Mixing battery AH ratings

[MadMaxWinny]

Yes, Wyatt...it's valid advice. However, unless your battery source does a very high volume business and faithfully rotates their stock (most reputable retailers have a consignment arrangement where the supplier does this weekly/monthly), you might be getting batteries of varying ages even if you buy them at the same time. And then there is the issue of when the batteries were actually manufactured. Larger (and higher quality) battery manufacturers usually use a little round colored sticker to indicate the production cycle (like "C1," which would be March 2021).

This is why I said "approximately" the same age. If they are new and manufactured within a year of each other, there will be no appreciable negative effects.

[BywaterYat]

I would like to expand the capacity of the stock system, but the 7K kit price seems a bit excessive seeing you can heated 300AH in the 2k range.