It was going to be the COLDEST 4 nights we’d ever spent in the RV and for a wimpy-butt-chill-kitty like me that meant serious stuff. We were headed deep into the Sierra Nevada Mountains at about 7,900 feet near Mammoth Lakes. Day-time running temps were forecasted at a civilized 55-60°F (13-15.5°C), but the nighttime thermometer was going to hit a MOST barbaric 18-20°F (-8 to -6°C) and we were dry-camping without hookups {{swoon}} ! If it weren’t for the incredible views and stunning hikes (and the fact that everyone else thought it was a good (?!) idea) I wouldn’t be here, but as things stood I was ready to bear it out and take it as a learning experience. Very magnanimous of me, I thought…
And a learning experience it was. As with all life experiences it turns out there were a few things we knew, but a lot we don’t know about cold-weather dry-camping. Now, we were lucky that it didn’t snow during our time in the Sierra’s and moisture levels were super-low (so, no real ice/sticking/condensation issues), but we did pick-up a few tid-bits for our next time (should I ever be so insane again) in the chill:
1/ Lead-Acid Batteries Lose Capacity In the Cold

Rough graph of Battery Capacity vs Temperature
Being an avid photographer I’ve always known that batteries go faster in the cold, but for whatever reason I hadn’t thought about it for the RV. Lead-Acid batteries are “cold-blooded” which mean they slow down (i.e. internal resistance increases) and they actually lose capacity as temps drop. The loss is pretty dramatic and gets faster the more load you draw (something called Peukert’s Law). What that means practically is your 220AH battery bank may only be worth ~150AH at 32° F (0° C), and even less than that if it’s colder and/or you’re drawing a lot of power (e.g. running a furnace). This little tid-bit explained why our 440AH battery bank was more than 50% discharged after a chilly overnight spell, even though we only drew ~150 AH from them. It was colder and so they had less to give! For more accurate graphs see the Lifeline Battery Technical Manual (Appendix section, page 34)
2/ Windows Are Major Leaky Cold Points
I love having large windows for views in the RV, but they sure are temp-suckers. Being nice, handy radiant conductors in summer they heat up the rig to a greenhouse boil while in winter they leak warm air out and manage to allow nice, chilly leaks to ooze inside. Closing out those leaks can mean MAJOR heat savings and as temps dropped below freezing we quickly realized we were woefully unprepared in this category. Here’s a couple of ideas we put in our back-pocket for our next trip:
- Insulation Material – Our RV partners have a nice, handy foil-based Reflectix insulator on their big, front window and have Polartec material that they’ve sewed and velcro-attach to the inside of the smaller windows. Both these things made a huge difference in their rig (compared to ours) and we’re definitely stocking up on insulators before our next trip. Bubble wrap is another great, simple idea.
- Plastic Shrink Film – I’ve talked to hard-core cold-campers that swear by those window insulation films that you shrink-fit to your windows. The positive is that they really seal things up. The negative is that you can’t open for air. Not sure we’ll need to go this route, but it’s a handy tip.
- Better Shades – There are lots of shade options that do a much better job than the day/night jobs that we currently have in our RV. Old-fashioned Cellular shades or sleek, modern MCD shades can make a difference to both appearance and heat/cold tolerance. The MCD shades are on our “wish list”.
3/ Portable Heaters Rock

Our "Big Buddy" Heater
We have a Mr.Buddy (“Big Buddy“) that’s a great back-up/support heater to our furnace. We’ll often run it for a few hours before we go to bed to get a snuggly, warm temp and it turned out to be a major bonus for our Sierra week-end. You always, always need to remember to crack a window/provide ventilation with these guys (and make sure your CO detectors are working), but they’re portable, cheap and easy to use. The
Olympian Wave Catalytic Heaters also get great reviews from RVers.
4/ Furnaces Can Suck You Dry
The fan in our furnace has a pretty significant power-draw (~10 Amps with both front and back going) and running it all night can easily suck us dry, especially when combined with other phantom draws and less battery capacity at low temps (#1). We managed to go below 50% batteries one night before we got wise to this one! We fixed this by switching to the portable heater (#3) before going to bed and sealing off our bedroom with only the back furnace on to keep us (and the pets) comfortable at night. As an additional back-up Paul set-up the auto-gen start on our generator to kick-in at 12.2V (~50% discharge point) on the batteries.
5/ Tanks Can Freeze, But It Needs To Be Reeeally Cold
If you’re consistently in freezing temps you’ve got to think about tanks and hoses. Typically cold-weather RVers will insulate or disconnect/put-away hoses and keep tanks warm with a small heat source or padding. Since we were dry-camping our hoses were already safely in the bay, but we did make the mistake of turning on our tank-warmer one night which (once again) almost drained our batteries. Duh! In reality our day-time temps were warm enough that we needn’t have worried about any kind of tank freeze, and if we’re ever in a situation that we do…well…I think it’s time to move the rig.
There are LOTS of other things that I’m sure we have yet to learn about. The good news is that our solar panels rocked the challenge (we managed to re-charge our batteries fully each day even though we didn’t bother tilting them), the cats did not turn into feline ice-cubes, and yours truly managed to survive with all fingers and toes in-tact. Oh…and it WAS worth it. The hikes, the views and the whole week-end rocked!








































































