Battery not charging (from chassis or generator)

Hi All, new to RVing. Thanks in advance for you help!

I've got a 2006 Four Winds Chateau 31p Class C with a Ford Superduty e450. RV has an Onan 4000 generator. I've got a 12V deep cycle house battery along with two 6V golf cart batteries for a total of ~350 amp hours of house batteries. The two 6V batteries are wired in series to equal 12V and they are then wired in parallel with the 12V battery. The 12V battery is brand new. The two golf cart batteries are 2 years old.

I'm having an issue with the house batteries not charging. I have a battery reading in the RV which isn't too accurate (it just shows 12V / 11V / 10V). Right now it is showing 11V. I thought it would be better to use a volt meter to be more certain.

I put a volt meter on the house batteries and they currently read 11.75V with nothing on (the generator is off and the chassis engine is off). If I disconnect the battery and measure the battery itself it reads 11.75V. The chassis/engine battery is at 12.29V (with everything off).

When I start the chassis engine I would expect the alternator to kick in and charge both the chassis battery and the house batteries. When I turn on the chassis engine I read the chassis battery and it shows 14.34V (which seems good and what I would expect...the alternator seems to be working). When I check the house batteries (with just the chassis engine running) I would expect to see them charging. But I don't...they remain at 11.75V. I measured the house battery terminals while connected to the battery (11.75V). As a test, in case maybe the house batteries are dead/etc, while the chassis engine is running I disconnected the house batteries and put a volt meter on the wires that would be connected to the batteries and the voltage on them was also 11.75V. That seems to tell me that the chassis alternator is not charging the house batteries.
Question: Shouldn't the chassis engine being charging the coach batteries? Are there any fuses/etc I should be measuring to pinpoint what the problem might be?

I turned off the chassis engine. The next thing I did was turn on the generator to see if it would charge the house batteries. With the generator running I measured the voltage across the house batteries, expecting to see them charging. The voltage was 11.71V. Ugh! With the generator running I measured the voltage of the chassis battery and it reads 12.73V. I tried running the generator with the 12V battery disconnected with only the 6V batteries (same result). I tried running the generator with the two 6V batteries disconnected and only the 12V house battery (same result).
Question: What voltage should I see across the house battery when the generator is running? Is it common for the generator to also charge the chassis battery?

Are there any fuses I should be checking?

What should I check next? Any ideas?

Thanks!

Sam_Spade
Explorer
Jan 16, 2018
SJ-Chris wrote:

Question: If I'm plugged into shore power (or running the generator) and I don't have any real load using power in the RV(ie plugged in at night), does anyone know how much of the 75amp capacity of the converter is getting pumped into my battery bank? I'm trying to get a sense for how long it might take to fully charge my 315AH battery bank if let's say it was drained to about 50%. Any thoughts?

Thanks all!

You need to specify the make and model of converter/charger that you have.

BUT.....if they are 50% discharged, reading about 12.0 volts no load, AND you are only 13.5 volts from the converter.....then it might take a LONG time to recharge. That's closer to float voltage than to bulk charging voltage, which would be above 14 a bit with a good converter that is working properly.

Even knowing the model of converter, it will be hard to answer your question. Some might give you a good estimate but a test run or two will be the best gauge.
SJ-Chris
Explorer II
Jan 16, 2018
I wanted to post an update...

After installing my 3 new 12v deep cycle house batteries I was able to determine that the solenoid from the chassis (alternator) was bad. Once I replaced that it seemed to fix that issue. Now when the chassis engine is running after about 20 seconds the solenoid kicks on (I can hear the 'click') and my house batteries get charged with a nice ~14volts from the chassis alternator. Problem #1 solved.
Question: Assuming I have the standard 95amp alternator in my Ford e450, does anyone know approximately how many amps are getting pumped into my batteries when I'm driving down the highway? I'm trying to get a sense for how long it might take to fully charge my 315AH battery bank if let's say it was drained to about 50%. Any thoughts?

Next, I had an RV shop test my converter. The max voltage it was putting out was only about 12.55v. This seemed much too low to provide a charge to the house batteries (...I would expect 13.5v or higher when charging). So I bit the bullet and bought a new converter (upgraded to 75amps from 45amps while I was at it). Now when I'm connected to shore power or running the generator I do see a ~13.5v charge being delivered to my house batteries. Problem #2 solved.
Question: If I'm plugged into shore power (or running the generator) and I don't have any real load using power in the RV(ie plugged in at night), does anyone know how much of the 75amp capacity of the converter is getting pumped into my battery bank? I'm trying to get a sense for how long it might take to fully charge my 315AH battery bank if let's say it was drained to about 50%. Any thoughts?

Thanks all!
westend
Explorer
Sep 28, 2017
Tip: When one of your engines are operating and batteries need a charge, you should see +13.6 V at the batteries. 6V GC2 golf cart batteries love + 14.6 V for charging but you will need to monitor electrolyte levels.

It may take awhile for a battery isolator to pass charging current from engine alternator to house batteries. The engine alternator needs to charge chassis battery after a cold start. Not knowing what exactly you have for hardware limits technical advice.

I may have missed this but you are using an adequate handheld meter for diagnosing all this?
MrWizard
Moderator
Sep 28, 2017
your shore power plug TO generator plug
is
the manual transfer switch AKA you
its one or the other, NO accidental connection to both, no automatic switch to go bad

Yes your converter seems to be working, and it charges exactly the same, whether its shore power or the generator

that outlet in the cord bay IS NOT 'inverter' it is the Generator power output

congrats on the new batteries and the problem solving
toedtoes
Explorer III
Sep 28, 2017
It should charge the same from either source as it's the charger that determines the rate.

What gauge wire is going from the house to the alternator? If smaller than 10 gauge, I would recommend re-wiring it. Then you can set it up so you can jumpstart the engine from the house batteries. It's easy to do and you can add breakers at either end. Biggest cost is the battery cable (you want 8 or 10 gauge). I did mine for under $100 total.

If the wire is already 10 or 8 gauge wire, then it would be cheap and easy to add the jumpstart capability.

Relays are cheap, you might want to try just replacing it. If it doesn't make a difference, return it.
SJ-Chris
Explorer II
Sep 28, 2017
Update: Okay...I'm learning.

I did find out a few things and the picture is starting to get a little clearer. Thanks all those for your help/suggestions.

I did learn that at least one of the 6V batteries was bad. I've decided to ditch the two 6V batteries that were wired in parallel with my 12V house battery. I will instead use three 12V brand new deep cycle batteries to start fresh and have them all matching (same capacity, same age). Will give me ~315ah which seems okay for the time being.

I had my RV plugged into shore power (at my house). Running the AC, etc all just fine. Then I put it back at the storage site yesterday. I was working on a few things on it today at the storage site and I turned on the generator. When I did, I noticed that I didn't have 110v outlet power and my appliances and roof AC weren't working. After much thought and investigation, I remembered that I had been plugged into shore power and I never plugged the 30amp line back into the plug (inverter?) in the electrical compartment. Once I did, I had 110v power and the appliances worked. Then I thought to check my house battery to see if it was charging and low and behold it was charging (as it should be!). So now it looks like my generator will in fact be charging the house batteries as it should be. It is possible that previously with the bad battery it was causing the low voltage readout making me think that the generator wasn't doing its job (...or perhaps I never had the 30amp line plugged in as it should be).

Question: If I am running the generator or if I am plugged in to shore power, is the battery charging exactly the same? Same rate and charging amperage? As I'm learning, it seems to me that regardless of whether the generator is running or the shore power is hooked up I *think* it's the same internal battery charger charging the house batteries, right? Let me know

I am still not seeing a charge on the house batteries when I am running the chassis engine. I traced the wires coming off the chassis battery and I think I can see a relay/isolator buried behind some items in the engine compartment. I think I'm going to leave this up to a mechanic (...unless someone can suggest an easy way to test/replace this component).

Thanks!
MEXICOWANDERER
Explorer
Sep 26, 2017
Car jar deep cycle 2.75% antimony. GC220 battery 5% antimony.

Hatfield's and McCoy's living in the Duplex. Either one type or the other or batteries get "eaten alive".

If 3-cell batteries failed to charge on a charger (?) it may be due to a Not-So-Smart charger being unable to count past "1" Try it with a different charger then start dipping cells with a hydrometer.

When the batteries are recharged, test again. May be just a battery failure.
jkwilson
Explorer III
Sep 26, 2017
Nothing you describe says your 12V battery was bad. It probably just needed charging, but having it paralleled with the bad 6V string prevented that from happening.

What kind of battery bank you need is a pretty individual thing. If you have a generator available for daily charging, you might be able to get by with less, but it depends on what you want to run and how much you want to run it between charges.
Sam_Spade
Explorer
Sep 26, 2017
SJ-Chris wrote:

I've been reading up online about having different battery capacities and whether that is okay or bad. The system I acquired has a 12v 105ah connected in parallel to two 6Vs which are probably ~220ah. Is that inherently a problem?

YES. And you have a prime example of why.

Good 6 volts in series usually have more total capacity than an equal number of 12 V is parallel.

IF.....you don't really need a huge amount of capacity, I suggest you convert to two of the largest 6 V deep cycles that you can find and be done with it. If that is not enough capacity, 4 6's in series parallel would be easier to deal with than the mess that you are starting out with.

It looks like 3 of 4 of your existing batteries are shot.
NO WAY should you try to duplicate that ill-advised lash up with new batteries.
toedtoes
Explorer III
Sep 26, 2017
I would go all new of one type.

I have an optima blue top group 31 agm battery. I can go 5 days without putting a dent in it. I don't have a generator or solar - I run my water pump the entire time, use overhead fluorescent lights as needed. I charge my cell phone and kindle as needed. I don't have a microwave, tv, etc.

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Battery not charging (from chassis or generator)

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