Bad EVE 280AH Cells

BusWithUs

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May 10, 2021
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Since everyone is raving about cheap cells these days, I thought I would post my experience. I built a 12V battery using 4 EVE 3.2V 280AH cells with a Daly 100AMP BMS. I've only been charging it to 13.8V and max discharge has been 2.8V. All cells were top balanced to 3.65V.

On initial build I had one bad cell. It would fall 0.5V below the others in discharge and about 0.3V above while charging. The vendor replaced the cell and I thought all was good. Now 3 months later, we go on a trip with our camper and after 3-4 days of use we find another bad cell. It triggered the low voltage cut off on us after about 30AH if discharge one evening. How annoying in the middle of a trip! I work from the road and need to power my laptop.

Anyone else having issues with these cells? I found if I keep the discharge rate low (under 5amps), it stays within 0.1V but as soon as I try to draw any current it drops. I've been using a Victron MPPT charge controller with a 410W panel to recharge it.Screenshot_20210803-094242_SMART BMS.jpg
 

DJSmiley

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As said, check busbars and wiring. Clean properly!

As for the topbalance: All cells were top balanced to 3.65V.

Did you parallel connect them and charge as 1 1120Ah pack to 3.65V or did you just individually charge them to 3.65V? (which is not a proper topbalance)
 

BusWithUs

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Cells were connected in parallel and left to stabilize for awhile. I've checked all the balance leads carefully as well.
 

Gazoo

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Cells were connected in parallel and left to stabilize for awhile. I've checked all the balance leads carefully as well.
Cells need to be properly parallel top balanced. Leaving them connected in parallel without charging them will not balance them.

As others have pointed out, just because the cells and busbars are new does not mean they are clean. The cells terminals need to be cleaned and the main problem with busbars is the slight burr. The holes in the busbars are stamped out with a press leaving a slight burr that needs to be sanded down. You should be able to feel the burr by rubbing the busbar with your finger. It's very easy to remove but can cause problems if not removed.
 

BusWithUs

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Cells need to be properly parallel top balanced. Leaving them connected in parallel without charging them will not balance them.

As others have pointed out, just because the cells and busbars are new does not mean they are clean. The cells terminals need to be cleaned and the main problem with busbars is the slight burr. The holes in the busbars are stamped out with a press leaving a slight burr that needs to be sanded down. You should be able to feel the burr by rubbing the busbar with your finger. It's very easy to remove but can cause problems if not removed.
They were charged in parallel, perhaps I was not specific enough. No burrs, bars are clean.
 

Gazoo

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Now 3 months later, we go on a trip with our camper and after 3-4 days of use we find another bad cell.
Did you put that cell in the same location as the other bad cell?

Not implying you don't have another bad cell. But I have seen many reports like yours and in most cases it was a bad connection. Did you verify the cells voltages at the cells terminals with a DMM to see if the readings are the same as the BMS?

If you could post a photo it might help.
 
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BusWithUs

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Cell is in a different location, and I redid the crimps on the BMS just in case!

I have not had it out of the van yet, but will check the actual voltages and get an picture when I do.
 
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