Batteries, Supercapacitors, and Metal Hydrides
Liion batteries feature ~135kw/kg. GM's 1996 electric vehicle used lead-acid batteries getting 25kw/kg and performed at industry standard, except for a 79 mile range. With 5.3X as much battery power, the new electric vehicle can have substantially greater performance.

Furthermore, supercapacitors are much like batteries.

Beyond this still, METAL HYDRIDES are much like batteries. They are basically big metal batteries like nickel metal hydrides, that hold hydrogen for power. Installing these metal hydrides in cars or gadgets is one of the easiest ways to store power. The metal can enhance structural integrity and can be seperated into about 4 packages for ease of replacement/refuelling. It is an infinitely reversible chemical reaction and holds hydrogen 2-3x as densely as liquid hydrogen, and will never explode. power.

I bet a piezoelectric handcrank or dynamo could recharge them using water, in the event of getting stranded. Or a small electrolyzer could recharge them from AC power. It might also be wise to begin using these infinitely rechargeable superdense batteries in, say, my laptop, as well as in cars.