Hi,Not sure about some of this, my 30amp B2B seems to work great with my 200ah lifepo4. What you put would say I should have greater than 60ah or am I reading it wrongly (quite possibly)?
no, not saying it won't work fine. Just saying that if you wanted as efficient (aka fast) system as possible, you would want a bigger charger (a 200Ah Lead Acid battery bank could accept up to 40-50A, a 200Ah LifePO4 could maybe accept up to 100A (BMS depending), so a charging system limited to 30A maximum is not optimal in terms of efficiency (the typical AGM battery can be charged at upto 20-25% - so 25A per 100Ah; Plain Wet Cell is maybe 10-15%, LiFePO4 varies by BMS but is often around 50% - so 50A per 100Ah).
Doesn't mean it doesn't work great, just means you could get a faster charge with a bigger B2B. Whether that extra speed is needed is another question entirely
(the same is invariably true of most peoples Solar/PV setup, but in that case, it is usually a limit imposed by roof real estate space).