How big battery can I charge with a Tystor charger?

Basically very big. It’s all about recharging time.
Do you have practical time to wait a week or month, a 10A charger can charge several 1000Ah.
As long as the charger’s current exceeds the battery self-discharge, the battery is charging (read more about this in Battery University).
The rule of thumb, 10% of Ah in A= the size of the charger, usually is a wise guide.