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LifePower4 Battery stack charge imbalance

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hayDay

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Nov 25, 2022
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I have a stack of 6 EG4 LifePower4 batteries in a cabinet from Signature Solar like the pic below
the middle 4 batteries are fairly well in sync, usually +/- 5%, but the top one could be lagging by 20% and the bottom up to 40%

this causes problems when the bottom battery falls below 15% and I need to switch from solar/battery/grid -> solar/grid/battery while I still have 50% + in the middle batteries. My connections are all solid and I have my inverter connections at opposite ends of the busbars to help spread the load.

I have thought of perhaps adding relays to each battery so I can disconnect them when they fall below 15% or above 95%
Is there a better solution out there?

1707785242358.png
 
Do a full charge cycle with float for at least 8 hours. Heck, if you have a separate charger, float the problem batteries for 24 hours. That gives the bms time to balance the cells.

Do you have one battery connection at the top of the busbar in the cabinet, and other connection at the bottom?

You could try this (just guessing) put the bad batteries at the bottom, and the good batteries at the top. Wire the busbar connection with both at the top. The top batteries will be worked a little harder than the bottom ones.
 
hayDay said:
I have a stack of 6 EG4 LifePower4 batteries in a cabinet from Signature Solar like the pic below
the middle 4 batteries are fairly well in sync, usually +/- 5%, but the top one could be lagging by 20% and the bottom up to 40%

this causes problems when the bottom battery falls below 15% and I need to switch from solar/battery/grid -> solar/grid/battery while I still have 50% + in the middle batteries. My connections are all solid and I have my inverter connections at opposite ends of the busbars to help spread the load.

I have thought of perhaps adding relays to each battery so I can disconnect them when they fall below 15% or above 95%
Is there a better solution out there?

View attachment 195120
Click to expand...
I suggest first verifying the voltage of each battery in the pack. If the voltages are within .5v of each other, confirm that each battery is running firmware version 3.26 or newer. After this, charge the pack using a user-defined settings from the spec-sheet to the overvoltage limit of 57.6v. Following that, I recommend deep cycling the batteries for 1-2 weeks, ensuring a discharge of 80% depth. This should help correct any SOC imbalances you're experiencing. Also, I would suggest putting any newer batteries at the top of the rack and the older ones on the bottom.

The firmware and spec-sheet for the Lifepower4 batteries can be found here: https://eg4electronics.com/.../eg4-lifepower4-48v-100ah...
 
DIYrich said:
Do a full charge cycle with float for at least 8 hours. Heck, if you have a separate charger, float the problem batteries for 24 hours. That gives the bms time to balance the cells.

Do you have one battery connection at the top of the busbar in the cabinet, and other connection at the bottom?

You could try this (just guessing) put the bad batteries at the bottom, and the good batteries at the top. Wire the busbar connection with both at the top. The top batteries will be worked a little harder than the bottom ones.
Click to expand...
I have the connections alternating top/bottom on the busbars to help give a uniform charge but I am only charging from the sun, so charge time can vary
 
hayDay said:
I have a stack of 6 EG4 LifePower4 batteries in a cabinet from Signature Solar like the pic below
the middle 4 batteries are fairly well in sync, usually +/- 5%, but the top one could be lagging by 20% and the bottom up to 40%

this causes problems when the bottom battery falls below 15% and I need to switch from solar/battery/grid -> solar/grid/battery while I still have 50% + in the middle batteries. My connections are all solid and I have my inverter connections at opposite ends of the busbars to help spread the load.

I have thought of perhaps adding relays to each battery so I can disconnect them when they fall below 15% or above 95%
Is there a better solution out there?

View attachment 195120
Click to expand...
What's your bulk charge voltage set at?

When's the last time that your batteries hit 56.5v?
 
hayDay said:
I am only charging from the sun, so charge time can vary
Click to expand...
If these haven't been discharged and fully charged, to full voltage (you can't trust indicated SOC, you must look at voltage), you don't have a clue about what the SOC is. I've been running 5 LiFePower4s for two winters now, and every day without a full charge the SOC varies more. But the batteries are perfect, all the same voltage and all cells great. The BMS just can't track small currents well.

Don't pretend to trouble shoot or try understand what's going on until you use BMS_Test to look at your batteries.
 
EG4_Jared said:
I suggest first verifying the voltage of each battery in the pack. If the voltages are within .5v of each other, confirm that each battery is running firmware version 3.26 or newer. After this, charge the pack using a user-defined settings from the spec-sheet to the overvoltage limit of 57.6v. Following that, I recommend deep cycling the batteries for 1-2 weeks, ensuring a discharge of 80% depth. This should help correct any SOC imbalances you're experiencing. Also, I would suggest putting any newer batteries at the top of the rack and the older ones on the bottom.

The firmware and spec-sheet for the Lifepower4 batteries can be found here: https://eg4electronics.com/.../eg4-lifepower4-48v-100ah...
Click to expand...
thanks for the detailed instructions

  1. I'll verify with voltmeter, but Solar Assistant is giving me uniform voltages. see below
  2. Firmware upgrade was done on all a few months ago, but I will connect to each and verify >= 3.26

After this, charge the pack using a user-defined settings from the spec-sheet to the overvoltage limit of 57.6v.

not sure I understand, should I change the whole pack to a battery voltage of 57.6V?
using my inverters (2x EG4 6500 EX), or an external charger?


Following that, I recommend deep cycling the batteries for 1-2 weeks, ensuring a discharge of 80% depth

so drain them all the way to 20% then up to 100% each day for 1-2 weeks?


Also, I would suggest putting any newer batteries at the top of the rack and the older ones on the bottom.

I purchased these in 2 batches, the older ones are at the bottom.


1707932324867.png
 
If you are able to manually top the batteries off once a month...that would be helpful. Winter is hard on solar production. My system went almost 2 months without sufficient solar and the SOC was getting way out of sync.
 
Zapper77 said:
If you are able to manually top the batteries off once a month...that would be helpful. Winter is hard on solar production. My system went almost 2 months without sufficient solar and the SOC was getting way out of sync.
Click to expand...
if I manually charge it, how do I know when its full? from soc or voltage at 56.6?
 
hayDay said:
if I manually charge it, how do I know when its full? from soc or voltage at 56.6?
Click to expand...
Look at the individual cell voltages to make sure they’re all ok, and total voltage is high enough. Until they’ve been cycled they may switch to reporting SOC of 100 too soon. Like Jared said, the SOC will be a better guess after a couple cycles.
 
Something I did a couple weeks ago I wish would have done back in December was raise my discharge cut off up until I was getting back to 100 percent once a week or so. I realized I wasn't gaining anything going down if never got it back same kwh regardless, just went up to 30 was able to go back down to 20 this week.
 
sburcham said:
Something I did a couple weeks ago I wish would have done back in December was raise my discharge cut off up until I was getting back to 100 percent once a week or so. I realized I wasn't gaining anything going down if never got it back same kwh regardless, just went up to 30 was able to go back down to 20 this week.
Click to expand...
this seems like a good idea to automatically do once per month or so in the dark months. thanks
 
hayDay said:
if V is more reliable than SOC, why not just use V to determine battery level then?
Click to expand...
Voltage varies tremendously according to current draw and other items. Voltage reading after several minutes of complete rest - zero charge or discharge - can be used in stead of SOC. But while a system is working, hard to nail down precisely.

I do use voltage to control my charge and discharge, and it works well.

To learn more about LiFePO4 batteries, look at the posts by @RCinFLA here on this forum. He's posted tons of excellent information that will be helpful.
 
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