Dave Solberg

RV Battery Maintenance: Checking Battery Charge

Dave Solberg
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RV battery maintenance has just become easier! The 12-volt deep cycle battery or batteries of your house system must be properly charged to prolong their life and reduce sulfation. You can check not only the current state of charge in your house batteries but also the charging system of your converter with a multi-meter.

House batteries are typically located in a vented compartment on the side of an RV or inside underneath the steps in the case of basement models. Travel trailers usually have the 12-volt deep cycle house batteries on the trailer tongue, and fifth wheel house batteries are in a front compartment.

Use a simple multi-meter connecting the red wire to the positive side of the battery and the black to the negative side. A typical 12-volt deep cycle house battery should read approximately 12.4–12.6 volts.

A multi-meter can also be used to check the charging system of the RV electrical distribution center and its power converter or battery charger. Once again, place the red lead on the positive and black lead on the negative. Plug the shoreline power cord into a 120-volt receptacle and you will find the system may provide up to 14.5 volts of charging power.

This can also be done by starting the generator if it’s connected to the distribution center either with a j-box or manual plug in or an automatic transfer switch known as an ATS. During this procedure, you should see the normal 12.5 volts climb to approximately 14.4 volts or more.

Some units will provide a charge to the house batteries while driving down the road via the engine alternator. Motorhomes with this feature will have a momentary switch while travel trailers will connect using the 7-pin connector on the pigtail to the tow vehicle.

While connected, start the engine of the motorhome or tow vehicle and using the multi-meter, you will be able to verify a charge coming to the house batteries.

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6 Responses to “RV Battery Maintenance: Checking Battery Charge”

  1. Ken Johnston

    Thanx for the informative video. I have a 2000 Gulfstream Tourmaster powered by an M11 series 450 HP Cummins, a Cummins/Onan 7.5 kw genset, a house battery system powered by 4 6 volt 230 amp hour batteries and a chassis 12 V starter battery system. I have several questions about how to evaluate features of the integrated system My first question emanates from the fact that I don't yet know which battery system powers my genset starter. (only bought this rig a few months ago) I have an AUX START rocker switch at the driver control panel. I understand it will power a depleted Cummins start battery using a charged house battery system. However, what if my house batteries power my genset and they become discharged? Can I start my genset with the AUX START switch? i.e. does the parallel switch work in both directions or is the electricity flow limited to one direction only? How can I test this? My second question is about the engine alternator's function. Does it charge just the start battery or does it charge the start battery first and then, if the start battery is fully charged, share power with the house batteries as well? How could I test that, please? Finally, is there any thing the charger system does to handle generator input differently than shore power, or is the AC input from the genset distributed the same as the shore power input. Thanx in advance for your response.

  2. Ken Johnston

    Hi folks. Please check your video at the 1:34 mark. I think an edit may be in order. Cheers! .. Ken

  3. Herm Vanderhelm

    hey need to learn about rv batts

  4. James

    I have a 08 Winnebago vista and am having the same problem. Not charging batteries even while plugged in, gen set also wont run. Could this be the same issue, inverter problem?

  5. Joseph

    my house batteries are not charging from engine or shore power - 2004 windsport 32R can't find wireing diagrams so I can troubleshoot - any ideas

  6. Edwin W

    Liked the brief summary but would like to have seen more info as to what is causing the house batteries not to charge when the engine is running. It gets expensive when you take your rig to a repair shop that has hourly rates of ove $100.00 per hour. Like to try and repair myself if knew where to start looking for problem.

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