EVE 280ah problem with 1 battery only?

[xristostsilis]

Hello to everyone!

I have installed 16s lifepo4 eve prismatic grade B 280ah batteries (the old ones with the threaded stud) for about a year now with the old style JK BMS (2amp balancing current). Everything worked great until now.

To be more specific I have one specific cell ( cell 14) that when being discharged it goes to around 2,6v while the others are to 3,3v thus making the jk BMS disconnect the battery due to low voltage disconnect.

I have tried fully charging this cell and the whole pack and this happened again for the 3d time this week. I am convinced that cell14 might have gone bad (which is weird for solar use with low loads and only after LESS than 1 year)

I would like your thoughts on this. I have already ordered a new 280ah cell on the way and hopefully I will get it soon to test. However I am also thinking that it might be a BMS issue but I have never heard anyone else have a problem like this with a jk so I would like your opinion guys.

 

[Alkaline]

I have experienced this, it just gets worse and worse, you can try the little heltech active balancers and it will help but it will also lower down other cells as it uses energy from them to help the bad cell...

replacing it is a much better option.

 

[sunshine_eggo]

Check all connections, crimps, etc.

Have you moved the cell to a different position to see if the problem moves with it?

Have you confirmed the BMS reading with a separate voltmeter?

"Grade B" cells may be classified as such for a multitude of reasons the consumer may never know. All you know is that they are defective according to the manufacturer's specification. This can very easily impact cycle/calendar life.

This forum and the proliferation of DIY LFP batteries is still in its relative infancy (<5 years). IMHO, insufficient time has elapsed to demonstrate that "grade B" cells have the longevity of cells fully conforming to the manufacturer's specification.

 

[xristostsilis]

Yes I have checked all connections, no I have not changed the cell place I was thinking to do it but too much hassle I have already ordered a new one but I am trying to revive this battery for as long as the waiting time for the new one. Plus I am hoping it’s not a BMS problem. I will try to top balance them once more and see if it gets me through this week at least.

Yes I have tested with the multimeter every reading is exactly the same with BMS.

Should I change the balancing voltage to my JK to a lower value just to be a bit safer? I have Andy’s settings currently form the off grid garage

 

[xristostsilis]

My Settings

I share here the settings of all devices I have configured for LiFePO4 batteries. As a beginner, it is very confusing to understand all these different options solar charge controllers, BMS, shunts…

off-grid-garage.com

 

[xristostsilis]

I have balance voltage at 3,45 should I try 3,3?

 

[sunshine_eggo]

Yes I have checked all connections, no I have not changed the cell place I was thinking to do it but too much hassle I have already ordered a new one but I am trying to revive this battery for as long as the waiting time for the new one. Plus I am hoping it’s not a BMS problem. I will try to top balance them once more and see if it gets me through this week at least.

Even active balancers can't compensate for cells taking a crap. With #14 at 2.6V and the others at 3.3V, it's unlikely that you're going to be able to meaningfully increase the usability unless your draw is less than your balance current.

The 2.6V limits you to a certain capacity. For the time being, you should consider whatever that capacity is to be the actual capacity. Perhaps even reprogram the BMS to reflect that.

Yes I have tested with the multimeter every reading is exactly the same with BMS.

For me, this definitely points to the cell as the point of failure.

Should I change the balancing voltage to my JK to a lower value just to be a bit safer? I have Andy’s settings currently form the off grid garage

I have balance voltage at 3,45 should I try 3,3?

Generally, less than 3.40V may be counter-productive, but experimenting in the 3.35-3.39V range might have some very limited benefit.

 

[ScrotusGobbleBottom]

I have balance voltage at 3,45 should I try 3,3?

No, That would be a lot of work for the same or worse outcome

 

[xristostsilis]

On thank you guys. I will try to top balance them for one last time and hope for the best.

 

[sunshine_eggo]

On thank you guys. I will try to top balance them for one last time and hope for the best.

If you're talking about disassembling and parallel top balancing, I wouldn't bother. You said you charged the cell to full individually. If so, parallel top balancing isn't going to benefit you.

 

[xristostsilis]

No have let them charge fully via sollar and set my inverter to not discharge them for 3-4 days to leave the integrated JK balancer do its job. Then I use them. I know it’s stupid but it’s the only way with the equipment I have now

 

[sunshine_eggo]

No have let them charge fully via sollar and set my inverter to not discharge them for 3-4 days to leave the integrated JK balancer do its job. Then I use them. I know it’s stupid but it’s the only way with the equipment I have now

If you still have a 30V/10A power supply from any parallel balance exercise, you can manually charge #14 without breaking down the battery or even taking the system offline.

If you need to balance as described, it sounds like the cell is losing its ability to retain a charge.

 

[xristostsilis]

If you still have a 30V/10A power supply from any parallel balance exercise, you can manually charge #14 without breaking down the battery or even taking the system offline.

If you need to balance as described, it sounds like the cell is losing its ability to retain a charge.

Yes that’s what I was thinking. The cell might be so bad that it kinda self discharges or something

 

[ScrotusGobbleBottom]

self discharges

Self discharges are INTERNAL shorts. They always convert your batteries energy into HEAT. Heat is bad mmmmK. If this were lithium cobalt chemistry I would tell you to get that cell out of your house.

 

[xristostsilis]

Ok so here are now:

 

[sunshine_eggo]

That's not quite as bad as you indicated earlier. Yes, one at 2.73 while the others are at 3.25V is not good, but it looks like you should still be able to use 50-60% of your 280Ah capacity.

If #14 is the first to fill, then the cell is just shot.

If it's first to drain and last to fill, it's almost certainly failed due to an internal short/self-discharge

 

[Muzzammild36]

That's not quite as bad as you indicated earlier. Yes, one at 2.73 while the others are at 3.25V is not good, but it looks like you should still be able to use 50-60% of your 280Ah capacity.

If #14 is the first to fill, then the cell is just shot.

If it's first to drain and last to fill, it's almost certainly failed due to an internal short/self-discharge

Please what do you mean that the cell is short?

 

[sunshine_eggo]

Please what do you mean that the cell is short?

shot. not short.

"shot" = bad, failed, worn out, done.

 

[xristostsilis]

So in any case I should replace the cell. I am hoping the new one will arrive as fast as possible