How do I charge two marine cycle batteries at 24v?

Hello,

I've built a mobile stereo ice cream cart that I have posted here on instructables. https://www.instructables.com/answers/Got-any-cool-ideas-for-our-Arduino-run-LED-dance-f/

We've been having a hard time with our SLA batteries. We have two 12v banks of three 7.2 sla batteries, run in series to make 24v. (six batteries total) We then use a car charger on trickle to charge the two banks separately. This is a pain, and the cells have been swelling.

We desire a bit more battery life. (currently at about 6 hours) and simpler charging.

My thought is two small marine cycle batteries (maybe 40 Amp/hrs each) and some sort of 24 volt charger.

Would this work? Is there a better way to go? 

Extra Points for Light, Cheap and Simple.

Thanks so much!

Tor

BTW totally open to a battery lecture, or to get pointed to a good read. I feel like I need to get schooled.



Picture of How do I charge two marine cycle batteries at 24v?
I'm guessing you've run those little batteries flat far too often. They don't like it, as you have discovered. The deeper you discharge a LA (S or not) the less life you get. Marine batteries or deep-cycle ones of some sort are definitely the way to go. Get a new pair, and a 24V charger. Its important the batteries are IDENTICAL and new, if you keep them in series connection, so the cells all age the same.