I Hate JK BMSes, So I Bought Two More - 48v LFP Battery Build (Ep. 36)

[@OffGridGarageAustralia]

Hello Maddy from the past 😎 It seems that this is all old BMS stock. I'm under the impression, QSO is just a re-seller of these BMSes and bought them quite a while back in larger quantities maybe. Dealing with Hankzor, they do a lot of R&D and work directly with JK in this regards. Still super annoying. Maybe you can send them back to QSO for a refund. Even it costs some shipping costs. Paralleling is not a problem at all with LiFePO4 as the curves are flat. Their concern is coming from using Li-ion packs where SOC is linear to voltage and 20%SOC difference could result in a huge current. Thanks for mentioning my name 73 times 😂

[@TheDigitalMermaid]

Only 73? I need to step up my game! :P My concern about JK is that they are so inconsistent. I am certain you are right about old stock, but to me that's not really fair to customers. If specs change so often that you need to be careful where you buy a given product is ... "not good", as a certain Aussie friend might say.

[@OffGridGarageAustralia]

@@TheDigitalMermaid 28:30 this thing should definitely turn on if the circuits are right. A bit hard to see with your spaghetti salad on the desk. 29:40 can keep this 24V configuration and just disconnect the balance cables of battery 5, 6, 7. You should see them reading 0V in the BMS. Also make sure the cell count is correct in the BMS. I'll send you an IM with my hardware and software version of the 4-8S JK I have. Maybe we can figure out if there is a difference. It's under the three dots in the app...

[@TheDigitalMermaid]

@@OffGridGarageAustralia Ya, I dun goofed. I'll do a follow up test / video tomorrow if I can. Keen to compile a list of versions, I'll watch for the IM. I can pop the covers off mine and take some pics as well, maybe there's internal hardware differences.

[@jk.ess.solution]

@@TheDigitalMermaid The starting voltage of the old version of BMS is 20V, and the starting voltage of the new version is 10V. If you need to support 4S batteries on your old version of BMS, Then you can add a boost module or a power supply to activate the BMS

[@a.m.philippo7677]

hey nice video. 28:02 you turn off the breaker to connect the grounds and on 28:20 you don't turn the breaker on, so you don't have 24V on line 8, you check the voltage but forget line 8 to check also that's why the faking test did not work, so no conclusive outcome.

[@TheDigitalMermaid]

OMG. If that's what I did wrong... Hahaha! I'll have to try again tomorrow. >_

[@a.m.philippo7677]

@@TheDigitalMermaid make it easy first. Use the 8s and disconnect lines 5-7, than you have what you intend to do, I think the BMS will turn on, but goes to alarm because of low Voltage on 5-7 and high on 8. After this test you can try with real 4s and the 24V on line 8.( just to speed things up on answers and real world answers.)

[@HG-Pilot]

Exactly, try drinking and thinking, your output would be similar...

[@TheDigitalMermaid]

@@HG-Pilot I'm perfectly capable of being oblivious stone sober

[@upnorthandpersonal]

Parallel is supported after I told them to use class-T fuses when doing so. I drew them a diagram, and that's now the recommended way on their site as well. The reason it was not recommended is that this BMS can be used with other chemistries where this is much more of an issue compared to LiFePO4.

[@TheDigitalMermaid]

Oh, that's good to know. I put a T-class on every battery, so that should help me here as well.

[@RulgertGhostalker]

the only reason they do Battery Management System per cell. is for configuration flexibility ... that would drive me insane. i would just desighn and build my own custom consolidated battery EQ...and pot it in thermal epoxy..

[@RulgertGhostalker]

@@TheDigitalMermaid oh, they stack into a consolidated unit??? ...that's not too bad. i would think a shore power smart charger would have integrated EQ circuitry, but then again, they don't know what pack your building.....and it's back to the same thing.

[@RulgertGhostalker]

@@TheDigitalMermaid but it could be done like that, for a single series string ...

[@xevitomas]

Some bms need to read voltage on all their wires. The 4s-8s configuration change is done with jumpers on the PCB itself or on the monitoring cables. Before ruling out that it works as BMS 4s, I would try to connect the cables of cells 5-6-7-8 directly to cell 4 and try to turn it on, if it does not work, the BMS should not suffer any damage. My BMS 20s needs to connect wires 16-17-18-19-20 to cell 16, to understand what is a 16s configuration. It is an automatic translation, I hope I have been able to explain it well.

[@sNEAKYnIGHTmUPPET]

I can add some insight to your parallel concern. It isn't that they don't recommend running BATTERIES in parallel, it is BMSs' in PARALLEL. the problem they are concerned with is one bms disconnecting and leaving the full load on the remaining BMS. I know this since I did contact JK directly and after struggling with the translation, this is what was conveyed to me. I have done a system with three 16S batteries in parallel without any problems whatsoever. Hope that this helps. I want to clarify, I have done PARALLEL BMS twice now

[@TheDigitalMermaid]

Thanks for this. Not sure how you could parallel the BMSes directly, but I think I get your point.

[@alanhollister9122]

I have 2 battery banks (560) amp hour 24 volt packs, 2, 280 amp cells parallel and 8 cells series totaling 16 cells per pack, I remember Andy saying you can’t parallel also but I needed a bms on each pack so I did it anyway and it works fine, JK bms. Watching your video and you need more than 5 volts to start your bms

[@TheCheopps]

The fuse should be conected to positive terminal bcs the BMS inner cirquitry is referenced to the negative terminal. When this terminal gets disconected by fuse, the first balance lead becomes the ground reference and the current keeps flowing. To avoid any danger of fire/explosion of the bms the outermost positive terminal should be disconnected by fuse in fault condition.

[@Digimer]

This makes sense, thanks!

[@terratrekker28]

I really like your patience, attitude and humor

[@immrnoidall]

In my instructions that came with the BMS, wiring for the 4s battery shows the b+, also going to the b4. for an 8s battery b+ also goes to the b8.

[@aday1637]

Problems I have with JK is the plugs like you mentioned. Plus the fact that on the 48 volt one's there is not legs to mount the unit. Either it must be taped or cable-tied on or allowed to just rest, dangling by wires. Also with most all the bms units I've used, the manuals are either missing, obscure, or not helpful. Most are online only and are difficult to cipher. JBD went out after 1-1/2 years. It just stopped working properly and began beeping. All of it's parameters had changed on their own when this occurred and were unable to be adjusted. Daly worked but the blue tooth didn't connect to my phone so I had no idea the parameters which made it unsafe to use. I'm just about sure, now, that there are no reliable bms devices made. I just got the JK 2 days ago and so far so good (once I figured out the plugs). But it's just laying on top a pile of wires which is sloppy and not very portable.

[@TheDigitalMermaid]

JK is meh, to be sure, but it's the best of what's available, so far. I don't trust mine to last over time though... =/

[@williamhustonrn6160]

I’m going off a hunch the BMS is not turning on because of settings in the BMS, it’s designed to go into “protection mode” when cell voltage is sensed under 1v I think, so when you connect it to only 4 cells it’s reading 0v on the other 4 and defaulting to protection mode. An easy way to test this would be to to hook it up to 8 cells on the balance leads , only run busbars to 4 cells and then supply 24v to it from the icharge. That may be enough to trick it, other option is to wire up 4 capacitors to create 24v battery in the eyes of the BMS but you truly only have 12v. Regarding the starting starting side for the Diesel engine, I would personally KZbin super capacitor starting battery, you could build a hybrid lithium/super capacitor starting battery pretty easy to support the cranking amps you need. You build a 12v super capacitor bank, then wire it in parallel to the 12v lithium battery you have now, but super important put a 1-10ohm starter resistor in circuit between them, what this starter resistor does is reduces the voltage of the lithium 12v battery viewed from the point of view of the super capacitor, so when the starter of the diesel motor is cranking its pulling majority of its amp load from the super capacitor bank and as the voltage drops from the super capacitors it will start pulling more amps from the lithium bank. This is how you protect the lithium bank from getting hit by to many amps from the starting motor. Then when you let off the starter, the lithium bank will recharger the super capacitor bank since that are in parallel. You would only worry about the lithium bank regarding balancing and charging and the super capacitors bank will self charge and be there for you when you need to start the Diesel engine. I built one of these hybrid starting batteries years ago playing around with the idea with 12v Computer 10ah UPS battery. I used a 1ohm starting resistor between them and it worked perfectly starting my pickup truck, which was a 6.8L v10 gas engine. I’m in IT so I had tons of UPS batteries sitting around and they are dirt cheap so I tried it and that hybrid battery started my truck for 7 years before I lost it to a wreck, which destroyed the super capacitors battery.

[@TheDigitalMermaid]

"cell voltage is sensed under 1v I think" - That makes a lot of sense, but it doesn't jive with Andy's video where he talks specifically about doing this with another JK BMS. It's possible they updated the firmware in this "8S" version I have though to require all cells. "Regarding the starting starting side for the Diesel engine" - This is all good advice, honestly, I like the concept. If I planned to keep the diesel. In my case, I want to invest the least amount possible to make the LFP cells/packs I have work until I get the boat home and rip the diesel out. If I can't make a pair of 12v turn the old girl over, then I'll live with a LA cell until I get home. :)

[@williamhustonrn6160]

@@TheDigitalMermaid If that is all you need to do, then just hook the LFP to 12v circuits and use a cheap jump box for starting the diesel engine and just plug it into the LFP to stay charged when not in use. My concerns is your grossly underestimating the amp draw to start that engine. My 6.8L engine spiked over 1000amps momentarily, then settled around 370amps during starting and knowing diesel engines typically have higher combustion pressure due to it being compression ignition is going to be slightly higher i would assume. I would go out to your boat with a meter and measure the amps on startup before you go trying to use LFP batteries on it, don't want you destroying your hard work underestimating it.

[@frankthies221]

BALLS!

[@denisebrooks4513]

Just found your channel and am loving it. This episode was pure gold! I really appreciate how you're coming at sailboat electrification in this battery forward way. I'm a full time sailor with a fairly similar boat to the one you just bought. I thought we should upgrade the house batteries to lithium, so I did what I thought was the simple thing and just dropped battle borns into the battery locker. This turned out to be a bad plan. I didn't understand all the knock on effects to the other parts of the battery infrastructure. So now I'm on a mission to learn more by following your adventures. Thanks!

[@TheDigitalMermaid]

Thank you for following along! Ya, switching to LFP tends to domino into upgrading chargers, MPPTs, etc. What kind of boat do you have?

[@bbrown_sc]

You should have kept your Overkill 16S's. My 2 batteries using EVE LF304 cells (from QSO) have been working flawlessly since early April. Never had an issue with the small passive balancers. With the exception of hitting the knee approaching full charge the cell deviation stays in single digit millivolts. Once they hit absorption, they drop down to 8-9 millivolts. They get fully charged and discharged to 50%-60% almost every day. They have 75 cycles on them a piece. I've only top balanced them once, when they were initially built. Overkill has great documentation and support. Plus their warrantee covers everything. Even if you blow it up for any reason.

[@loucinci3922]

Total bummer. Good information. Thanks for sharing

[@1over137]

On fusing the positive or the negative. If both are "floating" it's fine to do either. Where you might want to express caution is if you ever "reference" the battery to something, like an earth or the metal hull of a boat, body of a car etc.. Usually the minus. You would be wise to fuse the positive in that case. It's the same here (UK) with every plug having a fuse built in (as the house wiring is 30+A and the appliance cables are 5 or 13 amp). The fuse is on the "Live" or "Hot" side. The reason being, if you disconnect the nuetral from the appliance only, there is still >240V between "Live" and "Earth".

[@MichaKersloot]

Hi, you could try the 8s configuration and disconnect 1 balance lead at the time and see when it stops working.

[@shadowgenesis2877]

Check to see if your breaker is on. Last test with the power supply, it was off.

[@FutureSystem738]

I bought the 4s-8s BMS shortly after it was first available for my 12v system. It was a fail, kept on beeping and error message. The quickly acknowledged there was an issue, and asked me to return it. They have subsequently refunded my postage, and sent a new one which should arrive any day now. Cheers from downunder 🇦🇺

[@airgead5391]

By the way why not using REC BMS? It is a European company with good documentation and support. One could use a bistable relais for switching 500A as one wish.

[@TheDigitalMermaid]

Relay-based BMSes worry me about potentially welded contacts.

[@airgead5391]

@@TheDigitalMermaid The contacts are only activated at extremes that (almost) never (should) take place, and they are specified for the job. (for instance the Blue Sea 500A). I have much more faith in simple electromagnetic stuff than in a thin layer on a substrate. It is a no loss no heat solution too.

[@airgead5391]

@@TheDigitalMermaid And another thing: how is your engine switched on? I bet you can switch off the power to the solenoids of the motor before the BMS switches off the battery. By human intervention is also possible: to have a buzzer making noise before the BMS switches off the battery is anyway a good thing. Also other heavy users like electric winches a bowthruster, anchor winch can be de-powered before the BMS switches the battery total off using this method. So there are solutions to prevent the BMS switching off the bistable relay with large currents. However I must admit that for a moment I forgot the rather high battery voltage you are using, might take some searching for the right relay, really.

[@USA-GreedyMenOfNoIntegrity]

I put my class to fuse in the middle of the pack. It just works out that it's on the opposite end from all the breakers BMS, connectors and shunt.

[@keyem4504]

In order to test BMS' without a battery, I built myself a "Battery simulator" which is just a bunch of stunds I screwed into a board that are connected with resistors of equal strength so that I have a series of voltage dividers. It is then powered by a power supply connected to the outer studs. Works great.

[@svsathyanarayana6399]

Can you share circuit diagram

[@keyem4504]

@@svsathyanarayana6399 It's too simple for that. If S is a screw, and 1MR is a 1MOhm resistor, for a 4S system it would be: S--1MR--S--1MR--S--1MR--S Then connect your power supply to the two outer S, crank it to 12V and there you are. I did that with 16 Screws and 48V.

[@matthewknight5641]

Im glad you got the jkbms. I just ordered 2 of them with the 2 amp balancers. Hopefully i got the right ones that im needing. Im building a 16 cell 560 amphour 24 volt battery

[@1over137]

On the BMS, I am eyeing exactly this BMS as I currently have a 4S and awaiting another 4 cells to go 8S. I did consider the DIY option but there are devils in the details which make it non-trivial. Im hoping all you guys iron out the kinks with JK before I buy mine :D I did install a cell monitor though, even sat a made the JST connector.

[@TheDigitalMermaid]

It bugs me that the JK is still the best option currently.

[@Ether_Void]

5:06 "RS-485 used the GPS plug..." The "GPS" port is just a normal UART / RS-232 port. JK seems to use it for general communication, and converting UART / RS-232 to RS-485 only really requires a single transceiver chip. It could probably be used for GPS (like a ublox, neo-6m, bn-280, etc.) which all use UART so it makes sense from a technical standpoint, but I don't know why they don't just label it "UART" like Daly does. Especially since I can't find any information how the JK BMS would work together with a GPS. On to why the CAN/RS-485 is has the RS-485 on the label .... maybe they decided to finally put the transceiver in the BMS itself? I can't find any info on it (from a quit search), so maybe the adapter is unnecessary but for that a pinout would be good to know.

[@TheDigitalMermaid]

Aaaah, that's useful to know, thank you.

[@SkypowerwithKarl]

It’s a good thing that the bms didn’t work for 12 and you’re ordering the right one. Most of those little voltage booster boards are little power parasites that are always wired on. Given enough time without some sort of voltage maintaining, the battery will deplete much faster than other Lifepo4 batteries. You did the right thing. Everything you surmised about paralleling I believe is correct.

[@guywatkins]

At 28:20 you did not turn the circuit breaker on. That is why the final test of 4S failed.

[@bobbellar6238]

Try starting the jk 8s with a 30 volt charging voltage momentarily in the 4s configuration.

[@zoe..d]

I still don't understand why you can't use a 9v battery and use a momentary switch to boot it up with the leads from the 9v attached to the p- and b-. All its looking for is a 5v differential.... 9v battery is simple, no need to stuff around with dedicated external power supplies....

[@FishFish1995]

Admittedly I don't work with 4S configurations, so I can't really understand your frustration... Personally I have used JK BMSs multiple times on LFP and Li-Ion battery packs (13 and 16S on Li-Ion, 16S on LFP). They have been my favourite BMS so far... Maybe because it was the first smart BMS I've used. Maybe because Andy from off-grid garage is here on KZbin and has put out so kuch content about the JK BMS, so many comparisons with other brands. I have watched it all, because I wanted to pick a smart BMS. After using it, I find the JK BMS very solid. Although I have had an issue with one of them where it would state an astronomical cycle capacity. But that didn't affect anything else, so I don't care. It might get fixed with an update, but I don't update my BMS, too bored for that. All in all I am very satisfied with them. I have recently bought a 100Balance, soon I'll be using it. But there was no switch inside the box. I asked the seller and he told me that because there was an issue where users should first go inside the app and enable switch capability, and that confused many customers, 100 Balance (Dali) stopped including them inside the box. A switch costs 10€ if you want it. Nevertheless, I asked for a partial refund due to the lack of a switch (the description stated there was a switch cable inside). So, out of the box, before using it, I had issues with a Dali sub-brand. How can I not love my JK BMSs?

[@matthewknight5641]

I really hope ive not gotta send back the jkbms's also. Ive ordered a 300 amp daly a d everyone said its junk send it back but seeing how difficult the jk is being for you it makes me think.... wow i may have made another mistake buying a couple of these. Im running a 24 volt system so maybe they will be ok. Wish they would hurry up and get here so i can find out

[@peterrock2838]

You could live dangerously and run 4S 2P and have a BMS bypass switch for cranking the little diesel.

[@DaveVelo1]

I'm inclined to agree with you. My main complaint is the amount of power it drains from my batteries. There is no option to turn off Bluetooth in settings. Unplugging the BMS, then plugging back in turns off Bluetooth but it also turns off discharge. 😡😡 Addressing your parallel concerns, I have two identical batteries with their own BMS. I parallel charge them with no problems I can determine.

[@TheDigitalMermaid]

The JKs really feel like they were built to meet a certain set of features as cheaply as possible. Lots of little things, like standby power draw, leave a lot to be desired.

[@zuhairifirdauszakarin123]

Try connect wire like ant bms setting... Use black and 2 next wire... And 3 wire at the end include positive wire... Leave middle wire...

[@roborobo02]

I get the impression the BMS is powered via the JST lead and the positive pin 9 lead is connect to battery 4 positive. The BMS must be powered.

[@tommyb7632]

isn't there a negative B- for batt side to connect from batt to BMS, then you have the other connection with P- which is the output of batt with the positive pole of the batt. look on the BMS. so in fact . The batt + goes to charger and/or load, then - lead from batt goes to B- on BMS and then where you have on the opposite side - thats the P- output to load and/or charger

[@mausball]

I’ve been working with small companies in China for a long time. The manufacturing culture is completely different there from what we’re used to in the US. It’s always interesting.

[@jk.ess.solution]

Hi, this is Nami I watched your video, You bought an old version, The old version has only 5 interfaces and is sold in China The new version has a total of 6 interfaces and is sold overseas And I don't know where you got the news, So please contact the store you purchased to check whether he sent the wrong goods. Thank you

[@TheDigitalMermaid]

Do you work for Jikong? My main point was that the part numbers were the same, so I understand that you're saying they were meant for Chinese domestic market, but the point remains that if the part numbers match, but the features don't, I think that's a problem. This is the second time I've been told "you bought the old version", and both times it was right after I received them, so they were brand new to me. How is a consumer supposed to know what they're getting? This makes life very difficult and unpredictable.

[@jk.ess.solution]

@@TheDigitalMermaid In the simplest way, You can ask how many interfaces the BMS has before purchasing, BMS supporting 4S is equipped with an additional heating interface, If a heating function is required, a heating chip will be added inside, Unfortunately, photos cannot be sent here, You can also ask him what the starting voltage of BMS is, The starting voltage of BMS supporting 4S is 10V, All other BMS start voltages are 20V,

[@andrepallotta8633]

Hello wonderfull video. I bought the same bms i d like to connect with a computer with rs485 and can. Did you do ? could do a video about rs485 connexion ? Thanks.

[@davidniquot6423]

A 16S pack of 280A can go over 2000A of current... i suppose the BMS do not react fast enough and burn. Kind like a breaker of 20A got an absolute amperage value to never go over or it will melt (which is maybe 6kA for example)

[@TheDigitalMermaid]

The T-class fuse that hangs off the main pack positive terminal is the safety device. I might well lose the BMS, sure, but the fuse will prevent catastrophic damage / fire.

[@jackiedines5229]

It needs up to 8 volts more than 24v. So YES you will need a voltage booster to 24v, PLUS to get it started you need to ADD up to about 8v. By way of a couple of 18650 p together then touch the - wire to the p- on BMS and the + to b- on the BMS if that does not power it on just reverse the connections. Just a touch mind you because you are shorting. Your charger could do the job but needs to go at least 4v higher than 24v. After BMS starts turn charger down to 24v. But the issue still remains that to run the thing as 4S you need the booster thing. I bought one from JK it is a fixed sealed unit, and yes it draws power but very little, if you have PV charging all the time I doubt that it would matter unless you were very borderline. If you want more details let me know.

[@laxbeau11]

What about Orion BMS? Seems like they are a more appropriate fit for motor(high current). applications.

[@TheDigitalMermaid]

I had not looked at them before, just did. Seem like excellent BMSes, though they also seem very much focused on EV applications (high voltage, more specifically). The idea of having a Chademo connector on the boat would be amazing as hell, though I suspect it'll be a LONG time before fuel docks have chedemo or similar DC fast charging options. haha.

[@stevedutcher3875]

Hook the 12 volt BMS up like normal, the JK BMS requires 5 more volts to activate. ( 18-19vdc) touch the positive and negative terminals with the boost converter set 5 or 6 volts higher than your battery voltage for a micro second and that should activate the JD BMS. Actually I prefer the Daly smart BMS to the JK BMS. My Daly smart BMS keep cells voltages within 3 or 4 millivolts, just as close as my JK BMS!

[@TheDigitalMermaid]

I tried that with the batteries I had taped together to boot the original JK BMS I'm using in my 16s pack. Didn't work this time... However, it looks like I made a mistake and left the breaker off, so I'll have to try again.

[@caserio323]

you need to give power to it to turn on the bms boost converter and this will work fine. i got the same model and work for me just fine, get a boost converter is always need it for diy . the boost only will used to turn it on ather is one the bms will keep working ,,great video keep it up, from you friend Hector

[@juvilobayudan1452]

Goodjob Roberto!

[@Blueworld950]

Can you tell me how to connect with inverter, protocol function CAN

[@raymondcastro734]

You turned the CB off at 28:00 to connect the B- to the battery and never turned it back on. That is why the BMS never turned on. 🤣🤣🤣

[@TheDigitalMermaid]

Ya, another commentor noticed the same thing... >_

[@kenlillia]

Hi, I am in Australia and watch all of Andy’s vids and as a result also purchased the infamous JK 4 to 8s BMS model number B2A8S20P in late July 2022. What a disaster. It worked in my 200ah battery initially perfectly the overnight it would come up with errors and would not show voltage. I notified Hankzor BMS store gave them the batch number and waited for a week for a reply, nothing until I contacted them again and they replied a chip need replacement and could they send to me for me to fit chip. I said no but you can send replacement to me. They declined but said if I sent it back to them within 9 days they would refund me. I waited 4 days for the address. That gave me 5 days to return it. Impossible. I decided to keep it for old keep sake. I did not tell Andy as he may feel it is his fault for recommending it. It’s not his problem it’s the sellers bad arrogant attitude. Good luck with yours. I use Daly in my other batteries without problems. I did like the active balancer in the JK but, that’s a life experience. Enjoy your builds. Cheers Ken

[@OffGridGarageAustralia]

What a nightmare, Ken. Did you contact them via the AE chat function or what was your contact method?

[@kenlillia]

@@OffGridGarageAustralia I contacted back through the sellers site as well as calling jk themselves with no success. It only cost $160 not worth the drama Andy. Keep the vids coming. Cheers Ken

[@OffGridGarageAustralia]

@@kenlillia Cannot be that people don't get support from them. I'll escalate this back through my channels.

[@kenlillia]

@@OffGridGarageAustralia don’t escalate on my behalf. However for future business with us all they must offer better prompt after sales support with someone who understands English.

[@FutureSystem738]

@ken Lillia - I had the same problem. Via chat, they acknowledged the problem, knew the reason for the issue, and said post it back, which I did straight away, which cost me about AUD$33. They said they’d refund postage and send a new BMS once received , which is what they did. I’ve received my postage refund, and a new BMS is on the way and SHOULD arrive any day now. The problem SHOULD then be solved…. Hopefully.

[@francisdoll1253]

Hello,I have the same BMS model as you and have a schematic.In 4S configuration,the Main positive must have connected balance wire n° 4 and 9,also in 8S configuration it's wire 8 and 9.You have just one wire connected to main positive on your 12V battery !

[@shiroganekey9271]

I have 2 jk bms as well. in my 20s bms 16cell configuration, you need to connect *all* unused balance cables to battery positive. (got the shematics from aliexpress)

[@martehoudesheldt5885]

as for the parallel of bms were you talking about mutipul bat packs to 1 buss or multipul bms on 1 battery? did you get that across to them in china? i could see there concern for many bms on 1 battery. as for the starter bms bypass relay (starter solenoid) with separate fuse for starter ( within C rating of batt.

[@boringsoftware2093]

PS: if u are frustrated... currently trying to run 20s JKBMS with 15s, aint working either X-D can not set CELL AMOUNTS in the App lower than 16 :( WHY? WHY?

[@jujufurious2693]

The Digital Mermaid, In 28.43min, your breaker is not in ON position for me... It doesn't work just because of that, does it?

[@TheDigitalMermaid]

Ya, another commentor mentioned that as well... I'll have to retest.

[@lezbriddon]

i'd be taking a dremel or grinder to those terminals to shorten them away from the mosfets, anything after the hole isnt really carrying current of importance

[@keyem4504]

Did you open one of the 2A parts? I have such a thing myself, but on the PCB it states 1A. It does do 2A though. Would be very interested if this is the case for all these systems or if I was ripped off.

[@kuhrd]

Regarding JK-BMS releasing new BMSs under the same model number or even changing stuff without documenting, this seems like an industry wide thing these days as I always use ANT-BMS since they have been very reliable and I am familiar with them but they also will name ports differently although they have been good about documenting what the ports are each for. Every 3 months it seems like they change enough in their protocol that I have to wait for the 3rd party BMS software that I use to be updated to access new versions. I can use their apps to set things up but I prefer the 3rd party one I use as it is far more stable.

[@TheDigitalMermaid]

If it's an "industry standard", it's a silly one that needs to be called out. It makes it impossible for consumers to know what they're getting...

[@picobyte]

My 24s JK BMS runs my 16s battery just fine, it does need a buck converter for the display, newest displays sould have a boost-buck converter build in. Also I have the same rs 485 issue with that weird connector 😑

[@TheDigitalMermaid]

Have you played with the rs485 interface yet?

[@scoleri]

I'm so confused. Did you ever send in on the 4s set up like 15-16 volts from an external power supply? I think i have the same BMS and that's how i get it to come on every time?

[@awesomedee5421]

I bought some lithium ion battery resistance testers, and the Lithium warning label was on the shipment.

[@Xircom10]

Who is QSO? Im trying to get the 4S and 8s send to Denmark. Could you link to the place where you buy the JK BMS ?

[@TheDigitalMermaid]

"Shenzhen Qishou Technology Limited", they're a company I found from Andy's channel. When I was ready to buy the bulk order, I wasn't really impressed with Basen, so I reached out to them and their support (pre and post sale) was a lot better. qiso.en.alibaba.com/?spm=a2700.12243863.0.0.57c83e5fCTqAaz

[@jackiedines5229]

JK sent me a model no that I did not order, however it still had the right specs. It was for 8s but I wanted 4S, at that time they did not have a 4S, but by doing the trick of getting it powered on by adding about 8v. I just wired up a couple of 18650 then shorted the BMS between the B+ and the B-.

[@richardriehle4159]

interesting troubleshooting . that would give me headache and stress me to no end.

[@BeastMovies]

Seems like a lot of hubub. If it's only for small voltages and to get you out of trouble, you could've bought a buck converter. 24v to 12v or 48v to 12v. Quick fix.

[@Taiwanek]

Hello, when you tried the last configuration, you had the circuit breaker for the iCharger off, that's why it probably didn't work :)

[@TheDigitalMermaid]

Aye, another commentor noticed as well. I'll re-test.

[@scoleri]

i bailed on top balancing and just used the JK. I only had a 4sX at the time so i did each 4s 12 pack then built the 16 after all the 4s's were top charged with the JK.... Does that make sense? Top balancing 16 batteries takes WAAAAAAY too long and boring.

[@charlesmathias2197]

i watched ypu video been there as well i thought it was that as i used the same bms for my first battery and needed that to kick it into life.Keep up the good work i find your vids very interesting cannot wait for install of batteries in boat INSANE.I have a 14s 25kw lipo powerwall that i have built with 18650 cells.With the price of electricty going to nearly £1 gbp per kilowatt battery has saved me thousands of pounds not bad for the nutter building "that thing" down the road.

[@ValRigoli]

Hi Maddy, have you considered adding a capacitor pack to your 12V starting battery, then you would only need just the one battery and the BMS does not have to be so large? Seeing as I can't post a link on here, if you do a search for "Maxwell Super capacitor 16v-500F (6x2.7v-3000F)" that should get you some ideas and access to them in your area.

[@TheDigitalMermaid]

I hadn't thought of it seriously yet, I'm really hoping I can avoid it. If not, it's an option. I'd have to decide if it's better to add a cap or keep a small LA battery for the starter. It's temporary so I really don't want to invest more than I have to into anything related to the diesel. Cheers.

[@matija3791]

Hi, I think you talked about the maximum current you design your system for but I can't remember which value you said. I am just testing the 200A JK BMS with my 16s 280K battery system and the BMS gets pretty hot at 90A already after 3h. The values are the following: MOSFET temperature: 69°C, and apart from the T-type fuse and the China DC-Breaker (both 125A rating which I use) this is the only component which gets hot. The fuse and breaker are probably at about 60 to 70°C at hot spot, but I don't have any measurement device to be sure (using good old finger tips to check for a few milliseconds xD. After 3h system test, the Multiplus 48/5000 limited the power from 4600W to 3800W and everything cooled down again, so I could not test if anything breaks. Just for you to consider that the rating of the JK BMS is probably totally overrated. MOSFET temperature probably does not measure the MOSFETs direct but only some NTC "far away" from the chip, and when the circuit design is not totally balanced, the hottest chip is probably already at above 120°C in the hot spot. Those temperatures is not good for long term reliability of the components.

[@TheDigitalMermaid]

Amperage planning depends on what part I'm looking at. The battery packs themselves are limited to 175A by the Anderson connector I chose. The BMS can do 200A, but I also have the T-class fuse set to 200A, so I don't expect to ever actually pull that. I want the ability for rare cases, but generally I don't want to draw more than 150A, ideally even lower to keep things cool. The bus bars I've got for the battery bank is rated to 600A, but the SmartShunt is rated for only 500A, so I plan to keep the total draw across all packs below 500A at the very most. Really though, this is all quite over-rated given my motor and inverter, at absolute peak combined draw (which will likely never happen) is 22kw (550A if all packs are at dead minimum voltage, 430A at 51.2v). Even then, that's using the maximum peak wattage (10kw), which the inverter can only sustain for a very short time. Maximum sustained is only 4k, so really the very maximum _sustained_ load is 312.5A at 51.2v across the batteries, or 52A per battery. Now, realistically, I plan to stay at 1/2 trottle, and it's highly unlikely I'd be cooking while under power as the plan is to use the motor to get in/out of harbours. I also will only see heavier house loads when cooking (electric galley) or doing laundry, which would only happen when I'm not actually sailing 99% of the time. So realistically, 6~7kw draw is about the most I would see in a regular day, which is 137A at nominal pack voltage. So in theory, I could lose all but one battery and still be fine.

[@kblemandan]

I normally don’t leave comments but I hear this all the time about BMS not supporting parallel. I see there a misunderstanding of this in the KZbin community. BMS not supporting parallel have not been tested to have batteries connected directly together. When using buss bar this does not apply as this is a natural state at witch the battery will naturally equalize at this applies to AGM and LIPo cell. I have also watched Andy’s videos. I have been maintaining teloco -48 volt power plants for 20+ years. To understand why we use -48 volt is because that is the direction electrons natural flow and this reduces corrosion on terminals. Also in battery systems what side the breaker is on does not matter as this is a closed system.

[@TheDigitalMermaid]

Interesting. Well, I'm running all the BMSes to a bus bar, not directly together.

[@shanedenniscom]

I use a 250A continuous JBD BMS (jaibaida) for my 230aH @ 48V 16S cell bank. Runs my 12kW electric motor. Absolutely no problems for almost a year now. The motor usually uses 10-50A continuous. I thought Jiabaida was one of the biggest manufacturers of LiFePO4 BMSs. (I think Overkill Solar BMSs are just rebranded and beefed up JBDs.) Have a second 200A @ 12V LiFePO4 battery which acts as house and also runs the windlass. For cranking a diesel engine, I would use a cheap lead acid battery. It's just too hard to get the cranking amps needed from a LiFePO4 setup.

[@TheDigitalMermaid]

I started with an OverkillSolar (it is JBD), but I wasn't happy with it's balance capabilities, or the amp rating (for the 16s), which is why I gave mine to Andy to play with. That's the driving thing for me is that active balancing capability of the JK is, so far, the best option. =/

[@gemrough]

I’m still in the BMS research phase of my 57kwh pack build… why not go with something else and add a Neeey balancer? I added one to my last ncm build and it worked great.

[@TheDigitalMermaid]

@@gemrough I'm trying to avoid more complexity, so I really want a BMS that has the features I need.

[@truthhurts2149]

What's difference between black and silver jkbms. Same model but Seems the black are sold out more.

[@TheDigitalMermaid]

The black supports up to 24s (16s for us LFP people, really). The silver are 4s/8s (or only 8s, as I found out in some cases).

[@truthhurts2149]

@@TheDigitalMermaid thanks. I see that now. Do it you think the 46 dollar display is worth it? Maybe as a failsafe Incase Bluetooth fails I guess. I hate to spend the extra if not really needed though.

[@TheDigitalMermaid]

@@truthhurts2149 oh gosh, no, it's not needed. Is it worth the money? Probably not, but I think it looks neat.

[@truthhurts2149]

@@TheDigitalMermaid Thank you for your reply. So I'm looking at finally building my solar system. I purchased everything like 1.5 years ago and everything is still sitting including 16 280 ah cells. I want to build a 24v bank that can power a 4000 watt inverter. I believe it peaks at 5000 or so. it will only be used as a backup for now. I have to build my solar array also. I bought a chargery bms from a person on ebay but it seems complicated to set up and i still would have to buy contactor. Would i be better buying a jk bms? Im just not sure it can support my amps though if i ever max out the system. If i buy two maybe. i just want the easiest bms option. I swear if i could pay someone to draw me a diagram and everythiing i need to build this system it would make it so much easier. There seems to be so many options.....

[@jackiedines5229]

Andy has a vid on how to start these.

[@mannyfragoza9652]

Its got big nuts strike that reverse it LOL BTW why are you messing round with JK when you can buy a BMS from Overkill Solar?

[@ritchycamaro]

Hi, suppose 4s config, 8s bms. Connect bms to cel 1,2,3,4. Then connect bms 5,6,7,8 to battery + (cell 4) then you don't have loose dangling bms wires 5,6 and 7. I have tried this long ago on a very simple 5 s bms to a 4s config. and that worked then. Good luck.

[@TheDigitalMermaid]

If you have a BMS with resistive balancing, that might work. In this case, it's an active balancer so if the BMS pushed out current on any of the merged leads, it would drive that current back into the BMS via the other leads and likely damage it.

[@vaneay]

maybe try to connect all the non connected leads in 4S configuration to B+

[@bluejeanvanlife8627]

Why is JK the only option? OverKill Solar sells JBD BMSs (which is what I use) for 4S, 8S and 16S configurations.

[@davidkettell6236]

last time i checked overkill only go up to 100 amp

[@ascii892]

@@davidkettell6236 The JK also has 2 amp balancing, the JBD only has 60ma

[@MMMM2MMMM2MMMM]

You did not connect the LAST red wire of the loom to 12V (negative, cell 1 pos, cell 2 pos, cell 3 pos, cell 4 pos (5,6,7,8 not used) wire 9 on 12V! (or is it 10)

[@John.strong]

I know this is an 8 month old video at this point, but has anyone tryed setting the software to 4s?? seems to me one reason why it wont boot is because its not reading proper cell voltage and is below the voltage cut off, so setting it up as 8s then change it to 4s in the software may make it turn on as 4s? I have this feeling the reason why the newer ones work 4s /8s is because you set them in the software to be 8s but they are defult 4s... and they don't care about the extra cells till its told to just a thought

[@TheDigitalMermaid]

From what I understand, that wouldn't help. The problem was the voltage needed to power the BMS's logic was >14v.

[@quasiperiodic1]

Hey maddy, I have also ordered a 4s jk bms for my 12v lifepo4 pack in my boat. I've been running with a dumb daly for the past 12 months, but want the active balance and smarts of the jk. I first ordered it via Andy's affiliate link, but hanksor cancelled the order after 3 weeks. I've re-order it and it is now waiting for me at the post office......aftwr seeing your video I'm wondering if they cancelled my original order because the 4s bms's were not ready. I'll find out tomorrow if my bms is the 4s one..... Or will I, since I won't wire it up until I get a chance to tear the boat battery appart again, and I don't want to do that until I stop using the bait this year 😁 Also very interested in watching you re-power plans. I have a 32ft ketch with a nearly 40 Yr old 36hp volvo Penta in it. It's still going strong, but I keep thinking about adding a 20kw PMDC motor as a hybrid drive some day! Watching you with keen interest!

[@TheDigitalMermaid]

Please keep me posted. If if does work (or even if it doesn't), please share the version number you get. 20kw motor will be good for a boat that weight. I assume you'd drop it in where the old diesel was, so you'll get closer to the 1:2 kw:hp ration, so you'd have (very roughly) 40hp equiv. electric.

[@quasiperiodic1]

​@@TheDigitalMermaid SO my JK BMS and all the accessories I ordered turned up! So my model number is JK-B2A8S20P-H (I got the version with the heater pad output just in case). On the box label, it states Battery Strings: 4s-8s. When I opened it all up, it was all there and came with a push button to power it on as well as the screen I had ordered. As my 4S battery is on my boat and I am not - I work as a marine engineer on a ship as the Electrical Propulsion head (I have 4 motors on 2 shafts at 20Mw each, so a very different world to our sailing boats!) I hooked up the BMS to a 12v wall wart power supply I had from an old router. I connected the +ve to the BMS +ve (on the balance lead plug) and connected the PSU -ve to the Balance lead plug -ve and the B- on the BMS. This worked, and I could start the BMS - it obviously complained about the lack of cells, but I could test the screen and connect in the App and set it to 4 cells etc. As I said before, I ordered originally from Andy's affiliate link, but after 3 weeks of it being 'shipped' with no tracking, HanzorBMS store cancelled my order (full refund). I re-ordered immediately, because I really want to upgrade from a non-smart Daly. This time it all came through and got delivered. I should point out that the accessories as specific to the 4s BMS, or at least that is what they say, and there are different ones to order on the website. My next step will be to migrate it all over on my boat, but probably not for a few weeks, as I have to go to sea. Also, the electric boat options will be a long way off yet - My 40 yr old diesel is actually in very good shape, and I can maintain it quite well, so no funds for an electric setup just yet - I'm going to watch your build with great interest, because you are combining two of my interests - Battery and power tech, and sailing - oh and electrical propulsion! When I do it on my current boat, I intend to connect the motor and engine as a parallel hybrid system. The intent will be to be able to use the electric drive (SILENT!) for normal everyday sails (around the Solent for me) in the local area, with the diesel for the longer trips (over to France and long distance UK) and to use the diesel as a generator and charge the big battery bank if necessary - so I can go fully electric for everything else! Forgive the long post - I wanted to be thorough!

[@TheDigitalMermaid]

@@quasiperiodic1 Ah, so a DIY hybrid drive idea, sort of like the fancy setup that Leo's got going on with Tally Ho. On the BMS, I've been told that the versions with the heater interface are always 4s/8s.

[@alanhollister9122]

Oh ya, and I’ve been running them nonstop now for over 6 months now. And the bms should hold up to 200 amps for a little while anyhow. But don’t do what Andy did, push it over 200 amps or you may fry a mosfit

[@stoptheirlies]

Hi, excellent vids thanks. That JK R485 adapter you have there which has a cable sticking out the other end and no plug on it, what plug is supposed to go on there? I bought one but there is no information whatsoever, If one end is supposed to go into the JK, what does the plugless end go into? Thanks if you can help. Bob UK

[@TheDigitalMermaid]

I don't know yet, I figured I'll have to experiment to figure out what the pins are, then solder them to a DB9 connector to plug into my USB to RS485 adapter. A problem which I've not gotten to yet.

[@stoptheirlies]

@@TheDigitalMermaid OK thank you I will keep watching of course maybe you will get to it.

[@olavilentso]

@@stoptheirlies At least in the aliexpress page of the RS485 the pin layout information does exist and this module works fine with USB - RS485 adapters.

[@stoptheirlies]

@@olavilentso Hi Olavi, thank you for that, I did look at several pages on Ali for the information and never found it, may I have a link please Bob

[@olavilentso]

@@stoptheirlies Yellow: A White: B, look at recent Off-Grid Garage video about connecting BMS to Victron Venus OS.

[@martink9785]

Thanks for your vid 👍Hopefully you'll be able to return those 2 units. Had a panic because one hour ago I ordered a JK-B2A8S20PH and LCD display from the Hankzor store. I contacted them and they told me they have been 12v compatible since May. Hopefully the correct thing will arrive. I really dislike Ali...... It's almost impossible to know exactly what you're looking at.

[@UtubePolkinghorne]

I know nothing about Lithium really, but I cannot understand why your battery solution has enough heavy batteries to sink a modest boat, but the couple on KZbin “SV UMA” successfully changed to fully electric several years ago with far far smaller volume of Lithium ?

[@TheDigitalMermaid]

One of the most important things you learn when learning about boats is that there is no "best" boat, only best for you. This extends to power solutions... For Uma, they've got two capable sailors working together, and so they can do things a single-hander can not. There will be times when I have to run under power where, if I had someone else with me, I could have sailed. Also, I want to do river/canal runs, and for those I have to unstep and run on batteries for days or weeks at a time.

[@blacksblade]

while watching the last part of the video, i realised that you did not turn on the DC switch

[@PavolFilek]

Hi, why do U need FETs in current path, there is no need to disconnect battery this way, there is fuse and switch, BMS only needs to communicat with inverter and MPPTs. BMS needs to tell MPPT: Give me only 2 amps. Or BMS sends info to inverter or DC load: Please shut down. If BMS discconnects battery from MPPT, when MPPT is at 100 AMPS, what happens ? Where this energy from toroids inside MPPT goes ? To snubbers ? No, they are not designed to withstand this energy.

[@TheDigitalMermaid]

The way you're describing it is how Victron does it, and I understand why they do. For me though, I prefer the idea that the BMSes can disconnect if a given cell inside the pack is close to limits, and somehow a dumb load or charger is not listening to the BMS. I feel more safe this way.

[@PavolFilek]

@@TheDigitalMermaid LTO and LFP are OK, but if someone has NxMyCz, NCA .. etc. cells, BMS can do nothing, if one cell goes to TR, and cells around are not isolated, to withstand 1200 *C temp, I this chain reaction is so quick, that your 1000 - 10000 cells start to fly around like projectiles. Will BMS throw nets to catch them ?

[@TheDigitalMermaid]

@@PavolFilek I believe that I have made it very clear in the past that cobalt-based lithium cells belong nowhere near a boat. All my videos and all my testing is with LFP in mind only.

[@airgead5391]

A BMS with it's battery is a voltage source. Voltage sources can used in series (each having their own battery stack, and care should be taken as there is no common ground) current sources can be connected in parallel, but not in series. Fundamental electronic laws. BUT: if specially designed for it parallel voltage sources COULD perhaps work. In practical sense giving the way the whole topology one can imagine that it would work anyway, as the voltage of the batteries will be leveled automatically. So this only if each BMS has it's own battery, not switching only the BMS parallel. In the later situation it far less ideal, as there will be minimal voltage across the FETS, and there is no garantuee of a neat dividing of currents between the two (or more). One could I imaging take a rule of thumb and say that 1.5 times the solo current would be safe when using two BMS in parallel. I think that a 1.8 factor would be possible too is my guess but not a grantuee.

[@inmyimage1081]

Personally, it would seem like the vendor would exchange those two for you given the version used to support 4s, then didn’t with the ones you were shipped and now do again, that’s an impossible situation for a consumer. As another test using the charger, wonder if it will turn on if you have all the balance leads connected like leads 1&2 on cell 1 then leads 3&4 on the next, etc.

[@TheDigitalMermaid]

That would likely fry the BMS, each lead is expecting a voltage and when balancing, puts out a voltage on the lead, which would short to the pair.

[@inmyimage1081]

@@TheDigitalMermaid I had that thought but considered the fact that each of the pairs would have the exact same voltage so it would be unlikely that the BMS would attempt to both pull and push a balance current through each member of the pair, the more likely case would be that it might pull power over both leads to put into a different cell since if I recall correctly from Andy’s videos it will pull from multiple cells simultaneously while pushing the power into a low cell.

[@TheDigitalMermaid]

@@inmyimage1081 If the cell with all the connection is seen as lowest, the current will be sent down one of the wires (however it would decide), and that would back-feed into the others, I suspect.

[@1over137]

Interesting that you are trying to get rid of the lead acid cranking battery. The sailing channels I watch they would advice the opposite, keeping a cranking lead acid on a completely separate circuit from the house batteries and only float charge them from the house system. Losing the ability to start the engine in a navigation emergency, like if you drag your anchor in the middle of the night could get awkward if you find you flattened the house battery. But I'm not a sailor and I too hate lead acids. I have an old 100Ah marine start battery which after being used as a solar battery for 1 year could barely crank my car when it's battery went flat. It said 990CCA on it. Pffff. 365 charge cycles seen to that!

[@1over137]

Oh... I think I understand, you are replacing the cranking battery with a 4S LiFePO4. ah... ok. So it's likely to be on a separate circuit and not get flattened when you fall asleep with the heater on.

[@TheDigitalMermaid]

@@1over137 correct, and also just for the trip home.

[@Joe.Blackwood]

Enjoying the videos! I've got a very similar system, all victron with 8 cells 24v and the same jk BMS. I keep getting discharge short circuit protection errors come up, do you have any idea why? My suspicion is the MultiPlus-II? Please help

[@TheDigitalMermaid]

I'm sorry, I don't know what would be causing that.

[@danielwise4699]

I have a JK-B1A20S15P with 16 cells doing the same with a POWMR inverter

[@Joe.Blackwood]

@@danielwise4699 I'm not getting any help with it, I bought a second and it does it still. I've narrowed it down to my multiplus ii or my smart shunt. What triggers yours?

[@danielwise4699]

@@Joe.Blackwood still working on it

[@danielwise4699]

We got it fixed, in the discharge settings on the bms

[@bdaddy355]

Your are F****** awesome, keep up the great work. I have learned so much from you.............

[@BajanAlan]

Will Prowse connects unbalanced battery BANKS together. Says 'Let the BMSs sort it out"!

[@TheDigitalMermaid]

That's the approach I am planning to take. The worry was that this specific BMS said "ya don't". I think I understand why though, and will do some testing later to confirm.

[@markusdd5]

JK has a point with the batteries in parallel. To avoid this situation, when running batteries in parallel, it id advisable to have circuit breakers in each parallel strand in case one battery string shorts out (which can happen), it does not kill the whole system.

[@zxrjimmy1]

Did you try giving it 27v through the p-

[@sebastiankohler1292]

Hi, I had ordered a similar JK-B2AS20P-H (with heating output) in July and received it some days before. Not yet tested, but the sticker on the bottom side contains: "Battery Strings: 4S-8S". Does it only show 8S in your case?

[@TheDigitalMermaid]

I don't have a label that says "Battery Strings" at all.

[@sebydocky5080]

@@TheDigitalMermaid Nothing on the last line of the main white sticker ?

[@johnlittle3410]

i use overkill bms and have no problems

[@freeranger1677]

Sounds to me like they made too many of the 8s models and had to shift a load of them on to the market to get rid of them and minimise their losses. If they informed the buyers when selling them I wouldn't have a problem with that but it appears that they didn't make this key information readily available so buyers had no idea what they were buying. If that's the case it's very unethical business practice. Thankfully my JK-B2A8S20P was a 4s/8s model but the display socket fell off so had to wait for a replacement BMS.

[@TheDigitalMermaid]

I have no idea if that's what happened, but it's as good of a guess as I can imagine. I'm not impressed... =/

[@SylwerDragon]

Nice video. I would add one thing why it isn't big deal if those batteries have same SOC or not. .. you see this huge currents will apply only if you are connected to load in that moment if not voltage on all batteries will get to it's natural voltage about 3.2 Volts so even if you will connect another battery to your pack it will not cause any problems and wouldn't cause any issues

[@TheDigitalMermaid]

I don't think there needs to be a load for current to flow between batteries. In the video I linked from Andy, he reconnected a pack that had a higher SoC and it immediately started pushing out ~150A, though it quickly settled down to about 100A, ~50A going into each of the other two batteries. I think I need to do some tests where I see what kind of Amperage flows in multi-bank systems at different SoC / voltage spreads.

[@millzee60]

Something to try. Keep the 8 cells and remove the balance wires for cells 5,6,7 and 8 (but not the pack voltage wire) and see if the BMS boots up. And then try with balance wires 1, 2, 3 and 4 only removed. What could possibly go wrong :)

[@foxythedirtydog4494]

I was thinking the same except I would have removed them one at a time and then tried linking the unused ones together on the 24v positive. Some 2A fuses would be a good idea as well. I see Seplos link the unused sense terminals together on their 14s BMS which otherwise looks the same as the 16s BMS.

[@boringsoftware2093]

u can fuse BOTH + and -

[@ToThePointGarfield]

have the same model and use a converter 12v → 24v to turn it on. Make sure on the converter the - in and - out have 0ohm. The + in and + out are the ones being converted to 24v. Got the newer model 4s-8s also and that works without a converter. Happy smoke signal producing LMAO

[@MikeGrayM70]

JK sounds like a good company to avoid if possible. I know it's what you need for your project, and that you will get it figured out. Did I understand right that you're using the JK specifically for its balance function? I've got one of those active balance boards that Andy has done a few videos on. Not the Neey, but the more generic ones. I also added a programmable switch to turn the board on and off depending on the voltage of the battery. This allows me to use whatever BMS I want. I got one of those Daly BMSs that Andy hates so much, LOL. I agree the balance function on the Daly sucks, but the external balance board works great. And the Daly works fine for me, for everything else. I'm using my battery for a solar camping trailer which will be way simpler than a solar sailboat. Anyway, your project is really interesting. I look forward to seeing more of it.

[@TheDigitalMermaid]

It's a kicker because, when you get what you expected, their kit works well. The constantly changing / adding / removing things though, with no regard to compatibility... Ugh. Ya, balancing is the key reason, but also the 200A current. I don't want to add more parts if I can avoid it, so a BMS that "does it all" was appealing.