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EG4 LL bank out of balance

medic149

Cabin In The Woods
Joined
Nov 23, 2020
Messages
267
Location
Amboy, NY
My MPP 6548 with 3 EG4 LL 48v 100 amp system at my off-grid cabin has been working seamlessly for the past 2 years.

When I left two weeks ago the batteries were all three at 100% charge. When I arrived today the one closest to the bus bar and the inverter was 94% the next one was 15% and the furthest of the three was at 20% state of charge.

Any clue as to why that would happen in such a dramatic difference? I've never had this happen before. I currently have the generator charging all three batteries and will get them up to 100% and see how they do after that but just curious why that would have happened.

I do leave the system turned on while I'm gone to power the refrigerator and a single light but nothing else. The system does get turned off once winter hits.

TIA
 
My MPP 6548 with 3 EG4 LL 48v 100 amp system at my off-grid cabin has been working seamlessly for the past 2 years.

When I left two weeks ago the batteries were all three at 100% charge. When I arrived today the one closest to the bus bar and the inverter was 94% the next one was 15% and the furthest of the three was at 20% state of charge.

Any clue as to why that would happen in such a dramatic difference? I've never had this happen before. I currently have the generator charging all three batteries and will get them up to 100% and see how they do after that but just curious why that would have happened.

TIA
Simplest thing to verify first is that all the cable connections are good. Can you provide a picture of your setup?
 
Here are some photos of the setup and SolarAssistant screenshots. The EG4 charger is connected to the bottom battery, furthest from the inverter. Battery 2 and 3 are charging, but seem slower than usual, but could just be because I am watching it. Like watching a pot waiting for it boil LOL All connections seem tight and nothing is loose.

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I’m not sure if your charging with SOC parameters or voltage. But charge the whole pack up to at least 57v. And they will likely balance out great.
 
I’m not sure if your charging with SOC parameters or voltage. But charge the whole pack up to at least 57v. And they will likely balance out great.
Charger is set to 57v and 60a currently, which is where I usually have it.

Will let all batteries get up to 100% for a while before I turn off the charger. Fingers crossed they even out.

Thanks for the help!
 
LFP batteries need to charge to 100% periodically to balance & reset SOC. They will not balance at the mid-level SOC, the difference in voltage is too low. I bring mine to 100% weekly.
 
Looks like current sharing between packs is way off because your cabling is incorrect.

You aren’t cross connecting the AIO leads

Watch wills video on large battery rack wiring and soon as you fix it you should be good to go.
 
I’m not sure if your charging with SOC parameters or voltage. But charge the whole pack up to at least 57v. And they will likely balance out great.
X2.

Seeing how far out of balance your cells are I would only charge to 55.6V and hold.
I suspect you'll see the BMS going into protection for HVD if you try to go to 57V right away.
Pay close attention to the high cells and be ready to reduce charge current when the high cells start to run.
1000012395.jpg
 
Looks like current sharing between packs is way off because your cabling is incorrect.

You aren’t cross connecting the AIO leads

Watch wills video on large battery rack wiring and soon as you fix it you should be good to go.
Are you referring to using a bus bar instead of cabling to one another?
 
There was this thread discussing someone with same issue if that helps.

Might also be a bit cleaner install if the charger cables were connected to the busbar so you have only have to have single set of cables going to the batteries. Verify those cables from the busbar are of adequate size.
 
Everything is now charged up to 100%.
I labeled the wiring of the batteries in this photo:

View attachment 257423
I would recommend cleaning up the wiring just on principal, making that a lot cleaner would make it easier to see what's going on here.

These batteries have a lot of energy, battery cabinets should not look like a shoe box full of wires.
 
I would recommend cleaning up the wiring just on principal, making that a lot cleaner would make it easier to see what's going on here.

These batteries have a lot of energy, battery cabinets should not look like a shoe box full of wires.
Most of the excess wiring is for the communications with SolarAssistant to get it to see all three batteries. Also heating pads.
 
When the cells are a bit out of balance like you had, then 100% isn’t necessarily 100%. It’s best to charge them all to a higher voltage as a mentioned. It helps balance the cells within the pack, and balance the batteries between themselves. The packs can drift over time, especially as the weather gets worse during the winter months.
 
Most of the excess wiring is for the communications with SolarAssistant to get it to see all three batteries. Also heating pads.

That's fine, and I don't want to over-state. There are far bigger wiring disasters. And certainly many terrible wiring jobs can actually look neat....

But taking the time to do it neat will dramatically improve the safety.
1. Taking the time to do it right shows that you're doing it right. Not taking the time to do it right... is problematic.
2. Once you've forgotten which wire is which, it's a lot quicker to troubleshoot.
3. With a jumble of wires, you're less likely to notice something that isn't supposed to be there, which could lead to an accidental short.

And that includes cabling for SolarAssistant and heating pads.

I would clean that up, and maintain a higher standard for your builds. But that's just me. Feedback over.
 
Update

All batteries were brought to 100% soc.

They've all been within 1% of each other all day.

Appears to all be back to normal.

Thank you to most of you for the helpful advise and not being critical.
Out of curiosity, did you record the cell voltages when they hit 100% soc?

Glad to hear things are working better.
 
Out of curiosity, did you record the cell voltages when they hit 100% soc?

Glad to hear things are working better.
No I didn't. Totally forgot to do that.

I will look at that over the weekend when I get them back to 100% again.
 
Looks like current sharing between packs is way off because your cabling is incorrect.

You aren’t cross connecting the AIO leads

Watch wills video on large battery rack wiring and soon as you fix it you should be good to go.
740GLE is correct, the cables to the AIO are not landed correctly. Move the black cable up to the top (and leave the red one as it is).
 

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