EVE Borderline Capacity 272- 276 AH - Type 66/71 Model Blend

MrPhoton

Solar Enthusiast
Joined
Apr 19, 2021
Messages
33
RE: Borderline Capacity Finding - Interim - 272AH (0.5C) and 276 AH (0.3C)

Leaning toward "Accepting" this as "Close Enough" - even though part of me think 1C 280AH factory spec should be met.

HARDWARE: EVE 280 AH - x8 as 24V system.
-Stated as A - and factory matched/binned set.
-Stated as 280AH Model N x 8 in sales order. Actual received goods: 2x Type 66 (280 w/o N) and 6x Type 71 (280 w/ N)
-Charge BMS600T base with DCC_300 Common DCC

TEST PARAMETER
1. Original Top-Balanced 3.65V parallel set until < 1 A consumed
2. 1-Hour Settle Time given - running down first cell to hit 2.5V as endpoint.
3. 0.5C Test
A) 2x Electric Heater and Tesla charging at 11A/120V
0.3C Test
B) Electric heaters only
4. After several fails to reach 280AH - when LVD triggered at 2.5, some other cells at 2.6 - 2.7 range.
5. Terminals and Busbars: Re-Sanded (2000 grit), Re-Cleaned Isopropyl 70%. Minor amount of NoAlox/barely visible.
6. DMM vs. Chargery V variable w/o load - 3 - 7 mV observed. Chargery notes IR < 0.1mohm (0.7 or 0.8 for each cell).
7. Repeats Top Balance and terminal cleaning to see if it would improve yield - and did so only modestly.
8. Capacity rating measured with VICTRON 500A BT Shunt and Chargery Shunt. (Chargery 1st in line). Victron shows slightly lower figures than Chargery.

The Top-of-Mind item for me is to ORDER Chargery Power cable and draw external power from full battery instead of lead 1 - or with a separate external LiFEPO4 system. Wondering if the last 3% is the 2.5 vs 2.6 window being lost from chargery pulling power from cell 1.

Good news being - I think this is close enough capacity wise.
Bad news being - I feel jaded about ordering and paying for LF280N and getting 6x N and 2 x LF280 (non-N) with what appear to be different manufacture dates. Still wondering if the Type 66 vs 71 will manifest in 1 - 2 years as "runner" or higher IR.

Plenty of photos on request. Either way - happy to have 7.5kWH of hobbying capacity.

AND KUDOS to this Board - I greatly appreciate the wealth of knowledge and experience shared!
 

sunshine_eggo

Happy Breffast!
Joined
Oct 26, 2021
Messages
1,967
Location
USA
I'm of the opinion that anyone thinking they should get true grade A cells for grade B pricing is not being realistic applying local cultural norms to claims offered by a foreign business culture that is not particularly famous for being 100% honest and transparent (famous for the opposite).

Victron shunt is the reliable one. Chargery is not famous for accuracy.

Your results are very typical. Here are another member's results (individual cells tested):


You got 97% rated capacity. You need to read the datasheet very carefully to determine how capacity is tested and if you've faithfully repeated it. Furthermore, you need to conduct any prescribed follow-on testing when cells don't meet capacity.

Since you've tested in series, you can only say that a single cell doesn't meet spec. True, likely very little left in the cells > 2.50V, but again, you've only confirmed that ONE cell doesn't meet cap.

Ask yourself:

"Am I happy with 97% rated capacity for 1/3rd the cost of cells through authorized channels, or do I want to engage in the hassle associated with trying to get a return without thorough technical substantiation and the resulting p!ssing match?"
 
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