All good ideas!
I like the logic of deducting the cost of an alternator from a high capacity Li battery... but I already have a little pile of alternators that should work in the car. I'm just too lazy to do anything about it yet. (Getting the hammer out was significant progress!)
Besides, I'm currently spoiled and won't need my car until the weekend:
driving my friends' Prius Prime for the rest of the week while they're away.