[quote=“Ducked”]Always thought it was a pity there wasn’t some way one could use the starter motor independently of the engine, for inching along in traffic jams.
Seems like it’d be a fairly trivial modification, though idiot-proofing it to stop people stranding themselves with a flat battery/burned-out starter might be tricky.[/quote]
The starter motors, wiring, and batteries which are presently fitted the the majority of road cars are not up to the task of actually providing enough power, to propel a vehicle. The starter motor itself cannot handle enough current for an extended period, and isn’t fitted with the correct type of gearing to perform such a task. The flywheel is also only designed to handle, basic starting requirements. Most automatic gearbox designs can’t transmit torque, through such a low cranking rev range to the wheels.
It is sometimes possible to get a manual car going, from stationary, whilst in gear through the starter motor, but it causes severe wear and tear to the electrical and mechanical starting system, and can only be used as an emergency method, if for example the clutch mechanism fails and the clutch becomes permanently engaged.
There are plenty of stop/start systems on modern cars, which kill the engine at the lights to conserve fuel.
A system which actually powers the wheels and relies on electrical power only though is a dramatically different type of system, and is generally only found on hybrids and electric vehicles.
These various technologies are all quite different, and so it isn’t quite as simple as hooking a starter motor up to a stop-start electrical signal, and expecting this to work well. It won’t work well at all I’m afraid.
At some point in the future however, as electrical vehicles become more cost effective, more common, and more convenient to use, we might see the present old tech systems begin to diminish in popularity. That is, unless there becomes a more effective, easy to fit HHO system, which can be installed on present old tech cars. This latter system is the one which is sparking the greatest interest from shed-inventors right now.