On 19/05/2008 05:55, Bruce wrote:

Starting a car doesn't deep discharge them?

I should have thought that deep discharging was what they were
designed for.

Continually cranking an engine over, and over, and over, when it refuses
to start, until the battery is flat, *THAT* is deep discharge.

Deep discharge batteries (aka leisure batteries) are designed for e.g.
mobility scooters, golf karts, UPSs, caravans, and expect to be more or
less flattened each time they are used, before re-charging.