[rickst29]

and an occasional installer LFP batteries (INCLUDING Battleborns), I must advise you that the 50A "maximum charging rate" is not advice - it is a hard limit, and reaching it will cause problems. The Battery Management System ("BMS") internal to each of your two batteries will disconnect from charging when that limit is reached, and it might be a bit complicated to re-enable that function.

With my own home-built LFP batteries (not Battleborns), my cheap BMS might be recoverable by "restarting" from the cellphone App - or it might require physical shutdown by disconnecting and reconnecting the battery. My cheap one might even fry an internal circuit, if the overcurrent becomes "too excessive". You DON'T WANT TO FIND OUT the "recovery/reset" procedure for Battleborn's internal BMS (which probably is recoverable, but might involve significant delays or disconnect of the battery leads before automated recovery).

I know that you would like to reduce the generator run time, as much as possible. But, if you charge with "up to 90 Amps", there could be a moment when one battery has gone into "balancing mode" while the other battery is still accepting full charge. A 100A charger with sufficient voltage will happily overdrive the second battery by a larger margin, before it also reaches adequate internal Voltage to switch over to balancing mode. All BMS circuits can be over-driven for a short period of time, but it is too risky to overdrive by such a large amount.

Your alternative is to stay with a "normal" converter section. My own slightly modified "60 Amp" PD Converter actually charges my LFP batteries at a bit more than 60 Amps. 90 Amps would be both "unsafe" and only save 1/3 of the total charging time.

Over at another forum, where a lot of "home-built LFP Battery" people hang out, the Aims charger you're looking at has also had a few reported problems. I have visited AIMS. (Their warehouse and operations are in my home town, as is Dragonfly/BattleBorn). When I last visited their location, they were (and probably still are) merely an import-and-resale company for various Chinese products. At the time of that visit, they had no "repair and refurb" employees. (I ASKED.)

Aside from the initial "replace if it's defective" guarantee, AIMS probably can't offer any assistance with a maybe-repairable problem.

The internal batteries cells, incidentally, do NOT prefer to be charged at their maximum rates.