Braces wrote:
2014 Montana High Country Thinking of changing to two 6volt batteries. Don't have access to my trailer right now and need to know how much power the fan uses to see if running furnace at night when cannot run the generator would be practical. No genny 8 to 8 in national park. I realize there are a lot of variables so if you know the approx power draw of the fan motor maybe I could have a reasonable idea of the amp/hrs needed to keep reasonably warm.
Depends on outside temp and how big a barn you are trying to heat at what temp inside, of course, but for example with our 5er, we use about 70 AH a day with no furnace, which already means we need 140 AH of battery bank just for that--say two 24 size 12s at minimum.
So add some furnace. Fall, Spring, we use about another 70 AH but in Winter (around freezing outside overnight, but not colder than that) that can go to 100 or so AH for the furnace. The 70AH goes up too with it being dark out longer so more lights on longer time.
So now it is 140AH in one day but can go as high as 200. BTDT. How much battery bank? Double those AHs (50% used then recharge) so 280AH to 400AH needed and a recharge every day. A pair of 6s will do 225, so not enough for us, but others might survive by reading by candle light while wrapped in blankets in their 5er because they don't have enough of a battery bank.
But that's not the whole story! You can only recharge to about 90% with your generator, so the recharge is a "50-90" or 40% of the bank not 50%, so you need to survive on that 40% between recharges. So taking that 140AH as your daily 40% that means 100% is 350AH needed for the battery bank. Two 6s can't come close--needs four.
Another thing is in parks with gen hours, how long will the gen have to run to replace 140AH as a 50-90? That depends on how big an amp charger you have and how big a gen you have to run that big amp charger--which needs to get the batts to 14.4 or higher 14.8 is best. (except we are talking cold out, so add some voltage to those numbers for temp comp.-- 14.8 is 15.2 at 32F. Can your charger do 15.2?)
If you want it all to work out, you should fit the 5er out with four batteries 6s or 12s to something like 450AH of bank. Get a PowerMax 100 amp ADJ(ustable voltage) charger (or equivalent--if you can find an equivalent), and a 3000w inverter gen to run it (a 2000 is too small). Now you are good to go for Fall and Spring.
In winter we carry two more batteries for a six battery bank so we can do that 200AH a day without having to change our ways. No furnace quitting at 3am for lack of 12v power in our case--once as a newbie is enough to learn about that! :)
