Connecting 6 Batteries in parallel 'the wrong way'. Does it cause uneven wear and tear and charging?

[@FutureSystem738]

Terrific Andy, I’m envious. You will now have a fabulous system with an extremely large storage. (Just as you can’t have too much solar, you also can’t have too much battery capacity. 😊 BTW Andy I agree- if one bank “wears out” before another, who cares!

[@junkerzn7312]

It takes a lot of cycles to see any difference. I used to care a lot about balancing the current delivery to my batteries but once I started expanding and rearranging the system the banks started to get a mix of newer and older batteries and I realized that it just didn't matter. So I go for convenience now and I am only mildly trying to balance current delivery. Another thing I realized is that if we assume that older batteries have slightly higher internal resistances than newer ones... what should happen is that older batteries contribute a little less and take a little less and newer batteries will begin to catch-up in terms of wear. That is, the divergence in wear rates should limit-out or even re-converge. I don't think wear can really diverge more than maybe 10% before the divergence stops progressing. And I'm not just not going care too much about 10% more wear. Another thing to note is that voltage drop is a function of the current (dV = I * R) and power loss over the wires is a function of the square of the current (P = I * I * R). So when the battery busses are running such low currents... the C rates are just so blasted low with so many batteries... that also means the voltage drop is lower and the divergence is lower. Lastly, in situations where one is charging to full, the amperage is going to drop off to basically zero at the end of the charger cycle, which means that voltage drop over the cables will also approach 0.0V at the end of the charge cycle.

[@moestrei]

Thanks for sharing real life experiences

[@williammeek-h2o]

But that is the thing isn't it? the front battery sees more cycles because it will charge and discharge more often. It isn't that the last battery on a string can't fully charge, it is that the front battery gets cycled more on partial charges. At least at high charge/discharge rates. Now as to whether that is a problem, that is up for debate.

[@junkerzn7312]

​@@williammeek-h2o But here's the clincher... if your cycle depth is only 20%(ish) (per day), then cycle wear becomes completely irrelevant verses calendar aging anyway. It won't matter that the front battery, say, sees 25%/day DOD while the back batteries sees 15%/day. The deeper the cycle depth, the narrower the difference. If the cycle depth is deep enough such that cycle wear matters, the difference between the front and back battery should contract significantly. It would not be linear, but I think past the first 15% of depth the voltage will drop at a fast-enough of a clip to keep the SOC delta between the front and rear battery narrow, ultimately zero delta for 100% DOD. The difficult thing to estimate is the first 15% (100% to 85%). If you are doing an extremely shallow DOD you will be in the extremely flat portion of the discharge curve. Potentially a large DOD difference could develop between the front and rear batteries during that portion of the discharge curve. I'm guessing that a larger difference could develop when batteries from different vendors are mixed together, which is more along the lines of Andy's setup... that would simply be due to differences in the internal resistance of the batteries between vendors. But if one is tacking on random batteries of vastly different ages, then that will probably be the defining difference for the life of the system. -Matt

[@moestrei]

​@@williammeek-h2oNein. All wrong. All batteries are in parallel and cycle up and down together. Newer/higher Ah cells with less internal resistance will give/take a higher current because they can. Older / lower Ah cells with higher internal resistance will give/take less current which means it all works together just fine.

[@markmcm]

Why are there only 3 of the 4 batteries connected in the tower of power?

[@aniketos7336]

Your findings are exactly why its recommended to have all batteries connected with the same length cables to the busbar. That way the voltage drop is the same for each battery

[@Gary-wh7ce]

Thanks for the very informative and easy to follow explanation. I just bought you a spat beer as a thank you for your wisdom and entertainment to my small but growing solar installation. Gary from SE Michigan

[@Владимир-б4л3п]

I think cross-connect is needed to equalize the currents in each battery. Now you have a voltage on the top battery more than a voltage on the middle battery. And the voltage on the bottom battery is even lower. This is due to the fact that the resistance of the cables on the upper battery is less than the average. And on the bottom battery, the resistance of the cables is even greater. When the current in one battery is 50 amps, and in exactly the same battery only 20 amps, this is not good. If you use a cross connection, the current will become more uniform - for example, 30-35 amps on each battery. This makes sense if you quickly charge the battery or connect a powerful load.

[@Marzec309]

Before I finish watching this. I will say, mathematicaly it does matter. Due to the voltage drop of the cables. The battery that's directly connected will see more load and charge before the others. But, in practice, this might not be a big deal depending on the system load and charge currents. When diagonally connected all batteries, see the same cable resistance.

[@GordonGaz]

One conclusion this test does show is that you must design for significant differences in the charge rate of battery banks. As shown the 60a breaker tripped when the battery was close to full. So a permanent design would need to use a breaker rated at full current

[@jimginnyohio]

Always a fun and interesting learning session Andy! Wow! Nice work on the building process. The weather looks great there too! You’ve really got it going on!

[@BenBrand]

Everything you said is true and is great, but one advantage of hooking up all the batteries in a more balanced way is that you won't be blowing your 63 amp breaker once the battery shelf is fully charged and all of the current now can only go into the tower of power. It would be more split for the whole charge cycle so you wouldn't have to worry about these weird offsets when you get near 100%. Also in the winter time I believe you go months without fully charging so overtime you are going to get lots of mismatch between the two towers.

[@emrickacuna6754]

sir why not replace the circuit breaker from 63 to a little higher one so it wont always trip for the 2 stack of battery?

[@retrogear]

Thanks, Andy. Some common sense and in a world of sheep. Appreciate all that you do for the community. Cheers from Hot and Sunny Western Australia. 🇦🇺

[@rcguymike]

Pretty sure Will Prowse already proved this...but Andy is fun to listen to while he thinks out loud while testing😁

[@danakaiser2934]

I have batteries in parallel hooked top battery for charging and discharging. It may depend on the bms but what I've noticed is it seems to spread evenly between the batteries. You got me into solar watching your videos on the gtil. I think I made it too to much solar now. My wife says you are an influencer if I play videos at table. She hears your voice and says what are you getting now. 20 kw in panels 18kw of inverters 40 kwh of batteries Went from 1mwh a month a year ago to less than 75kwh off last bill. Basically totally of grid now. Thanks for all your information and tests.

[@BobHannent]

Only just passed the introduction, but sharing my hypothesis, waiting to be proven. If the bottom battery is under charged then it will have a lower internal resistance compared to the closer battery. Therefore the last battery will pull more power than the top one to compensate!

[@avalon_64]

One advantage of the prescribed connection method is that the current is distributed more evenly over the cables.

[@TheDefpom]

@9:30 the voltage sensing accuracy of each BMS may not be that accurate, they may have an error of 1% for example, the only way to know for sure is to use a single voltmeter and connect it to each battery directly to determine the error present. You could have one battery that reads 1% high, and another that reads 1% low, but could actually be exactly the same in reality. Also consider that the voltage drop through each BMS could be different.

[@MrDonking1967]

You are correct Signature Solar has done extensive tests o this topic and found no difference

[@DanBurgaud]

23:50 re SOC deviation It is frustrating to see the SOC deviation across the batteries. No matter how we rewire it, there will always be deviation of a few percentage. A friend suggested to JK BMS to add SOC Balancing when paralleled: 1. Every minute, the Batteries in Parallel compares SOC%. 2. The Highest SOC% battery disables Charging or enters Current Limit Charging. rinse repeat Of course this is purely cosmetic. After a week or two, the batteries' actual SOC% will still deviate unless fully charged or fully discharged.

[@uselesseater5916]

That sounds like a nightmare. BMS tripping off all the time.

[@DanBurgaud]

​@@uselesseater5916 Why would it trip? Just look at Andy's setup of 4+ batteries, each capable of 200A charging current. And when paralleled, barely 50A goes into each one as seen. If you disable charging a single Battery, the other BMS will get 70A.

[@Juergen_Miessmer]

Hello Andy, i think it's time to replace this connection through the 63A breaker by one with a way bigger MCCB. Why did you not connected the 4th gobel battery?

[@Thunderst0rn]

Agreed

[@dennismyles8450]

Andy, thank you for doing your videos. They have helped me immensely. Can I ask you what camera you use? I like the clarity of yours better than most people. My name is Dennis and I live in Texas, please keep up the good work.

[@Koernell]

How did you get the individual batteries into Home assistant? I am currently building my own HA system and only get the overall voltage and amperes. I operate 2 battery packs with the jk-bms. Can you do a video on that? Or give a description on your website?

[@at906]

Batmon addon. Works a treat.

[@Koernell]

​​@@at906thx. I couldn't understand the name of the integration he used. - Found it in the Addon store.

[@Koernell]

@@at906 thx. I couldn't understand that name of the add-on. Found it in the add-on store.

[@TheDefpom]

With the cross connecting of the batteries it is more to do with discharging, when there is a big load on the system it will draw more power from the battery with the lowest voltage drop, so if you are trying to draw a large load one battery might be seeing 50% of the current draw, with the others making up the remaining 50%, what happens then is that one battery ages much faster as it is under more stress, and that battery can then drag down the rest of the battery bank, as the other batteries will be discharging into the weak one trying to bring its voltage up.

[@kenbone4535]

This is so useful as I'm about to put another repurposed Leaf pack onto my system.

[@MMMM2MMMM2MMMM]

Updating the JK firmware to V15.38 result: JKbms no longer supports data communications to PC and "link" between the JKbms's no longer works!

[@marktheunitedstatescitezen185]

The rain is also why we watch from around the world ! To watch you’re wisdom improvise with the rain still get electricity !

[@paulsmalser3261]

@Andy for the shelf battery with the aluminum bus bars. I would remove and clean both the bus bars and battery terminals then add a bit of Noalox (Product in US) or equivelent for you in AUS. This product is made for the electrical industry for connecting Al power cables, it is electrically conductive but prevents Al oxidation. Here in the US most main service cables are made of aluminum and it is US code to coat the end of these cables before making connections into say your meter base or breaker panel.

[@NicklausJ]

Hi Andy! Can you pleaseeeee do a capacity test on one of the cells in your battery shelf? It is a long time ago that you did this and I'm curious how the degradation is. Many thanks!!!!

[@sjdtmv]

One large factor is the capacity of the BMS, as you have note earlier build that the 100a JK BMS only uses one of the two terminal at the main BMS neg posts, this is a resistance load compared to a 150a or 200a BMS resistance load through the BMS

[@typxxilps]

4:03 - sorry "how these 6 separate batteries" is what you said but tbh I see 3 in the shelves and 4 Gobel power cases or is 1 Gobel power unused ? I also wonder about the capacity figures cause if I remember right at least one of the gobel power had gotten EV M31 which would mean 314 Ah ... and combined with 3 other 280 Ah gobel power we would see a figure close to 1200 and not below 900 Ah. Or do you have piled up 4 cases and one is not connected ? 4:30 shows a shematic of 3 plus 3 batteries.

[@typxxilps]

the 2nd from the top seems to be empty and not connected - 6:38 shows the details.

[@simontillson482]

@typxxilps Indeed it is. He said he was only using 3 right at the beginning of the video.

[@kenbone4535]

Can I ask what integration you are using for Home Assistant, thx.

[@АрчебальдАрчебальдович-х9ч]

please help, the deye + jk bms inverter charges the battery up to 58.4v with all restrictions, then the bms disconnects the charge at a current of 30A, and the bms generally asks the inverter for a voltage of 60.8v. I configured the bms according to your videos, but it seems that the bms ignores these settings.

[@Кристофгуткнешт]

Can you tell me how do you have integrate your battery system to home assistant with the bluetooth protocol ? I have a battery with a JK BMS. Thanks for your help in advance.

[@VolodymyrPavlyuk]

So much copper in all those cables and busbars. I wonder if that’s a part of the retirement plan investments :)

[@swolath]

I do like the idea of on replacing 1 set of batteries at a time instead of 7 at a time. Very expensive hit changing everything at once.

[@bildad1234]

Why not set a tail current in absorption phase of Solar controller instead of increasing the absorption time?

[@polvincompoundsadmin5402]

I agree with your argument if you are able to actually charge the batteries to 100%, then of course it will charge them all. Where the problem is---- is when the batteries are not charged to 100 % but in winter, say they only charge to 50% then you draw them down to 40% then the cells and the banks go out of balance- because the balancers never get a chance to balance. This happened to me- then some cells will go under voltage and the BMS will shut down one bank even if "SOC" is 40%. So I alternate banks charging, so one bank gets fully charged every second week at least.

[@DanBurgaud]

There is a very long thread at DIY Solar Forum regarding parallel battery connections.

[@MMMM2MMMM2MMMM]

And what is the final verdict? (Eager to know.)

[@peterjones2411]

its not so much the charge imbalance from top to bottom as the current tails off towards the end its the discharge that unequally loads one battery more than another more so the higher the discharge current as this current normally never tails away.

[@jasonwilkerson7085]

Andy I'm new to HA. Can you share how you setup this up and created all these very Nice dashboards? If not it's ok.

[@swolath]

You should do a test with the tower only charging to 90% or less for a week and then see the difference state of charge from the three or four sets of batteries. That would be interesting. How much they would go out by.

[@dejanlupo]

The wire length ad connections are important when you use battery on very heavy way. For example you charge and discharge the battery with more than 0.5C. in Andy's situation this will be approximately 800A or more.

[@L_O_M]

That is a bit moot since he can't pull 800A through those cables or its connectors . Paralleling batteries in a stack with short feed cables between them should not be used for increasing the discharge current but for increasing the hours before battery is depleted (more hours not more current). If you want to increase current then double up the connection to the inverter with a feed to the bottom battery.

[@chriskemp695]

Whats your thoughts on paralleling different capacity batteries? I was looking to parallel 16x230ah pack with a 16x314ah pack?

[@Thunderst0rn]

Lifepo4 is pretty forgiving due to its flat charge/discharge curve. 314 ah will not fully cycle when used to the max, e.g. in offgrid situation. C rating of 230 ah will also determine max power for both.

[@firefly2472]

I have an 100ah and a 308ah battery connected parallel. Works great. They mostly discharge and charge around the same %. So the 100 would be at 45% and the 308 would be at 48%. But at 100% and at 15% they are the same voltage. Same milivolts diverens between them.

[@CollinBaillie]

If they're paralleled, they should be fine. The batteries with the highest voltage will provide most of the power, so in discharge, they should match. For charging, the cells with the highest voltage will take less charge current, and so overall they should charge nicely together also. As you can see in this video, there may be some lag time, but in the end it all evens out. It's when cells, or batteries, are in series that you will be limited by the "weakest link". So use all the same capacity cells when building a battery. If you use say 12v batteries in series to make a 48v battery, they must be the same capacity. And so on...

[@marktheunitedstatescitezen185]

The wall looks good !

[@SamiiEsra]

What cable diameter you normally use? 25 mm² ?

[@Thunderst0rn]

The one you design your fuse for 😊

[@HellTriX]

That's true, i always thought that was wierd advice to cross connect the batteries. I have 48 batteries some 304ah some 280ah. My 280AH bank discharges the fastest, and charges the fastest. It definitely takes the most abuse. Been running it like this for 3 years. if they wear out, or when they do. I will simply replace them with nicer batteries.

[@IoTAlertWerks3000-fy9qv]

You are right. I am using Solar since 2013. Two years ago I changed to LiFePo4. So almost ten years I used many paralleled AGM (Lead Acid) Batteries. With those having way less cycles I experienced always the closest to chargers/inverters dying first. With LFP and modern BMS you can see the difference from BMS´s cycle count. The closest battery counts more cycles then the farest. But 200 out of 400 is a difference to 200 out of 6000-8000. 400 being here cycles for AGM. The DoD of AGM (max 50%) versus LiFePo4 is not THE point here. Side note. After ten years experience with AGM even today I get a bit of nervous with a SoC of 50% for my LFPs.

[@tujuprojects]

What hass graph is that?

[@Dutch_off_grid_homesteading]

Heya, even wen you would have the same batterie cell's. there are so many differant factors we should keep in mind too that will be inflouding the total battery differantses, but of cores can we try to reach a gigh precentisch goal.

[@1mrgraphix]

What about paralleling 14s 3.7v battery pack with 16s 3.2v battery?

[@RobSteve1]

Regarding the busbar connections, look into stabilant 22 for the connections. I have used it for years and just used it on my mb-31 pack. It is a compound that was developed by an audio engineer and later adopted for making reliable connections in marine, auto, military and air.

[@mflo1970]

It is simple,electricity looks for the shortest path ,the obly problem is having enough solar field or at the espense or solar hours so that the charging of the banks is as even as possible

[@RichardSteigmann]

As we say in Germany : scheiß der Hund drauf 😂😂😂

[@MMMM2MMMM2MMMM]

Some people say you should NOT daisychain more than two battery boxes, others say it is possible if you do NOT connect both cables onto ONE, you should connect one on TOP and the other in the BOTTUM. And again.... others claim busbars should be used using equal lenght of cables..... (like in the battery shelves) Others say you should place the highest capacity box on the end of the daisy chain, and again others say it should be the box with the lowest capacity. 😮

[@apsleyflyer]

I have 20kw a 24 volt main system and a backup 12kw at 12volts, this runs 2 fridges 24/7 /365 . All of this is split between 4.5kw of solar for the 24 volt system and 1.2 kw on the 12 volt . As for connections in parallel. The 24 volt system is on a battery switch 400 amps each bank times two and , then connected to the inverters, this is on the positives . On the negatives two/two are connected to the inverter . I use two 3kw inverters and one for my shop the other for the cabin . After 24 years of being off grid , yes connections make a difference . I have found , The battery monitors get out of sync.I balance all battery banks once a week. Batteries are a major investment treat them like your house. Moved to lithium 2 years ago but still keep 6 kw of lead acid for back up. Long Canadian winters seem to easier on lead acid. I have a surplus of power 9 months of the year and also run two heat pumps,

[@tedhamilton2362]

A big difference I see is each pack of Goebel stack does not attach to a common bus bar. Not equal lengths to power source either.

[@322-Dota2]

Show please which are discharge faster when charging ELECTRIC VEHICLES.

[@Tezza66]

also . some people say diff, length cables effect the charge an discharge, i say not. but is also something you could test.

[@HybridShedIraq]

I have 3 batteries connected to one house with 1.5meter cables in between the middle one always had like 20% lower cycles 😅.

[@Slackware1995]

Actually the best way is having each battery directly connected to bus bars, via a 2 pole DC mini breaker.

[@jasonbroom7147]

Is my math correct? 90Kwh worth of storage between those 6 batteries?

[@bloodcarver913]

You misunderstand. It is not a question of wearing out faster. It IS a question of DISCHARGING unevenly when you do not connect a "tower" without going diagonally.

[@PavelBrand]

pylontech is the prime example here,since it is the crappiest and most used battery,at least in my country...but i think andy will be fine,he could probably go with one battery...contrary to most installations with pylontechs,where mostly every instalation is under-batteried anyway...

[@CollinBaillie]

It probably also is affected by the connecting cables or bus bars. If you have bus bars like Andy does in his shelf, capable of 1500A or the cable to the tower capable of 250A amd the same between each battery, but you're not pulling anywhere close to that, the draw will be pretty much the same. It all comes down to how the batteries are paralleled. A lot of these drawers and other DIY examples out there using insufficient cabling that you begin to see the detrimental differences.

[@davidrknowles9792]

Yeah I agree with collin, also when your system becomes large enough the amount of draw across each paralleled bank is minimal. I designed my system to have 125A each bank, but even when banks are unbalanced like at the top or bottom of the charge cycles, the amount of difference is max 60A at full load. I also have different chemistries that perform better on the top/btm of the lifepo4 charge cycle so those systems are designed to hold the majority of the load at that point in the cycle. Having every bank with its own bms and also a quality breaker that is below the max draw will ensure worse case you trip a breaker a a bank goes off-line.

[@FutureSystem738]

Really, it makes bugger all difference. Sure one might do a bit more work, but at the end of the day: who cares. Cycle life will be slightly different but these things are good for a hell of a lot of cycles.

[@joncoop2873]

That's exactly what this video is showing

[@marktheunitedstatescitezen185]

The Rust gives the wall Texture !

[@CollinBaillie]

Patina?

[@rdcabal]

8:34 20mv difference highest to lowest of the 96 cells. No, the stack is even, will wear even, will charge enenly.

[@petersiegrist4153]

150A Ladestrom ist lächerlich für die 6 grossen Batterien. Das sieht anders aus wenn man bspw 4x5kwh Batterien mit einem Deye Sun 12k lädt. da fliessen dann auch mal 240A bei 400Ah. das ist was anderes als 150A auf 1700Ah!

[@marianilie7321]

you forgot the C-rate and temperature difference

[@PavelBrand]

lead pased paint then?at least you are shielded :D

[@centerrightproudamerican5727]

The test proved that if given a chance, all of the batteries will charge to 100%. I have never doubted that. However, the test proved little about wear and tear. To understand wear and tear. We need a long-term comparison of the cumulative WH discharge of each battery. The conclusions at the end of the video are based on a couple of things that may or may not apply to everyone: if you are adding batteries over time, yes each new battery is starting a different phase of its total life. However, Many (most) people are not doing that. They are installing a new system and probably not expanding it. In the end, they will change out the whole bank of batteries when they quit working for the application. If one of the batteries wears out faster and is no longer contributing, will the system still be able to provide enough power? if not, all of the batteries are going to be swapped out even though there may be life left in some of them. However, if different wiring could have kept the wear and tear down, the user may have gotten more time out of the batteries. What we can not tell with the data at hand is how much longer might the system continue to function with a diagonal hook up. If it is 3 months longer after 10 years of service..... who cares. If it is 12 years vs 10 years, that is worth striving for. When it comes to whether or not to do the diagonal there is an important point to keep in mind: The only time diagonal is 'balanced' is two batteries. Each additional battery added will create more of a disparity in the wear and tear. 3 batteries in a diagonal is not perfect but not too bad. I have seen 8 paralleled with diagonal outputs.... that is going to start seeing differences in the usage rates. However diaganal of 8 batteries is still approximately 1/2 the difference in wear and tear as non-diagonal. (Of course that is assuming no other factors creep into the system. The other factor is how hard the batteries are being driven. The higher the current, the higher the voltage drops and the more uneven the wear. If the bank is being driven hard, the difference in wear will be greater than if it is lightly used. Now, back to Andy's question: Does it all matter? The definitive answer is Maybe, Maybe Not. * The thing that Andy's video pointed out is that very small differences can make noticeable differences in the charge-discharge rate. Even if you buy 'identical' batteries, will these small differences overshadow any difference in the wiring? * Trying to predict how the system is going to behave 10 or 15 years from now is a fool's errand. In the end, I come to a different conclusion than Andy. I can't say it makes a significant difference in the long run, but I am confident in saying diagonal is better..... so why not do diagonal.

[@FlorinUrzica]

👍👍👍

[@olafschermann1592]

What is a realistic limit of paralleling 51.2V batteries? 60kWh? 100kWh? 200kWh? I own a lot of apartments and could install a ship container. Selfbuilding cost me €1.200 per 16kWh, i guess in 2026 price will drop to €800. But i do have tooooo much respect about DC-HV. As it is for different buildings i need 4-5 inverters anyway, but i want to have a central battery. I would interconnect the 51.2V by a 20x20mm busbar which could be bought cheap from metal traders. 400mm2 can transport lots of amps…

[@MrCadilLACI]

The voltage drop always depends on the current. If Andy charges the gobel tower with low enough amperage, it will charge to 100% just fine. The same with discharging it. If Andy charges/discharges the tower with large amperage, the voltage drop won't allow the whole capacity. It mainly matters with discharge only...

[@mflo1970]

Yes ,yes si muy correcto ✔️ así es

[@sudosu4133]

The cross connecting method comes from lead acid/gel/AGM batteries without balancing BMSes. For quality BMS equipped batteries it doesn't matter, as you have clearly demonstrated. Thanks!

[@eloyschoorl]

yeah

[@cyberplebs6577]

🐸🐸🐸

[@taj-ma-haul9094]

Like# 337

[@bildad1234]

Why not set a tail current in absorption phase of Solar controller and just have a long absorption time?