allanhurst:
Hmmmm...Depends on the type of lead acid battery. 'Leisure' batteries are designed to be charged and discharged slowly and can be discharged almost completely without damage. A long float at under 14 volts seems a good compromise between not-quite full charge and overcharging.
The old deep-cycle myth again - lead-acid chemistry simply does not tolerate 100% discharge, it
trashes the battery capacity:
(2nd para - note the recommendation of only using 55% of capacity for regular use, never more than 80%)
Vehicle batteries have strengthened plates to withstand very high discharge rates (1000A is not uncommon
spec). Deep cycle are not specially ruggedized for high current.