Do I have to charge to 3.65 to be "balanced"?

[denverdmax]

Hello everyone. I'm trying to decide if this is going to work for top balancing or not.. So long story short I have new 280ah EVE cells will be configuring in a 2P4S setup. I have them hooked up in parallel currently and have been top balancing at 3.65V with the longwei charger. Today is the end of day 5 and all the cells are at 3.36. When I received the batteries they were all 3.32V or 3.31V. I am wondering if I would be safe to take them off the charger and charge the rest with my solar?

I see 2 different schools of thought, but I am thinking that they are all currently balanced pretty darn close. If each 3.2V cell is at 3.36 (up from 3.31) then they would all be near balanced. Correct? I will be hooking up a JBD BMS as well as the 1.2A "active" balancer from amazon to each 4S pack. If I hook up my solar and run the max charging V to 13.9, would you think they would all come up somewhat close to each other?

I would ideally like to wait for them all to hit 3.65, but I don't really have the luxury of waiting another 5-10 days for that to happen.

Thank you in advance.

 

[sunshine_eggo]

Hello everyone. I'm trying to decide if this is going to work for top balancing or not.. So long story short I have new 280ah EVE cells will be configuring in a 2P4S setup. I have them hooked up in parallel currently and have been top balancing at 3.65V with the longwei charger. Today is the end of day 5 and all the cells are at 3.36. When I received the batteries they were all 3.32V or 3.31V. I am wondering if I would be safe to take them off the charger and charge the rest with my solar?

I trust you've thoroughly read and are religiously following the balancing guide?

I see 2 different schools of thought, but I am thinking that they are all currently balanced pretty darn close. If each 3.2V cell is at 3.36 (up from 3.31) then they would all be near balanced. Correct?

No. Balance does not refer to voltage. It refers to state of charge, which you can't get from voltage when the cells are charging or discharging.

The only time voltage is reasonably indicative of balance is when the cells are nearly full, or the battery has been completely at rest for about 30 minutes.

I will be hooking up a JBD BMS

This is the step before you parallel the cells in the top balancing guide, so I assume you're not following it.

as well as the 1.2A "active" balancer from amazon to each 4S pack.

No data on this. Amazon sells a lot of stuff.

If I hook up my solar and run the max charging V to 13.9, would you think they would all come up somewhat close to each other?

Maybe. Holding cells at 3.475V for long periods of time with active balancers will eventually get the cells at extremely high SoC.

I would ideally like to wait for them all to hit 3.65, but I don't really have the luxury of waiting another 5-10 days for that to happen.

Had you followed the guide, it's almost impossible that it would take more than a few days.

2 * 4 * 280Ah = 2240Ah. They typically come in at 30-50% SoC. At 3.31V, they were likely closer to 50%, so you need to input 2240Ah * 50% = 1140Ah. Assuming that you could pull the full 10A for most of the charge (because you read the guide and fabricated new leads that don't suck), that's only 114 hours, 4.75 days.

Starting with the BMS installed on a 2P4S battery and charging at 10A/14.6V, you'd only need at most 28 hours of charging. If the battery didn't fully charge due to BMS intervention, then you'd need to parallel and likely only need a day or two to top them off at 3.65V

Since it's clear that you're not following the guide, I would have to surmise that you didn't fabricate new higher quality leads to prevent voltage drop and you've just been trickling a few amps to the cells.