Battery charging issue? I think.

[Cowboy0001]

Had a trip that the inverter/charger showed the batteries on charge while on shore power and stayed there for three days until we packed up to go to our next stop. We found out we had to run the generator the whole trip because our batteries were so low. Don’t know why that happened but it taught me a few things. While driving with the generator running, I noticed the alternator was fluxulating on the charge. It would drop below 12V off and on so... I’m wondering if having a second charging system is warranted and if wise to have one what would be a good system? Can anybody share their experience on this subject? Thank you and Merry Christmas

[hamm2018]

Originally Posted by Cowboy0001

Had a trip that the inverter/charger showed the batteries on charge while on shore power and stayed there for three days until we packed up to go to our next stop. We found out we had to run the generator the whole trip because our batteries were so low. Don’t know why that happened but it taught me a few things. While driving with the generator running, I noticed the alternator was fluxulating on the charge. It would drop below 12V off and on so... I’m wondering if having a second charging system is warranted and if wise to have one what would be a good system? Can anybody share their experience on this subject? Thank you and Merry Christmas

We have a toy hauler, 5th wheel, but I am wondering if the batteries that are used for the fridge are good? Do you have 2 sets of batteries, 1 for chassis and 1 for the house?

[deandec]

I suspect your question is about your house battery, not your starting (chassis) battery.

While driving with the generator on, the alternator is charging the chassis battery and possibly the house battery. The generator is charging the house battery and possibly the chassis battery.

The possible charging actions vary from coach to coach with most rigs providing charge to both chassis and house battery from both sources.

So you might get some fluctuation on your dash battery gauge for the chassis battery. We do not.

You do not mention whether the viewed voltage charge fluctuation is at the house battery or chassis battery (two different gauges).

Your gauge might show that the battery in question is being charged, but it does not show the state of charge of the battery.

A full DC battery should show 12.6 dcv when full, not being charged, and after a resting period (to shed the "float charge" following a charging event).

A half full house battery will be at about 12.0 dcv. The battery then should be recharged to 12.6 dcv to give the battery a longer life.

If you have a voltmeter to attach or which is permanently attached to the house battery, you should see about 13.6 dcv being applied to the battery when being charged. If lower, either the charger, battery connections, or the battery could be bad.

Because it appears that your question is about your house battery being low after a three day shore power charging event, I suspect your batteries are at the end of life.

Maybe, if a wet cell battery, you need to top off the battery cells with distilled water?

[okcnewbie]

Most likely your alternator should be charging both sets of batteries.
If the alternator is dropping below 12 volts than you have a problem. Can you use a hand-held DMM and double check the chassis battery with and without the engine running? Should be 12.5 or so without the engine on. Should be 13.5 -15 with the engine on.

[BrianGlenn]

I agree the alternator is starting to fail. The gauge in the dash is the alternator output.

Same thing happened to me and I removed and rebuilt the alternator. Solved the fluctuation issue.

Leece Neville alternator. 2007 Allure

[deandec]

Originally Posted by BrianGlenn

I agree the alternator is starting to fail. The gauge in the dash is the alternator output.

Same thing happened to me and I removed and rebuilt the alternator. Solved the fluctuation issue.

Leece Neville alternator. 2007 Allure

I agree that the above is true. If the battery being low is the chassis battery.

Needing the generator to maintain chassis operation would signify alternator failing.

Start the engine. Do not start the generator. Place the meter leads on each terminal of the chassis battery. You should see about 13.6 dcv as a result if the alternator is working.

[twinboat]

If you have a battery isolator ( diode based ) then don't assume its the alternator just yet.

With diode based isolators, the alternator output goes to the center terminal of the isolator and then out to both chassis and house batteries.

That center terminal is where you should test for 13 to 14 volts, with the engine running.

You also need to confirm that the belt is tight. A slipping belt will effect alternator output.

[Cowboy0001]

Hello Twinboat, I replaced the belt yesterday, the old belt had a lot of cracks in the ribs and I kept it as a spare. The tension pulley seems strong so I suspect the alternator. I’m curious to know that point to check between the alternator and the batteries you suggested, thanks.

[twinboat]

Look for a thing that looks like this, back near the battery control center.

[Ironwood]

Check both banks of batteries with the engine running. Both should show a charge, somewhere around 12.8v or higher. If the start bank is charging but not the house than the battery isolator is likely at fault. If neither bank shows an increase with engine running then probably your alternator is dead.

A voltmeter is your friend. If not familiar with one then start studying how to use one.