"Dave Plowman (News)" wrote:
You'd need an awfully large charger to get voltage spikes past the very
low impedance of a car battery.

If the battery is knackered, won't that impedance increase? As an endpoint,
imagine if the battery was completely dry - it's open circuit and so
wouldn't accept any current at all, and all the current would be put into
the car electronics.

Would sulphation raise the impedance?

Properly designed car electronics should have voltage regulators (and
components) rated up to 40 volts.

Indeed. Although I wouldn't be surprised if some weren't as
tolerant as they should be (also that aftermarket radio you got from
China...)

Theo