H6/Group-48 Lithium Car Battery
Antigravity H6/Group-48 Hi-Power lightweight Lithium Automotive Battery with RESTART Technology. Replace lead/acid battery in Hi-Performance Cars.antigravitybatteries.com
This is what I bought, a standard h6 battery which is stock for our trucks. If it would ld go.bad you could pick up another of the same batteries anywhere.
you can get like 5 AGM batteries for one of those