Battery back up

[kinsmanstoves]

If you have a battery and inverter hooked up to your stove, I have a few questions for you.
1.) what size inverter do you use?
2.) what is the size of battery or batteries do you use?
3.) how do you keep your battery topped off?
4.)What is the length of time do you get when running on the battery?

I carry Breckwell stoves and have one in my house and two running in the store. I have yet tried an inverter but prior to getting one or three I want to know what to expect. Please help. Eric

 

[WarmGuy]

Using my kill-o-watt meter, I determined that the fan in my warmhearth fireplace uses 20/40 watts on low/high. When the power goes out, I connect this to an inverter that's plugged into my car. It can run for hours.

 

[begreen]

Our Quad 1200i used about 4.1a startup current and 1.1 running. If we kept it I was considering running it on a large 1.5kw UPS. That would have given me about 90 min. run time and would protect the electronics 24/7.

Here's a homebrew system that adapted a UPS to marine, deep cycle batteries:

http://www.butkus.org/ups/ups.htm

 

[kinsmanstoves]

My Breckwell Tech. manual says it needs a 500 watt inverter during the run cycle and 800 on start up due to the igniter. I thought that was slightly high. I need to run it on a meter.

 

[nshif]

Look at the rated wattage. that will tell you the inverter size. Most inverterters have a built in start up surge built in. Once you know that you need to know how long you want it to run in back up mode. This will determine battery amp hour need. convert watts to amps and amps to amp hours and that will give you the battery(ies) size. Dont use cold cranking amps.

 

[stoveguy2esw]

My Breckwell Tech. manual says it needs a 500 watt inverter during the run cycle and 800 on start up due to the igniter. I thought that was slightly high. I need to run it on a meter.

actually , thats pretty close to normal, google "stovesentry" and look at their spec's they specialize in battery backup systems.

 

[Corey]

A couple of years ago, we had an ice storm and the power was out for three days. This info is based on that experience:

1.) what size inverter do you use?
120W

2.) what is the size of battery or batteries do you use?
Pulled a group 24 battery out of the truck - about 75 amp hours

3.) how do you keep your battery topped off?
Driving the truck - but when it was in heavy use during the outage, I took it to work and used a battery charger to get it ready for the next evening

4.)What is the length of time do you get when running on the battery?
About 9 hours


You can get a rough estimate of your own setup by:

Calculating the power draw of your fan - either voltage x current (ie 120V x 0.5A = 60 watts) or directly by using a Kill-o-watt, then calculating the power storage of your batteries (ie 75 amp hours x 12V = 900 watt hours), divide your battery capacity by your fan draw (ie 900 watt hours / 60 watts = 15 hours) At some point, you have to calculate the efficiency of your inverter and figure that in. Mine was about 65%, so 15 hours x .65 = 9.75 hours.

You can figure the inverter efficiency in a couple of ways. It might be stated by the mfr, or you can measure the current and voltage on the battery side and measure the current and voltage on the output side. Mine was something like 120V, 0.5A out, 12V, 7.7A in. So (120*0.5) / (12*8) = 60/92.4 = 65%

One other thing to consider is that if you are drawing a large current from your battery, you probably won't get the rated capacity. Generally, the capacity is rated for a 20 hour current draw. my battery was 75 Ah / 20 hours = 3.75 amp discharge - I was drawing about double that, so I got a little less than the full 75Ah.

Corey
On a side note - after three days without power I got a little bored and decided to measure the efficiency of a couple different inverters I had. One was a Fortress UPS, one was a Hewlett Packard inverter, one was a little Chinese job from Harbor Freight. Surprisingly, the Chinese model was the most efficient. The UPS had axillary fans that ran for cooling and gobbled power. I further suspect that both the UPS and the HP inverter were putting out a much better sine wave on the 120V - but they were gobbling more power to do so. The HF inverter probably had a little sloppier waveform, but most of the battery power was going into it.

 

[begreen]

One other note. You don't want to draw the battery down much below 40% of its capacity. More can damage it. So when sizing a system figure at half of the battery's capacity. As Corey noted, a group 24 battery will be about 75-80 amp hours capacity.

Here's a site with a lot of info about inverters. There's a nifty calculator for figuring capacity at the bottom:
http://www.donrowe.com/inverters/inverter_faq.html

and here is a packaged power supply:
http://www.crutchfield.com/S-8H7UAcYA5D1/App/Product/Item/Main.aspx?i=539PS1800

 

[MrWinkey]

I just snagged a few battery backup systems for computers.

They have them on E-bay all the time for pretty cheap and they do everything. I have a generator I use to charge it back up when it's discharged and it will turn off to prevent battery damage.

Do a search on E-bay for APC. I have a 2200 and a 1400. I use the 2200 for the stove and the 1400 for the computer/stereo but when I get a nicer TV it will go for that. No need to have a power surge killing an expensive TV/pellet stove/computer.

(broken link removed)

Edit: I got both of mine from old computer scrapyards. Brought an extension cord and plugged in about 10 of em till I found 2 that worked.
Depending on your area many computer recycler's will have old UPS's and other neat stuff to paw through!

 

[Henz]

thats very interesting..I ahve one of those bigger portable battery packs and a decent inverter..may have to try it on my fan..although I also just bought a generator..