And yet, most of the electric cars and PHEVs on the road right now, whatever their range or 0-to-60-mph time, depend on a relic to get moving: a 12-volt battery, usually of the lead-acid variety.

Not only does the 12-volt battery on board do that job, it also means the rest of the car’s systems should continue to work – not least electric windows and the increasing number of electronic ...