Can active balancing take the place of "top balancing" when building a new battery pack?

[kc130up]

I am finalizing plans & budget for building my third battery using MB56 cells. I am fully aware of how long it takes to top balance and accept that is just part of the process.

In the last few months I have read about a short cut beyond using multiple bench power supplies running at once (i have 4).

Can temporarily adding a 4a active balancer to a 48v battery pack accomplish the same thing as traditional top balancing?
Programming the balancer it to get the cells to 3.65v and hold them there for a few hours?

I am not proposing operating the battery with the active balancer, just being able to reduce overall project time by using an active balancer starting at 56v to get each cell to 3.65v versus using separate bench power supplies to charge each cell to 3.65?

 

[Ramses]

The problem with top balancing on new batteries comes from the times when the active balancer on a BMS was the exception.

Now:
- all the cells are coming with ± 3.2V
- We have cheap BMS with integrated active balance (2-3A), like JK.

So, there is no need for big preparations if your BMS has an active balancer.

1. Create your battery using the cells.
2. Use the charger/inverter to charge the battery to 100% SoC at 3.500V
3. Wait for the active balancer to do its magic to bring all the cells to 0.005V delta, or even less, for the first time.

 

[lexscripta]

I saw a video a week or 2 ago somewhere on this forum of a complete build of a DIY box - the guy balanced all 16 batteries at once with a Zketech charger/capacity tester. I was looking for that but its lost somewhere on this forum...

 

[kc130up]

ZKE has a small 30v 5a

and a big one EBC-A40L

EDIT: You can't balance an entire 48v pack with either. They are mostly used for discharge tests.

 

[Ramses]

I use ZKETech BC-A40L for top ballancing with 16P mode for MB31.
The problem is that it takes 1 week at ±140W (3.5V * 40A).

For MB56, it takes two weeks, so this is the problem.

See this charger in the video (60V, 20A), but is used in 16s

 

[kc130up]

I thought I saw videos of the EBC-A40L charger being used to top balance, but the spec sheet says 0-5v so I edited my post to not mislead anyone...
But now I see it says for 0-5v battery cells.



Alibaba has this

 

[Kornbread]

Yeah, the ebc-a40l only does one cell at a time.

IMO, using an active balancer negates having to top balance. With large cells it is going to take several cycles, but it will eventually get there. I have eight banks of +304ah cells, all with active 2a balancers. One of the banks with 'b' grade cells has two cells that like to not fall in line, but internal differences are not something a top balance is going to fix. That one misbehaving bank took an active 5a balancer to keep in line. It still likes to drift during this time of the year where it might not often see full charge for several weeks, or longer. It then takes several full charges to those cells back in step.