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Pack Will Not Balance

Kornbread

Solar Wizard
Joined
Sep 16, 2021
Messages
1,963
This pack of 'b' grade Eve cells has been a pain in the butt from the beginning. The second worse 'b' grade pack has a delta of .004v (3.455-3.451), third .003v delta (3.456-3.453). Those are fine, but this pack has me scratching my head.

jk 2amp active balancer. Cell wiring is correct. Could the balancer be flakey? Is there just that much variation in the cells?

Fix it ideas ...

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While the balancing is going on supplement it by charging the lowest cell with a lab power supply set to 3.45v, move to next lowest once it gets to 3.45v. For the highest cell place a 12v headlamp bulb across the terminals to drag the V down to 3.45v, move the next highest once down. I got a pack down from 0.140 V delta to 0.060 V and then let the jk finish.
 
If you can, set balancing to above 3.4 and to “always balance” instead of “balance only when charging,” then leave the batteries a few days charging and see if this evens it out.

I did this to a cell that was not balancing when balance was set to “balance only when charging.” Just not enough time was spent above 3.4 volts to do any meaningful balance. I came back 5 days later and it was fine.
 
How long do you give the battery to balance at full charge? If you see a balance current of around 2 amps and a + or - depending on what cells it’s working on (red or blue cell voltage flashing) the balancer is working.
I get the same problem when my batteries haven’t been to full charge for a few weeks, but not as much as yours.
My CATL cells seem to balance quicker than my EVE cells. Since I’m not going to change my charging profile I decided to add more balancing power to one problematic battery. Heltec 5 amp balancer and A30-U1 voltage module(“Off grid Garage” idea) Now the batteries are balanced within the approximate 30 minute absorption time dictated by the inverter’s algorithm. (Open loop).

IMG_1730.jpegIMG_1731.jpeg
 
This pack of 'b' grade Eve cells has been a pain in the butt from the beginning. The second worse 'b' grade pack has a delta of .004v (3.455-3.451), third .003v delta (3.456-3.453). Those are fine, but this pack has me scratching my head.

jk 2amp active balancer. Cell wiring is correct. Could the balancer be flakey? Is there just that much variation in the cells?

Fix it ideas ...

View attachment 273113
If you don't change your password in time your JK BMS is going to lock you out...soon
 
Here’s a link to the episode where I first learned of this device. I have used the Heltec before years ago but with a different controller that was terrible. This one is far better.
 
Here’s a link to the episode where I first learned of this device. I have used the Heltec before years ago but with a different controller that was terrible. This one is far better.
Why not use the neey? price? I'm considering turning off the jk balancer and getting the 5amp neey. yes/no?
 
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If you can, set balancing to above 3.4 and to “always balance” instead of “balance only when charging,” then leave the batteries a few days charging and see if this evens it out.

I did this to a cell that was not balancing when balance was set to “balance only when charging.” Just not enough time was spent above 3.4 volts to do any meaningful balance. I came back 5 days later and it was fine.
I'll have to go out to the shop and check settings to be sure, but balancing starts at 3.35v. The pack has been able to reach 55.2v (3.45v)and set there for a couple hours for the past 10days. Don't think these older jk has the option to only balance on charge, as long as it's above 3.35v. and balance is on, they balance.

What gets me is that 5cells sit at 3.3x, 7cells at 3.5x and this is the only pack close to being this bad. The difference in delta between this pack vs the other 3grade 'b' packs doesn't make sense. Why are all the errant cells in one pack? It would be odd that out of 64cells, almost all the errant cells went into this pack. Possible, but odd.
 
Why not use the neey? price?
I have two Neeys in reserve LOL
My first build was 16S 2P 280ah with Daly, which of course failed. The Heltec was also used on that with a controller and worked well.
Form what I’ve observed:
The JK bms 2amp balance works excellent for any 300ah battery(if given proper absorb time) but it only works on one cell at a time, taking from the high then deliver to the low cell. Regardless of how close it gets to balance, it still delivers about 2 amps of balance current until it’s done.
The Neey uses the same balance scheme as the Jk, just 4 amps of current.
The Heltec shines on balancing big imbalances and works on several cells at a time, however the closer it gets to balance (low delta), the less current it delivers.
I went with the JK plus the Heltec for the best of both worlds also I was concerned if the sudden switching balance in and out of a Jk and the Neey might become counter productive as the delta is diminished(over correction or conflicting). So if I used the Neey I’d probably disable the balancer in the JK. Short answer, no it wasn’t the price 😂
 
I'll have to go out to the shop and check settings to be sure, but balancing starts at 3.35v. The pack has been able to reach 55.2v (3.45v)and set there for a couple hours for the past 10days. Don't think these older jk has the option to only balance on charge, as long as it's above 3.35v. and balance is on, they balance.

What gets me is that 5cells sit at 3.3x, 7cells at 3.5x and this is the only pack close to being this bad. The difference in delta between this pack vs the other 3grade 'b' packs doesn't make sense. Why are all the errant cells in one pack? It would be odd that out of 64cells, almost all the errant cells went into this pack. Possible, but odd.
Balance start at 3.35 might be the problem
 
The only other thing that could cause an imbalance is poor buss bars connections along with high discharge or charge. Example, if you charge slowly resistance on terminals isn’t as much of a factor but when heavily discharging, that when power is lost as heat and some cells aren’t doing even work hence imbalance.
 
Balance start at 3.35 might be the problem
Higher or lower and why? That's about the start of the knee and where the imbalances starts showing. In a thread, or somewhere buried in a thread, there was an issue of starting balancing at too low of a voltage working against top balance.
 
The only other thing that could cause an imbalance is poor buss bars connections along with high discharge or charge. Example, if you charge slowly resistance on terminals isn’t as much of a factor but when heavily discharging, that when power is lost as heat and some cells aren’t doing even work hence imbalance.
Recently added 60kwh more cells which required a total disassembly and rebuild of the battery pack/racking. All cell terminals and (new flexible) busbars were cleaned with scothbrite and torqued to 5nm. All balance leads carefully crimped and in proper place.

Since bank #3 was an issue before the recent disassembly/rebuild, I wanted to remove as many variabled as possible. Which still makes me wonder about the bms.

The bank sees very light service. It may have reached 50% soc a time or two in the past couple years. Charge/discharge rates are low.
 
Higher or lower and why? That's about the start of the knee and where the imbalances starts showing. In a thread, or somewhere buried in a thread, there was an issue of starting balancing at too low of a voltage working against top balance.
It’s been found that balancing below 3.4 can play havoc on the balance at full charge. The crazy thing, not every system has that issue. Many balance all the time and get away with it. I’m guessing it got to be related to pattern of use/average state of charge for the system. All I can say is try it. For a 55.2 volt system I like 3.42 start balance.
 
Recently added 60kwh more cells which required a total disassembly and rebuild of the battery pack/racking. All cell terminals and (new flexible) busbars were cleaned with scothbrite and torqued to 5nm. All balance leads carefully crimped and in proper place.

Since bank #3 was an issue before the recent disassembly/rebuild, I wanted to remove as many variabled as possible. Which still makes me wonder about the bms.

The bank sees very light service. It may have reached 50% soc a time or two in the past couple years. Charge/discharge rates are low.
It could be a bad bms. They are definitely not infallible. If you are running multiple JKs you should be having some spares anyway. I’d be ordering. You might even get it tomorrow
 
It could be a bad bms. They are definitely not infallible. If you are running multiple JKs you should be having some spares anyway. I’d be ordering. You might even get it tomorrow
Have 2extra bms. Have spares or extra for most everything except the aio's. As fast as solar technology is advancing, I figured having a spare aio might be a waste of money.

May plug in a new bms or get something like the neey and turn the jk balancer off. How complicated is the heltec to setup?
 
Have 2extra bms. Have spares or extra for most everything except the aio's. As fast as solar technology is advancing, I figured having a spare aio might be a waste of money.

May plug in a new bms or get something like the neey and turn the jk balancer off. How complicated is the heltec to setup?
Yeah, I’ve noticed that too. Things are discontinued NA a lot quicker these days. Kinda like finding something good at Costco, if you don’t snatch it up right away, you are SOL.
My arrangement is little more complicated in the setup than the Neey. The Heltec + controller has two extra wires to sense and power the controller (see the two fused 2amp leads to the pos & neg terminals. 2amps because of the devices inrush, then it only draws .05 I always fuse both leads for power taps, it’s not a place for “glow worms”. And there is the play time with controller. The Neey is easier setup because of the app. Oh, and I had to extend the wires on the Heltec. IMG_1731.jpeg
 
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