RV Battery Maintenance: Checking Battery Charge
Dave SolbergDescription
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.
To check the charging system of our house batteries, we can do it right here in the step well of this unit, some of the house batteries are gonna be inside a compartment so all we have to do is take the cover off. And right now we're not plugged in so we're gonna check the battery with our meter, just lay it right down here and we're gonna come in and we know these red are positive so we go right to positive and to negative. And this is probably gonna range pretty high, these are Optima batteries, they're the AGM so they're gonna hold a charge really well. And we've been plugged in most of the day so we see here we're at a 12.62. So now what we're gonna do is we're gonna plug the unit in, we're gonna let the charger start to connect on it, and we're gonna see we start to rise up to 12.78, 12.79. Now, if my batteries were a lot lower than this, we'd have a little more charge going onto it. Now, one of the things we can do is let's unplug the unit, we heard the click going in here, With this unit, we have a system where when we're traveling down the road, our engine alternator is gonna be charging our house battery here but we're also gonna be able to charge the house batteries, driving down the road. And then in turn when we're at a campground, if we need to jump to the engine batteries, we've got this solenoid system in here where we can actually hit the momentary switch and provide a jump. So, I'm gonna put these on the terminals again, I'm gonna start the unit up and we should see this climb. And we have no change in the voltage so we go over to here, and we see that our alternator is actually producing 14 volts. Okay, shut it off, and once we shut it off it goes down to 12.47, 48. So our alternate is charging our engine battery but the system is supposed to be providing a charge back to our house battery so evidently we've got a closed circuit that's going back to this unit here. This is something we're gonna have to take into the dealership or service center and have them check that momentary switch and that relay that allows that to go back through. Now, you can also do this by checking the generator, if you have an onboard generator it's gonna do the same thing as plugging it in, we'll see where that rises in the batteries as well. So take your multimeter, check your battery charging, make sure you're getting it back into your... And like in this case, we're gonna need to see a dealer.
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.
Hi folks. Please check your video at the 1:34 mark. I think an edit may be in order. Cheers! .. Ken
hey need to learn about rv batts
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?
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
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.