How do I charge two 12V batteries using two solar panels that are 15V each and 5 AMP each?

Senior Project – We’re trying to build a solar powered go kart. We have two 40Watt panels that are 15V each, and 5 Amps each. We are going to use two 12V batteries to run the motor. We want to charge these batteries using the panels, however we don’t know what type of charger we need. Where can we find a charger that is DC in and out? Any info will help Thanks in advance!
Is it better to get an altenator?