Dry camping with furnace on

[ragdogs]

I was dry camping this weekend and had to put the furnace on for the first time. I was worried that I would kill the battery if I ran the furnace overnight. I was right :(. The house battery was dead in the morning. I have only one deep cell battery. Did it die because the battery is not that great ? It charged up quickly by starting the motor but was wondering why it drained the battery. Bi am going away last week in October and will need the furnace overnight. If I buy another battery will this solve the issue?


Thanks,

[garyhaupt]

ragdogs..well now..you have opened a can of worms, haven't you. Not bad for a newbie. Once you ask a question that has to do with batteries, generator output, solar...prepare to be here a long long time reading.

I do want to comment on something you said..."battery charged quickly with motor"..naw..it didn't. Batteries charge from the bottom up BUT..when really down like yours? will grab what is called a surface charge...a floating charge that sits just on top of the plates and gives a false reading on your panel. It was already noted by a poster, that a flat/dead battery needs to be charged for an extended time. If you have a battery charger at home? 12 hrs..if you don't have one..it would be like a 14 hr drive..no kidding. So..for one thing..go to CDN Tire and get a battery charger. Not a jumper..a charger. They are a good thing to have on board anyway but for sure, at home. If you have it on board and you have same problem..you find a plug-in. I have two..on board and home.

If you don't understand all of the texts about amps and volts and testers and that stuff...you are not alone. Most of us don't but we don't like to admit it.
Find someone you think you can understand and send them a note asking for help. I can recommend someone if you like.

You will want to find a good RV shop, if you don't already have one..one that has folks that talk to you, not at you. That can tell you what you need to
know about power and your RV. Here..let me start...an RV has..HAS..to have power. It gets it in one of three ways. A generator, solar or plugged in. Batteries are the recipient of juice and then the giver...but they need to get it from somewhere. Yes? Batteries need to be replenished/fed....all of the time.


Gary Haupt
BC, Canada

[pnichols]

I'm a bit confused by the short battery life with furnace use comments here.

In high 30's temps at night our furnace cycles nicely when set at 60 degrees - about 5 minutes ON every 15 minutes or so. It's blower draws round 7 amps when it's running ... so cycling such that it's ON 5 minutes around 4 times every 60 minutes means it runs about 4 times X 5 minutes = 20 minutes every 60 minutes. This means that it consumes about 1/3 of 7 amp-hours = 2.33 amp-hours every hour on a high 30's temperatures night.

For a 10 hour night run this means that it consumes only about 23 amp-hours of our 230 amp-hour 12V AGM deep cycle battery bank's capacity.

We also run a couple of CPAP machines at night (room temp air only - no heat). Our batteries easily go 2-3 days this way before needing charging after dropping them down to around a 40 per cent state of charge (60 per cent of capacity used). We have a small 24 foot Class C that we block off the cab area on and our furnace is a 26,000 BTU one. We keep all shades drawn to better trap a layer of insulating air between the shades and the window glass. We also wedge a sheet of insulating material between the the shade and the window glass on one window by the bed. We do not have any solar on board.

I wonder why some of you are experiencing such short battery life with furnace use? Our propane furnace has worked well so far without seeming to be a battery hog at all - but we have not yet tried to drycamp in 20 degree weather!

[wrybread]

Its a really big job to upgrade your batteries to accommodate that blower. I have 4 Trojan T-105 batteries (the big expensive 6 volt batteries) and 600 watts of solar panels, and I *still* don't have enough power to reliably power my furnace blower over night. The things pulls 80 watts, which is just crazy for an RV. I'm surprised these are used in RVs at all.

My solution was to mount a Buddy heater on the wall. It costs all of $80, and is "tent safe". Get a CO detector of course and crack a window. And plumb it to your propane tank so you're not using little bottles of propane.

My heating needs are pretty easy since it doesn't really get below 40 degrees where I live, but you could always get multiple Buddies, or go the cadillac route and get a Wave catalytic heater:

https://www.amazon.com/Camco-57331-Olympian-Wave-3-Catalytic/dp/B000EDQR8M?th=1

Note that they have different capacities at that link.

They mount beautifully on a wall. Aim a fan at it if your rig is large.

[Sam_Spade]

Harvey51 wrote:

I get your idea of a load clearing the surface charge more quickly. But how quickly?

Pretty fast. That is the first charge that comes out. It is like static electricity kind of, in that it has voltage but not much current.

[Sam_Spade]

Harvey51 wrote:
The OP and I are two of many people who ruined batteries by trusting the voltage chart for state of charge.

I highly doubt that was the ONLY cause.
I think a bit of mis-interpretation might be involved too. 😉

For instance, with everything disconnected if the battery voltage reads 12.5, that means something entirely different than if you put a healthy load on it and it drops to 12.5.

[Harvey51]

They really should come with a battery my monitor.

Heating varies tremendously among people. DW and I rarely have the heater on for sleeping. And we camp in western Canada, often in April and October.

Sam Spade wrote:
Also I don't understand your logic in saying that a battery that reads 12.6 volts could be half charged.

Yes a bit of jumping to a conclusion from the measurement showing that the voltage at full charge was more than 0.3 volts higher than the voltage chart for quite a while. Maybe it wouldn't be so bad at half charge. Someone should check.

"And lastly, what do you think your "battery monitor" has to go by in estimating the state of charge except voltage ? It doesn't have a specific gravity probe into the acid does it ?? "
A battery monitor reads the current going into the battery and coming out. This is multiplied by the time duration to get the number of Coulombs or amp-hours of charge in and out. The count is updated every second or so, maintaining an always accurate count of the number of amp-hours stored in the battery.

I get your idea of a load clearing the surface charge more quickly. But how quickly? Someone with a battery monitor ought to do a graph with a load showing the voltage and the % of full charge over time. It would have to be done for various currents to get a full picture. It is all very complicated to tell the state of charge from voltage. The OP and I are two of many people who ruined batteries by trusting the voltage chart for state of charge.

[Sam_Spade]

Bordercollie wrote:
It would be nice if RV owner's manuals clearly stated what to expect when running the furnace overnight with a typical house battery setup.

OR the dealers who sell the things.
I suspect, however, that you would be hard pressed to find anybody at most dealerships who even understand it.

[Sam_Spade]

Harvey51 wrote:
It seems it takes hours for the "surface charge" to be absorbed.

So you see, the fully charged voltage is well over 12.6 volts for the first hour or three and a 12.6 reading could mean half discharged, where damage begins.

An expert here posted that this effect varies with the type and age of the batteries.

You have some good data at hand but have gone a little off track with the conclusions you have drawn.

The surface charge will disappear within a few minutes with the application of a moderate load, like a couple of light bulbs (headlights on a vehicle).

Also I don't understand your logic in saying that a battery that reads 12.6 volts could be half charged. I don't think that's possible with a healthy battery. It may read 12.6 and not be able to give back anywhere near it's rated capacity but that does not mean that it is not fully charged.

And lastly, what do you think your "battery monitor" has to go by in estimating the state of charge except voltage ? It doesn't have a specific gravity probe into the acid does it ??

[Rolin]

Like many others have stated we have to be very careful to manage our 12V power requirements.

We have a catalytic heater which we use in the morning, daytime, and evening. Have a accumulator on the water line to reduce pump time. No TV or DVD use. Installed LED lights. Cover the opening to the front cab area. Set the furnace temp at night time to 50-55 degrees. Depending on outside temp....we could get up to 2 nights on one battery. Now have two batteries and makes things much easier.

[Bordercollie]

It would be nice if RV owner's manuals clearly stated what to expect when running the furnace overnight with a typical house battery setup. Including a DVD with hints on 12 volt power usage, battery monitoring and maintenance, and how the engine alternator and converter charger or RV generator work to maintain the house battery(s) would help beginners avoid dead battery and battery damage.

[Harvey51]

So you got misled by the voltage method of estimating state of charge. Me, too! I killed my house batteries on our first long trip.

The voltage on the batteries is artificially high for at least 8 hours after all charging is stopped. With the voltage method you can't tell how much charge you have until it is too late to be useful - the batteries will already be damaged. To see the problem charge your batteries, then with no significant load measure the voltage every hour or so for at least 8 hours. This is what I found:
Note that the battery is 100% charged for the whole time and all those different voltages. It seems it takes hours for the "surface charge" to be absorbed. So you see, the fully charged voltage is well over 12.6 volts for the first hour or three and a 12.6 reading could mean half discharged, where damage begins. I have to wait about 12 hours for the voltage chart (12.6 is 100%, 12.0 is 50%) to be accurate. But do check out your own batteries for yourself. An expert here posted that this effect varies with the type and age of the batteries.

The only easy way to know the state of charge is to install a battery monitor. If money is no object go for an American made name brand such as Trimetric. If you would rather get a bargain from China, this is a higher current version of the one I have (looks like it is improved with the shunt separate): Ebay item

Mine is the 30 amp version with shunt built into the monitor
The trouble with it is that the monitor needs to be located near the batteries and the terminals are too small for heavy wires.

[Bobbo]

Two batteries, and set the thermostat to 50 at night. It will be cold in the RV, but nothing will freeze. Cuddle up under quilts. In the AM, get up, turn up the thermostat, and jump back in bed for 15 minutes.

We learned this at Yellowstone National Park in September 2011.

Leaving the thermostat at 65, we had 2 dead batteries by 2am.

[navegator]

This is what we do for cold boondocking 2 to 3 days only after that run the generator to recharge the battery and have more time.

1 we have kerosen lamps, the ones that get shot in the western movies, light and heat.
2 we also cook on the stove, spaghetti and use the oven for dinner, x-mass simple dinners pre prepaired.
3 limit the amount of water usage, also have an accumulator for water pump saves battery
4 have a small opening on the window of the galley need ventilation while kerosen lamps are lit, do not use roof vent heat loss is faster
5 do not turn thermostat on heater above 68 during day and 60 for sleeping
6 have an outside and inside thermometer, can see both at the same time
7 limit the opening and closing of door going in and out
8 we have front windshield cover and hanging curtain inside, can feel temp diff from window to cabin on both spaces
9 have warm blankets to wrap arround when sitting
10 we lower thermostat at night to 60
11 we have a minus 40 double sleeping bag
12 snugle up with wife, buddy warmth!
13 only turn heater in morning to brake the chill
14 boughht carpet runners, our floor is wood laminate

I found that the biggest source of heat loss is at the entrance door, not even more foam insulation on the oppening helps, those doors are not that good.

We only have one 12v deep discharge gel cell marine battery for the cabin, the whole idea is in conserving the power to run the heater fan when needed and use alernate sources of light, led lamps were not available when we purchased our unit, latter they were a bit pricy so I only installed four, one in the head, one for wife to read, one in the galley and one out side, I can read with my kerosen lamp, and no tv or radio or music from CDs, some times we do not even see the park rangers at all, we mail the payment to the office, we found out that some people steel the payments from the collection boxes.

navegator

[midnightsadie]

best to have two batteries THE SAME. mixing a older battery with a new one is not a good thing, and you can buy a volt meter that plugs into a 12v socket . for a couple bucks.it,ll tell the voltage all the time.

[Sam_Spade]

ragdogs wrote:
If I buy another battery will this solve the issue?

It will certainly help.

So will being sure that the batteries are fully charged when the sun goes down.

With two batteries mine does just fine overnight, with enough left to start the generator the next morning.

BUT....getting some additional blankets will probably be cheaper and better in the long run by allowing you to set the thermostat a bit lower.