Lithium battery for a VTR BJ 97?

Hello, I am proud owner of a SC36, BJ ’97. Since I come to drive only occasionally, my GelBattery makes quite often off the field, or. At a charging level of about 50% the good ones no longer jumps. I think to install a LithiumBattery, however, is at 2-3000 U/min a charging current of in places over 15V. That would grill the LiBattery Would that fix a new (favorable) voltage regulator? Or are there batteries that can do that? Thank you for your help!