Adrian wrote:

Indeed. If you're not 500 miles from the spare battery pack. Or do you just
carry half a ton of spare battery in the boot?

All of Drivel's theories are blown away by the poor thermal
characteristics of current battery technology. The high charge density
lightweight batteries have much lower thermal efficiencies than
lead-acid batteries.

As you wil notice if you try charging any LiIon, NiCd or NiMH battery.
See how toasty and warm it gets while charging? And feel how warm if
gets while discharging as well. It's a lose/lose technology.