You guys really need to know the limitations for litium batteries before using them with total loss.
Most will state that you cannot discharge them below 13 or 12v, depending if its an A123, lipo, round or square cells etc- they're all slightly different. You should be checking voltages after every 2-3 tanks to make sure they're not going below minimum voltages.
They cannot be overcharged above spec and you cannot leave them for days on end without charging them to full or storage capacity. You may want to encase them or modify to make them watertight too because not many are.
Yes they are 10 times the work, but its worth it in the end.
Dry/wet cells are for care-free amateurs, lithiums are for ocd crazy pedantic enthusiasts. I spend 30mins prepping my ski after every single ride, every day- call it ocd if you will, but mainentance is the key to longer lasting jetskis in the end