Battery Compartment


After spending the winter in Park City Utah with full hookups, we decided travel to Moab and do some Boondocking. This was our first real Boondocking experience with our Grand Design Momentum 380th. Within the first week realized that we needed a bit more battery power than the one supplied by the dealership. 

The first place that we Boondocked we could run our generator whenever we wanted but we didn’t want to run it all night. We would charge our battery just before going to sleep and we figured that would be enough to get us through the night. For the first few days it worked well but one night it dropped below 20° so we turned on our tank heaters to be safe and that is when the trouble started. At about 3am the first night, with the tank heaters on, our refrigerator started beeping to alert us to a low voltage warning and that it couldn’t run the fans. We immediately turned off the tank heaters and everything else we could think of that was drawing power from batteries. This allowed the fridge to have enough remaining voltage to run for the rest of the night. 

The following day we ran our generator to completely charge the battery and left it running a little later into the night. Once again it was below 20° so instead of turning on our tank heaters we kept our propane furnace at a slightly higher temperature thinking that that would have a lower draw on the battery. Around 2am that night our CO2/Propane sensor blared it’s alarm and woke us all.  We weren’t sure what was going on because the CO2 sensor sounds like the smoke alarm, so we proceeded to open all the doors and windows in the RV. Once we discovered that it was the CO2 sensor, we quickly checked what the flashing lights meant, and found out that it was also registering low-voltage and had an error warning. A quick push of the button to reset it was all that was needed to silence the ear shattering alarm. Once again we turned off everything that was using the battery except for the fridge and CO2 sensor. This got us through rest of the night without incident.


In the morning we began to discuss a possible solution to our battery problem. Being over one hundred miles from the nearest RV store, or any other major shopping venue, we were limited on our choices for an immediate solution. In an ideal situation we would’ve had an RV dealer install a battery box that could accommodate multiple 6v batteries, but seeing as we were going to be Boondocking for a month we didn’t have that luxury.

We decided that it would be best if we tried to build our own battery box and with that we began searching the local stores for the parts we needed. The general store had a surprising selection of Rubbermaid containers and we found one that fit our needs almost perfectly. The two auto parts stores in town only had 12v deep cycle batteries so instead of replacing our dealer battery we just added another 12v. We also ordered a 120w Gopower solar panel to help keep our batteries charged during the day. This turned out well, as the solar panel not only kept the batteries fully charged during the day, it also kept charging late into the evening until sunset, which is usually enough to get us through the night with plenty to spare.

Now that I had all the components to build my new battery box I started to disassemble the old one. I switched off the main battery switch in the underbelly as well as flipping the breakers inside my RV. I disconnected the battery from the cables and taped them up to make sure they wouldn’t rub. Then I took apart the old battery box. I decided to keep the existing tubes that were used for ventilation. That the new battery box would need breather holes so I decided to use a hole-cut drill bit that was just slightly larger than the existing tubes. I put the new battery box into the compartment and measured spot for the bottom hole. I screwed down the battery box and I moved under my rig and drilled a small hole through the center of the existing tube. I used the small hole as a guide for my hole in the bottom and then drilled a hole in center the removable top. 


With the breather holes in place and the base screwed down in the compartment I proceeded to cut holes for the battery cables. Because of the way they designed the compartment and the length of the cables supplied, I needed to cut separate holes at the middle and end of the box. I ran the generator cables through the middle of the compartments and the main RV lines through the corner. I also ran the connector cables for the solar panel through the end closest to the generator compartment so that we can run the line down the side of the generator and out through the bottom. This allowed us to shut the bay doors when using the solar panel. With the lines safely out of the way, I placed both batteries in the next box. I use the standard automotive battery cables to connect the two. Because I have two 12v deep cycle batteries, I connected them in series to keep the voltage the same but double my amp hours. After the batteries were secured and connected properly I attached the generator line and the the RV line. After I was done connecting all of the lines I rechecked all of my connections to make sure everything was secure and tight and then switched on the battery switch. 

For anyone else trying to do this I cannot stress the importance of keeping the cables separate. The capacitors in the RV still contain a charge even with the battery switch turned off. It is possible to still damage your RVs electrical system if the lines touch. 

Once the switch was on and everything checked out, I finished up by ensuring the batteries were secure by placing spacer blocks between the wall and the batteries to keep them from moving while in transit. After I made sure that they were secure in their new box, I put the lid back in place and sealed them up.


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