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Author Topic: 12v Dometic refrigerator sucking the house batts charge  (Read 4915 times)

marcortez

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12v Dometic refrigerator sucking the house batts charge
« on: July 31, 2015, 10:17:04 AM »
Can someone please confirm that a trucks (Ford F-150 2014) charging system can keep up the charge on a campers 2 AGM house batt setup with the 3 way Dometic refer on DC, drawing 15amps.

After a 10 hour drive with the refer on DC, the solar charge controller showed those house batts at under 12V....11.6V.
That same controller shows 13.7+ while on AC.

I don't think the house batts are getting the juice from the trucks charging system.

This house batt system uses a batt separator setup.
Maybe it's not allowing the trucks charge to get to the house batts?

A call to the factory was not so helpful.....with them saying the trucks alternator cannot keep up, as it only puts out under 5 amps??

Thank you
« Last Edit: July 31, 2015, 10:21:31 AM by marcortez »
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Rene T

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #1 on: July 31, 2015, 10:59:16 AM »
Why not connect the cord to your truck, start it and measure the voltage across the posts of your battery with a voltmeter. Then disconnect your cord and take another reading.  this will tell you if your truck alternator is charging the battery.  I think.   :o ::)
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Tinmania

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #2 on: July 31, 2015, 11:15:21 AM »
And if the test Rene suggest shows the truck is charging the trailer batteries then I wouldn't be surprised if it is not enough to keep up with a 15a draw, assuming the fridge is actually drawing that much.




Michael

marcortez

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #3 on: July 31, 2015, 11:55:59 AM »
And if the test Rene suggest shows the truck is charging the trailer batteries then I wouldn't be surprised if it is not enough to keep up with a 15a draw, assuming the fridge is actually drawing that much.


Michael

Which cord might that be Rene?
This is a pop up truck camper that has a plug in marine style connector on it from the camper to a plug in mounted inside the truck bed.
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marcortez

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #4 on: July 31, 2015, 12:05:28 PM »
And if the test Rene suggest shows the truck is charging the trailer batteries then I wouldn't be surprised if it is not enough to keep up with a 15a draw, assuming the fridge is actually drawing that much.

You mean to say a 80 amp output alternator cannot produce enough amps to keep 2 house batts fully charged while on the road?
If that is the case, it's useless to try and run a 3 way off of DC.....the truck charging cannot keep up. Incredible.

If an alternator is rated at 80 amp output, how much is it putting out in real terms?....I know it keeps the truck battery topped off.
Electric usage was during daylight...no lights other than stop and turn signals, AC fan and a radio, plus ignition requirements.



Michael
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Ned

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #5 on: July 31, 2015, 12:21:12 PM »
Since the refrigerator is 3 way, run it on propane.
-- Ned -- Fulltimer 1997-2013
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marcortez

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #6 on: July 31, 2015, 12:48:06 PM »
Since the refrigerator is 3 way, run it on propane.

I have done that very thing when driving around at less than 70 MPH freeway speeds.
The concern is that the propane flame will blow out and fail to re-ignite (it's an auto re-ignite system) while during hours and hours at freeway speeds.

Do you know if a truck alternator puts out enough amps to run the truck and keep 2 house batts topped off?
I think my alternator is rated for 80 amps.
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Tinmania

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #7 on: July 31, 2015, 01:02:35 PM »
f an alternator is rated at 80 amp output, how much is it putting out in real terms?....I know it keeps the truck battery topped off.
Electric usage was during daylight...no lights other than stop and turn signals, AC fan and a radio, plus ignition requirements.
The wire carrying that current travels all the way to rear of the truck, and it is not heavy gauge wire. It also has the converter to contend with so it is not powering the fridge directly. But, again, you need to verify if the truck is actually supplying power on the charge circuit. There is a separate line on the trailer connector, with its own fuse (in the truck's fuse panel), that handles it. So first verify that part is working and the fuse is not blown.



Mike

Gary RV_Wizard

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #8 on: July 31, 2015, 05:30:02 PM »
The alternator can probably keep up, though it won't last forever if it has to provide 70-80A all day long. Your problem is more likely undersized wiring to the camper.

If you are driving with headlights & dash HVAC running, the truck may be using much of the alternator output. Maybe half or more.  A bigger alternator than 80A would certainly help. 120+ is more typical for campers, ambulances, etc.
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marcortez

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #9 on: August 01, 2015, 12:25:20 PM »
The alternator can probably keep up, though it won't last forever if it has to provide 70-80A all day long. Your problem is more likely undersized wiring to the camper.

If you are driving with headlights & dash HVAC running, the truck may be using much of the alternator output. Maybe half or more.  A bigger alternator than 80A would certainly help. 120+ is more typical for campers, ambulances, etc.

Thank you.....

After some research I discovered the OEM alternator is rated at 110 amp output. Not 80 as stated before.

Would this change the equation any?

For reference, the camper is a new, light weight pop up model using 2 new AGM group 24 Exide batts wired in parallel.
Dometic 3 cu ft, 3 way refer that has an amp draw of 15 on DC power.
Installed and wired by a factory installer.
One would assume that this factory uses suitable sized wiring.
The truck is a 2014 Ford F-150 with 5.0 engine and 4x4.
All wiring connections are tight and clean.....it's new camper and install.

The conditions over the road at the time were daylight (no headlights) winding and hilly conditions from the South Oregon coast over to the Sacramento CA valley floor with temps in the valley hoving around 100 degrees. Drive time was close to 10 hours to my destination at the CA/NV border below Carson City......with only fuel and toilet breaks with the engine off.
At my destination, the solar panel charge controller showed the batt state of charge at 11.6V. The start point state of charge was 13.7.

I spoke with the wiring "guru" at the factory about all this and his statement has me lacking confidence.
He stated that an alternator only puts out 4-5 amps and with the refer on DC and drawing 15, it's a matter of time before the house batts drop below 12V. The "charge" amount from the alternator to the house batts, via a batt separator, is insufficient.
Sounds pretty hinky to me really.

I can work around not using DC for the fridge but boggles my mind why an alternator cannot keep up....especially when it's supposed to be putting out 110 amps.

My main initial concern was if the alternator was in fact, suppling a charge current to the house batts.
Do you happen to know how I can confirm the house batts are indeed receiving this charge current and how much is that charge? Volt meter on the house batts with the engine running?
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Great Horned Owl

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #10 on: August 01, 2015, 12:57:05 PM »
Trucks are generally wired to charge the trailer or house batteries. However, there is a fuse in the circuit that is frequently not installed at the factory. It should be located in the truck's main fuse block. Yours may very well be missing.

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marcortez

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #11 on: August 01, 2015, 05:48:02 PM »
Trucks are generally wired to charge the trailer or house batteries. However, there is a fuse in the circuit that is frequently not installed at the factory. It should be located in the truck's main fuse block. Yours may very well be missing.

Joel

Bingo......checking the fuse panel in the engine compartment and referencing what was what from the owners manual....the #9 relay for the trailer tow battery charger is not there. Same for the #21 fuse that is for trailer tow battery charge relay power....not there.
I am hoping this is the solution to the no house batt charging from the truck system

Now that completely blows my mind why a factory trailer tow setup with a factory 7 way plug does not have the proper relays/fuses installed.

The challenge will now be to find the #9 relay....I am 700 miles deep into Baja CA, Mexico from the border at San Diego and finding one locally will test my wits.
The # 21 fuse appears to be just a 30 amp blade style fuse and I can get that locally.

Thank you Joel for pointing me in the right direction and thank you to everyone who offered up suggestions.

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Gary RV_Wizard

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #12 on: August 01, 2015, 05:57:23 PM »
Quote
One would assume that this factory uses suitable sized wiring.

The camper and fridge wiring is probably suitable. Whether the wiring that delivers power from the truck to the towed trailer is sized for providing that much power is another story. An additional 15A is not trivial in an automotive system, and, other than trailer brakes (a separate circuit), a trailer tow package is probably not intended to provide a lot of power.

It may also be that your trailer tow power circuit was never activated. It comes from the factory wihout fuses in place and usually the selling dealer or owner has to insert those to activate it.
Gary
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marcortez

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #13 on: August 01, 2015, 06:57:57 PM »
Now on second thought.......the wiring run to the camper is directly from the truck battery and does not run thru the 7 way plug at all.

I don't plug in the camper to the 7 way plug......that circuit is directly wired to the battery and ran back to where a plugin on the inside bed wall was installed........where the camper then plugs in it's wiring plug.
I am sure that is the common installation.

I am afraid that inserting the missing fuses won't have any affect at all......if the missing fuses controls the relay to the 7 way.

I could understand the dilemma if a normal trailer wiring plug was used in the 7 way to get power to the trailer battery but a slide in camper is not set up that way......all that I have ever seen, use a truck bed plug setup.....all wired up directly to the truck battery.

I hope there was no confusion on if my unit was a camper trailer or a slide-in.....it is a slide in.

« Last Edit: August 01, 2015, 07:03:30 PM by marcortez »
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Gary RV_Wizard

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #14 on: August 01, 2015, 08:07:31 PM »
OK, it's a truck camper. So who installed the plug, and how is it powered (wire size, fusing, etc.). What is the voltage at that plug with the engine running? It takes at least 13v to do any battery charging.  And do you know how, or even if, the power at that plug is applied to the camper batteries? Just because the lights work does not mean batteries are being charged.  [I confess to total ignorance about how slide-in campers employ the 12v received from the truck.]

When plugged to 120vac, there is an onboard charger that works to do charging (the 13.7v). That doesn't come into play when driving.
Gary
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marcortez

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #15 on: August 02, 2015, 08:58:10 AM »
OK, it's a truck camper. So who installed the plug, and how is it powered (wire size, fusing, etc.). What is the voltage at that plug with the engine running? It takes at least 13v to do any battery charging.  And do you know how, or even if, the power at that plug is applied to the camper batteries? Just because the lights work does not mean batteries are being charged.  [I confess to total ignorance about how slide-in campers employ the 12v received from the truck.]

When plugged to 120vac, there is an onboard charger that works to do charging (the 13.7v). That doesn't come into play when driving.

Gary......the camper was installed brand new on my truck by a factory rep in January of this year.....including the wiring.
The camper unit was transported from the factory in CA, to a location handy to me near Las Vegas, by trailer, along with 3 other pop up campers destined to other locations.
The man who drives the delivery truck is also an installer...employed by the factory. That is all he does.....deliver and install campers on customers trucks who can't get to the factory....not to mention the customer sales tax savings by delivering out of state from CA.

The camper power wire/harness/marine style plug are installed at the factory....all the installer had to do was connect the wires to a plug he installed on the inside truck bed.....then plug it in to the factory installed camper harness plug...all before lowering the camper into the truck bed.

I can only assume this man knows how to wire up a camper/truck and is supplied with the proper wire and connectors. I cannot see any size markings on the white wires that are attached to the truck batt and run back.

Access to this plugin...from the inside truck bed wall to the camper harness, is not visible from either outside or inside the camper.
I can reach that plug-in with my hand through a turnbuckle tie down access hatch inside the camper. But I cannot see it. It "feels" secure and is not dangling loose. I gave it a push inward as much as I could...seems to be engaged.

I won't be able to put a meter on that plug...I can barely get one hand on it as is.
To access that plug, I would have to jack up the camper off the truck bed. I really don't want to do that at this point.

A friend of mine is coming over today with a meter and we will start the verification process.....starting at the source (alternator/battery) and working back

I think what I will do is start the refer on DC and let it start draining the now fully (AC power) charged batts and get a baseline of voltage then and there.......then start the truck and see if that voltage increases with flow from the truck alternator.

From what I do know, the voltage from the truck alternator/battery current is sent back to the camper via this plug-in connection. That plug-in then goes to a battery separator inside the camper. The separator then is wired to the 2 house batts.
I am sure it is the same manner as if the current were going to the 7 way plug and then via a trailer plug, to the trailers batt system.

I suppose this thread should wrap up now and I truly appreciate your help and suggestions.
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Gary RV_Wizard

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #16 on: August 02, 2015, 10:09:38 AM »
Quote
I can only assume this man knows how to wire up a camper/truck and is supplied with the proper wire and connectors.

Ever the optimist, eh? Having seen the many shenanigans that RV manufacturers have perpetrated over the years, I would not be so sanguine!

In any case, one of the major questions here is whether the electrical set-up is even designed to charge house batteries while you drive. Without some more detailed knowledge or description of the 12v electrical system, we can also conjecture. Lacking any specs or schematics, voltage measurements at various points would help pin it down.  "Assumptions" won't help.
Gary
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marcortez

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #17 on: August 02, 2015, 12:10:15 PM »
Ever the optimist, eh? Having seen the many shenanigans that RV manufacturers have perpetrated over the years, I would not be so sanguine!

In any case, one of the major questions here is whether the electrical set-up is even designed to charge house batteries while you drive. Without some more detailed knowledge or description of the 12v electrical system, we can also conjecture. Lacking any specs or schematics, voltage measurements at various points would help pin it down.  "Assumptions" won't help.

Update Gary.......
DC refer on for a few minutes.....voltage dropped off from 13.1 to 12.7 quickly.....stabilized at 12.7 for 15 minutes.
Meter put on the house batts.....motor started.......voltage came up quickly to 13.4 and stabilized there.

Truck charging system is sending current to the house batts.
That is what I wanted to confirm.

Now if that incoming charging current is sufficient to keep the batts topped off with the refer on DC, and on the road and over hours, is the next hurdle.
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Gary RV_Wizard

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #18 on: August 02, 2015, 05:19:11 PM »
You started out saying the batteries were not receiving a charge from the truck engine. Now you have verified that they are indeed being charged. Does that mean there is no problem?
Gary
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marcortez

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #19 on: August 02, 2015, 06:27:51 PM »
You started out saying the batteries were not receiving a charge from the truck engine. Now you have verified that they are indeed being charged. Does that mean there is no problem?

I sure as hell hope so Gary.
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Gary RV_Wizard

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #20 on: August 02, 2015, 08:59:35 PM »
Us too! Let us know how it works out!
Gary
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Tinmania

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #21 on: August 03, 2015, 09:56:31 AM »
You started out saying the batteries were not receiving a charge from the truck engine. Now you have verified that they are indeed being charged. Does that mean there is no problem?
Well I think the issue was if it was charging "enough" to keep up with the fridge. So the first thing suggested was to verify it was charging at all. Since it is charging he is back to the original issue: if it can keep up with the fridge.

If it isn't he can always run a separate wire, heavier gauge, just for the battery charging circuit.

Yet another example of why those 3-way fridges are not all that great on DC, and you don't see many of them these days. Now one of these bad boys can even act as a freezer and only draws 5a at 12v and then only when the compressor is running: http://www.amazon.com/gp/product/B002W8BLUG/ref=s9_simh_gw_p265_s30_d4_i2?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=desktop-1&pf_rd_r=11BGHS232ZYA19M1G31A&pf_rd_t=36701&pf_rd_p=2079475242&pf_rd_i=desktop




Michael

Mopar1973Man

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Re: 12v Dometic refrigerator sucking the house batts charge
« Reply #22 on: September 23, 2015, 09:40:58 AM »
First off take a look at the fridge burner assembly. I bet money that the burner is totally enclosed burner with a shutter window for inspection. I've driven many many miles with RV's while the fridge was on propane. I've never had one go out yet. That includes my old 76 Dodge Jamboree with a Dometic Fridge with manual light. Propane system are very safe and also have fail-safes that if it doesn't light all propane will be shut down to the burner so there is no explosion issues. With the auto-lighting system like my Norcold it will attempt 3 times to light if no flame sensed the it locks out and displays No Fl on the display chiming. Even with the 6 years I've now owned this RV Fridge has never blown out even with heavy cross winds.

So propane is a solution.

12V is a heavy draw period.

120v is ten times lighter of a draw.
Mopar1973Man (AKA: Michael Nelson) located out in the state of Idaho with...
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