I sensed a question on charging batteries in series or parallel. When hooking batteries up in Series, you hook the + of first battery to the - of the second battery, thus doubling your voltage from 12 to 24 volts. When hooking up in Parallel you are hooking the + from first battery to + of second battery the - of first battery to - of second battery thus increasing the size of your battery, not the voltage.
If you are hooking batteries up in parallel, you can use a single 12 volt charger to charge both batteries, by hooking the charger to the + of battery one, and the - of battery 1. This will charge both batteries, but it will take longer, however very doable.
note the restrictions on output of your charger vs battery
you can call or email them if you are unsure or want more specific answers