seems to me you're exactly right Stuart, no one here will have a charger able to supply 100amps - also the amount of amps will depend on the voltage delivered and the level of discharge of the battery, and it's actually the condition of the battery that dictates how it should be charged
optima's are AGM batteries, and ideally should be charged with a "smart charger", which supplies 3 stage charging, few of us have them, aside from RV owners with good electrical systems
Bill
