question andy how do you get around the low voltage regs that are currently in force ??? with regards to powerwalls anything below 60 volts is ok for diy anything above is not

[@dtec30]

either cell 14 is on its way out or the bms is doing something funky

[@PausM1142]

Try the Heltec 5A active balancer. It works great for top balancing.

[@MachielIedema]

I find it strange that if one cell is to high, the complete battery is shot off by your BMS. You loose all power at ones. can you change your settings of the BMS so that it keeps giving power to the invertor and only stops the charging? with my BMS only the charging stops, but the battery remains to give power to the invertor so that the highest cell will drop to a 'normal' voltage more quickly. my 1Amp BMS balancing only works if there is a charge going in to the cells. I have two Daly 8s 100A in two battery packs on board where I live on.

[@mavrickcustoms1280]

You made the comment you haven’t been able to keep batteries charged. I think you should take all the extra panels you have and do an experiment on how much voltage do you actually loose on long runs of cable. Place them away from your trees. And in 100% sun. Your loosing money by having them in the garage and not mounted. I think you’d be surprised on how much sun you get. Thanks for your channel and I hate your haters. I got you back.

[@lenfryers2839]

hi, I have the same problem, so my inverter is connected direct to the battery, so an over voltage cut off does not shut down the inverter, also I now think i know why its better to get a single port BMS, where the load and charge shut downs are seperate, ie if on overcharge shut down only the charge curent is dissconected, and on low voltage the load is then disconnected, this still does not resolve compleately the balance issue, but is a bit better because if the inverter is still connected and drawing current the over voltage cell will come back down , giving time to sort the balance issue. The whole problem existes because i bet my cell are A, old, B, not from the same batch or both, they will never stay balanced, only solution is a big active balancer, more expense!! Begin to wonder if the new Lead Acid batteries would have been a better choice. Price wise and piece of mind

[@PyjamasBeforeChrist]

Stuart Pittaway's DIY BMS??

[@jasondevine6014]

+1 for this. That is what I run. I have had bad experiences with these get based BMS.

[@Josh-b3c]

Balancing is going to be extremely slow even at 200 milliamps that could potentially take 24 hours or more to get it to be more reasonable

[@OffGridGarageAustralia]

In 24h it could balance (bleed) only 4.8Ah at best... This is just not designed for such large capacity cells.

[@r.igormortis149]

You don't need time to balance. If you go with a passive balancer, what you need is one that can sink more than your max charging current (e.g. 2x). At approx 300W peak (if I understood your video correctly), this equates to a maximum charging current of approx 6A, so your BMS should be able to sink at least 10A. If it can't, you will alwas get these overshoots. It seems that while your BMS can handle a load current of up to 600A, the balancing current is only 160mA. In that case I recommand reducing the input current to approx. 200mA as soon as the first cell starts to overshoot. Further more: Your turn on voltage (3.351V) is too low, as in that region (3.2 - 3.4 V) the cell voltage is not a good indicator of the cells carge status. I recommend moving the starting voltage for the balancer to 3.45V (try looking up the charge diagram for your cells. At >90% you should see the voltage rising qurite drastically. Try to configure your BMS to work on the right side of that knee). I hope you find at least some of this helpful.

[@wavestyle]

Your smart shunt probably never sees 55.0 V at all because it's much closer to the battery compared to the chargers. Consider the voltage drop on the cables! Chargers think they are going to absorb at 55.2V. But closer to the battery, the voltage is still slightly lower like maybe 54.8V. Depends all on your wiring length and diameter. In my 12V Camping setup I have the charger set to absorb at 14.3V and the shunt to reset at 14.0V. And there is not even 1meter of 6mm2 cable between the charger and the shunt. Nevertheless the voltage drop is already quite measurable.

[@OffGridGarageAustralia]

The solar chargers are actually getting the voltage fro the smart shunt vie the BT network theu are connected in. So there is basically only one voltage which is the one the smart shunt measures.

[@wavestyle]

@@OffGridGarageAustralia Sorry did not know you are using the network. Another reason might be a load that pulls down the voltage below 55.0V for a fraction of time, before the 2 minutes are over. When the compressor of my DC fridge is starting up, I am observing this effect. But since your load is stabilized through the Victron inverter, I doubt that this is the reason in your case.

[@AveRage_Joe]

Im wondering why the bms isnt staying off until the release voltage

[@uhjyuff2095]

I think Lifepo4 cells don't hold 3.65 volts when you stop charging them.

[@OffGridGarageAustralia]

I was wondering the same as it should have re-connected at 3.55V. The voltage clearly stayed at around 3.63V all the time though

[@AveRage_Joe]

@@uhjyuff2095 They will hold for a bit but not long.

[@AveRage_Joe]

@@OffGridGarageAustralia Yeah had me thinking. Could there be another setting thats not letting it?

[@SkypowerwithKarl]

Andy Heltec 16S $85 US on Amazon = balanced cells = less stress = more beer time. Been there, done that. Something that actually works.

[@OffGridGarageAustralia]

My understanding is they start balancing only at 0.1V difference?! Edit, the balance current is 1A at 0.1V. 5A is only been reched if there is a hug cell difference.

[@SkypowerwithKarl]

@@OffGridGarageAustralia No, they are balancing all the time unless you use the provision to turn it off. They only say it’ll work down to .005 V delta but I’ve seen it still busy down to .002 difference. I can’t feel any heat during charging, the time when things normally go bad. Very efficient, robs virtually nothing to operate. Hard to believe it’s doing anything but the Xiaoxiang graphics tell me otherwise. I’d be putting one on that problematic battery (with same BMS) in a heartbeat and put it to a head to head comparison with that secret😉 BMS you got for the new batteries.

[@pcMuneer]

What will happen if I keep my three stage mppt charger settings as same voltage (CC,CV,FL=3.5V / cell ) from your point of view ? By the way you resembles as a soft copy of MK Gandhi 😁❤️

[@TopAdvenTours]

Love your channel. 💗

[@OffGridGarageAustralia]

Thank you very much.

[@MrSummitville]

Did you order a *DUAL* *PORT* BMS to replace this *Common* *Port* BMS ?

[@michaelbouckley4455]

Was thinking the same, have been looking for one. Separate Port BMS are more rare, and costly. Even Daly make one, but I’ve never seen it for sale.

[@MrSummitville]

@@michaelbouckley4455 With Common Port, if you hit High Voltage on just one cell from charging, you lose the entire battery bank that powers the Off-Grid Home = Ouch! Over-Voltage should disconnect only the Charger. Under-Voltage should disconnect only the Inverter. A BMS with separate Charge & Discharge control pins that energize an externally connected Contactor or SSR works well for high amp battery banks...

[@OffGridGarageAustralia]

Nah, I didn't do that. It's still a common port BMS. Is separate port not more been used in e-bikes and scooters that sort of application?

[@nigelcharles511]

With regard to the low voltage disconnect of the inverter I don't think that you need a BMS to do that. I have a 48Kwh lead acid pack with a Victron inverter without BMS. During the colder weather the battery voltage dropped prematurely during a high current discharge causing the battery voltage to drop excessively. The inverter sensed this and shut itself off. Someone mentioned using a diode across the BMS to allow discharge with the BMS turned off. I think that this is a great idea. Is there anything wrong with that?

[@ab_ab_c]

Your BMS should discharge cell 14 when an over V event is triggered. Given that your BMS is apparently not discharging cell 14 properly, I suggest you stop charging & manually discharge cell 14 using a 1Ω resistor (make sure your resistor is capable of dissipating >=15 W or put multiple 1Ω resistors in parallel to share the heat dissipation). All you have to do is connect the resistor to cell 14 terminals to begin the manual balancing discharge. Stop the manual discharge after the V of cell 14 drops .1 V below the average V of the other cells. Then start your charger to see if cell 14 behaves proper or races ahead of the other cells again when charging. As cells age & lose capacity, they tend to charge & reach cut-off V faster than a new or good cell. You definitely don't want your relays popping on & off very often. Your options seem to be: 1. Replace cell 14 (probably not necessary & expensive unless it can be done via your warranty) 2. Get a better BMS that can more quickly balance an out of balance cell 3. Make your own BMS to auto-discharge cell 14 to a certain V Best wishes in finding a cost efficient solution... :)

[@fransstroetmann3423]

If the battery BMS switch off, the inverter can better see a supercapacitor as source then a MPPT controller

[@JeremyAkersInAustin]

Would this be a bad time to say "I told you so"? On the BMS relay shutting off charger and inverter at the same time? :D haha This is also what I don't like about using the Victron shunt for SoC monitoring. I think I've written comments about this before, but the Victron Shunt can't see individual cells, it can only see the pack voltage. And if you have all your cells at 3.4v and one cell hits 3.6v you're basically at 100% SoC... but the pack voltage is only 54.6v which isn't high enough to trigger your shunt's SoC reset of 55v. You have an even worse problem at the bottom end. You could have one cell drop to 2.9v while the rest of your cells are still at 3.2v. At this point you're basically at 0% SoC but your shunt might still be reading 20% or so. Regarding your cell #14: I wouldn't worry too much about that cell being a bit high. Having one cell his 3.6v while the rest are at 3.4 is not unusual. Remember at 3.4v the cells are at like 99% SoC. So just a 1% difference in balance can cause cell 14 to hit 3.6 while the rest remain around 3.4-3.5. However: even a 1% difference can mean a difference of 2.8 Ah. With only 160 mA of balance current it would take about 18 hours to finish balancing. This is why with such large cells active balancing becomes necessary. It would be really ideal if your BMS could just turn off the MPPT chargers when a cell gets high instead of turning off the relay because that disconnects your inverter from the battery which causes all sorts of additional chaos. But I've only mentioned that a few times now. :D Also: See my comment on your earlier video about my experiments with balancing at 3.35v. :D

[@longdistancerider691]

place a extra Active Cell Balance ?

[@PyjamasBeforeChrist]

ElectroDacus SBMS?

[@OffGridGarageAustralia]

only 24V unfortunatelly...

[@dayvan6550]

IT'S ALIVE!