# Run stove on car inverter?



## movemaine (Dec 21, 2013)

Has anyone done this?

And what size?

I don't have need for a generator, but I'd like to have some sort of backup just in case.

Additionally, I know there are sine wave considerations - what does a Harman require?


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## jackman (Dec 21, 2013)

I've run my stove on a cheap Harbor Freight power pack that has a 400W inverter. It lasted long enough to get the stove shutdown during a power outage to prevent the smoke from filling the house.


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## movemaine (Dec 21, 2013)

jackman said:


> I've run my stove on a cheap Harbor Freight power pack that has a 400W inverter. It lasted long enough to get the stove shutdown during a power outage to prevent the smoke from filling the house.



I'm looking for an inverter I can run for extended stretches (2-6 hours) in the case of a power outage. I'm thinking it might be best to go with something in the 1000w range, to prevent any chance of spikes/overheating.


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## Pellet-King (Dec 21, 2013)

http://www.harborfreight.com/750-watt-continuous-1500-watt-peak-power-inverter-66817.html

My stove uses like 60 watt's running, I have no Igniter


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## IHATEPROPANE (Dec 21, 2013)

movemaine said:


> I'm looking for an inverter I can run for extended stretches (2-6 hours) in the case of a power outage. I'm thinking it might be best to go with something in the 1000w range, to prevent any chance of spikes/overheating.



If you plan on running it for a long time I would think you need a pure sine wave inverter.  It seems the Harman can sense a modified sine wave and will shut it down.  There is a thread regarding Harman and shutdown.

Also, the motors do not like a modified wave.  You can hear them labor.  But if Harman have motors that run on DC this may mot be an issue


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## gfreek (Dec 21, 2013)

You could run it off a car battery while the engine is running.  But the larger ones need to be connected directly  to the battery.


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## P38X2 (Dec 21, 2013)

I was thinking the same thing regarding a Harman sensing the change in waveform and shutting down. 

You may want to look into whatever Harman recommends for a battery backup, then DIY one of your own using a marine battery. I bet you could get at least a few hours out of a single charge.

Hmm...may look into this myself. I use a marine battery for my telescope...which is NO fun to use when its 7 degrees out.


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## briansol (Dec 21, 2013)

They do make pure sine invertors, but they are expensive.  And then, you'll have to run the car off and on to keep the battery going.  It's almost not worth it.


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## Mt Bob (Dec 21, 2013)

Don't know what you drive but almost all newer light duty vehicles are not set up,engineered to idle for long periods of time,even diesels.You can do a lot of damage and cause upcoming problems.


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## Madcodger (Dec 22, 2013)

movemaine said:


> I'm looking for an inverter I can run for extended stretches (2-6 hours) in the case of a power outage. I'm thinking it might be best to go with something in the 1000w range, to prevent any chance of spikes/overheating.


Those inverters are normally far from "clean" in the power produced, producing a very square, not smooth, wave. A stove designed to detect this just won't run.  A stove not designed to detect it but subject to damage from a square wave (often due to heat within board components) will often be damaged.  That leaves stoves that can run on dirty (i.e., square / modified wave) power and the folks on here who - often by sheer chance - have them, but no knowledge of wave forms.  They may tell you, "Sure, it'll work fine".  It's like listening to a lottery winner telling you that it's a good retirement plan, in that dumb luck is a bad strategy.  Check with your manufacturer, then buy what's recommended.  Boards are not cheap.

Check out the 9 gazillion threads on "sine wave generators" to see more debate.

And the whole idea of idling you car for hours is equally bad, but a whole different topic.


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## moey (Dec 22, 2013)

I think Id rather sit in my car with the heat running.


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## Madcodger (Dec 22, 2013)

moey said:


> I think Id rather sit in my car with the heat running.


OK, that was funny.  I actually snorted.  My neighbor actually did that once.  I told them to just stay with us, but then the power came back.


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## notch (Dec 22, 2013)

If you happen to own an electric golf cart, you are already half-way to being "off-grid" as the deep cycle batteries have huge amp hour storage potential. Using a good pure inverter will allow you to run the stove and other sensitive electronics for days, maybe weeks. A small generator will run other things (lights, freezer) and also recharge that batteries if the ice storms knocks out the power for weeks.

I use this one because it has a built-in automatic transfer switch which will detect loss of grid power and switch to the golf cart batteries to keep my central heating system going if I'm traveling.

http://thesolarstore.com/inverters-...oogle&k=1269&gclid=CKyg55K2wLsCFRBnOgodLlAAwQ


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## gfreek (Dec 22, 2013)

Yes running a car, or my tractor, or my plow truck, for the inverter is not a good idea but in case of emergency I think it's do able....I have a pure sine wave inverter, run on a marine battery, and have run my Harman for a short time on it...will post make and model later..


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## Madcodger (Dec 22, 2013)

notch said:


> If you happen to own an electric golf cart, you are already half-way to being "off-grid" as the deep cycle batteries have huge amp hour storage potential. Using a good pure inverter will allow you to run the stove and other sensitive electronics for days, maybe weeks. A small generator will run other things (lights, freezer) and also recharge that batteries if the ice storms knocks out the power for weeks.
> 
> I use this one because it has a built-in automatic transfer switch which will detect loss of grid power and switch to the golf cart batteries to keep my central heating system going if I'm traveling.
> 
> http://thesolarstore.com/inverters-...oogle&k=1269&gclid=CKyg55K2wLsCFRBnOgodLlAAwQ


Great idea, but do need to "do the math" depending on the stove and other loads being run.  A day or two is certainly possible, but I confess to raised eyebrows at "weeks", without a fair amount of recharging.


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## notch (Dec 22, 2013)

Madcodger said:


> Great idea


Thank you.



Madcodger said:


> but do need to "do the math" depending on the stove and other loads being run


You are absolutely correct. The different Cotek inverter models are rated at different running/surge watts. I sized mine to run my Forced Hot Water circulator pump (big start-up surge watts needed) and my internet router (to stay connected to hearth.com, of course ). Charges my laptop when the heating system is not running. A watt meter helps a lot with this. 



Madcodger said:


> A day or two is certainly possible, but I confess to raised eyebrows at "weeks", without a fair amount of recharging



If you use a blow torch to start your pellet stove rather than the igniter, then you are really only needing to run the augur motor, combustion and distribution fans. At <200 watts with all of them running, running the stove for weeks without charging the batteries is indeed possible. If the temps allow, shutting down the stove for a few hours here and there would probably help to maximize the battery life.


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## Woody1911a1 (Dec 22, 2013)

http://supergenproducts.com/shop/refurbished-2000w-inverter-red/


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## Madcodger (Dec 22, 2013)

OK, somebody check my math here...

I completely agree that a blow torch to light is a great idea (or gel).  But you still need much more battery than most people realize, according to my calculations.  Here goes...

The most efficient pellet stove of which I'm aware (in terms of electricity) is the Quad Mt. Vernon AE.  I've measured mine at 27 watts when only the combustion and convection blowers are running, and the auger motor of course.  In reality is would be safer to assume about 30 - 35 watts, but let's go with 27 to be generous.

27 watts at 12 volts produces 2.25 DC amps (27 / 12).  So, in a 24 hour period we would use 54 Amp Hours (AH), calculated as 2.25 * 24.

Now, you CAN buy batteries of several hundred - even several thousand - AH.  But try finding them at a local distributor, and try moving them (pretty darn heavy).  In reality, something near 110 AH at 12V is about the practical limit for most people in home use, at least for a single battery.  You can vary your combo of amps and volts in terms of putting various batteries together, but you're basically dealing with the same physical limitations of space (and $).  The cheapest you'll normally find that type of deep cycle battery is in one designed for marine use (at about $90), which isn't "true" deep cycle, but it's good enough for our purposes.  A car battery would do in a pinch, but you might sacrifice many months of its life so it's not advised.

So with 54 AH being used per day you could theoretically get about 2 days out of a single 110AH, 12V battery.  But if you want to keep that battery healthy and ready to fight another day, you don't really want to take it below 80% discharge (or 88 of our 110 AH).  Many people will recommend not going below 50%, but we're not going to be cycling these batteries often, so we'll be liberal with their use.  That would give us about 39 hours of use for an efficient stove that operates on DC power internally, like the MVAE. (54 * .8).

However...  Most stoves aren't designed to operate on direct DC inputs like the MVAE, so we'll need to connect our battery to an inverter to get AC power, and they are just not efficient in terms of how they convert DC to AC.  In fact, a 20% inverter loss is commonly recommended as the figure to use for modeling and planning.  So with our 20% inverter inefficiency factored in, we're going to need to back things off a bit more.  In fact, we're now looking at just over 31 hours out of our 110 AH battery.  Looking at it another way, if we want to get through a full 24 hours (at which point we will need to recharge) we need an 81 AH battery, again assuming 27 watts, a 12V battery, maximum discharge of 80% and 20% inverter loss.

Having access to a golf cart would of course help, as you would have more than one battery (probably 6V batteries, actually) and they would be big honkin' things.  But you would also need the skills to wire them in parallel, rather large cables to safely connect them, etc.  And personally, I don't have a golf cart lying about...


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## TheMightyMoe (Dec 22, 2013)

I have a 1500 pure sine inverter to run my stove, it takes about 380 watts to ignite and 180 to run,

The idea behind using a car is, you have a mobile fuel tank, multiple tanks if you have multiple vehicles, I would plan on running the house HOT and letting it cool down, rinse/repeat. Part of the reason I oversized to a P68 is to crank out more heat then I need in emergencies / shorten recovery periods from setback. Plus at -40, I'll need to be running the car often if I want it to run when I need it.

When it comes to a generator there are maintenance concerns, and if you don't run it annually your asking for other problems. Then there is fuel storage etc...

Each has pros and cons.


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## notch (Dec 22, 2013)

Madcodger said:


> OK, somebody check my math here...


Wow, Madcodger - I'm impressed. I really don't know about the electrical science behind it, but you sure do. Thanks for the detailed explaination!

I was really just throwing out an idea to folks who may have a golf cart.

Not sure how this affects the calculations, but my cart has six 8-volt batteries (Trojan T-890 rated at 190 AH each) that are wired in series for 48-volt output. Oh, and the inverter is rated at 95% efficiency.


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## Mt Bob (Dec 22, 2013)

I have seen a lot of ruined alternators from inverters.I have seen ruined cat convertors,plugs,sensors,etc. from prolonged idle times.Plus most auto alternators are not efficient at low rpm,can overheat also.ASE master tech since the 1970's.


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## Mt Bob (Dec 22, 2013)

Madcodger said:


> OK, somebody check my math here...
> 
> I completely agree that a blow torch to light is a great idea (or gel).  But you still need much more battery than most people realize, according to my calculations.  Here goes...
> 
> ...


 You are right.Take a typical camper,winter camping.Furnace draws 4.5 amps.Only runs every hour.Will kill 4 batteries in 2-3 days.We all carry generators!


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## rickwai (Dec 23, 2013)

IHATEPROPANE said:


> If you plan on running it for a long time I would think you need a pure sine wave inverter.  It seems the Harman can sense a modified sine wave and will shut it down.  There is a thread regarding Harman and shutdown.
> 
> Also, the motors do not like a modified wave.  You can hear them labor.  But if Harman have motors that run on DC this may mot be an issue


Harman motors are AC


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## bill-e (Dec 23, 2013)

Seems Harman's inverter is kinda pricey at over $600.

Here's a thread on an alternative.  https://www.hearth.com/talk/threads...rter-from-xantrex-battery-backup-power.39864/

Personally I think the maintenance on a small generator is pretty painless, I have two.  The larger one get's run once a year and then run until the carb is empty and put away.  We seldom loose power.  I have a Yamaha inverter generator for camping that gets used all camping season and is just one pull away from going into service.

I also have faimily close so even if I wasn't home during an emergency things would get taken care of.

And lastly the stove is on a UPS which will allow it to automatically shut down if nobody's home when we loose power.


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## Harvey Schneider (Dec 23, 2013)

Madcodger said:


> OK, somebody check my math here...
> 
> I completely agree that a blow torch to light is a great idea (or gel).  But you still need much more battery than most people realize, according to my calculations.  Here goes...
> 
> ...


Your numbers seem about right but..... If you measured the input power with AC input, your stove will do better with DC input. The AC power supply has it's inefficiency too. When I measured the DC input to my MVAE I saw it vary from 18 to 24 W over a short interval (one hour). The reason for the variability is that the stove adjusts blower speeds as needed to maintain an appropriate burn level (automatic mode). 
With minimal off time for required cleaning I was able to get over two days of use on a 110 Ahr battery during the aftermath of a 2012 storm. Now I remember that although it was uncomfortable, the air temperatures weren't that bad so the stove wasn't running full force during that two days.

 Most other stoves can't manage this kind of miserly behavior and their battery life will be shorter.


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## SwineFlue (Dec 23, 2013)

Madcodger said:


> somebody check my math here...


Looks good for your DC-motor stove.   Most of us have variable-speed AC motors, where the power factor can be as low as 0.5 and effectively double the electrical load.  My stove uses under 100 Watts, but is drawing 1.2 Amps.

Looking at it in terms of current draw,  1.2 Amps at 120 Volts is equivalent to 12 Amps at 12 Volts.  Now add that 20% inverter loss and it's around 15 Amps to supply a small stove.   So the car's alternator would need to provide 15 Amps in addition to the vehicle's normal electrical load and recharging the battery.  That's a heavy load on the alternator at a 600rpm (or whatever) idle speed.


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## briansol (Dec 23, 2013)

You could always prep your car to have a different pulley size to 'overdrive' the alt.   but of course, that would kill it for daily driving at higher rpm.


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## Madcodger (Dec 23, 2013)

Harvey Schneider said:


> Your numbers seem about right but..... If you measured the input power with AC input, your stove will do better with DC input. The AC power supply has it's inefficiency too. When I measured the DC input to my MVAE I saw it vary from 18 to 24 W over a short interval (one hour). The reason for the variability is that the stove adjusts blower speeds as needed to maintain an appropriate burn level (automatic mode).
> With minimal off time for required cleaning I was able to get over two days of use on a 110 Ahr battery during the aftermath of a 2012 storm. Now I remember that although it was uncomfortable, the air temperatures weren't that bad so the stove wasn't running full force during that two days.
> 
> Most other stoves can't manage this kind of miserly behavior and their battery life will be shorter.


Those wattages seem reasonable, Harvey, and you're right - some off time will extend battery life.  I try to plan for a fairly cold day to be safe, so we're all in the same ballpark with estimates, I think.


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## gfreek (Dec 23, 2013)

SwineFlue said:


> So the car's alternator would need to provide 15 Amps in addition to the vehicle's normal electrical load and recharging the battery. That's a heavy load on the alternator at a 600rpm (or whatever) idle speed.


I wonder what would be the vehicle's normal electrical load, say with no accessories on??


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## SwineFlue (Dec 23, 2013)

gfreek said:


> I wonder what would be the vehicle's normal electrical load, say with no accessories on??


Don't know, but in a "loaded" car there's got to be some reserve available if you turn off those lights/defrosters/stereo/AC/heated seats/etc.   Also, some towing packages include heavy duty alternators.


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## gfreek (Dec 23, 2013)

This is what I have:
http://www.hodgesmarine.com/Xantrex-Prowatt-Sw600-600-Watt-True-Sinewave-Inver-p/xan806-1206.htm


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## KC7NO (Nov 17, 2014)

Does anyone make a DC motor that can replace the AC combustion motor in a Harman .... the AC motor itself looks common ... 
(and the auger motor too)


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