Guru
Joined: 13/10/2014
Location: AustraliaPosts: 2232
| Posted: 02:29am 28 Jan 2024 |
The fourth 48V battery is up and running, I now have a total of 655ah.
The last three of the old 12v batteries also had genuine EVE cells, I scanned them and it came back with date of manufacture 2020, almost four years old now.
So the bank has twelve 4 year old EVE cells, and four new fake EVE cells from the 12v battery that I was gives as a warranty replacement.
I charged the four new cells up to the same resting state as the twelve EVE cells. I used an adjustable 0-5v @ 30A top balancer supply to do that, but I did not top balance the pack at this stage.
Connected to solar, I was able to limit charge current to 50A and the bank charged up without tripping the balancer. Either the old cells are still good or new cells are a bit aged, but dam they tracked well considering age difference and cell quality, I have not top balanced them, but obviously my lower charge level makes a big difference as it's set just below the steep knee in the charge profile, which will obviously really amplifies any cell variation.
BTW: My new 5 1/2 digit 0.0015% accuracy bench DVM arrived. I am sick and tired of trying to figure out which meter is correct. I do have a fairly accurate 0.1% 3.3v reference, but I soon realized that the typical meter is not linear enough across the range from 3v to 60V for it to be of much use.
Every meter I had is inaccurate, some by 40mv and another at 120mv, and obviously ebay/ali low cost panel meters (random number generators) were all over the shop.
This is very frustrating when measuring 3.2v LFP cells, where 100mv can be over 30% resting SOC difference in LFP. Now I can adjusting them and also monitor the drift.
The JUNTECK were only 10mv out at 53v, so 53.24v read as 53.25v on three units, the fourth unit read low at 53.23V, I was able to bring the three high reading units down 10mv, good enough for monitoring the four 53V battery packs.