Expanding an existing lithium battery bank with cheaper batteries from Walmart
We are picking up a new fridge and about to go boondocking tomorrow. I don't have time to order more lithium batteries and I don't want to spend so much money as they cost because I'm not sure that we'll need it. I want to get one or two less expensive batteries from Walmart in case we do end up needing them.
I can theoretically make two separate banks and only have one connected to the electrical system at a time but that might mean swapping wires around multiple times a day.
I'd like it if there is a way to just wire everything together permanently, have it work, and have it not kill the life expectancy of anything in the bank.
Any advice? (other than not getting the fridge... I've tried to argue against it and been unsuccessful)