First, a car charger should charge the gel cell just fine, and charging at a lower rate usually won't make a difference except to take longer to charge it. Personally, if were charging a 7amp battery, I would charge it at no less than 5amp.
Now, the question I have for you is, what are you using the gel cell for that is draining it so quickly? Perhaps it is to small for your application?
"Experience is the best teacher, and is best learned from others experiences"
"Just because I HAVE to grow old, does NOT mean I have to grow up!"
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