I believe Scott means that you should use an automotive type charger and charge each battery separately. Gel batteries have a special charge rate so you should try and use a charger with a " gel " selection on it. I'm assuming these are 6V batteries. Honestly, you will have problems just running the cart with mismatched batteries. I would try and find another gel battery that matches your others in amp hour rating. If you are just buying time, what you want to do will work, but figure on replacing all of the batteries pretty soon! It's very easy to overcharge gel batteries and once they have been overcharged ( gas bubbles ), they do not recover as the bubbles stay in the gel and interrupt proper current flow.
