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Old 09-20-2020, 01:01 PM   #1
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Low Voltage from a fully charged house battery

I have a problem with my 12 volt electrical system when running on the house battery alone. The lights dim , the awning will not extend and the generator cannot be started, all symptoms of low house battery voltage.

All 12 volt systems work when connected to shore power, or with the generator running. With the Ford engine running, the lights, frig etc work.

I had the house battery load tested checked out ok. Still thinking it was the battery, I had a new one installed and the problem was still there.

The three stage converter is working as it should with up to 14.45 volts measured at the battery.

Looking for help. Cant understand why the 12 volts system will not work with a fully charged house battery.

Here is the electrical schematic drawing for the 30X, hoping it may be helpful.
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File Type: pdf Electrical Schematic for 30X Grey Hawk.pdf (482.5 KB, 33 views)
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Old 09-20-2020, 01:11 PM   #2
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Hmmm, since you're getting some power, but not enough to power up those items, first place I would check is the ground connection of the battery to the frame. Make sure it's clean, attached well, and not corroded.

I'm assuming that the battery connections are clean, since it's a new battery. Could also be the positive connections at the relay in the battery compartment or when the positive connects at the converter could be loose/corroded.

What voltage due you get at the battery after it's been sitting awhile (over 1/2 hour), not hooked to shore power or running the engine or genny?
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Old 09-20-2020, 01:51 PM   #3
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There is usually a fuse or breaker near the battery. It may work but it may also have corrosion that is cutting the power flow down. Take a look. Also, are the battery cable ends corroded where the wire is crimped to the ring connector?
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Old 09-20-2020, 02:50 PM   #4
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This sounds like a resistance of some sort in the system. It doesn't take much of a resistance for a high current device to drop dead when running. Troubleshooting is actually not that difficult (of course that is said through the eyes of an experienced electronic field tech).

Here is an example of something I encountered in my 2017 Greyhawk. I have a constant display of my battery and never let it get critical. Overnight my fridge will go into a low voltage error even though my battery was showing above 12.2 volts. The fridge was not suppose to go into this error until the voltage was in the low 11s.

Simple test was to measure the voltage at the fridge. When it was turned off I was getting basically the same reading as my battery gauge. But when I turned it on, the reading dropped to about a full volt less than battery. According to the Jayco wiring diagram for my unit, the fridge was fed power using 16 gauge wire. There is no way I should have been losing a full volt with the length of wire going to the fridge. It was not pulling enough current to drop that much voltage across a wire.

Looking at Jayco's method of wiring I found they like to use Scotch Lok connectors. I am guessing they spliced the wire run and that was causing my voltage drop. My fix was simple - I just piggy backed 2 new wires to the fridge right across the old wires. The 12 volt positive was tied in at the fuse panel and the ground was tied in at the chassis ground connection.

Problem solved, no more voltage drop and error condition. Now, in your case you are probably fighting the same type of problem but probably not due to a spliced cable. Since it is affecting multiple items, the common denominator is the main feed to the distribution panel. This can also include the chassis ground connection as that is also part of the power feed.

What you need to do is take some voltage readings at various points to see when the voltage drop is occurring. With the rig running completely off the battery only, measure right across the battery. Now try one of your devices that won't work under battery. The voltage at the battery should remain mostly stable (may drop a few tenths depending on how big the load is). If it drops dramatically your battery is bad or the connections to it are crap. Take the same reading at your fuse panel and see if it drops a few volts under load. If there is a resistance in the line the voltage will drop under load. The more the resistance, the more voltage you will lose and the worse your devices will operate.

Assuming the voltage is dropping by the time it reaches the fuse panel, you now have to look at things inline with the power feed. The first thing I would do is remove the chassis ground connector and sand/grind/file or whatever it takes to get a clean bare metal connection. No paint or crud between the connector and chassis ground, period.

With the ground being good you can focus on the positive feed to the panel. Assuming it goes though a fuse or breaker plus possibly a disconnect relay, you now take voltage readings at these items. You can measure it in one of 2 ways - from the connection to ground or right across the item. With a fuse or breaker if you measure across the connections you should measure zero volts meaning you are not losing voltage across it. If you measure anything, there is resistance and you need to replace it. If you measure from the connection to ground, you first measure from one connector to ground and then the other. Both readings should be near battery battery voltage you measured previously. If one side reads good but the other does not, you have resistance so just replace it.

Same test holds for the battery disconnect relay. There should be no voltage drop across the heavy lugs.

Remember, you need to be pulling a load with these measurements. If there is no current draw you will likely show full battery voltage everywhere. When current is being drawn that is when you will start losing voltage.

Hope this makes sense.
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Old 09-20-2020, 04:03 PM   #5
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Quote:
Originally Posted by DLB View Post
I have a problem with my 12 volt electrical system when running on the house battery alone. The lights dim , the awning will not extend and the generator cannot be started, all symptoms of low house battery voltage.

All 12 volt systems work when connected to shore power, or with the generator running. With the Ford engine running, the lights, frig etc work.

I had the house battery load tested checked out ok. Still thinking it was the battery, I had a new one installed and the problem was still there.

The three stage converter is working as it should with up to 14.45 volts measured at the battery.

Looking for help. Cant understand why the 12 volts system will not work with a fully charged house battery.

Here is the electrical schematic drawing for the 30X, hoping it may be helpful.
Trun ON your Battery Disconnect. (Salesman switch)
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Old 09-20-2020, 06:42 PM   #6
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Hmmm, since you're getting some power, but not enough to power up those items, first place I would check is the ground connection of the battery to the frame. Make sure it's clean, attached well, and not corroded.

I'm assuming that the battery connections are clean, since it's a new battery. Could also be the positive connections at the relay in the battery compartment or when the positive connects at the converter could be loose/corroded.

What voltage due you get at the battery after it's been sitting awhile (over 1/2 hour), not hooked to shore power or running the engine or genny?
thanks Retiredone. I will check battery voltage after 1/2 hour without shore power tomorrow.
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Old 09-20-2020, 06:44 PM   #7
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Originally Posted by Cavie View Post
Trun ON your Battery Disconnect. (Salesman switch)
Cavie Battery Disconnect is turned on ie disconnect is closed.
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Old 09-20-2020, 06:46 PM   #8
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This sounds like a resistance of some sort in the system. It doesn't take much of a resistance for a high current device to drop dead when running. Troubleshooting is actually not that difficult (of course that is said through the eyes of an experienced electronic field tech).

Here is an example of something I encountered in my 2017 Greyhawk. I have a constant display of my battery and never let it get critical. Overnight my fridge will go into a low voltage error even though my battery was showing above 12.2 volts. The fridge was not suppose to go into this error until the voltage was in the low 11s.

Simple test was to measure the voltage at the fridge. When it was turned off I was getting basically the same reading as my battery gauge. But when I turned it on, the reading dropped to about a full volt less than battery. According to the Jayco wiring diagram for my unit, the fridge was fed power using 16 gauge wire. There is no way I should have been losing a full volt with the length of wire going to the fridge. It was not pulling enough current to drop that much voltage across a wire.

Looking at Jayco's method of wiring I found they like to use Scotch Lok connectors. I am guessing they spliced the wire run and that was causing my voltage drop. My fix was simple - I just piggy backed 2 new wires to the fridge right across the old wires. The 12 volt positive was tied in at the fuse panel and the ground was tied in at the chassis ground connection.

Problem solved, no more voltage drop and error condition. Now, in your case you are probably fighting the same type of problem but probably not due to a spliced cable. Since it is affecting multiple items, the common denominator is the main feed to the distribution panel. This can also include the chassis ground connection as that is also part of the power feed.

What you need to do is take some voltage readings at various points to see when the voltage drop is occurring. With the rig running completely off the battery only, measure right across the battery. Now try one of your devices that won't work under battery. The voltage at the battery should remain mostly stable (may drop a few tenths depending on how big the load is). If it drops dramatically your battery is bad or the connections to it are crap. Take the same reading at your fuse panel and see if it drops a few volts under load. If there is a resistance in the line the voltage will drop under load. The more the resistance, the more voltage you will lose and the worse your devices will operate.

Assuming the voltage is dropping by the time it reaches the fuse panel, you now have to look at things inline with the power feed. The first thing I would do is remove the chassis ground connector and sand/grind/file or whatever it takes to get a clean bare metal connection. No paint or crud between the connector and chassis ground, period.

With the ground being good you can focus on the positive feed to the panel. Assuming it goes though a fuse or breaker plus possibly a disconnect relay, you now take voltage readings at these items. You can measure it in one of 2 ways - from the connection to ground or right across the item. With a fuse or breaker if you measure across the connections you should measure zero volts meaning you are not losing voltage across it. If you measure anything, there is resistance and you need to replace it. If you measure from the connection to ground, you first measure from one connector to ground and then the other. Both readings should be near battery battery voltage you measured previously. If one side reads good but the other does not, you have resistance so just replace it.

Same test holds for the battery disconnect relay. There should be no voltage drop across the heavy lugs.

Remember, you need to be pulling a load with these measurements. If there is no current draw you will likely show full battery voltage everywhere. When current is being drawn that is when you will start losing voltage.

Hope this makes sense.
JinD. I will try your suggestions tomorrow and feed back to this forum what I find.
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Old 09-22-2020, 09:07 AM   #9
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Thanks everyone for the help. Yesterday , I went on a hunt for the electrical problem following the guidance I got form this forum and in particular Jim.
First, with the battery supping power, I put on the interior lights and fan. The voltage at the battery was 12.46 and at the 12 volt distribution panel, 11.3 after 10 minutes of load.

Next step was to check the battery ground connection to the frame. It looked ok from the exterior. I had previously covered all frame ground connection with dielectric grease to minimize corrosion. However when I placed my socket wrench on the bolt , it fell off the frame. The self tapping bolt sheared level with the frame. I reattached the ground to the frame at a new location after removing the paint and cleaning up the ground connections. This seems have have solve my issue. I tried running the awning with all the lights and fans on, and all worked.

To be sure all the frame ground connections were good, I remove the other two frame ground clusters, cleaned up any rust and corrosion from the frame and the copper connectors.


I am going back out to the motor home today and check the voltage across anything in the power feeds, breaker , isolator etc to make sure there is nothing else lurking under there that could bite me this winter
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Old 09-22-2020, 10:18 AM   #10
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Thanks everyone for the help. Yesterday , I went on a hunt for the electrical problem following the guidance I got form this forum and in particular Jim.
First, with the battery supping power, I put on the interior lights and fan. The voltage at the battery was 12.46 and at the 12 volt distribution panel, 11.3 after 10 minutes of load.
That's sounding like a weak or bad battery. Fully charged it should be over 12.6. After running some lights and a fan for 10 minutes, it shouldn't drop into the low 11's. Maybe low 12s at most.

You said it was a "new" battery. New to you, or brand new? It might have issues too? How many times has it been discharged into the low 11's, that can damage it?

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Old 09-25-2020, 08:32 AM   #11
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Update on my investigation.
The battery in use now, is the original battery, a Harris Deep Cycle 27DC170 which was supplied by Jayco when I got the unit new in 2018. When I had the chassis in for service, the garage installed a new battery to see if it would correct the electrical problem. It did not help so they re-installed the original battery.

The voltage as measured at the battery remains at 12.48 volt after 45 minute run of fans and lights, however the voltage, measured at the 12 volt distribution panel is 11.3. volts.

I tried running the furnace along with the lights etc to increase the load on the system and found that the lights dimmed , the furnace fan seemed to run slower. The voltage measured at the battery was 12.4 and was only 10 volts at the 12 volt distribution panel. All test were done without shore power connected, battery only.

I am not sure if the battery should be replaced.

There must be a high resistance connection in the system. I have taken the grounds off, battery and the two others ground clusters (except the generator), cleaned up the contact surfaces, installed dielectric grease to improve electrical contact. The battery cable connection are clean and in good shape. I am pretty sure that there is not high resistant connection on the ground side of the circuit.

I have not yet checked voltages across the inline auto reset breaker, battery disconnect solenoid, in the power or positive side of the circuit. Had to order alligator clips for my multimeter to check these. Hope to do this Saturday.

I have booked a service appointment at a local RV repair centre on Oct 6, in case I cannot solve the issue. We are heading out on Oct 12 to Vancouver Island BC for the winter, so I am hoping this gets resolved before we leave.
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Old 09-25-2020, 09:07 AM   #12
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Thanks everyone for the help. Yesterday , I went on a hunt for the electrical problem following the guidance I got form this forum and in particular Jim.
First, with the battery supping power, I put on the interior lights and fan. The voltage at the battery was 12.46 and at the 12 volt distribution panel, 11.3 after 10 minutes of load.

Next step was to check the battery ground connection to the frame. It looked ok from the exterior. I had previously covered all frame ground connection with dielectric grease to minimize corrosion. However when I placed my socket wrench on the bolt , it fell off the frame. The self tapping bolt sheared level with the frame. I reattached the ground to the frame at a new location after removing the paint and cleaning up the ground connections. This seems have have solve my issue. I tried running the awning with all the lights and fans on, and all worked.

To be sure all the frame ground connections were good, I remove the other two frame ground clusters, cleaned up any rust and corrosion from the frame and the copper connectors.



I am going back out to the motor home today and check the voltage across anything in the power feeds, breaker , isolator etc to make sure there is nothing else lurking under there that could bite me this winter


12.6 is chassis battery voltage. 11.3 is house battery voltage. 2 different batteries. 2 different systems. Work on 1 at time.
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Old 09-25-2020, 09:31 AM   #13
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12.6 is chassis battery voltage. 11.3 is house battery voltage. 2 different batteries. 2 different systems. Work on 1 at time.
He's measuring house battery voltage, go back and re-read his description.
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Old 09-25-2020, 07:35 PM   #14
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Looks like you are making some progress. At this time don't worry about replacing the battery as your main problem is a resistance somewhere in the power feed. If the battery can maintain mid 12s, it will be good enough for your testing. After you fix the voltage drop problem, then you can see if the battery has the capacity you need.

OK, the 12 volt power system basically consists of 2 lines. One line will be the positive cable from the battery to the power distribution box and the other will be the negative line which will be chassis ground.

The ground system will be the cable from the battery being bolted to the chassis. The other half of this line will be how all 12 volt accessories are connected to the chassis. They may all be routed to a common ground point on the chassis. Since you already repaired the battery ground connection, look at wherever the other grounds are connected to. I saw under my rig a common tie block that connected to the chassis and a number of ground wires were screwed to terminals on this block. Since many of your accessories are affected I would look at the connection to the chassis rather than individual screw connections.

The positive feed will probably go through a fuse or circuit breaker, maybe a disconnect switch, and maybe a junction block. No idea what they actually have inline. Any of these things can cause a resistance but they all should offer no resistance. You will have to trace the feed and measure across each inline item and see if there is a voltage drop across any of them. There should be no real measurable voltage across any of them or at most just a few milivolts.

You can also measure from each item to ground and see if the voltage is the same as the battery or drops noticeably. All of these measurements MUST be done with some 12 volt item pulling current as there will be no voltage drop if no current is flowing. Bath fan, lights, whatever. The more current draw the easier it may be to find the offending resistance.

All of this assumes Jayco used a heavy gauge cable from the battery to the junction box. I doubt if they undersized it.

Please let us know of your progress. It may help others who encounter the same problem.
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Old 09-25-2020, 09:29 PM   #15
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The voltage as measured at the battery remains at 12.48 volt after 45 minute run of fans and lights, however the voltage, measured at the 12 volt distribution panel is 11.3. volts.

I tried running the furnace along with the lights etc to increase the load on the system and found that the lights dimmed , the furnace fan seemed to run slower. The voltage measured at the battery was 12.4 and was only 10 volts at the 12 volt distribution panel. All test were done without shore power connected, battery only.

Distribution Panel means the converter, I'm assuming.


12.5 on a rested battery doesn't bother me. Strikes me as "good enough".

I'm not sure what counts as "fans" but if I run my LED lights and Fantastic Fan for 45 mins, I'd be at 12.3 or 12.2 on the battery.


So I agree with your approach too. Something's gone kaflooie.


I've read it's not uncommon for those wire connectors at the converter to come loose. You might want to tug and tighten every doggone wire connection you see.
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Old 09-26-2020, 10:24 AM   #16
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DLB dielectric grease does NOT improve electrical connection as it is actually an insulator.
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Old 09-26-2020, 12:18 PM   #17
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dynarider, thanks for your comment.

I thought that dielectric grease would conduct electricity. I just looked up on the web and found this.

[QUOTEDielectric grease, or tune-up grease, is a silicone-based grease that repels moisture and protects electrical connections against corrosion. It is also used to keep dirt, water, and other elements out of electrical connections. It has many uses, including automotive tune-ups, home electrical work, and recreational vehicle wiring. Dielectric grease does not dissolve in most liquids, so it is good for marine and outdoor applications. You can use this grease to lubricate the rubber parts of electrical connectors, spark plug wires, and to protect electrical connections on your boat or recreational vehicle from corrosion. Since dielectric grease is a silicone grease, it should not be used on silicone-based rubbers or plastics, as it will break them down over time. The grease does not conduct electricity, so it shouldn’t be applied directly to the mating surfaces (pins and sockets) of an electrical connection./QUOTE]

I have been coating the bolts, the connectors and the bare metal frame with this stuff on all my ground connections. Perhaps I am causing my problem....
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Old 09-26-2020, 12:45 PM   #18
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Interesting find!!


Do a little wiping and see if the voltage increases!
Good luck!
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Old 09-26-2020, 12:58 PM   #19
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Take the battery to a battery store and have it load tested.
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Old 09-26-2020, 03:50 PM   #20
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I have now removed all the dielectric grease from the mating surfaces of the grounds, which I had previously put on.

The problem still exists, low voltage at the 12 v distribution panel, when under load (furnace running) while the battery voltage is 12.4. I guess my using dielectric grease was not the problem but would not have helped the way I used it.

I found this on a motorcycle maintenance forum which I found helpful to me, explaining the use of dielectric grease on electrical components
[QUOTE]What makes electrical connections hot? High resistance across the electrical connection.
What causes high resistance? Oxidation.
What causes oxidation? Oxygen and moisture from the atmosphere interacting with the metal.
How do you keep moisture and oxygen from attacking electrical connections? Dielectric grease.
A good, mechanical fit between the male and female parts of the electrical connection will displace the grease at the point of contact. Many an all-weather motorcyclist has their switch gear and electrical connections packed with dielectric grease. (including myself)
You need to have a shiny, clean, mechanically strong, low-resistance connection to begin with. Dielectric grease will only help to keep a good connection from going bad over time by keeping moisture and oxygen from coming in contact with the metal surfaces of your electrical connections.
If you are not having any electrical problems, leave the grease there. If you were already having electrical problems and thought dielectric grease would be the cure, you were wrong. Find the root cause, fix it, then re-pack with grease. Most likely the root cause is a poor mechanical fit or existing oxidation./QUOTE]

I have not tried measuring for voltage drop across devices in the power side of the circuit yet. will try next week
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