How long will coach battery power last when running furnace?

[LJ-TJ]

Hey gang, heading out to the drag races this weekend boon docking. Never done it before. How long will the battery hold up running the furnace all weekend. Any suggestions on how I might pull this off.  i?? Thanks

[ClydesdaleKevin]

Depends on how many amp hours your battery bank holds.  The furnace fan draws a LOT of amps, so it will run down all but the biggest battery banks in a hurry.

If you don't have kids or pets that can knock it over, get yourself a Buddy Heater and a few cylinders of propane, and just set it on your dinette table with a window cracked open.  It'll heat your whole rig and they are very efficient...and won't draw any power from you batteries.  They cost about 75 bucks, but I've seen them a lot cheaper on sale.


Kev

[Froggy1936]

Hi TJ I have 2 large 12 V batts when fully charged and thermostate set at 72o (outside temps in the 40,s) my batterys will be below 12 V in the morning (after 1 night) i Would not count on them for a weekend  Frank

[ClydesdaleKevin]

Yep, the Buddy Heater is the best way to go on the cheap and in a hurry...you can get them at any Tractor Supply, Harbor Freight, Outdoor World, Cabellas, Northern Tool, etc...and I seem to recall seeing them at Walmart once, but I could be wrong.  They might even sell them seasonally at places like Home Depot and Lowes.  Worth the money, and if you don't have pets and kids, you can get the adapter hose to run it off a BBQ tank instead of the small cylinders, and it makes it super cheap to run.


Kev

[LJ-TJ]

Thanks Guys, Thanks Frank. I think I'll be throwing a few extra blankets on. See if I can't get the gen set running good enough to warm her up before bed and then refire her in the morning. Just can't seem to bring myself to put her up for the season just yet. Going to get an awning put on sometime next week. D:oH!

[DonD]

I just returned from a 2 nighter in the mountains. Ran the furnace all night, still had 12.5ish in the morning with 2 golf cart 6v in series.

[ClydesdaleKevin]

Not bad Don!  But the furnace fan probably doesn't run nearly as often, even in the mountains of Arizona, this time of year as it would in Canada this time of year, when things are getting COLD...lol! No way around it, furnace fans draw a lot of amps out of your batteries when they are running.


Kev

[LJ-TJ]

Wasn't so much that as it was when we both woke up at 2:30 to take a pee. Started laughing like a couple of kids cause no buddy wanted climb out from under that warm sleeping bag. Gads it sucks getting old. :)rotflmao

[tiinytina]

2 weeks ago ran the furnace all night hooked to shore power... and before bed the fan kept running but no heat.. (brad as witness).... turned furnace off.. back on furnace fired up and ran.. about 4am woke up and cold fan running constant, but furnace not on.. turned furnace off.. back on after waiting a minute. Fired right up warm air again...  i was having a charging issue converter wasn't converting and brand new batts were at about 1/2 charge at this point (once home found out) Genny also refused to fire from dash switch (recent replaced) but fired from on genny switch....

Getting up to use the facilities in a COLD RV WAY better than having to find shrubbery in the dark and cold.. LOL...
Tina

[DonD]

Added another battery, now have 515 ah.   
My Suburban draws 4.5 amps, I'm good for a while!!
I'm all LED too. 

[DonD]

17f tonight at Grand Canyon, still not Canada cold  N:(

[ClydesdaleKevin]

LOL Don, I didn't know you were up at those elevations, and yep, it gets cold!  That's the reason we haven't seen the Grand Canyon yet and we winter in Arizona every year!  Its too cold when we get there in early December, even the south rim is bound to be iced in, and the north rim is out of the question.  Then we do the Arizona Renfaire in Apache Junction, from February to March, and while the south rim is then at ideal temps, its packed full of kids on spring break and we can't get a hotel room or cabin...lol!  Gonna have Patti make reservations this week for a dog friendly cabin or hotel before they are all booked so we'll finally get to see it this year!  Not gonna beat up our RV climbing those elevations, so we'll take the dogs and cat and the Jeep and go see it.  Even in April the north rim of the Canyon is still iced in, so I get it...lol!  Its cold where you are!

Great amp hour capacity!  What do you charge it back up with? 

Electrical draw aside, don't forget how much propane a furnace uses and how inefficient they are.  We just bought a Wave 8 Catalytic heater which uses way less propane and no electricity, so I'll let you know how it works out in the cold months.  Last year we used a Buddy Heater, same concept, just not permanently installed and I was always worried about the dogs or cat knocking it off the desk.

Have fun winter camping!  What are the daytime temps like where you are at right now? 

And kudos on the LEDs!  They are definitely the way to go, and manufacturing process to make them is way kinder to the environment than incandescents and florescents.

Kev

[DonD]

"Great amp hour capacity!  What do you charge it back up with? " Just plug it in at home. I do run a portable charger too. The 105 ah alt works well.

"What are the daytime temps like where you are at right now?" I live at 4000 ft, mid 70's daytime. Gets into the teens in winter sometimes, mostly 20's tho'.

I have the furnace out and checked the actual amperage. Draws 3 amps when running, a bit more to start. This 30,000 btu unit is not really a gas hog. The fridge is a constant user so that's the thirsty one.

The GC is always a crap shoot weatherwise.
I've been trying to see Crater Lake for a few years and have never had  clear wx up there, one of these days I'd like to drive around the lake.

[DaveVA78Chieftain]

Calculating Amp hours per day requirement (Ah = Amp hours):

Amp hours per day = Amps x Quantity of item (ie: 3 lights) x hours of operation per day

Example situation:

Item	Amps   x	Qty    x	hours   =	Amp Hours
Lights	1.5 amps	3	4 hrs	18 Ah
Water Pump (Includes 2 Showers	5 amps	1	0.75 Hrs	3.75 Ah
TV	4 amps	1	2 hrs	8 Ah
Misc (Clocks, etc.)	Various	Various	Various	2 Ah
Total Ah per Day				31.75 Ah

For 2 days of usage thats a total of 63.5 Ah (31.75 x 2 = 63.5 Ah)

Furnace: 4 amps; 40% On/Off cycle per hr
Add a furnace at 4.5 amps x 1 x (24 x .4) = 43.2 AH /day

43.2 AH + 31.75 AH = 74.95AH per day

Given you should only use 50% of total battery AH before recharge 515AH / 2 = 257.5 AH max available.  Regular draining a battery below 50% capacity greatly reduces it's service life.

257.5 / 74.95 =  3.4 days of battery power available.

Due to chemical makeup, you have to charge a battery 110% to get it back to 100% state of charge.

Depending on type, a 30 amp charger can take (257 / 30) * 1.1 = 9.4hr to recharge a battery to 100% capacity.  Most cycle between 50% to 90% charge with a full 100% charge every 4th or 5th cycle.

Schools out - Dave 

PS: some other related info: http://www.classicwinnebagos.com/forum/index.php?topic=5603.msg20299#msg20299

[LJ-TJ]

  Dave your two funny  :)rotflmao