How To Charge Camper Battery From Vehicle Battery While Being Towed

Question:

I see that someone has ask how to charge their trailer battery while towing and you have recommended BDW20043. If you connect this from the battery in the tow vehicle to the battery in the trailer and one needs more charge than the other is that a problem. Is this all you would need to do to accomplish this?

asked by: Jim K

Expert Reply:

To charge your battery on your camper properly while towing I recommend the Redarc In-Vehicle BCDC Battery Charger - Dual Input - DC to DC - 12V/24V - 25 Amp Item # 331-BCDC1225D combined with Jumper Cables with Blue Quick Connect - 28' Long Item # 3375601026. Because the BCDC system requires a minimum of 4 guage wire, the clamp connectors on the cables can be removed.

Installing the BCDC Charger allows your vehicle to fully charge your trailer battery without draining the vehicle battery, while protecting both. It works with both 12v and 24v systems and is ideal for battery banks rated between 75 and 200 amp hours. It uses a three stage charging process, Boost which provides a constant charge while monitoring auxiliary battery voltage, Absorption which keeps voltage stable to avoid overcharging while bringing battery up to 100-percent charge and Float which maintains charge on auxiliary battery.

This system has fault recognition to prevent overheating, voltage spikes and reverse polarity as well as a battery Isolator to prevent charger from pulling power from the vehicle battery when the vehicle is turned off. It is also compatible with solar panels so if you wanted to add them later they can be wired directly into the unit. Adding solar panels allows the charger to pull power from the panels before pulling power from the start/vehicle battery.

For installing this setup I recommend using 40-Amp MIDI Fuse Kit for Redarc In-Vehicle 25-Amp BCDC Battery Charger Item # 331-FK40 and Primary Wire Heat Shrinkable Tubing - 8 to 2 Gauge - Black - 6" Long - Qty 6 Item # DW05402.

If you have a smart alternator you will need to add 60-Amp Relay Kit for Redarc In-Vehicle BCDC Battery Charger Item # 331-RK1260. This allows the charger to recognize the smart alternator without a direct connection to an ignition source on the vehicle.

The reason you don't want to use just the cables from your vehicle battery to the trailer battery is because there is no protection for either battery. There is nothing to recognize when your vehicle battery is getting too low, if the trailer battery is overheating or if there is a wiring issue such as reverse polarity. Any of these situations could accrue unnecessary cost later on. Just using cables you also will not get a full battery charge.