diy solar

diy solar

Stuck getting my battery cells to equalize.

T

Tirade

New Member
Joined
Jul 10, 2024
Messages
5
Location
UT
In October I picked up 2 x EASTAR BTS 12V 100Ah LiFePO4 batteries to replace the 2 marine batteries on the camper I purchased. The camper can charge them to 12v roughly but it lacks the charge controller to get full potential so I picked up a ECO-WORTHY smart charger to keep them topped off.

I use the xiaoxiang app to monitor the batteries and after my last camping trip I noticed that the cell balance didn't seem right with cell 1 sitting at around 3.3 and cells 3-4 reporting 3.6. I read somewhere that if I make sure there is no load on the batteries they will automatically rebalance and sure enough after about 4 weeks all cells were reporting 3.33x.

So today I hooked up the charger again and now I'm back to cell 1 sitting at 3.3 and the other cells at 3.6 (see attached pic).

So now I'm stuck trying to figure out what's causing the imbalance and how to fix it. Any help is appreciated.

1000024762.jpg
 
Open up the battery. There are 3 methods since this BMS only has passive balancer (150ma probably) and it gonna take forever to balance those cells:

1) The manual light bulb connection to discharge the overcharged cell manually?
2) Replace the BMS with JK-BMS with 2A active balancer
3) Buy NEEY/Enerkey 4A active balancer and connect it to the cell

Remember, each Lifepo4 cell has it own internal self-discharge rate. If you rarely charge the battery to full, it gonna goes out of balance as time passes.
 
AshleyL said:
Open up the battery. There are 3 methods since this BMS only has passive balancer (150ma probably) and it gonna take forever to balance those cells:

1) The manual light bulb connection to discharge the overcharged cell manually?
2) Replace the BMS with JK-BMS with 2A active balancer
3) Buy NEEY/Enerkey 4A active balancer and connect it to the cell

Remember, each Lifepo4 cell has it own internal self-discharge rate. If you rarely charge the battery to full, it gonna goes out of balance as time passes.
Click to expand...
I totally agree. Put a 4A active balancer on my 16S after charging every cell individually to 3.64 and everybody is happy. I probably should have gone to 3.65 but I am concretive ;)
 
Don't open up the battery, dont add any additional balancers.

The xiaoxiang app has the ability to turn on the balancer when not charging. You can see this is turned off on yours because it is not currently balancing.

If you can enable balancing when not charging, and you hold the cells over the 3.4v threshold, then it will balance on its own in due time.
 
Lt.Dan said:
Don't open up the battery, dont add any additional balancers.

The xiaoxiang app has the ability to turn on the balancer when not charging. You can see this is turned off on yours because it is not currently balancing.

If you can enable balancing when not charging, and you hold the cells over the 3.4v threshold, then it will balance on its own in due time.
Click to expand...
150ma resistive balancer......how long it gonna take?

Time in hour = capacity imbalance amount in Ah / balance bleed current in Amp

If he has 4AH imbalance, that means it gonna take 26.67 hours.
With two* battery packs..........assuming he has same 4Ah imbalance.....err...roughly 53 hours?
Does he have proper adjustable power supply in first place to keep the voltage constant :unsure: ?

Edit: Let try Lt.Dan method first and see how it goes.
 
The only thing I would add is that if you leave the existing BMS and add an active balancer, be sure and turn off balancing by the existing BMS so the active balancer can do its job without confusion,
 
First I would check into a warranty replacement.

If that does not happen, do the passive balance again but hold the voltage at 14.2 until they are close, increase to 14.4 until they are close again. May need to do this balance thing monthly or a couple weeks before the next trip. May need a low amp variable power supply to hold steady at these levels.

Last resort to me is open it up to add the active balancer. Could be a cell issue at this point that is beyond staying in balance. Good luck.
 
AshleyL said:
150ma resistive balancer......how long it gonna take?

Time in hour = capacity imbalance amount in Ah / balance bleed current in Amp

If he has 4AH imbalance, that means it gonna take 26.67 hours.
With two* battery packs..........assuming he has same 4Ah imbalance.....err...roughly 53 hours?
Does he have proper adjustable power supply in first place to keep the voltage constant :unsure: ?

Edit: Let try Lt.Dan method first and see how it goes.
Click to expand...
It's in a camper that goes into storage. Even if it takes several weeks??? Does it matter?

I too have a 100ah battery in my Motorhome with the same BMS, it also had cells out of balance just like this when I installed it. I set to balance when not charging, left it at 14v, and came back 2 weeks later with all the cells within 5mV. Idk if it took a day, or the whole 2 weeks. I didn't care.
 
Post up the setting of the BMS, also you can use the overkill app (which I find more intuitive) maybe there’s some settings we can improve.
 
Lt.Dan said:
It's in a camper that goes into storage. Even if it takes several weeks??? Does it matter?

I too have a 100ah battery in my Motorhome with the same BMS, it also had cells out of balance just like this when I installed it. I set to balance when not charging, left it at 14v, and came back 2 weeks later with all the cells within 5mV. Idk if it took a day, or the whole 2 weeks. I didn't care.
Click to expand...
And all you had to do was fiddle with your phone and beep boop some settings and walk away.
 
740GLE said:
Post up the setting of the BMS, also you can use the overkill app (which I find more intuitive) maybe there’s some settings we can improve.
Click to expand...
Screenshots attached
 

Attachments

  • Screenshot_20240711_103422_xiaoxiang.jpg
    Screenshot_20240711_103422_xiaoxiang.jpg
    68.3 KB · Views: 6
  • Screenshot_20240711_103432_xiaoxiang.jpg
    Screenshot_20240711_103432_xiaoxiang.jpg
    82.5 KB · Views: 7
  • Screenshot_20240711_103441_xiaoxiang.jpg
    Screenshot_20240711_103441_xiaoxiang.jpg
    86.3 KB · Views: 7
  • Screenshot_20240711_103452_xiaoxiang.jpg
    Screenshot_20240711_103452_xiaoxiang.jpg
    80.7 KB · Views: 6
  • Screenshot_20240711_103504_xiaoxiang.jpg
    Screenshot_20240711_103504_xiaoxiang.jpg
    38.9 KB · Views: 6
Lt.Dan said:
It's in a camper that goes into storage. Even if it takes several weeks??? Does it matter?

I too have a 100ah battery in my Motorhome with the same BMS, it also had cells out of balance just like this when I installed it. I set to balance when not charging, left it at 14v, and came back 2 weeks later with all the cells within 5mV. Idk if it took a day, or the whole 2 weeks. I didn't care.
Click to expand...
I have balance set to enable (see screenshots in reply above) is there something else I need to change?
 
Tirade said:
I have balance set to enable (see screenshots in reply above) is there something else I need to change?
Click to expand...
On the last picture, there is a "Charge balance" slider. Turn it off.

Also, set your balance turn on voltage (on picture 3) to 3.4v. We don't want it do balance below 3.4v or you might inadvertently un-balance the cells.
 
High voltage protection is set for 3.70v, set to 3.65v.

Low voltage charge temp protection is set to -10c set to 2-3c.

Under voltage protection is set for 2.2v, set for 2.5v.

Balance start is set for 3.3v, set for 3.4v

Balance delta is .015v set to .005v or .001v if you like the BMS to keep working.

Charge and discharge current limit is 110a, set to 100a or 90a.

I second my short legged friend, disable balance while charging.

If you have the ability to hold voltage at constant 14v for hours on end, this will bring the cells up to full and balance as long as the voltage is there.
 
740GLE said:
High voltage protection is set for 3.70v, set to 3.65v.

Low voltage charge temp protection is set to -10c set to 2-3c.

Under voltage protection is set for 2.2v, set for 2.5v.

Balance start is set for 3.3v, set for 3.4v

Balance delta is .015v set to .005v or .001v if you like the BMS to keep working.

Charge and discharge current limit is 110a, set to 100a or 90a.

I second my short legged friend, disable balance while charging.

If you have the ability to hold voltage at constant 14v for hours on end, this will bring the cells up to full and balance as long as the voltage is there.
Click to expand...
Made the changes you suggested and left it to charge for a few days. Went to check today and didn't realize those changes were per battery... So I've made the changes to the other battery and now it's back in the charger. Thanks for the help, I'll reply back with the results.
 
Well that took less time than I expected. Here are photos of both batteries now.
 

Attachments

  • Screenshot_20240716_145924_xiaoxiang.jpg
    Screenshot_20240716_145924_xiaoxiang.jpg
    71.7 KB · Views: 3
  • Screenshot_20240716_145941_xiaoxiang.jpg
    Screenshot_20240716_145941_xiaoxiang.jpg
    71.7 KB · Views: 3
Glad we can help.

The JBDs and weak balancer can work wonders, you don’t need 2A active balancer if you have a long time to kill at >3.4v and disable balance when charging.
 
You must log in or register to reply here.

Similar threads

D
DIY battery bank help please!
Replies
10
Views
224
Suijkerbuijk
S
P
What is my BMS telling me about my cells?
Replies
17
Views
508
PipHelix
P
B
Messed up top balancing - how to proceed?
Replies
13
Views
747
houseofancients
houseofancients
P
Got some cells from EZealco and I’m wondering…
Replies
11
Views
398
PipHelix
P
H
Daly BMS problems.
Replies
5
Views
459
sunshine_eggo
sunshine_eggo

diy solar

diy solar
Back
Top