Upgrading RV Battery Capacity

Peter & Kathy Holcombe Peter & Kathy Holcombe  |  05.25.2018

Almost 18 months ago, we boosted our solar generating power by adding two 160-watt panels to our factory installed Zamp Solar system. (You can learn more about how we installed the panels here.) Immediately there was a noticeable improvement in how quickly we were able to fully charge our house batteries, even in cloudy conditions. And during the day, our upgraded system easily met our regular energy demands. But once darkness descended, we were often forced to fire up the generator to augment our power supply, especially in the winter when our furnace was working overtime throughout the night. We decided that new batteries were in order to capitalize on the additional input we were receiving from the 420-watts of intake from our rooftop panels.

Battery options

When we started researching batteries, we realized there were endless possibilities and much debate about which type of battery is best for RVers. But there seems to be a consensus that a deep cycle battery is preferable, because it is designed for better long-term delivery and has a better capacity to withstand a greater number of discharge cycles. (As opposed to a starting battery that is designed to deliver quick bursts of power). The next decision was between flooded and AGM/gel batteries. Flooded batteries are less expensive, but require more maintenance, i.e., you have to check and refill the water levels periodically. AGM/gel batteries have a better discharge and recharge efficiency, and deliver the best life performance as long as they are recharged before they drop below 50% of their storage capacity. We opted to invest a little more for the maintenance-free AGM batteries for their additional performance, longevity and ease of use.

rv battery upgrade winnebago viewOur new group 31 deep cycle batteries compared to our stock group 27 batteries. You can see the difference in size, and therefore capacity.

Voltage

The big decision was choosing between 6 volt and 12 volt batteries, and there are two very divided camps as to which configuration is best. One option is four six-volt, deep-cycle golf cart batteries wired in series. Fans of this option claim that the golf cart batteries are designed for a slow, steady discharge (much like that in an RV) and are better able to withstand repeated discharge/recharge cycles. The second option is two 12-volt, deep-cycle batteries wired in parallel. Proponents of this camp claim that the two 12-volt batteries have the same amp hours and take up less space.

After reading endless articles and watching dozens of videos on the topic, we ultimately concluded that this debate is essentially “six of one, half dozen of another” when it comes to performance. However, when it came down to it there was a factor that made the decision easy for us … space. The six-volt batteries take up quite a bit more area, and we wanted to continue to use our existing battery compartment under the stairs of our View. So, we opted for the 12-volt configuration and increased our capacity by upgrading to two group-31, deep-cycle batteries.

Installation

Even with the space-saving option, we still had to modify the battery compartment under the stairs to accommodate the larger 12-volt batteries. When we removed the stock batteries we realized that there are two tabs on the bottom of the battery compartment that keep the group 27 batteries from shifting during travel. We used a grinder to cut away the two vertical tabs that capped the ends of the old group 27 batteries.

rv battery upgrade winnebago view

After rounding out the sharp edges with the grinding wheel, Peter applied a liberal coating of under-body paint to the fresh cuts to prevent rust. The new batteries were a tight fit, and at first try, seemed too large for the space. However, with a little creative maneuvering, the larger batteries just barely slid into place and filled the entire compartment.

rv battery upgrade winnebago viewThe group 31 batteries are a snug fit, but a welcome modification that practically eliminate the need for a generator for our day-to-day power needs.

Now having this added battery capacity, we (almost never) worry about power usage. This completely takes care of our needs on all but the most cloudy weeks. I think this is a very worthy upgrade for anyone who wants to cut the cord from the RV parks and stay in more out of the way scenic, private or economical locations.


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7 Comments

  1. Clive and Pam Moulton Posted on 10.15.2018

    Thank you Peter it was very good reading your installation of 2 additional solar panels and the additional batteries installed in your Winnebago. My wife and I will be touring again in the USA for around 3/4 years and to have a system that will recharge these units will fit our bill very well. We live in England and don’t have the facilities of a work shop to install these units and carry out the alteration required. Do you have any suggestions on the best way for us to have this work done? We will be buying another new Navion J

  2. John F. McIntosh Posted on 10.05.2018

    Hi Peter! Where did you buy the panels and the 3 M tape?
    We’re headed to Baja in November in our 2016 View (G), now that they have ULSD..propane gen set eats too much of the small propane tank..

    1. Peter & Kathy Holcombe Posted on 10.15.2018

      Hi John: I got my panels from Zamp Solar. If you go on their website, you can find a dealer near you. The 3M tape is a little harder to find, but I’ve ordered it off Amazon. You are looking for “3M 4991 VHB”. Some VHB tape is thin, but this is the thicker 2.5mm variety – it has foam in-between the sticky part. This allows it to form to any imperfections in your roof and get a good stick. This is the same adhesive used on the GoPro camera helmet camera mounts. Make sure to wipe your solar panel mount and roof mounting location with rubbing alcohol and let dry before sticking the tape to it. This will remove any oils or residue from your mount/roof to get the best adhesion possible. Also, this tape is nearly impossible to remove once you touch it, so be very deliberate when you set it down. Hope this helps!

  3. MARK DUERR Posted on 09.18.2018

    I’m wondering how much longer you have to drive or run the generator to recharge these larger batteries? In our View with two 24 series batteries, I found it take about six hours to bring them back from about 60% down; I would assume these take much longer? This has been an ongoing issue for us because we nearly always boondock, and it’s hard to keep the batteries charged.

    1. Peter & Kathy Holcombe Posted on 09.21.2018

      Hi Mark,

      This is a great question. But I’m not sure I have the answer you are looking for… We boondock almost exclusively too. We rely heavily on our 420 watt Zamp Solar system to handle the recharge. Honestly we rarely use our generator either. The only exception is if it’s unbearably hot and we need the A/C or we need to run our microwave oven. In that case we will fire up our diesel generator for a short time. Often times, I’ll go to bed with the batteries at 60% and by noon on a sunny day the solar has it most of the way back up. It works so great that I really don’t even have to think about it much. I just have power when I need it barring the A/C or microwave.

      -Peter

  4. Joe Posted on 07.09.2018

    Do you miss your Air Conditioning on a really hot day?

    1. Peter & Kathy Holcombe Posted on 09.21.2018

      Hi Joe:

      Nothing can make you more happy than a frosty air conditioner on a hot & humid day. It is one of the best creature comforts of having an RV. We chase year round 70 degrees as a goal, but it isn’t always our reality. In the though times when it gets hot, we will use our generator or look for a power outlet to run the AC. In fact, this is the main reason we will generally plug in for a night.

      -Peter