If you have AC power available to plug into I also suggest a Batteryminder that has the ability to maintain and desulfate that also has a temperature compensator built in. If you plan to keep an alarm on in the van the amperage of the charger needs to be high enough to let the charger go into the float mode.
http://www.batteryminders.com/batterymi ... esulfator/
It's also probably best to keep the starting batteries separated from the house batteries during the charge. Most SMB's have a battery separator that can be set to an open state. That means you should use a charger on each battery system. Sometimes different style batteries require different charging characteristics. Many owners (including myself) keep the batteries topped off via a single charger & don't set the separator to stay open, and that's fine but it takes a larger amp charger like shown in the link. I also have AGM house batteries and AGM starting batteries that require similar charging voltages.
With a small solar setup you probably wouldn't have an overcharging problem and the same with a small charger that operates about the 2 amp range but with a small charger or small solar panel, you need to keep most all
of the load off or the batteries will never reach their float level.
It's still a good idea to keep an eye on the batteries during any charge especially if there are several batteries involved. If one battery goes bad it will kill its partner. Test voltage from time to time.