u n d e r a c h i e v e r wrote in message news:slrnc6nib7.buc.takeme2yourNOMORESPAMPLEASE@s cratch.garylaw.net...

ARRRRGGGHHH for the
love of god WHY NOT stick a couple of batteries in it, enough for a twenty
or thirty mile journey, and let me use the (expensive) petrol when my
(cheap) electricity has run out???

Hmm. Petrol has a calorific value of 48,000 kJ/kg, a density of 0.7
kg/litre and a price of 0.7 pounds/litre. Conveniently, the latter two
mean that a quid buys you pretty close to 1 kg of petrol, yielding
48,000 kJ.

I pay 7.694p per kWh for electricity, so the same quid would buy me
13kWh, which is just under 46,790 kJ.

As incoming energy, there is therefore practically no difference
between buying electricity and petrol.

Of course, you have to take account of various storage and conversion
efficiencies. Not to mention the cost of upgrading domestic wiring, as
the 3 kW available from a 13A plug will take ages to charge any
appreciable batteries and be pretty inefficient as a result.

In short: using a small petrol engine to charge the batteries of a
hybrid car is just as sensible and cost-efficient as using mains
power.

Ian