We have a Sprinter Thor 24HL, 2017.
Our original coach battery was switched out for a couple of Deka 31 flooded batteries. The original battery was in bad shape due to low charge and lack of use just sitting on the RV dealers lot.
Our coach batteries work as a two battery banks. We added the second battery, for us it was a matter of a battery strap and a two cables to join the batteries together. They have worked well.
We can charge our batteries 4 ways. Via the Sprinter engine, the generator feeding the inverter/charger that is build into the coach, the 120v cord plugged into the grid and finally via solar that we have added. Its all automatic.
If you coach is like our coach, your coach batteries are under the entrance steps. If so you will be limited to 12v batteries. There is nothing wrong with 12v batteries they will work quite well.
I would have your battery tested, most of the national auto stores will do it for free. Replacement, we went with flooded, if I had it to do over again I would probably go with AGM, they are about twice as expensive, but I do have to shift my flooded batteries around to check the water level and refill. Not necessary with AGM.
FWIW, if your coach battery gives out, you may be able to start the generator using the Sprinter engine starting battery, start the Sprinter engine, operate it about 2000 rpm's and that should give you enough power to start the generator, then you can shut down the Sprinter engine and use the generator for charging the battery if necessary. We have to start the engine because of the battery cut off switch between the coach batteries and the Sprinter starting battery.
Good Luck
Rick
