New to motorhome..HELP!

[Isaac-1]

If you checked it while plugged into shore power with the power converter running the voltage you saw was the charging voltage, not the current battery state, which needs to be measured when the charger is not connected. In fact you need to wait 15-20 minutes after disconnecting from power to let the surface charge discipate in order to get an accurate battery reading.

 

[Gary RV_Wizard]

If I read all this correctly (it's a bit disjoint), you get 6.05v each with the 6v batteries disconnected but 14.74v for the pair when connected to the charger. The 14.74v proves the charger is producing adequate charge voltage, at least to the point where you measured it. It does not mean the batteries themselves are at 14.74v - only that the charger is pushing hard to bring the charge up. The 6.05v (x2) shows the battery pair is actually low on charge - a fully charged 6v should read 6.3v at rest (no active charging). 6.05v is about 50% charged.

The possible conclusions from those numbers is either (1) corrosion at the point where the battery cables connect to the batteries is prohibiting the full charge power from reaching the batteries, or (2) one or both batteries are weak and unable to come to full charge (6.3v each). A common cause of #2 is either a lack of electrolyte in one or more cells of the batteries or internal damage to the lead plates resulting from repeated ultra-deep discharging (using power until the batteries drop to a combined voltage under 11.9v).

 

[Dtalley]

Can't see your hookups, but if usual clamp on post, would simply stick the probe into the top of the post w/o touching the clamp. The description you have given suggests that the clamp is not making connection to the post!

Ernie

Here is a pic of my batteries ( both new a week ago and fully charged). I unplugged from shore power for 30 minutes took off the cables to isolate each batter and took readings putting probe into the tops of post. 5.66 and 5.69 volts. I’m at a loss as to what is going on here.

 

[ChasA]

Okay, those are indeed 6 volt. If you're measuring between the + and - posts on each battery your meter will read 6.3 volts on each battery if fully charged. Your readings indicate you need to charge them. If you have a charger that will do 6 volt batteries you can charge the separately. But if your charger only does 12 volt you'll need a jumper cable between - on one battery to + on the other battery. Before you start charging remove the plugplugs

 

[ChasA]

Okay, those are indeed 6 volt. If you're measuring between the + and - posts on each battery your meter will read 6.3 volts on each battery if fully charged. Your readings indicate you need to charge them. If you have a charger that will do 6 volt batteries you can charge the separately. But if your charger only does 12 volt you'll need a jumper cable between - on one battery to + on the other battery. Before you start charging remove the plugs and look into the holes . Make sure the plates are covered with electrolyte. If the plates are exposed add distilled water to cover the plates. Do NOT fill the holes. Now charge the batteries for a day.

 

[Dtalley]

ChasA,
Ok I have charged one with my charger ( can do both 12v and 6v) And I have it on the second battery as we speak.
Typically where does the power (DC) from the converter go after it leaves the converter? Since it appears the convertor is putting out over 14 v I wonder where the issue is? I was looking through paperwork from previous owners and they indicated that they thought the batter d/c switch was not working but the dealership claimed it was and closed out the ticket. This, along with the fact that I just replaced the two 6v coach batteries as the previous ones were dead ( coach is only a 2019) makes me suspicious that something hasn’t been working correctly for a while. The pictures below are the compartment right next to the batteries and contains the inverter as well as more wires than I know what to do with?? Any chance something in here is the issue??

 

[Ernie n Tara]

I may be repeating the above, but :
a. Ensure the Converter and batteries are connected properly. It must be a complete series circuit >______+____-___ + ______ _ ___>
Conv pos14V/+12V B1. B 2. -12V/conv neg.14V (prob a ground connection).

b. Measure conv pos 14V to Conv neg.14V --- should be above 13V; if not you have a bad connection between conv and battery. If conv positive to conv+out is 14V, equals bad connection between conv + and batt B1. Else bad connection between conv - out and battery.

C. Measure B1 +12V to B2 -12V. Should be about 13.3V else bad connection post to converter cable.

Ernie

Note: Converter 14V may be anything above about 13V depending on battery charge state and loads.

 

[Gary RV_Wizard]

Typically where does the power (DC) from the converter go after it leaves the converter? Since it appears the convertor is putting out over 14 v I wonder where the issue is?

That's not easy to answer because it depends on the type of converter/charger and how the RV maker engineered the system. Basically the converter/charger has + & - cables that go to the corresponding battery posts, but there may be a battery disconnect relay or switch in between, or a battery charge controller (BCC) device. And in some designs the converter/charger powers a separate 12v bus (fuse panel) in parallel with the batteries, while in others that bus draws its power from the battery terminals. Those two are electrically the same, but the wiring path differs. There are probably some major fuses or breakers in those circuits as well.

None of the photos show the entire 12v charge & bus bar system and I can't trace the path from the converter to the batteries. You will have to do that yourself if the measurements below determine that charger voltage is NOT reaching the batteries.

Do the 12v measurements that Ernie described at the battery posts, once with the converter/charger connected and operating, and again with the converter/charger off (120v power removed), either by unplugging it or flipping the supply breaker off. You should see 13-14v with the charger running and something less when off. Measure the charger-off voltage a couple times, once immediately after turning the charger off and again an hour or two later. The voltage with power off reflects the state of charge of the batteries, though it may be a bit elevated for a couple hours because of residual charge voltage.

 

[ChasA]

I see a battery switch in those pictures. It's the red box on the wall. I can't read the lettering on the switch, but that might be the reason for the converter output not getting to the batteries. It could be set to isolate the batteries.

 

[Gary RV_Wizard]

Yes, I saw that too. And a couple major fuses (100A-300A) and a big 12v breaker as well. But we can't see if they are in-circuit with the converter, which is in a different photo that has none of that stuff in the view. Could be for inverter input, or maybe a chassis disconnect.

There is also a B?M 60 device that I'm not at all familiar with.

 

[Dtalley]

OK so this is really late but I finally solved my issue with my coach batteries not charging from shore power. Apparently these circuit breakers in the compartment where the inverter is located have little tiny (like 3mm square) buttons on the side to reset them if they get tripped!) I would never have seen them nor known what they were if I had not had an RV repair person come out and trouble shoot it. So he suggested getting several automatically resetting 50 amp breakers which I did. Mystery solved.

 

[Gary RV_Wizard]

Thanks for letting us know the solution. And good that it was nothing serious.