The best "econony" charger I've found is the Schumacher unit that has a 2/10/80 amp selector. The 80 amp setting is labeled "boost" and is only used for short bursts of heavy charge to wake up a totally dead battery. Walmart sells a generic charger that closely resembles the Schumacher, and is probably their item with a "house brand" relabel. Fortunately, real battery chargers aren't expensive. The big box-shaped ones on wheels usually cost less than $200.00, or close to half that price when they go on sale. "Buy once- - - -cry once!"
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!