How did the coach turn over with no batteries connected

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How did the coach turn over with no batteries connected

February 20, 2023, 08:12:09 pm

A couple of weeks ago I disconnected the house and engine batteries to charge and desulfate them. Turns out both of my house batteries are weak/bad, that's for another topic. Anyway, today I had to fix an air leak underneath and wanted to check it after said fix. I went to crank the coach and it turned over but was slow and I thought the batteries were dead again. Well, turns out I never reconnected the coach or engine batteries. The coach was plugged into my house 50A plug.

This made me wonder, how was I able to turn it over? Any residual power in the starter/alternator would have surely been gone in the 1.5-2 weeks.

Re: How did the coach turn over with no batteries connected

Reply #1 – February 20, 2023, 08:25:16 pm

I hope you are not like the last member that had a similar issue that never came back with the solution. Whether you know it or not you have some connection putting power either in or out of the batteries. There is no other way to have power to the engine. Capacitors etc. would never hold that kind of power.

Re: How did the coach turn over with no batteries connected

Reply #2 – February 20, 2023, 08:30:37 pm

I don't think your inverter charger has enough power to turn your engine over and the only thing I
can think of is you did not disconnected all your starter batteries.

Re: How did the coach turn over with no batteries connected

Reply #3 – February 20, 2023, 08:36:40 pm

Also ........ there is no residual power in the starter or alternator.

Re: How did the coach turn over with no batteries connected

Reply #4 – February 20, 2023, 08:57:23 pm

Right? It just doesn't make sense! I have 2 house and 2 engine batteries, all were disconnected, 100% positive because I had to hook them up.

I do have one of these that the PO installed, never messed with it so I hopefully it's doing something
Digital Voltage Sensing Relay (DVSR) 12/24V

Otherwise I am at a loss. Unless there is a hidden battery bank that I am not aware of!

Re: How did the coach turn over with no batteries connected

Reply #5 – February 20, 2023, 09:11:25 pm

I will darn sure be following this one because this one takes the cake.

Re: How did the coach turn over with no batteries connected

Reply #6 – February 20, 2023, 09:12:57 pm

If no battery was connected and you are sure of that............. then it had to be the output of the inverter/charger as you stated that it was plugged into shore power.

Re: How did the coach turn over with no batteries connected

Reply #7 – February 20, 2023, 09:24:54 pm

Quote from: Jason – February 20, 2023, 08:57:23 pm

I do have one of these that the PO installed, never messed with it so I hopefully it's doing something
Digital Voltage Sensing Relay (DVSR) 12/24V

Nope.

I agree with Justin, if you really had all of the batteries disconnected then the boost switch had to have been activated in order for power to get to the starter or possible bad battery isolator from the house 12v side.
How long have you owned this coach?
Do you have one of the newer gear drive starters?
What wires did you remove from the batteries?
Got a picture of your battery wiring and setup?
The U295 comes with 3 house batteries.

It could be as I believe Elliot said in the other thread about power in coach was he had a bad flux capacitor.
http://www.oreillyauto.com/flux-capacitor

Re: How did the coach turn over with no batteries connected

Reply #8 – February 20, 2023, 10:10:32 pm

Quote from: Jason – February 20, 2023, 08:12:09 pm

I went to crank the coach and it turned over but was slow and I thought the batteries were dead again. Well, turns out I never reconnected the coach or engine batteries.

Quote from: FourTravelers – February 20, 2023, 09:12:57 pm

If no battery was connected and you are sure of that............. then it had to be the output of the inverter/charger as you stated that it was plugged into shore power.

AFAIK the inverter DC power/charging cable connects directly to the house batteries. If all batteries were disconnected, there would be no way for the inverter to power the starter. At least none that I can imagine...

Re: How did the coach turn over with no batteries connected

Reply #9 – February 20, 2023, 10:43:58 pm

Quote from: turbojack – February 20, 2023, 09:24:54 pm

Nope.

I agree with Justin, if you really had all of the batteries disconnected then the boost switch had to have been activated in order for power to get to the starter or possible bad battery isolator from the house 12v side.
How long have you owned this coach?
Do you have one of the newer gear drive starters?
What wires did you remove from the batteries?
Got a picture of your battery wiring and setup?
The U295 comes with 3 house batteries.

It could be as I believe Elliot said in the other thread about power in coach was he had a bad flux capacitor.
http://www.oreillyauto.com/flux-capacitor

Appreciate all the replies. The 50A input inverter/charger is the only thing I can come up with as well. But I don't know the systems in/out like some of you, so wanted to get any insight b/c it just doesn't compute. I know it sounds crazy, but it happened. Maybe one of you can try it? It would be great to know if someone can replicate it.

To answer you questions though,
- I have had it 1.5 years.
- Yes, in Aug I installed a 39MT Remy Delco gear reduction starter. Works great.
- Disconnected + and - cables, one set per battery, 4 batteries total
- Correct, long thread on it here Prosine Temp Error, Battery is hot In short, I removed the bad one and with Brett's advice, wrapped up the 3rd battery terminals. There is a pic of the house batteries Prosine Temp Error, Battery is hot.

That is pretty funny, kudos for them to have it listed.

Re: How did the coach turn over with no batteries connected

Reply #10 – February 20, 2023, 10:48:58 pm

Quote from: Jason – February 20, 2023, 08:57:23 pm

Right? It just doesn't make sense! I have 2 house and 2 engine batteries, all were disconnected, 100% positive because I had to hook them up.

How did you disconnect the 2 battery banks and do you have solar?

Re: How did the coach turn over with no batteries connected

Reply #11 – February 20, 2023, 10:59:48 pm

Gear starter does not need as many amps as a regular straight starter.
Charger can put out 100 amps.
Guessing that the relay you described above is used in place of boost solenoid and had both house 12v and coach 12v tied together.

It's possible

Might check and make sure your charger is still working.

Re: How did the coach turn over with no batteries connected

Reply #12 – February 20, 2023, 11:04:48 pm

Quote from: Michelle – February 20, 2023, 10:48:58 pm

How did you disconnect the 2 battery banks and do you have solar?

No solar (yet). I used a 13mm wrench and removed the terminals from the posts. I laid them down or hang without touching each other.

I looked in the manual and it says that the 120V charges the house batteries but not the engine batteries, and to charge them weekly. That confirmed to me that the systems were separate.

Oh, wrt the boost switch, mine does not work, I need to troubleshoot it. I bought it like this, it was one of the items Keith put on the PPI report.

Re: How did the coach turn over with no batteries connected

Reply #13 – February 20, 2023, 11:08:13 pm

Quote from: turbojack – February 20, 2023, 10:59:48 pm

Gear starter does not need as many amps as a regular straight starter.
Charger can put out 100 amps.
Guessing that the relay you described above is used in place of boost solenoid and had both house 12v and coach 12v tied together.

It's possible

Might check and make sure your charger is still working.

Interesting! I am not familiar with the BEP I linked above, but have you heard anyone purposely disengaging the Boost button in lieu of another product? I will take a pic of my engine bay tomorrow where it is and how it is connected, perhaps someone can tell me what it's doing with certainty.

Re: How did the coach turn over with no batteries connected

Reply #14 – February 21, 2023, 12:13:30 am

Quote from: Jason – February 20, 2023, 08:12:09 pm

A couple of weeks ago I disconnected the house and engine batteries to charge and desulfate them. Turns out both of my house batteries are weak/bad, that's for another topic. Anyway, today I had to fix an air leak underneath and wanted to check it after said fix. I went to crank the coach and it turned over but was slow and I thought the batteries were dead again. Well, turns out I never reconnected the coach or engine batteries. The coach was plugged into my house 50A plug.

This made me wonder, how was I able to turn it over? Any residual power in the starter/alternator would have surely been gone in the 1.5-2 weeks.

Disconnecting parallel batteries can have unusual insults.

If you have two batteries wired in parallel and the coach is connected to the terminals of one battery, the other battery can be disconnected; the coach will have 12v power.
If you connect the coach to the pos terminal of one battery and the neg terminal to the other battery disconnecting either battery will disconnect the coach from 12v power.

Tim

Re: How did the coach turn over with no batteries connected

Reply #15 – February 21, 2023, 09:48:09 am

Here are the pics. Looks like 2 cables going to the isolator. I don't know what all of the soleonids do on the wall, but can someone confirm everything is OEM except the BEP?

Re: How did the coach turn over with no batteries connected

Reply #16 – February 21, 2023, 10:29:13 am

Best thing you could have done is take all cables/wires off all batteries,if so there is no way starter got power,by the way,looks
like those cables on the isolator could use a cleaning.

Re: How did the coach turn over with no batteries connected

Reply #17 – February 21, 2023, 10:46:45 am

I looked at at least one coach that had a battery boxed in. You could not see it without removing a panel in an adjacent compartment.

Re: How did the coach turn over with no batteries connected

Reply #18 – February 21, 2023, 11:10:00 am

When the BEP was put in why was the diode isolator left in as now you have two isolators. I just
put in the Blue Sea System in my coach which does the same thing. One of the advantages to that
type of system is that your start batteries are charged when the house batteries are being charged.

Re: How did the coach turn over with no batteries connected

Reply #19 – February 21, 2023, 12:43:24 pm

Quote from: oldguy – February 21, 2023, 11:10:00 am

When the BEP was put in why was the diode isolator left in as now you have two isolators...

I'm thinking the BEP was added to charge the chassis battery when on shore power, like a Trik-L-Start.

Re: How did the coach turn over with no batteries connected

Reply #20 – February 24, 2023, 10:13:52 am

Our U295 also had a BEP DVSR when we got it. I had noticed that the red light was always on, even when the RV was not plugged in. After sitting for a few days, the engine batteries were low and after a little testing, I found that the BEP had apparently failed and wasn't doing anything other than showing the red light.

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