What to do after top balancing

[cajocars]

I’ll soon be top balancing my 16 EVE 280Ah.
Since I will later want to compress them (just a snug fit) when at 30%, is there any point in discharge them to 30% while still connected in parallel, then connect in series and compress? Would this make top balancing pointless?
Is it better to top balance, then connect in series while still at 100%, connect the BMS, discharge to 30% and then compress?

 

[robot_zombie]

hmmm it really depends on what you have available regarding connectors / busbars etc, and how much effort you want to spend pulling things down and rebuilding... you could assemble, compress (at supplied SOC), rewire for P config, top balance, rewire for S config, if you have have enough bus bars or connectors to do it.
Discharging your balanced 100% P cells to 30% before assembling and compressing them shouldn't affect the balance significantly (in either P or S config), whatever is easier... and yeah, generally you want to get your enclosure set up at 30-50% soc, The other option is to throw them together in S config and see how you go with a full charge, the balance may be OK as is, you can always rewire to P and balance after that if required.

 

[Ampster]

Don't discharge to 30 percent while in parallel, or you could undo the top balance.

 

[Bob B]

I would wire them in the final configuration .... even if not using the final components ..... before discharging them after the top balance.
As Ampster indicated, discharging them while in parallel could undo the top balance.

 

[cajocars]

So that would be
1) arrange in a row in parallel (batteries are currently at 3.29V)
2) compress
3) fit busbars
4) top balance
5) uncompress them while at 100%
6) arrange in final layout (in my case it will be two sets of 8 on 2 shelves)
7) fit bus bars, bms and connect to inverter
8) start using the battery and discharge to 30%
9) compress

Is this right?

 

[TomC4306]

1. Slap together WITH BMS and do an initial charge to get all of the cells from their shipping SOC to closer to 80 or 90%. 54v. No compression.
2. Disassemble. Parallel all the cells. No compression.
3. Perform your top balance to whatever voltage you're going to use. 3.55, 3.6 ?
4. Disassemble.
5. Build your battery in its final configuration with a loose compression fixture if that is your want. Commission the battery. Discharge the battery to 30% or whatever. Tighten your compression fixture.

 

[Pi Curio]

Don't discharge to 30 percent while in parallel, or you could undo the top balance.

Is this valid for cell ballancing, or parallel battery bank as well, in general?

Thanks

 

[TomC4306]

Is this valid for cell ballancing, or parallel battery bank as well, in general?

Thanks

Yes.
When connected in parallel, the cells act as one huge 3.2 volt battery. You bring them all up to the same state of charge at the top end together. Then, when you assemble the cells in series, they are each acting as individual cells. That have been matched in state of charge to one another at the top of the state of charge range.

 

[Pi Curio]

Yes.
When connected in parallel, the cells act as one huge 3.2 volt battery. You bring them all up to the same state of charge at the top end together. Then, when you assemble the cells in series, they are each acting as individual cells. That have been matched in state of charge to one another at the top of the state of charge range.

Just to be certain,
If I set 2x12V 100Ah Lifepo4 batteries in parallel, for a total of 12V 200Ah, I shouldn't discharge below 30%?

Factory built 12v batteries.

Thanks

 

[Ampster]

Is this valid for cell ballancing, or parallel battery bank as well, in general?

@TomC4306 explained it well.

If I set 2x12V 100Ah Lifepo4 batteries in parallel, for a total of 12V 200Ah, I shouldn't discharge below 30%?

That is a different configuration and does not affect the balance of the individual 12V batteries, which presumably were balanced before assembly.

 

[Pi Curio]

@TomC4306 explained it well.

That is a different configuration and does not affect the balance of the individual 12V batteries, which presumably were balanced before assembly.

Thanks for the clarification, very much appreciated.

New to this and about to double my storage with another 12v 100Ah, just want to learn as much as possible about such configuration.