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Battery Charging Strategies in Super Cold Weather - Help!!

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peacepedalers

RVF Newbee
Joined
Feb 8, 2021
Messages
4
I'm taking my family on a 4 night campout at the ski hill and we're calling for 0 degree weather. Here's my questions:

1) At Home Now to Feb 11: I got 2 brand new 6-volt batteries hooked up and they are fully charged. Should I leave the batteries on the RV now until we leave plugged in and topping off (cold like 25-30 degrees at my house at night) or take them both off and put on a maintainer?
2) At Mountain Feb 11-15: Up at mountain will be very cold. I have a generator and plenty of fuel. plan to charge up batteries so they are topped up just before going to bed like 7PM and hope for the best from then to morning. Any suggestions to keep from running out of battery in the middle of the night? should i wake up and check levels and see if should fire up the generator? dont want to wake up with a freezing family...thoughts? We're packing cold weather sleeping bags and extra blankets for a family cuddle fest if crap hits the fan.

any suggestions are welcoen. our first-time cold weather - no plug in. thanks!

Jamie
 
I am not sure I am understanding your dilemma.......you didn't mention what you are planning to do with those batteries.....what are you using them for? Are you using them to power a huge electric 200A/h blanket for the whole family and four dogs or are they just running the fan of your furnace?
Regardless of what you are planning to do with them, it is always a good idea to keep them charged up and there are fine devices that let you know how much charge you have left in 1% increments until they are depleted.
If you can please elaborate a little more, we can probably give you better advice.
 
Wow, I'd love a big electric blanket! But no, it's just for the furnace of a 2018 Jayco 4-season 24 foot trailer. I have them hooked up to the coach now and they have 100% charge. I have a battery maintainer here in the warm house so was thinking to take them in to keep them toasty and topped off but now the coach is plugged in and keeping at 100%. If i bring them in then my wife won't have lights when prepping so just not sure how "crucial" it is in these last prep days to disconnect the batteries from the coach or is a few days in the cold okay as long as they stay at 100%. just want to do my best to keep batteries ready for the big "unplug" ;). Thanks, Pablo! so kind to help!
 
This is the bottom line........you have to know the capacity of your batteries and what the amp draw will be for, let's say one night (assuming that you will fire up the generator to recharge them the next morning).
Let's assume that you have two 12V 105A/h batteries. That will give you (in theory) 210A/h capacity between the two of them. That is not entirely true because much will depend on the chemistry of the batteries. But if you know, and if you don't, it is very easy to find out (look at your furnace manual), that the furnace fan draws 3 A/h, then 210 A/h divided 3 A/h (draw) will give you, assuming that the fan runs every minute, 70 hours of run time. Again, this is not entirely true because you cannot deplete those batteries to 0V. But if you are planning to run a single furnace fan, you will probably draw only 12/20 Amps out of your batteries in 8 hours assuming that the fan runs 50% of those 8 hours, which is also a lot. Your voltage will drop as your amp draw goes but you will still have plenty of juice. The next morning you can recharge them back up to 100%.
I am sure you will have other appliances going too. Anything that does not have a motor is low amp draw unless the microwave or high output appliances.
You can always get the Victron BMW 712 smart battery gauge. Awesome device. You need to do a little install but it is very, very useful. Not cheap though.
 
thanks so much! I'm feeling more relaxed now. We'll only run furnace at night and we'll get them back to 100% in the AM and just before bed :)

thanks again!
 
For the future....

double check freeze temp vs charge state. If your batteries get really low...then Zero Fahrenheit will freeze the electrolyte, Good practice to keep the charge above 50%.

More batteries help...

Getting batteries that don’t require venting and place them in the warmer living area.

Adding auto start on the generator..setting a reference voltage for startup should they go too LOW.

if running a propane furnace at sub freezing temps...depending on insulation, and thermostat setting, you are gonna blow thru a lot of propane. Our 5th wheel had two 20# bottles on an auto change valve, and a stored third 20# bottle. Seems I went to fill one every three days at least. When connected to shore powe we supple,eyed with two small ceramic heaters on low power setting...that helps a bit on stretching how many days the propane lasts.

Make sure if you have a propane furnace that the exhaust isn’t directed into the wind. On a windy night...you might get a flameout if the wind blows hard...and the furnace faults. Turn it off then on...it will relight...but you’re gonna find yourself in a very cold camper.

Have fun!!!
 
I’d find a campground with 30A service. That’s enough of an adventure in that kind of weather. Boondocking slope side is really cool, but you might at least have a plan B in mind at a local RV park to fall back on if things aren’t comfortable. Your bigger issues might be keeping your water lines and water pump from freezing, 4 season coach or not, and those strategies, (heat lamp in wet bay or belly) take shore power.
 
thanks for the comments! we are going to stay winterized so no risk of lines freezing. and yes, we have a plan b. we're going to camp close to the plug in spots and run an extension cord from thier place if poop hits the fan!! thanks!!
 
thanks for the comments! we are going to stay winterized so no risk of lines freezing. and yes, we have a plan b. we're going to camp close to the plug in spots and run an extension cord from thier place if poop hits the fan!! thanks!!
Sounds good then. You have lots of options. Enjoy the skiing
 
Don't forget the 50/30A-15A adapter for your shore power cord.......It happens!
 

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