RV House Batteries (Replacement, System Upgrades)

We bought our motorhome about five years old so it just passed its sixth birthday as we’ve had it a year. We’ve been doing more boondocking also known as dry camping (no electricity/water/sewer hookups) sometimes for just an overnight stay, other times as long as five days which is about when the grey tank gets full and we need to dump the tank.

We have noticed that our original RV house batteries, which can run pretty much everything except the air conditioners, do not seem to be lasting as long as they should be based on their capacity and what we think is the electrical load. We rely on the battery bank when we are not plugged into shore power or the generator. After our analysis detailed in our How long will RV battery last boondocking? article, we decided it was time for an RV battery replacement, to add an RV battery monitor, and upgrade the inverter remote control. We only recommend products we love and your support means a lot to us! This post contains affiliate links and if you make a purchase after clicking on our links we will receive compensation at no additional cost to you.

RV Battery Replacement

After leaving Arco, ID we stopped in Idaho Falls to replace all six house batteries with new ones from Batteries Plus (did the labor ourselves! thanks Youtube!). The batteries cost $135 ea, plus tax, but we got a 10% discount for ordering online and picking up in the store. Grand total was $772 for the batteries. The batteries were 6V GC2 235AH so that means our 12V battery bank is now increased from 630AH to 705AH. Discharging to 50% gives us a usable 352AH.

We installed the BMK and new batteries in the parking lot at Batteries Plus since they let us park near the employee entrance and do the work there. Then we were able to give them the old battery cores to save the core charge. Very convenient! The longest task was cleaning the battery tray & compartment with baking soda and water which had a decent amount of corrosion.

Towards the end, three cables to wire up the new batteries in series were too short because the terminals were spaced further apart on the new batteries. Fortunately, the Batteries Plus guys had a recommendation so I ran down to an RV supply store nearby and had them fabricate some custom length cables ($25) using 2/0 gauge wire and connectors. After that, we were all set. This RVgeeks video was the primer on how we did the whole project.

RV Battery Monitor

We decided to add a Magnum Battery Monitor Kit (BMK) for $135 which sits between the battery bank and all the main negative cables so it can monitor the real flow of electricity in/out of the battery bank that will give you exact measurements for the combined 12V DC load and the 12V->120V inverter load. It uses a battery temp sensor so it can factor in temperature impact to the capacity, and you can tell it the battery type you have along with the capacity so it can figure out the real SOC % and how to most efficiently charge your batteries automatically. No more guessing based on voltage!

Our Real Load

The new BMK is showing we actually have a typical “real” load (as in just running all the stuff we normally like to use while we are awake) of about 32 AH which includes the fridge compressor running and about half that when it is not running which is about half the time, less if it’s colder outside. So that means our original estimates for AH usage was way low! Now that we had better numbers, we spent an hour turning off various appliances and circuit breakers to see how much power everything used while monitoring the BMK meters and now have a better idea on how to make our batteries last longer before we need to recharge them with the generator when we are dry camping.

For example, the weBoost antenna uses 2-3AH so we leave that off unless we are actually using it which is fairly rare. Also before bed, make sure all non-essential loads like laptops are off, and turn off the 12V circuit breaker which stops apparently quite a bit of vampire loads from eating away at the batteries all night when we are sleeping (although now the light switches and water pump don’t work until you turn it back on!). We can bring our average AH usage to <10 overnight and still wake up >70% batteries and only need to run the generator a couple of hours to get the SOC % back up to 90%.

Why 90% and not 100%? Well, it takes only a couple hours of bulk charging to get 80% or more and then at least another 2+ hours more than get that last 10-20% through absorb/float charging so it’s not worth the fuel consumption (around .5ga/hour) or wear and tear on the generator to get that last bit. We run the generator for an hour in the morning while making breakfast (some things need the convection oven anyway) and another hour in the evening when making dinner.

Upgraded Inverter Remote Control

One final upgrade we did was replace the basic ME-RC50 remote with the ME-ARC50 (Advanced Remote) which has more granular options and improves the accuracy of several of the meters it has. I got a used one off eBay for half price at $135 and it was a direct replacement. Just remove four screws on the bezel, unplug the data cable into the back, and reversed the process using the new remote since it’s an identical form factor.

Best new features:

Set specific generator start/stop times to match campground quiet times (instead of picking from a short menu of specific choices that do not always align).
Set generator start and stop based on SOC % thresholds (accurate) instead of voltage readings (inaccurate).
Bookmark favorite menu items so they are quicker to get to.
Future-proofing when we go to add solar panels. The advanced remote has better options for co-existing with solar charging.

If you’re interested in AGM maintenance-free batteries, try these 6V GC2 225AH AGM type (maint free) battery but note they are about 2x the cost but charge faster.

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