Twice the battery, twice the power, twice the fun.
If you need extra power out on the road to power your rig for longer, including the heater furnace fan, lights, water pump, and even help charge your iPad or mobile phone, then adding a second battery is a fairly cheap and easy upgrade.
6 Volt versus 12 Volt
A lot of campers go with a 6-volt battery system, which combines to 12-volts when wired in series. This does provide better power, but the batteries weigh more and are harder to find and thus harder to replace out on the road.
I choose a 12-volt system, using common marine batteries purchased at Wal-Mart. Easy to install, easy to replace (even under warranty at any Wal-Mart in the nation). You can also find nicer, more expensive options like the Optima Blue Top.
12 Volt Wiring
For maximum effectiveness, battery life, and a consistent, even charge, you shouldn’t simply wire your batteries in the typical parallel mode, but instead employ the following technique:
It’s important to have equal wire lengths between the two batteries. This helps keep a good balance between the two, both during charging and while sitting dormant. Otherwise, one battery could constantly be pulling from the other and thus decrease battery life.
I ended up making the positive and negative wire running to the battery as equal lengths, just to be extra careful (or I over analyzed things as my wife often says).
Make sure and put a fuse in the system – which allows you to both cut power in an emergency and prevent battery drain during storage. Without pulling the fuse, your propane / CO2 detector and other appliances could draw down and kill the battery.
Speaking of storage, you’ll likely want to remove your batteries during long term storage and keep them on a battery maintainer.
These devices are better at keeping your battery in a healthy state, throughout the winter months for example. I use the Black & Decker BM3B shown above.
Once you have twice the power, keep a close eye on your voltage with a charging system monitor.