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RV Battery from Tow Vehicle 12V

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Grant177 View Drop Down
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Post Options Post Options   Quote Grant177 Quote  Post ReplyReply Direct Link To This Post Topic: RV Battery from Tow Vehicle 12V
    Posted: 22 Mar 2020 at 3:38pm
Hey all,

Never had a RV before (with a battery) and/or a TV with a 7 pin connector, so just collecting general information at this point and making sure I have an understanding of how it all works...

My understanding is that the amperage coming from the TV on what I think is Pin 4 (12V AUX) at the 1:00 position, is basically enough to maintain a battery charged but not enough to charge if depleted any significant amount?

Additionally, I also see threads where some say to actually use propane to keep your fridge chilled (while driving), and other say this is not a good idea (crash/safety etc).  Will the fridge run on 12V when the TV is running or is the amperage not high enough?

Sorry for the newbie questions....

Grant

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Post Options Post Options   Quote StephenH Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 4:03pm
Welcome and congratulations! What RPod did you get? I hope you have many fun adventures and make many great memories doing so.

Some general thoughts:
1. On some vehicles, there is not enough power going through the connector to both charge the batteries and run the refrigerator. Other vehicles can do both.
2. On some vehicles, a fuse/breaker needs to be installed before the power will go through the wire to the trailer.
3. Because I have experienced the inability of the tow vehicle to both charge the battery and run the refrigerator at the same time, I have been running with propane almost since we purchased our RPod. I have not had any trouble doing so. The main area of concern is tunnels or other places where leaking propane could accumulate and cause an explosion. The flame is well contained in the vehicle and is well sheltered, so it won't go out while driving. Even if it did, the refrigerator should re-light itself.
4. If you have not done so, invest in some screens to keep mud dauber wasps from building  a nest in the refrigerator's  burner area or flue.

No problem with the newbie questions. We all were newbies once.
StephenH
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Post Options Post Options   Quote mcarter Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 4:15pm
Hey Grant,

In a standard RV configuration. The TV side at the 1300 position is the 12V power connection. If your TV is configured correctly with a fused connection you should be able to charge the TT battery thru your 7 pin connector. I have two different TVs and they both will charge the TT battery thru the 7 pin connector. Are there cases where that charge is not sufficient, I have heard so, but I can't testify to that with my assets. Mine work.

Many use the fridge on propane when traveling, I can't find an instance of that being a significant accident issue. Some say it is. I have traveled with fridge on 12V and on propane, no issues thus far. I know there are regulations that stipulate you have all propane devices off (tunnels) primarily on the east coast.

Lastly, my fridge runs fine on 12V power while traveling, however my 12V AUX is configured correctly, it is fused and it works. It is adequate to charge the battery, while the battery is in use. Again, I am not against switching the fridge to propane. I have done so in past.
Mike Carter
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Post Options Post Options   Quote Grant177 Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 4:59pm

Appreciate the responses and info.

2011 R-Pod 177....brand new, 10 years old (see below).

TV is a 2019 Nissan Frontier, factory wired with towing option with the 7 pin trailer connector etc.  I'll go dig out the fuse/specs on it, but I would be greatly surprised if it was not factory fused etc.  I am just not sure of it's specs/ratings etc.

I've also added a CURT Manufacturing 51170 Spectrum proportional brake controller.  Just had to plug it into the factory harness and all good to go!  Cool little controller and looks factory on the dash...

I'm considering the Anderson WD / Sway chain hitch, but have added Sumosprings to the rear truck suspension and it easily tows...going to do a few test highway runs this year, and see if I need the added WD and sway control.  The Sumosprings dampen any bounce and can easily handle the weight...so it's really more sway I am concerned about.  I'll load it carefully weight-wise.

In terms of battery, I would like to do some boondocking (mostly) so I've also just made myself a portable solar suitcase and solar charge controller setup as well to feed the existing battery (Group 31, 105Ah flooded).  I'm considering a lithium upgrade depending on how this year goes and wife enjoys things...

I picked up the 177 at auction last fall.  It is literally a brand new R-Pod...looks like it was never used...it just happens to be 10 years old.  I have the "spoiler" running lights recall scheduled to be added, and am going to get it fully safety inspected etc.  Even though the tires look like they are brand new, they are 10 years old (2010 date code on them) so they are going....Goodyear Endurance replacements ordered.  I have yet to test the heater, AC, etc as I picked up it late last fall and only had time to give it a quick winterizing before the snow came....

Can't wait to get at it again....


Grant
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Post Options Post Options   Quote Tars Tarkas Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 5:05pm
You may have to test carefully regarding keeping the RV battery charged from the TV.  Some setups allow for that, others don't.  Some vehicles shut off that wire when the TV stops so as avoid the TV battery being depleted during a lunch stop or overnight, for example.  Other vehicles will let you run both batteries down if you forget to disconnect the RV.  There doesn't seem to be any consistency in all this.  The situation can be exasperated  by running the fridge on 12v power.

As a guy on the internet, I can tell you that there is no reason not to run the fridge on propane while traveling.  I've done a good bit of research.  There are no laws or regulations against running the fridge on propane while traveling, except, as noted above, on the odd ferry or tunnel.  Gas stations don't blow up when you go into fill up.  Many RVs, especially the big ones, don't even have fridges that run on 12 volts.

All that said, some people have strong opinions on the subject.  Other people on the internet will tell you the opposite , so you'll just have to decide for yourself.

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Post Options Post Options   Quote mjlrpod Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 5:07pm
If you use a multimeter and check your 7 pin connector, you will be sure if you can run on battery or not. If you put one lead on the 1'oclock position (12V), and the second lead on the 7'oclock position (ground). you should see a number like 13.8 - 14.3 or so on the meter (set to 20 DC volts). If you have that, you can charge the battery as you run the fridge while towing. You should of course, already have the fridge cold the night before you leave, so it takes very little power to keep it cold. I never used to use propane while I tow. My new pod doesn't have a battery option. But I get it cold then put ice in it. On long runs, I'll stop 20 minutes here and there for bathroom, etc.. and run it on propane till I get going again. I see no real need to run on propane while towing. 
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Post Options Post Options   Quote Grant177 Quote  Post ReplyReply Direct Link To This Post Posted: 22 Mar 2020 at 8:11pm
Thanks again all.  I tested the 12V AUX pin earlier today and it does have 13.8 - 14.4 Volts on it while the engine is running.  I am still trying the verify the amperage capacity, but it seems there is a 30A fuse on that circuit...

When the vehicle is off, I'll need to test if V is supplied so as to not run down the battery.

Propane being so cheap and the system easy to manage, I think I'll be looking at that as the go-to for the fridge.  I do have a CPAP machine, so making sure I have solid 12V power for at least 6 hours every night is important to me...I've got a 200W solar suitcase setup, a small generator (if need be), and a DC-DC power supply for the CPAP which is much easier on the power usage (turning off humidifer etc), so should be OK.

I'll swap out all the lights in the R-Pod for LED...what else uses DC in these?


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Post Options Post Options   Quote mcarter Quote  Post ReplyReply Direct Link To This Post Posted: 23 Mar 2020 at 7:54am
My vehicles - 12V is present with engine OFF. Must unplug. Fridge control board uses 12V, as does the slide.
Mike Carter
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Post Options Post Options   Quote StephenH Quote  Post ReplyReply Direct Link To This Post Posted: 23 Mar 2020 at 9:49am
Originally posted by Grant177

Thanks again all.  I tested the 12V AUX pin earlier today and it does have 13.8 - 14.4 Volts on it while the engine is running.  I am still trying the verify the amperage capacity, but it seems there is a 30A fuse on that circuit...
I haven't tested the voltage on my AUX pin. Empirically though, I have seen that the vehicle is not adequately charging my LiFePO4 battery though. I think I would need to invest another significant amount to get a DC to DC charger with a suitable profile for LiFePO4 and run a dedicated wire for it to work.

When the vehicle is off, I'll need to test if V is supplied so as to not run down the battery.
On my Frontier, the vehicle's power shuts off. It seems to be on the same timer as the automatic off for the headlights and other lights. That is good in that I can be fairly sure that the starting battery in the Frontier won't be drawn down if I leave it plugged in.

Propane being so cheap and the system easy to manage, I think I'll be looking at that as the go-to for the fridge.  I do have a CPAP machine, so making sure I have solid 12V power for at least 6 hours every night is important to me...I've got a 200W solar suitcase setup, a small generator (if need be), and a DC-DC power supply for the CPAP which is much easier on the power usage (turning off humidifer etc), so should be OK.
What CPAP machine do you have? I have the Respironics Dream Machine. It uses 12V natively. If you need one, I have a spare 12V power cord that plugs into a standard 12V power outlet. When I purchased the 12V cord for my Dream Machine, I did not realize that it was the same as the one for my prior Respironics System One machine. If it would work for your machine, cover the postage and you can have it.

I'll swap out all the lights in the R-Pod for LED...what else uses DC in these?
Yes, swapping out the interior, the porch, and the hitch lights are the best bet. As for others, such as marker lights, they are only on when the vehicle is plugged in and the lights are on so they are not as important.  As for what else uses 12V power? Just about everything electrical uses some. The water heater uses 12V power for the control circuitry, even if you are using propane. The furnace uses 12V power for the fan and controls. The LP/CO detector constantly uses 12V and is hard wired and does not go through the fuse panel so it can't be turned off. If you have an electric jack, that uses 12V. The slide-out uses 12V. The refrigerator, even on propane, uses 12V for control and lights. The vent fan uses 12V. Still though, if you have an adequate setup (and it looks like you do), the 12V power usage should be okay for you to run your CPAP machine for multiple nights, especially since you do have a pretty good solar setup with generator backup.

What you can do is add a small voltmeter to monitor the battery state better than the panel lights can. You could also install a battery monitor to keep track of the amperage for charging and discharging and that will be even better than a simple voltmeter. I did that. You can look in my mods to see what I did for my LiFePO4 battery modification. There is a picture of the battery monitor I purchased and installed which is the AiLi Voltmeter Ammeter. You may need a Custom Cable for this monitor because the cable that came with it is relatively short. I wanted to mount the monitor in a group with the other meters/switches so I purchased this. If I had the tools to fabricate it, I would have made it. I could have cut the wire that came with it and spliced in additional wiring, but I did not want to do that.
StephenH
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Post Options Post Options   Quote Our pod Quote  Post ReplyReply Direct Link To This Post Posted: 23 Mar 2020 at 2:36pm
I switched to two 6 volt batteries after my 12 volt battery was stolen. I then added a 12 volt power outlet (cigarette lighter socket), splicing into the stereo 's power supply. I won't be using both at the same time.

I can then recharge the batteries completely using my Zamp PV briefcase, although that requires moving the PV. Luckily, moving the PV synchronizes with recharging my beverage container.

I can also monitor the battery voltage, and hence the state of charge, with a digital meter that plugs into the 12 volt outlet.
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