High voltage to charge 3.2V battery cells - is it ok?

[MrMatt]

Ok, seems like a simple question but want clarification..

Cells; Eve 3.2V 280AH
Capacity test

In wanting to do a capacity test on my eve cells,
Say the cell is at 3.2V
IF I were wanting to bring them up to 3.5V, charging them at 3.5V with my DC power supply ( 30V, 10 A max) shows maybe 2 amps.

If I turn the voltage up on my charger to say 4 or 5V, the current goes up to 10A (which would take less time to charge up - of course I would monitor it until the cell reaches say 3.4-ish then drop my charger to 3.5V so as not to miss my upper target).

Is charging at a higher voltage initally a bad thing?
I would not think so, consider this bulk charging.. the only way to increase the amps is to increase the voltage.

If it ok to charge say at 5V, how about 12V, with a charger I have which can put out 45A?

Thank you for helping to clarify this.


I

 

[time2roll]

All is fine until you blink and the cell is at 5 volts. takes forever to get 3.4 volts and less than a minute to get to 5.

I recommend revisiting the connection to the cell. Use proper ring terminals and #10 wire for more amps at 3.5 - 3.6 volts.

I recommend assembling in series with a BMS and place the battery in service. The capacity will be known soon enough. No risk to the cells.

 

[MrMatt]

Thanks for the quick reply!
I do have heavier gauge wire than #10
Yes, am very aware of the quick charge to 3.5, have to watch it like a watching a toddler with a fork by an outlet.
Hmmm. may put them together then do the BMS.
Thanks

So, again even a 12V 45 amp charger would be fine.. not that I am going to do it, just curious.
If I remember right theorectically, these batteries can be charged a 0.5C( maybe 1C) but the point is.... to charge them at this high rate, how cannot one not use a very high voltage? There is no way around this.. correct?

 

[Skypower]

You can use a powerful power supply but I wouldn’t attempt it without a WELL TESTED voltage sensing shut off. As mentioned, things happen fast depending on how much current to how big the cells. I mean you can’t go take a leak, I’m not kidding. Even watching is like watching water boil. Your mind will get preoccupied or not even register what’s happening. The power supply pictured uses a rewound secondary microwave transformer and an air cooled rectifier. It’ll top balance sixteen 300ah cells in a few hours and it has two shutoffs. Now there’s some powerful smart balancers that if you have patience lower the charge rate it’ll take a couple days the first time around.

 

[MrMatt]

Yes, i agree,
Very nice setup..
Thanks for the input, much appreiciated!