Top Balancing Issues

[GetOut]

Hi All,

Doing my first build and I got 4 - 280AH Eve cells from Docan. The cells arrived at 3.1 volts. Put them in parallel and using a newly purchased Dr. Meter 30V/ 10A DC Power Supply, went on to charging. Set the charger to 3.65 volts at max amps. Three days later, the cells are at 3.35?!?! I am not sure if the charger is actually working. The amps don't go above 4 while it's charging, which does not make sense to me. I read that it would take a long time, but this doesn't seem right. I'd think that it should be charging at 10 amps until the cells got somewhat close to the target voltage. I am thinking about returning the charger. Given that I am a newbie, it is totally possible that I am doing something wrong!! Has anyone else encountered this?

Thanks for any help!!

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[RobertGreen]

Please read the top balancing tutorial in the resources section of this website here: https://diysolarforum.com/resources...ls-using-a-low-cost-benchtop-power-supply.65/


Are you using the wire leads that were provided by the manufacturer, or did you crimp/assemble your own?
Several people have apparently found the OEM leads to be of dodgy quality, and it's often recommended on this forum to put together your own using some 10-12awg wire, some appropriately sized ring terminals and a decent crimper. If the leads aren't making a great connection, that could be bottlenecking the current.

As far as the supply taking 3 days... if the cells you received were at 3.1v resting voltage, then that represents quite a low state of charge (perhaps in the 10-15% range??)
If they were at 15%, then at 4 amps charging current, it could take 10 days or more to reach full charge. (4 280AH batteries in parallel is a 1120AH battery.... 1120 x 0.85 = 952AH needed to reach a full charge.... at 4 AH per hour, that's 238 hours, or nearly 10 days..... In reality, new cells often start out at a capacity slightly over nameplate rating, which means your time could be even longer!)

It's often a good idea to go ahead and throw the battery together into a 4s arrangement with your BMS and then charge it normally using a mains charger or even your Dr.Meter supply turned up to an appropriate 4s voltage. This will charge the cells 4 times as fast as the way you're doing it.

 

[time2roll]

Very common to expect 10 amps through the included wire but it generally does not happen.
Get some 10-12 awg and proper ring terminals. Although it is making progress.