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okcnewbie · 12-26-2018, 06:04 AM

You mention that both your chassis and house batteries are 13.2 or 13.3 at rest. It's hard to believe that the resting voltage would be above 13.

I do agree with others to start looking at the ground cables. I guess you could start by using jumper cables to make good temp ground connections.

Good luck.

c_oneil · 12-26-2018, 07:29 AM

Looking at your picture I see that your chassis batteries are on the left side and the two in the middle and rear row. Its two 6V batteries wired in series. Are you sure that setup is capable of providing enough amps for the draw of the engine starter or HWH motor?

paul65k · 12-26-2018, 07:34 AM

Getting ready to go dig back in this morning but here's my last question:

I get the bad ground idea it makes the most sense and I'm gonna start there but.......would this cause the engine to actually stop running when I try to run the HWH system and turn off all the gauges and light up the entire driver info center (like a reset)???.............this sure seems more like a short.....Hmmmm, could be another long day

twinboat · 12-26-2018, 07:52 AM

The engine may be running on marginal power from the alternator. Once you add a high amp draw, the voltage drops off, killing the engine.

The battery is the buffer for that.

paul65k · 12-26-2018, 08:04 AM

Quote:

Originally Posted by twinboat

The engine may be running on marginal power from the alternator. Once you add a high amp draw, the voltage drops off, killing the engine.

The battery is the buffer for that.

Looks like the main Ground line is under the engine....I'll start there with a thorough cleaning, also going to check the connections at the Xantrex just to make sure it hasn't worked loose somehow. I also still have all the old cables (even though smaller gauge wire) that I can re-install one by one......I'm bound and determined to find this thing

I also ordered enough material to remake all the lines again on Friday if I can't track it down today.

Thanks again everyone!

Old Scout · 12-26-2018, 08:05 AM

….off the wall, but did you get the ground cable between the two battery banks replaced when you replace yr bats/re-cabled???? Does sound more like a bad connection vs a short.

c_oneil · 12-26-2018, 08:16 AM

I went back and looked at your previous thread on replacing all your batteries. The specs you showed for amps were:
Cranking Amps @ 32°F 0°C:
1255
Cold Cranking Amps @ 0°F -18°C:
1045
I suspect the two chassis batteries you removed were two 12volts in parallel for about 950+950 = 19000CA.
The two 6v batteries in series are still only 1255CA.
Just for an easy test you might switch the positive cable from 4 house batteries over to the chassis hot buss connection and remove the 2 chassis batteries connection for now. That would give you 1255+1255=2510CA at 12v for the starter and HWH motor.

azpete · 12-26-2018, 08:18 AM

i found this exact problem on a coach that had the batteries replaced.
engine would start and run, but using the hwh system would kill the engine.

the bolt holding the hwh battery cable and the engine cable was on a bolt that had the two cables nutted together, and then went into the battery connector on the engine battery.
it had a loose bolt into the battery. the cables were tight to each other, but not into the battery. hope this was clear enough. anyway, check the battery connections carefully. thats the problem

paul65k · 12-26-2018, 08:19 AM

Quote:

Originally Posted by Old Scout

….off the wall, but did you get the ground cable between the two battery banks replaced when you replace yr bats/re-cabled???? Does sound more like a bad connection vs a short.

It sure does......I did make a new cable from the Shunt to the battery where all the grounds come together, but reused the existing ground to chassis cable on the other side of the shunt. I did yank and crank on it a bit so going to check that cable as well and will have the material to remake it on Friday whether or not I track it down in the mean time.......it's been down there for 18 years so it's probably time anyhow

I've checked and re-checked the connections at the one battery where everything terminates and I'm going to try the old known good cables one by one as well as trying to troubleshoot with jumper cables.

Also going to remove and clean all the connections at both Buss bars and all other cable connections as well as it just makes sense from a maintenance standpoint....gonna figure this damn thing out!

Thanks for taking the time to help

paul65k · 12-26-2018, 08:24 AM

Quote:

Originally Posted by azpete

i found this exact problem on a coach that had the batteries replaced.
engine would start and run, but using the hwh system would kill the engine.

the bolt holding the hwh battery cable and the engine cable was on a bolt that had the two cables nutted together, and then went into the battery connector on the engine battery.
it had a loose bolt into the battery. the cables were tight to each other, but not into the battery. hope this was clear enough. anyway, check the battery connections carefully. thats the problem

Definitely will check that again......I will probably also remove, clean and add some dielectric grease to all those connections as well.........Thanks Pete!

paul65k · 12-26-2018, 08:28 AM

Quote:

Originally Posted by c_oneil

I went back and looked at your previous thread on replacing all your batteries. The specs you showed for amps were:
Cranking Amps @ 32°F 0°C:
1255
Cold Cranking Amps @ 0°F -18°C:
1045
I suspect the two chassis batteries you removed were two 12volts in parallel for about 950+950 = 19000CA.
The two 6v batteries in series are still only 1255CA.
Just for an easy test you might switch the positive cable from 4 house batteries over to the chassis hot buss connection and remove the 2 chassis batteries connection for now. That would give you 1255+1255=2510CA at 12v for the starter and HWH motor.

Makes sense, I'll give this a try but they did crank right over (real strong) when I first installed.......but I wonder why would Cummins only specify 950 CCA if in fact they require 1900 (950 x 2)

Thanks for the idea

paul65k · 12-26-2018, 09:15 AM

Batteries at rest overnight (no charge) this is what I woke up to this morning.

Remember these are very large AGM batteries😉

c_oneil · 12-26-2018, 09:24 AM

I forgot you had that Victron battery monitor installed. It could help diagnose the problem for you. Watch how much the voltage drops and the amperage draw is when you engage the starter and/or the HWH motor. If you have a bad connection somewhere the battery voltage shouldn't drop much and show low amp draw.

RVPioneer · 12-26-2018, 10:27 AM

It is frustrating when something works perfectly one minute and then stops working the next. A loose connection is the most likely culprit. It probably was snug when you first started the engine and has now become loose.

I would expand on Carter's observation of having 2, 6V batteries for starting and chassis functions. My experience is that a 12V starting battery and a 6V deep cycle battery are designed to perform different functions. Sure, either can perform the others task, it just may not be the appropriate application. My 2¢.