Dave Plowman (News) expressed precisely :
In article ,
Paddy Dzell wrote:
Google for 'starter motor current'. If a car wont start, I either put it
on charge or just go an buy a new battery using a different vehicle.

A normal starter motor draws upwards of 300A when cranking the engine
but there's no starter motor in a hybrid and all the 12V battery does
is power the entry/exit system and boots the computers to get the
hybrid system to the READY state, a draw of less than 20A.

How does the IC engine start without a starter motor? it may well be a
combined generator and starter, though.

The traction battery is located under the back seat and is around 288V.
There's an invertor/convertor that changes that to 650V to feed the two
motors (well, motor/generators) underneath and it's MG1 that acts as a
starter motor for the internal combustion engine.

There is also no alternator and both the power steering and the aircon
compressor are electric, driven from the traction battery. Because the
internal combustion engine (ICE) doesn't run all the time, you can't
have anything that in a 'normal' car would be belt-driven from the
engine. There's no reverse gear either - reverse is achieved by turning
the electric motor in the opposite direction to normal.

Because the 12V battery doesn't have to provide a big cranking current
they tend to be smaller and less capacity than usual and if the car is
stood, say, in an airport car park while you're away on holiday for a
couple of weeks, it's not common but not exactly unusual either, for
the battery to be flat and the car won't start, hence why I fitted this
convenient jumping point.