All, your help is sincerely appreciated!Traveling down the road, we'll occasionally fire up the inverter to power computers and charge phones. Nothing else.In this case, we can usually make it an hour before the inverter automatically turns off with a message saying it turned off due to low battery voltage.The alternator, by all indications, functions normally, and should be charging the house batteries as we drive.Is it normal that a few charging phones and a computer would deplete the charge of the house batteries faster than the alternator keeps the charge up? Is it possible my alternator is not charging my house batteries while we're driving?

What kind of coach and what brand of inverter? On my Monaco coach, the inverter is never turned off, either automatically or manually, and I have no problem using 120 volt items when on the road. I have a Xantrex inverter with a 140 amp alternator.

When in doubt, call the manufacturer, they can tell you if your batteries are being charged while going down the road. Your inverter should not shut down after a short period. I turn my inverter on when I need it, otherwise it stays off.

Yes, OP, it is possible. Evidently you have exactly the rig upon which it happens, whatever that is.If you are towing a trailer, for example, and have a high capacity inverter, you need to know that your tow vehicle probably will only send 8-10 amps to the house batteries for a number of technical reasons. So, yes it is charging the house batteries, but not very vigorously.If you are using a large inverter, say a 2000 watt one, it is going to draw a lot more than 8-10 amps just being turned on, let alone powering any load. So, yes, you can easily deplete the house battery while towing, especially if your house battery isn't fully charged to begin with.And indeed, it is also possible that the alternator isn't charging the house batteries, either by design or because there's a problem.

Check the voltage to both batteries, coach and engine. One might not be charging. .. I found this problem while at a air show in San Diego. The drive home should have fully charged my batteries, but it did not. Normally I might expect the battery to be depleted after a long weekend of camping, but this one day trip, I did not expect it to be depleted at all, with the 20 amps of solar keeping it full. On the way home, I did not expect it to be discharged. Anyway it was the time that I discovered that the engine to coach battery relay was bad, and I installed a new one myself.Good luck,Fred.

Sorry:2007 Itaska Horizon 40' DP2000W inverter. Offhand, not sure which kind/company.I do tow a frog, but it is not electrically connected to my coach except to power a set of magnetic brake lights.

Inverter/Alternator Question | Good Sam Community

MrWizard
Moderator
Nov 25, 2014
You have received excellent advice
Either the charge circuit relay has failed
Or
There is way more load on the inverter circuit than you think
If the fridge is set to "auto" instead of L.P.
This will draw a lot of power approx 400 watts about 35 amps dc into the inverter
The fridge ice maker might also be using inverter power
The water heater usually does not, unless it is a while house install
That will be about 1200 watts meaning 100 amps
So your inverter could be using as much as 140 amps. Most Of it from the batteries
YC_1
Nomad
Nov 25, 2014
Ditto Richard and Clay. No guessing with a voltmeter and the Monaco line has a relay this fails often enough that I carry a rebuilt one. Yes, I took it apart and repaired mine.

For some excellent information do a search for BIRD systems on rv's.

You should have no problem running the inverter with the engine running. Do the test Richard describes and you will know in five minutes what is up.
Clay_L
Explorer
Nov 25, 2014
Winnebago uses a continuous duty solenoid that is activated by a wire from the RUN terminal on the ignition switch to connect the alternator output to the house batteries. When the engine is running you should see about 14.4 volts on the house batteries.
The solenoid does not have a good record and it seems to be an item that fails fairly often.
Bikeboy57
Explorer
Nov 25, 2014
Ok, let's stop guessing at the problem. Do you have a digital voltmeter? If not, go get one. No motorhome owner should be without one and the knowledge to use it.

Before you do anything, measure the voltage at your engine batteries and your house batteries. Write it down.

Now, crank the engine, and measure both voltages again.

The engine battery should now be reading somewhere around 13.5 to 13.7, and the house battery should be reading higher voltage than you recorded in step 1.

Do this simple test and report back. We'll go from there.
pianotuna
Nomad III
Nov 25, 2014
Hi,

You should be able to power small loads literally forever if the alternator is charging the house battery bank.

Here are some things to consider:

There is an isolator of some kind between the alternator and the "house" battery bank. The contacts might be burned.

There is a fuse in that circuit before the isolator. It may be blown.

If the alternator does the "whole house" and is after market and does not utilize a transfer switch, it may be powering the "converter" which can deplete the battery bank rather quickly.
Ivylog
Explorer III
Nov 25, 2014
I'd say your alternator is not charging your house batteries and that they are not in very good condition. This ASSUMES that the item mentioned are the only things drawing power from the inverter. The 200amp (2600 watts) alternator on your engine should keep up with your inverter even if you were using the microwave all the time.
Matt_Colie
Explorer II
Nov 25, 2014
Lurker,

Yes, you have a problem with so many variables that it is impossible to answer here. No, you should not be able to deplete the house bank with the main engine running. You should get some knowledgeable person to look at and maybe measure things and point out the problem.

Matt
CT_WANDERER
Explorer
Nov 25, 2014
Is it possible that your reffer is on electric along with water heater? or are they isolated from your inverter?
Tom_N
Explorer
Nov 25, 2014
Do you have your house batteries turned OFF??
wolfe10
Explorer
Nov 25, 2014
What does your dash voltmeter indicate when this occurs.

With that large an inverter it is possible to overload an alternator, even a large one on your DP. I would start looking at what other loads are on that you are not aware of.

With the appliances you mention, there should be no problem. Also check for loose connections at the battery and inverter that could be causing the voltage drop.

If no extra loads and no poor connections, next step would be to stop when this occurs and use a digital voltmeter to check voltage AT THE INVERTER. That will tell you if it is an internal issue in the inverter.

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