Example.
Typical LFP battery is 1C Charge/Discharge rate capable with a preferred charge rate 0.5C max. At 100% SOC with every cell at 3.65V the cells will take 0A. There are higher capability cells which can go up to 5C discharge and High Charge rates but Big $$$. These are not what people use here. Each and every battery added in parallel needs to be able to be charged. The "cumulative" Amp Hours of all the battery packs in the bank is what needs to be addressed. So if you have 200AH collectively you will need 100A to reach 0.5C, for 400AH = 200A for .5C. Obviously, most folks don't get there unless they are doing a Large System with stacked SCC's and so on.
As Samsonite correctly states, in a properly paralleled battery bank the charge & discharge capacity is shared across the packs within the bank. IF each battery pack is identical (BMS, Cells, Config & Cell Quality
[read as matched & batched] ) then the entire process is usually pretty flat across the packs. They will vary a slight bit but will always level up with each other (does not mean cell balanced).
If you have mixed packs, or standard Commodity cells (most of what is used here are these) then there will be fluctuations between the packs in the bank. Individual cell variances affect the specific pack which the BMS will react to accordingly by various means depending on the BMS.
I can use my own system as an example. I run a hybrid of LFP, FLA or Both.
My LFP is 2x175AH & 2x280AH (910AH) @ 24V. So this is a good example of how different packs in a bank can behave.
~ specifics: Chargery BMS8T-300's (passive balancing off), 300A-DCC's, QNBBM-8S Active Balancers on each pack.
Right now actually, I am using Genset to charge the LFP bank (all 4 packs) while also doing Pass-Through AC.
The Charger is pushing 100A out, I am using 6.6A in pass-through, so 93.4A is hitting "the Bank" of 4 LFP.
* This is part of a testing & abuse cycle I am running, so some numbers reported on BMS for SOC etc are out of whack.
As shown below, the individual packs are taking what they want at this stage. As they reach actual Full and the amps accepted reduce, the other packs "can" take it if needed which will increase their charge rates.
* The higher rate the more heat is generated in the cells.
Click on thumbnail to expand.
Hope it helps a little.