Sunday, October 2, 2022

MENU

Ask Dave: I get a 13.2-volt reading on house batteries. What should it be?

Dear Dave,
I have a 2017 Jayco Alante and I would like to know why, in testing my house batteries, I am getting 13.2 volts. I have been advised by the dealer I should be getting 13.6 volts. What is the correct number I should see on my voltage meter? —Dave

Dear Dave,
Since I’m often accused of not answering the direct question, I’ll start with the basic answer and then provide a little more detail for others that may have a different charging system.

The 13.2 volts you are seeing with your meter is the maintenance charge coming from your converter, as the batteries are already at full charge of 12.6 volts. When the batteries drain down, the typical converter/charger in your rig will charge at 13.6 volts until your batteries reach 12.6 volts and then drop to the maintenance charge. The typical lead acid battery that is fully charged to 12.6 volts will not accept a charge below 13.2 volts.

Different charging sources and battery types

There are several different charging sources for your house batteries as well as a few battery types. Since your Jayco Alante is a Class A gas model, I believe you have two lead acid batteries in the stepwell of the entrance door, or back in the exterior compartment above the propane tank on some floorplans.

The charger for these batteries is commonly called a converter and can be part of the distribution center or standalone. I was not able to find any specifications on what type your unit has. You should be able to identify it by the type of distribution center which is the main power supply that has your 120-volt circuit breakers and 12-volt fuses.

 

Here is a WFCO converter we took out of a 2015 Thor Challenger and upgraded with a Progressive Dynamics Lithium charger as we installed two lithium batteries. This unit was under the headboard section of the bed platform!

We had to pull the front section of the bed platform to access the old converter, and here is the new one. This will provide an initial charge of 14.6 volts to the lithium batteries and then drop to 13.6 volts

Another form of charging

Another form of charging is through a larger inverter that is designed to take house battery power and provide 120-volt power to outlets for TV and even residential refrigerators. These larger inverters also charge the batteries and typically have a multi-stage charge feature if you have lead acid batteries.

In this case, the Freedom 2000 inverter above these batteries supplied a high-voltage charge of 15-16 volts to break up sulfation that coats the plates in a lead acid battery. It then drops down to a float, and then an equalizing charge.

You can also have a solar array and charge controller that can provide a wide variety of charging options, depending on the type of system you have and the type of battery.

What I recommend

Here is what I would recommend. Unplug the unit from shoreline power, which will shut down the converter and inverter, if you have one. Shut off the charge controller if you have a solar panel system. This will show the battery charge without any external power coming in. If the batteries are fully charged, you will see 12.6 volts.

Turn on a few items like interior lights or the furnace on LP, as that drains house battery power quickly and let the batteries draw down. Not knowing what type of batteries, amp-hour rating, and sulfation condition, it’s hard to tell how long it will take to get them down to approximately 10.5 volts. However, if the refrigerator stops working on LP or the furnace blows cold air, you know the batteries are down and can check them with your multimeter.

Plug the unit into shoreline power and make sure you have sufficient power for the unit. If you plug into a garage outlet, it’s only going to be 20 amps and most likely “ganged” to other outlets that are drawing power, such as a freezer or air compressor. It’s best to test this on a 30-amp circuit, if possible.

Now test the charge going to your batteries and you should see 13.6 volts as the charge stage on a typical converter. Winnebago has spec’d a Magnatek converter that gives 13.8 volts for 8 hours of charge.

Once the batteries are at 12.6 volts, the charge should drop to 13.2 volts.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

Read more from Dave here

HAVE A QUESTION FOR DAVE?

We have started a new forum link for Ask Dave. Please be as brief as possible. Attach a photo or two if it might help Dave with his response. Click to visit Dave’s forum. Or send your inquiries to him using the form below.

Click or drag a file to this area to upload.

##RVDT1872

Comments

Subscribe
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

4 Comments
Newest
Oldest
Inline Feedbacks
View all comments
Terence P Hennessy Jr
4 months ago

A few points: 1) To use lead acid battery voltage as CHARGE INDICATOR, you need to allow 30-minutes after charger disconnect for (False High surface charge From charger) to dissipate (allow the 13.2+ to drop back to 12.6vdc or lower); 2) Should NOT allow batteries to drop below 12.0 (static/ NO LOAD**) if you follow the “never below 50% or “=damage shortens battery life” rule? (** Realizing the static NO LOAD voltage is always higher than the IN USE/ Under load voltage, and the 10.5 in article is an IN USE voltage).

Last edited 4 months ago by Terence P Hennessy Jr
Tom M
4 months ago

You can’t please everyone and some people can never be pleased. Thanks for your good work.

Steve
4 months ago

And if you discharge them below 12.1 volts (50%), you can ruin them. That’s the problem with lead acid batteries, you only get 50% out of them. They are antiquated technology.

Jesse Crouse
4 months ago

You did a great job of explaining a complex problem with possible complex number of answers. People always want a simple answer to a complex problem. I get the same “crap” in the Plumbing & Heating profession.

Sign up for the RVtravel Newsletter

Your information will *never* be shared or sold to a 3rd party.

Subscribe to our newsletter

Every Saturday and Sunday morning. Serving RVers for more than 20 years.