Running furnace with just batteries

[tslanier]

We are heading out for our second trip to the NC Mountains and planned to stay at the Julian Price Park on the Parkway which has no hook ups. It is suppose to get pretty cold Friday night. I have purchased a Honda 1000 generator. How long should my furnace fan run on the batteries and how long should I have to run the generator to recharge my batteries?
Stewart

[2airishuman]

hi stewart...

well the really short answer is 1-2 nites max for the furnace fan and 6-8 hours on the generator each day.

really there are too many variables and unknowns to give you any more accurate answer.

you have a 34 footer? how many people, how warm do ya like it?

what batteries do you have and in what condition?

have you used a hydrometer to measure sp. gravity of each cell?

one bad cell greatly reduces the overall battery potential.

how cold will it be?

at 72f, most lead-acid batteries will give 100% of their potential but at 20degrees f. they only yield 70%

what other drains on the batteries, lights? fridge, water pump?

their are loads of threads here that discuss battery usage and furnace demands. IF you know how many amps the furnace uses and the duty cycle it's possible to calculate the best case...again assuming some knowledge of the battery chemical state.

so search and read.

here is an outside link on battery basics...
http://www.batterystuff.com/tutorial_battery.html

the 1k genset will take 5-6 hours to restore the batteries to 80-85% potential...each day.

100% takes many hours more, again depending on the condition of each cell and ambient temps...

and don't forget the metering system in the airsteam is a pretty crude estimate of battery state...

chemical reactions are much slower when it's cold. so lead acid batteries provide less capacity as the temp drops.

good luck and have fun. take some blankets and don't forget to vent out all the moisture during the day.

cheers
2air'

[CanoeStream]

Hi Stewart -- I'd agree with the general guidelines 2air' has provided. With two new Group 24 batteries I've been without hookup for 2 nights in 30 degree weather with no problems. It'd be good to avoid discharging any lead-acid battery below the 40% charge point. If you run your generator for a couple hours each day it would probably sustain you through the following night -- assuming you use some alternate form of illumination after dark and minimize other current draws (fridge on propane should be minimal). Recharging via the towing umbilical is overrated -- it often takes 200 miles or more with low alternator demand (no A/C, low light usage) before you'd recharge substantially. I have good bedding and get too hot when the thermostat is set higher than 62 degrees. At a 62 or lower setting I probably decrease demand to run the furnace constantly.

We had a couple snow pellet flurries today!! Now ... my Safari sits in the driveway and the current temp is 29, headed for 21 degrees by morning. That furnace is running an awful lot right now. At least I'm plugged into house current. I'll switch it over to my one full 30# tank before bed so the floor spaces have good heat and the water pipes will stay cozy.

[Pahaska]

The best way, if your generator is so equipped, is to charge directly through the 12v system. The converter is meant for slow, long-term charging.

If your generator has a 12v output (as my Honda 1000 does), you can rig up a cable to tie directly into the 12v wiring of the trailer. Going directly into the 12v wiring charges the batteries many times faster than going through the AC system. The 12v output of the generator, actually 14 volts or so, is meant for charging batteries.

In my case, I have added a cigarette lighter plug tied into the wiring in the outside refrigerator compartment. My cable has a igarette lighter male on one end and spade lugs that go on the binding posts in the generator on the other end. Make real sure you have the polarity correct.

You could also tie into the ground and 12v lines in the TV umbilical using a cable constructed with a TV end connector.

I found that even running the generator for an hour with direct 12v gives me a good battery charge.

[bryanl]

I'm just waiting for those 34' owners to start their own interest group - there's something special about that bunch! ;-)

I do not agree with the hydrometer business - it is a high risk and low benefit activity and the accuracy provided is usually well beyond what any RVer needs, especially when out in the woods.

Your furnace runs at about 5-10 amps. You have maybe 40 AH usable from the typical pair of group 27 Airstream setup. The max is up to 100 AH before you have to start to really worry about the batteries. That is 10 to 20 hours of furnace run time. In cold temperatures well below freezing, that might last one full day. For moderate temperatures that will often last two or three days.

Charging can be speeded up somewhat with a good intelligent battery charger designed for the purpose. It will still need 3 or more hours and at least a 2kw power source. Faster is possible but that gets into battery temperature monitoring and outgassing considerations. Slower is usually better. (generator 12v 'charging' is usually very dumb which means worse that your modern converter)

As far as detecting low battery condition: a good digital volt meter is easy to use but requires a proper interpretation. Most charts provide voltage references for when the battery is at rest and has been unused for several hours. That gives folks a fright when they measure voltage of the battery in use. Generally, the voltage at the battery terminals shouldn't go below 12.0v or maybe 11.8v during moderate use. If the furnace fires up and the voltage drops more than this, then the battery needs a charge.

It is your experience that will tell you what to expect from your batteries. If they don't do what they used to, then it is time to replace them.

Also keep in mind your furnace burns about a third gallon of LPG per hour. That means maybe 20-25 hours furnace run time per propane tank. (30k BTU/hr input furnace and 30# lpg tank assumptions)

[wheel interested]

John am I understanding you correctly, that to directly charge your AS batteries from the Honda 1000 generator you can make a special plug and not have to physically haul the batteries out of the tight fit Classic compartments to get at the terminals (is that the right word?- the top) to connect the batteries to generator?

[Pahaska]

Originally Posted by wheel interested

John am I understanding you correctly, that to directly charge your AS batteries from the Honda 1000 generator you can make a special plug and not have to physically haul the batteries out of the tight fit Classic compartments to get at the terminals (is that the right word?- the top) to connect the batteries to generator?

That is correct. You can connect to any "hot" 12v circuit in the trailer to charge the batteries. Electricity flows both ways in wires. As I posted, I connect my generator in through a cigarette-lighter-type plug tied into the refrigerator circuit.

It would be easy to rig a cable from the generator to a tow-vehicle end connector and simply plug the trailer umbilical into it. After all, that's precisely how the TV charges the batteries while underway.

If you look on the 2005 Classic 28 thread, you will see that I have added extra battery switches so that I can either use or charge one battery at a time.

[Steve Heywood]

Originally Posted by Pahaska

The best way, if your generator is so equipped, is to charge directly through the 12v system. The converter is meant for slow, long-term charging.

Not always! I replaced my factory converter with a 60 amp Progressive Dynamics Intellipower. My 2000 watt Honda only puts out 8 watts when using the 12 volt feature AND you have to disable the ecothrottle. After 2 days of dry camping I plugged my trailer into my generator and my new converter put a significant load on the generator.

[davidz71]

I have one grp. 27 115 amp. hour battery in my '86 Sovereign. I arrived at the deer camp 11:45 p.m. last Thursday night. I found that I could run my furnace for 2 nights in 33 to 38 degree weather for 8 hours to keep the trailer at a 56.5 degree temp. It was after the second full night I noticed the panel showing a slight flickering from GOOD to FAIR battery condition. The fridge was not turned on until Fri. morning when I retrieved items from the cooler. I only use one light at a time in the trailer and the one staying on more often is the flourescent over the sink. The light near the rear bed was turned on before turning the flourescent off and I tucked myself in to sleep. I use a good sleeping bag to stay warm and conserve propane and electricity. I ran my Yamaha 3000iSEB for 2 hours through the 30 amp power cord Sat. afternoon and then for one hour Sat. night. When I left camp Sun. at 2 p.m., the panel light was still on GOOD. Total light usage is hard to compute but I figure that a light was on maybe 5 hours over 3 days, usually in the evening hours fixing dinner. Hope this helps.

[john hd]

and, did you get your deer?

john

[davidz71]

Originally Posted by john hd

and, did you get your deer?

john

John,
I saw a doe run across the road Fri. afternoon before the evening hunt and a buck standing 20 yds. off the road in a field on my way to my stand 3 miles further down the road Sat. morning. I placed my stand 50 yds. from the edge of the field where I saw the previous buck and saw a large deer (never saw the head) slip away on the next ridge at 8:20 a.m. Sat. morning. I moved my stand to the next ridge Sat. evening, saw nothing and then tried Sun. morning. I only saw squirrels, redheaded woodpeckers and one healthy coyote Sunday. That's the story of my life. I still believe that buck is traveling those ridges so will have to be a little slicker and pull out the muzzleloaded Nov. 4th when that season starts. Skunked again.

[Pahaska]

Originally Posted by john hd

and, did you get your deer?

john

I got mine this morning!

I had a dental cleaning appointment at 7:30, so I turned out at 5:30 am and drove across Austin toward a restaurant near the dentist's office. For the first 7 miles of hill country, I watched carefully for deer, but when I reached the city, I was a lot more leery of other drivers.

Fortunately, the traffic was fairly light that early. Right in the city, a doe bounded out of the bushes and across the freeway with me at 65 mph. I tested both the antilock brakes and the electronic stability system trying to miss her. She fell trying to change direction and I ran over at least her legs. No damage to the car since she apparently went under me. With traffic coming behind me, I couldn't stop, but the impact was great enough that there must have been broken bones at least.

Not a fun encounter.

[fastrob]

We ran our furnace in December while waiting for our home to be delivered.
We charged with the power converter and huge 10,000 W generator which seemed ineffieient. We made it for a month barely.
If we did it again I would buy a second battery and probably use a dedicated battery charger.

There were 7 deer within 100 yards of our house a couple of days ago. They ran the goats up by the deck, a couple were by the goat house. The house was surrounded. 2 were by my archery targets, 1 was by the rifle target. Youth day is Saturday, gun season starts the 28th of October.

R

[Silvertwinkie]

Having just come back from boondocking and using a Yamaha propane powered 1000 generator, I can say this.

Before I damaged my batteries (2), by allowing them to fully discharge (because I didn't want to cook my batteries with the Safari being plugged in all the time) I would typically get about 4 days of heat running other items like the water pump, lights, etc. With my batteries damaged due to total discharge 2 times this past summer, I was able to get a bit over 2 days.

In 5 days of boondocking, running the 1000 about 6 hours total, I was able to keep the batteries over 60% charged.

On a side note, the Yamaha generator comes with a 12v charging cable. All you have to do if your goal is to simply speed charge the battery is to connect the factory supplied cable to the gen and the batt and you're off. No fabrication required. I haven't used that yet, cause I was thinking it would charge too quickly, but in retrospect, the batteries being in the condition they are, I should have tested it.

[Pahaska]

Originally Posted by fastrob

There were 7 deer within 100 yards of our house a couple of days ago.
R

During my walk in the dusk this morning, I flushed at least 15 deer out of a neighbor's yard. All doe. With no enemies (other than the automobile) the deer are proliferating and becoming terribly destructive. When I moved here 9 years ago, I would see one or two occasionally and my plants were fairly safe. Now, my yard is paved in deer pellets and everything I grow is either enclosed in a fence or high enough that they can't reach.

One town nearby is trapping deer and having them butchered to give to homeless shelters and the like. They tried trucking them to Mexico, but the fatality rate was too high. They wanted to use professional marksmen, but the "bambi lovers" kicked up a fuss.

[fastrob]

As a Massachusetts refugee the experience of hunters on Plum Island by the Mighty Merrimac river is similar. The wealthy residents fought deer hunting until they tested positive for deer tick fever, Lyme disease. The attitude is much different now. I do not hunt in Massachusetts any more though.

[rseagle]

Originally Posted by Pahaska

The best way, if your generator is so equipped, is to charge directly through the 12v system. The converter is meant for slow, long-term charging.

If your generator has a 12v output (as my Honda 1000 does), you can rig up a cable to tie directly into the 12v wiring of the trailer. Going directly into the 12v wiring charges the batteries many times faster than going through the AC system. The 12v output of the generator, actually 14 volts or so, is meant for charging batteries.

I'm puzzled by this. A Honda EU-1000 can only charge at 8.8 Amps/Hr DC to DC. (1000 Watts / 12 vDC = 8.5 Amps). But if you use the AC through your trailer it goes through your Converter and converts to 55 Amp DC (in my case on a 22' CCD). If you have 2 Gp. 24 batteries @ 85 Ah rating (170 Ah total) and charge from 50% to 80% State of Charge ((30 %) x 170 Amps = 54 Amps.) Neglecting the inefficency of the batteries (usually 26% for flooded cell) then your charge time would by 54 Ah / 55 Ah = .98 hour, say 1 hour.

However, by going directly DC to DC, 54 Amps / 8.5 Ah = 6.35 hours.

That's a big difference.

[rseagle]

Originally Posted by rseagle

A Honda EU-1000 can only charge at 8.8 Amps/Hr DC to DC. (1000 Watts / 12 vDC = 8.5 Amps).

I'm sorry. The Honda produces 8.3 Amps according to the literature, regardless of whether it's going toward DC or AC usage. The 1000 watt rating is for AC (8.3 Amps X 120 VAC = 1000 Watts). The DC rating is (8.3 Amps X 12 VDC = 100 Watts.