Depends if your intent is charging off a power pole or charging off a generator. I've never generator charged GC220 batteries with less then a seventy ampere bulk charge. Twenty amperes rate goes well with a massage and mud bath power pole connection and seven divided into 110 usable amp hours means using a calendar to time the charge. For home charging it's tough to beat the old roll-a-round vertical chargers with wind up timer when speed is at need.
If you decide on buying a -smart- "Syntho-Charger" if they offer a 5-year optional warranty plan, I'd go for it.
I'm still repairing those old fashioned transformer manual chargers. Except for the Schumacher 10-amp which has pure garbage button diodes mechanically sandwiched between two aluminum plates, these old fellas have only one weak point - the circuit breaker. The slider selection switch on the Harbor Freight chargers ain't too hot, either. But at least these units are fixable. Smart chargers are Chew & Spit.
