# How to Build a Battery Back up for the Blower?



## Srbenda (Sep 14, 2010)

My insert has a 8amp, 115v, 60hz blower motor, and I want to build a relatively small backup power supply for this motor.  

I have zero electrical engineering knowledge, so how do I calculate how much battery power I need to run the motor for approximately 8 hours?

I would like to have a setup that would keep the battery on a charger, and during a power outage would be moved to the blower motor with an inverter. 

Any help?


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## 73blazer (Sep 14, 2010)

8amps*110v=880watts.
You'll need an 880watt inverter, probably more like 1000 because it's a motor and takes a startup surge load. 
Then you just need to pick enough batteries to to run 880watts for your specified period of time.
Is that what the motor is rated at or have you ammetered it out and find it's running load? Running load is probably a bit less than rated. But you never know.

If your going to keep the batteries in the house, you'd need nice sealed batteries, like Optima's. The biggest deep cycle (blue top) optima they make is 75 amp-hours (D31). 
Meaning, it'll run 75amp load for 1 hour at 12v.That's 900  watts for 1 hour.  FOr your situation, inverters are usually only 80% efficient at converting DC to AC power. So your actually wattage for an hour is 720. So you'd probably need 2 Optima D31's to really run your motor for an hour or slightly more.
Then your going to have to charge and keep charged those batteries, so you can either get an inverter with a built in charger. Or have a separate battery charger and keep them topped off at least once a month. 

In all your costs involved would be something like:
2 Optima D31's (approx $200/each): $400
   1000watt inverter                            : $120
   or 1000watter inverter/10amp charger: $200
 misc 8 gauge wiring                         : $20

So your in for $520 at a minimum and possibly more if you don't already have some other means to charge batteries and alot more if you want to run it for more than an hour (you'd need 2 batt's for every hour of operation, roughly).

I supposed you could disassemble the fan motor unit, because it'll have a giant AC to DC converter built into it (most all small motors run on DC anyway), if you wired the motor direct to the battery, you could not lose the 20% both ways and lose the cost of the inverter, so effectively a 40% gain on the system. But then you'd have to wire in a switch to be able to run it on normal AC. 

My advice, buy a small gas Generator, far more useful for other things and less maintenance.


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## ANeat (Sep 14, 2010)

Thats a lot of power to ask from a battery or several batteries. 

 8amp @ 115volts is 920 watts,  now thw actual draw may be less than that.

 To get 920 watts out of a 12 volt battery is 76 amps.  Thats a lot of current for 8 hours.


 If you insist on battery backup higher voltage will reduce the current load.  2   12 volt batteries in series (24 volt) would cut the current in half,  3 (36 volt) would only need 1/3 the current (25 amps)  but the appropriate inverter would be required


 A small generator might be a better solution.  1kw or 1.5kw....  Or just be happy with the radiated heat and live without the blower if the electric is out


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## ANeat (Sep 14, 2010)

+1 to what 73blazer said,  he typed it faster than me :lol:


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## 73blazer (Sep 14, 2010)

ANeat said:
			
		

> Or just be happy with the radiated heat and live without the blower if the electric is out



Even better!


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## Srbenda (Sep 14, 2010)

Wow.  

I thought a couple of batteries, and an inverter would do it. 
I have a generator, I guess I'll just use that.


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## 73blazer (Sep 14, 2010)

I think the real issue is that 8amps. That seems really high for an insert blower. I bet if you amped it out it's really only pulling 3 or 4. But, you just don't know unless you put a meter on it. 
STill, if it was 4 amps, those 2 giant optima's would only run it for 2 hours or so.  Still $520 for 2 hours runtime, plus charging (inverters w/built in chargers cost alot more). 
I think Generator is best route!


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## btuser (Sep 14, 2010)

8 amps is a hell of a draw from a blower.   Are you sure that's not .8 Amps?  With that kind of fan you'd have to tie down the furniture.


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## Srbenda (Sep 14, 2010)

Here's what I am basing it on. 
Do you see 8A?


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## ANeat (Sep 14, 2010)

looks like .8 to me


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## Srbenda (Sep 14, 2010)

ANeat said:
			
		

> looks like .8 to me



Yep, I just looked at the original photo, and it's .8A

This should make the calculations different!


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## ANeat (Sep 14, 2010)

Yea instead of trying for 1000 watts you only need to worry about 100 watts


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## Treacherous (Sep 14, 2010)

If you did go with a generator I highly recommend the Honda EU series.  I have a couple EU2000iA's.  They will run nearly 10 hours on a gallon of gas at 1/4 load.

I also have some 6 gallon marine tanks so I could run it up to 70 hours straight if needed.

http://picasaweb.google.com/audreyappliance/HomemadePortableCoverForHondaEU2000i?feat=directlink


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## 73blazer (Sep 14, 2010)

Srbenda said:
			
		

> ANeat said:
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So, one Optima D31 would run it for approx 7-8hrs. 
Still need the inverter/charger. But, far more feasible@0.8amps!


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## KB007 (Sep 14, 2010)

You could prolly buy a few hundred or 1KW UPS for a couple of hundred bucks


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## billb3 (Sep 14, 2010)

even with a generator, you might want to protect  the stoves circuit board from voltage and hz variants from the generator  with a UPS.


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## Slow1 (Sep 14, 2010)

KB007 said:
			
		

> You could prolly buy a few hundred or 1KW UPS for a couple of hundred bucks



That's the route I'd suggest - watch the sale fliers or the net.  They come up periodically from office supply stores etc.  Off brand UPS systems etc sometimes for amazingly low prices.  With the UPS you will get the automatic failover as well (a bit harder to wire in your home made solution). Now the question is how long do you want to be able to run it for?  I would think that if you get 30-60 minutes out of it you are fine, any longer than that go hook up the generator that I think you said you already have, right?


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## oldspark (Sep 14, 2010)

If you go with a UPS make sure you get the right one as some of those do not like to run motors.


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## Treacherous (Sep 14, 2010)

billb3 said:
			
		

> even with a generator, you might want to protect  the stoves circuit board from voltage and hz variants from the generator  with a UPS.



Agreed.  You would definitely want to utilize one of the inverter generators from Honda, Yamaha, Kipor, etc.

I would never use a standard square wave generator with electronics.


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## oldspark (Sep 14, 2010)

Treacherous said:
			
		

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 Not sure I understand what you are saying , you are not going to have a square wave with a motor driven gen.


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## Treacherous (Sep 14, 2010)

I should rephrase... it is actually a squarish wave in the cheaper non-inverter based generators versus a pure sine wave in an inverter based generator.


I don't claim to be an expert but that is what I am told.

The Hz difference alone will make a PC clock skew fairly quickly.




			
				oldspark said:
			
		

> Treacherous said:
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## oldspark (Sep 14, 2010)

A motor driven gen. puts out a very good sine wave not squarish at all so you may be mixing things up a little.


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## Treacherous (Sep 14, 2010)

I may have been thinking of an old 12V inverter that did a square wave but isn't the sine wave in a non-invertor based generator called a "modified sine wave"?

I find that I am able to power up full size refrigerators and freezers with my EU2000i that choked my old 1850 Coleman Powermate.

[I apologize for taking this somewhat off topic]


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## oldspark (Sep 14, 2010)

Sorry about the hyjack also , this site can explain it better than I can if you want to take a peek.
http://bellsouthpwp.net/j/o/johngd/files/rv/inverter_generator.pdf


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## cycloxer (Sep 15, 2010)

That's only .8 amps. A small computer UPS is the easiest method. Of course, this all depends on how long of a backup you need.


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## keydiver (Sep 16, 2010)

Honda generator = quiet when running


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## Cowboy Billy (Sep 16, 2010)

There are two types of inverters. The std inverter has a square wave or modified square wave. Then there are pure sine wave inverters. The cost more and use more power even at a when not being used. They run a square wave through a transformer which smooths the wave out.

   A 24v inverter uses the same total power as a 12v inverter but since the voltage is higher it uses less amps so you can use smaller cables. One good thing about a 12v battery bank is in a emergency you can charge it back up by running jumper cables off you car. I have a car alternator on a 10hp engine that I can charge my battery bank up with if I have to.

   We have no electric service at out farm and were having to run a generator anytime we needed 110v which was a pain and cost a lot. 1 /12 years ago we got a 5000 watt inverter and a forklift battery. Now I run the whole place off of a std modified wave inverter microwave, tv, computer, furnace., power saws, small aircompresser. I run 3-4 days on the battery the fire up the generator for five hrs or so and charge the battery back up on about 2'5 gallons of diesel.

This is my battery bank and inverter. The inverter is on the back wall on the post is a charge controller. We have two small solar pannels on it but that just makes up for natural losses in the batter while we are not there it will also control the 750 watt windmill when we get it up.







Billy


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## oldspark (Sep 16, 2010)

Billy-Nice to know that a std modified wave invertor will run everthing with out a problem, I think the system yu came up with is cool. Did they charge you by the pound for the fork lift battery?


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## central_scrutinizer (Sep 16, 2010)

From the picture you posted it looks like an old Buck Stove with the 3-speed motor in the aluminum housing.


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## maverick06 (Sep 20, 2010)

my expirance:
1) I have an insert. Without the blower on the radiated heat is not an acceptable means of heating the house. It does not put out neatily enough

2) I have a 450 watt inverter (square wave). The Blower motor was *EXTREMELY* unhappy when i plugged it into the inverter. It buzzed and hummed and made all sorts of crazy noise. But the inverter still can power other things, even flourscent light with no problems... 

3) I now have a generator. The hondas were too much for the little I use it. So i bought a honeywell 2000i (inverter generator). So far so good. Some people report logetivity issues, but if i use it more than 12 hours a year I would be surprised. So i am not concerned. 


Thats an awesome battery system! Bet its a nice place to be! Espically when the zombie apocalypse happens  haha


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## Singed Eyebrows (Oct 1, 2010)

I'm with the generator crowd, so you get the best sine wave. From what I have been told any motor run on an inverter should have inverter duty insulation, typically Nomex. The bearings are also subject to pitting unless protected. I'm not sure if a single speed inverter uses Pulse Width Modulation, it is the up to 20,000 pulses a second that can pinhole regular insulation. Others can answer some of my concerns better, Randy


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## tickbitty (Oct 1, 2010)

We did this whole backup battery thing for our sump pump in the basement.  Only to find that it isn't powerful enough for the pump, so we had to buy a littler backup pump that uses a garden hose to pump it out.  Only to find that when the water is that bad in the basement, that pump won't do it and will run constantly till the battery runs out.  Generator a much better idea for us too!  I had hoped that the backup system would help for the stove blower at least, but sounds like it's not that good for that either!  Good thing we got an insert that sits so far out of the chimney, we will get a lot of heat out of it anyway.


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## Griny (Nov 14, 2010)

```
[quote=tickbitty]We did this whole backup battery thing for our sump pump in the basement.  Only to find that it isn't powerful enough for the pump, so we had to buy a littler backup pump that uses a garden hose to pump it out.  Only to find that when the water is that bad in the basement, that pump won't do it and will run constantly till the battery runs out.  Generator a much better idea for us too!  I had hoped that the backup system would help for the stove blower at least, but sounds like it's not that good for that either!  Good thing we got an insert that sits so far out of the chimney, we will get a lot of heat out of it anyway.[/quote]

How about this, [url]http://s7d5.scene7.com/is/image/FisheriesSupply/9154_Rul_24_PPM?wid=450&hei=450[/url]
runs on 12V DC and doesn't draw a whole lot of amps. It's got a float switch so it will turn on and off on its own.
```


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## hh3f (Nov 15, 2010)

I bought a small generator for the sole purpose of suppling power to the blower on my insert in the event of power loss. I made up a cord with 2 male ends. I installed two receptacles ,1 on the outside of the house and another wired to it on the other side of the wall inside the house. Now all I have to do is start the generator and plug it into the 120v outlet outside, then run an extension cord inside from the  inside outlet to the blower. This set ups sole purpose is to keep the house warm during power outages.

This is the generator I use.
http://www.northerntool.com/shop/tools/product_200313480_200313480


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## maverick06 (Nov 15, 2010)

before the wide world rip[s that post apart. The double male cord is a safety concern and powering your house through one is illegal. BUT since you have a small generator, I ASSUME that th plan here is there are a pair of outlets (one inside and one outside, NOT powered) then you can plug the blower into one and the generator into the other. 


Now, you can sort of do this with just your male-male cord and just the house circuitry... its illegal... and i dont know what would happen to the 220 side of the circuitry.... I would like to know. Obviously i am not using this method. I just have a circuit breaker and a lot of extension cords.


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## hh3f (Nov 15, 2010)

No the 2 outlets are not apart of the house circuity and yes using two male ends is not the smartest thing to do. Its just something I made up one day to get power to the blower without running extension cords through windows or doors. Thank you for your concerns


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## Adios Pantalones (Nov 15, 2010)

I've used my car battery and an inverter.  Worked great- I had to run the car for a bit every so often to charge up the battery.  Now I have a generator.


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## moosetrek (Nov 15, 2010)

Just curious, is the blower the only thing you want to run if the power's out?  Fridge, freezer, well pump, lights, etc?  I think it would be easy enough to rig it, but I think for the cost a small generator (3-5KW or so) would be the most cost-effective long-term solution.  That was the first thing I installed in the new house - a 220V plug, wired to the entrance panel, double isolated from the power pole.  Since then, I've found dozens of uses for the generator including running a small welder in the field, etc.  Champion 3500W generators are a good Honda knockoff, quiet and less than your inverter system would be.  Just an idea...


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## moosetrek (Nov 15, 2010)

maverick06 said:
			
		

> before the wide world rip[s that post apart. The double male cord is a safety concern and powering your house through one is illegal. BUT since you have a small generator, I ASSUME that th plan here is there are a pair of outlets (one inside and one outside, NOT powered) then you can plug the blower into one and the generator into the other.
> 
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> Now, you can sort of do this with just your male-male cord and just the house circuitry... its illegal... and i dont know what would happen to the 220 side of the circuitry.... I would like to know. Obviously i am not using this method. I just have a circuit breaker and a lot of extension cords.



Not sure it's necessarily illegal depending on the OPs location.  Not smart, but our electric co simply said make sure that there's redundant isolation from the grid if we want to hook up a generator.  Maybe against code though... 

Nothing would happen b/c you would prudently shut breakers on 220V circuits first; you'd effectively power only one leg of your panel.  More importantly, the amperage produced by the generator may exceed that of the 12-14 gauge wiring to the outlet, overheating the outlet and/or wiring.


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## oldspark (Nov 15, 2010)

moosetrek said:
			
		

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 He had the outlets isolated from the house wiring and was just used for the blower, sounds like he new what he was doing.


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## maverick06 (Nov 15, 2010)

agreed... I was just trying to clarify that. Man have I seen some %^&storms; on other forums about those male-male plugs.


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## oldspark (Nov 15, 2010)

maverick06 said:
			
		

> agreed... I was just trying to clarify that. Man have I seen some %^&storms; on other forums about those male-male plugs.


 I dont like them either, I wire my gen direct into the fuse block on the pole, I have a fuse block that you can remove so not kill any lineman working on a pole some where.


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## moosetrek (Nov 16, 2010)

I hear ya - I put a 50A plug with a breaker, with big red labels and instructions how to shut off main at pole, shut off main at house, then turn on generator, then flip switch from generator...


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## velvetfoot (Nov 16, 2010)

What are those little 2-stroke gennys like?
Noise and smokey, or not so bad?


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## oldspark (Nov 16, 2010)

velvetfoot said:
			
		

> What are those little 2-stroke gennys like?
> Noise and smokey, or not so bad?


 What 2 stroke gen?


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## velvetfoot (Nov 16, 2010)

"This is the generator I use.
http://www.northerntool.com/shop/tools/product_200313480_200313480 "


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## oldspark (Nov 16, 2010)

velvetfoot said:
			
		

> "This is the generator I use.
> http://www.northerntool.com/shop/tools/product_200313480_200313480 "


 I had no idea they made a 2 stroke gen, learn something new every day.


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## moosetrek (Nov 16, 2010)

Can't be shipped to CA...  Wonder why?


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## oldspark (Nov 16, 2010)

moosetrek said:
			
		

> Can't be shipped to CA...  Wonder why?


 2 stroke-dirty emisions maybe.


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## barnartist (Nov 16, 2010)

Generators are a nice option... but only if you are there to make'em work.

I like the UPS idea. I worry about if im not at home and we have one of those outages for no reason days. Then you arent even aware of the problem.

For many using hydronic wood heat, we need to figure enough power to run a pump as well as a fan, really the pump would be more important.


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## hh3f (Nov 17, 2010)

oldspark said:
			
		

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It had very good reviews for a generator at such a low price. Ive yet to have an outage during the winter so all I do is run it for 15 mins. every 3 months and on occasion running a tool away from the house. Takes a few pull after sitting for a while.
If you think about it you can buy 3 of these for the same price of 1 honda or yamaha.


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