shirley_hkg wrote: Fully discharged and re-charged. During daily use, it took 10 mins to balance ; quite similar to PL8.
This is the usable BMS I met so far , for large Ah battery.
I will still use PL8, but can be an alternative to it.
Burgerman wrote:Why does it have that huge dip?
Can we tell how fully the battery is charged, by looking at the volts of the following hours ?
Burgerman wrote:Every time its reconnected it goes overvolt and has to be disconnected. So a low current cannot be done. Just rinse and repeat with too much voltage.
I didn't see it over-volted. Even if it did, it wouldn't do much harm, as it was only superficial when PL8 couldn't see it at all.
No.
We need to apply a voltage above 3.5V preferably 3.55 to 3.60V and then watch the charge current decay over time. And after balance has ended. Then we know its charged. Otherwise, we dont. And balancing as you are doing below 3.5V will not balance at all or very badly. It mayeven unbalance othwerwise balanced cells.
It's 99% charged @3.45V. I seldom charge up to 3.6V , and have been balancing @ 3.4V.
It's 99% charged @3.45V. I seldom charge up to 3.6V , and have been balancing @ 3.4V.
shirley_hkg wrote:
The battery :
It's a 70Ah pouch cells , with loose, messy connections.
It's pre-balanced by PL8 , and is removed 60Ah out of it , and it is also deliberately unbalanced by taken 3 to 5 Ah amongst cells 3 to 8 as well.
It is in every way an out of balance pack now .
It was a demo , John .
Will you still want the pack that it could be 5ah out of balance in every cycle use ?
Immediate recharge showed that balance completed in minutes , so it could be set to ≥ 3.5V .
Burgerman wrote:Balance should never start at 3.4v though. You can unbalance a pack by attempting to balance at 3.4v.
3.5v is the lowest level. And it must happen at 3.5 not while bouncing up and down!
This BMS balances cells by taking the highest cell to charge the lower cells. After the BMS cuts off charging, all cell volts drop under 3.500v or even 3.450v. I think that's why Shirley set the balance starting voltage to a low value 3.400v.
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