Yes, the caps. Classically the reason we use lead-acid in cars is its tremendous power density. Here they are combining LiPo (high energy density) with caps (hi

Yes, the caps. Classically the reason we use lead-acid in cars is its tremendous power density. Here they are combining LiPo (high energy density) with caps (high power density). My truck battery pumps out 750CA for short bursts. That's about 12 horsepower. Lithium batteries can only accomplish that in large parallel banks.