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From: Ted Heise <theise@panix.com>
Newsgroups: rec.outdoors.rv-travel
Subject: Re: Charging from tow vehicle
Date: Tue, 4 Mar 2025 14:20:47 -0000 (UTC)
Organization: My own, such as it is
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On Mon, 3 Mar 2025 21:44:52 -0600,
  sticks <wolverine01@charter.net> wrote:
>  On 3/3/2025 7:39 PM, Ted Heise wrote:
> > On Tue, 4 Mar 2025 00:37:03 -0000 (UTC),
> >    Carol <cshenk@virginia-beach.com> wrote:
> >>   Ted Heise wrote:
> > 
> >>> I'm now wondering if my best bet may just be to minimize use 
> >>> of the battery so it might last a couple of days.  The 
> >>> fridge seems likely to the biggest draw, and is probably why 
> >>> the batterys has lost a significant portion of its capacity 
> >>> after a day of towing.  Would it be unacceptably dangerous 
> >>> to run the fridge from the propane tank while towing?
> > 
> > Any thoughts about running the fridge on propane while towing?
> 
>  As far as I know, it's not illegal.  You can do it, but it does 
>  open up a slight bit of risk should something happen to the now 
>  open gas tank.

Yeah, that's sorta been my read of the situation too.  Though some 
of my web searches suggested it might not be strictly legal.


>       ...Seems to me the little juice those fridges pull you'd 
>  be better off just using the trailer battery and figuring out 
>  how to keep it charged up.

I would also think the fridge (Norcold N4000) has light electrical 
use, but the 100 Ah LIon battery is down to 80 or less after a 
half day of towing.  I can't think of much else in the unit that 
draws meaningful power while towing.

If I'm reading things right (from web searches), it seems the 
fridge should run at somewhere in the 50-100 W range.  Assuming 
worst case 100 W for five hours, I think that's 6 Ah used, so the 
battery should not be getting drawn down as much as I'm seeing.  
Maybe my calculations are off base.

On the other hand, I seem to recall that the fridge has stopped 
running after a modest (less than an hour) time on the 12 V 
system.  I suppose I need to check this out further.

Regardless, it seems pretty clear my Acadia tow vehicle is not 
producing enough juice to help.  Maybe my assumption that power 
could be supplied by way of the seven pin connector is wrong.


>  ...Save the gas for hot water and heat if you need it.

Yeah, makes sense, but the quick searches I've done suggest the 
fridge should run for weeks on a standard tank, so that doesn't 
seem like a few days should wipe it out.


>  FWIW, I think you've gone to the expense of installing a 
>  Lithium battery in your unit, and we should go back to the 
>  start here and help you work through this problem of getting 
>  and keeping it charged.

Yeah, a Li Time 100 Ah battery.


>    ...I am still recovering from surgery, and not in top form, 

Thanks for the reminder, hope your recovery continues to proceed 
well!


>  but this effort could be used here as a study in how to help 
>  fellow RVers with similar problems. One way or another we 
>  should come to some kind of consensus on what the group thinks 
>  is a good way to solve this problem.  There will be others like 
>  Ted who are going to have the same questions.

LOL, you sound like some of the folks I work with in writing ISO 
standards.  Not that there's anything wrong with that.  :)


>  The first problem is whether or not you can use the tow vehicle 
>  to charge the trailer when moving from site to site.  I assume 
>  you would leave for any trip with it fully charged, so this 
>  would be for mostly when packing up and going elsewhere.  I 
>  still think a DC-DC charger is your best bet here, and not as 
>  complicated as it might initially appear.
>    Probably more affordable than you think too.  We'll have to 
>  look for good options on that.  Once you have that, it could 
>  also be used in an emergency to charge the trailer batteries 
>  flatspotting, as well as using your generator.

Yep, I always start from home with everything fully charged. I 
only have standard 110 outlets, so learned from experience that if 
I run the trailer's AC it melts the plug of a light duty extension 
cord.  All seems to be okay with the larger gauge cord(s) I've 
since picked up.

I do agree that beefing up the towing system feels like the best 
option for me, not least because I could use it in a pinch to 
charge the trailer battery when flatspotting.  As I mentioned in 
another post, the small generator I've used seems not worth it.  
The car runs more quietly, and there wouldn't be the weight and 
fumes we get from the generator.

I'm just a little daunted by the idea of installing additional 
equipment in the car (convertor plus heavy gauge wiring to an 
additional plug in at the rear of the vehicle).


>  Next, if your boon-docking, you need to get the battery charged 
>  back up as it gets depleted.  I know there were some additional 
>  notes recently on what you have currently in the Lance, but I 
>  was a little too under the weather to get into them too much.  
>  I'll try and give a look tomorrow.
> 
>  That said, it is my understanding you don't have a solar panel 
>  of any type at the current time.  So, we have to know if the 
>  Lance does have a controller in it, just not hooked up, and if 
>  it does have a plug in for the solar panel.  I know you have 
>  the generator you could use to charge the battery if you had 
>  to, but to me the proper use of a solar panel and controller 
>  that could keep the Lithium charged is the solution you should 
>  be aiming for.  Then, you'd only really use the generator if 
>  you don't have shore power and need AC.  On my unit it is 
>  installed on the roof and keeps my pair of deep cycles fully 
>  charged quite easily, with the fridge running too.  I do like 
>  the idea of having a portable panel that allows you to park the 
>  Lance under a more shaded area and then place the panel more 
>  out in the direct sunshine.

I think the trailer has only the Power Dynamics unit for power 
management.  It includes a setting for LIon batteries, but I don't 
believe it would accomodate a solar panel without needing an 
additional controller for the panel.  It does have the solar on 
the side connector, but I think a controller would be needed for 
any panels I might use.

I'm also a little daunted by the notion of installing panels on 
the roof.  On the other hand, putting out panels after arriving at 
camp would be playing catch up after the drain from a day of 
towing.


>  Maybe I am just still under a little brain fog from the 
>  procedure, but it just seems like we are getting into the weeds 
>  and not being helpful recently.  But, I do think we can all put 
>  our heads together and help you make a good decision on this 
>  battery charging problem of yours. It's a universal concern for 
>  RVers.

Really appreciate your kind and thoughtful help here.


>  ---snip---
> 
> > So if I'm reading this right, the concept would be to use some 
> > kind of portable power station as something like a backup for 
> > the trailer's installed battery?  Seems it would be handy, and 
> > might be simplest to set up with solar panels.
> 
>  IMO, this power station idea is not what you need.  You already 
>  have one, an expensive and capable one, with your lithium 
>  battery.  A solar setup is another thing.  You just have to 
>  figure out how to get the power to it.  Answer the questions 
>  posed above about what you have now and let's work through this 
>  again, Ted.

That makes sense.  I guess one thing that caught my eye with the 
power station was the 110 V outlet.  Other than the AC, we would 
have to do without the microwave and the electric kettle for 
coffee on 12 V only.  We have to have our morning coffee (dark and 
strong with an Aeropress), and I have yet to find a kettle that 
could run on 12 V.  We could use the stove and a tea kettle, I 
guess.

Anyway, I think I answered all your questions, but maybe not in a 
very concise way.  Thanks again for the help!

-- 
Ted Heise      <theise@panix.com>       West Lafayette, IN, USA