# Homemade Battery Backup



## TimfromMA (Mar 7, 2014)

I built this battery backup system for my St Croix Hastings after 1 too many short power outages that caused my house to fill up with smoke.

It is simply a store bought APC with it's own internal batteries removed. In their place, I wired in (2) 90AH marine batteries. This sits in a room just below the stove. It's wired through the wall directly upstairs to the outlet the stove plugs into.

This set up will run my stove for about 8 hours in a power outage.


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## hoverfly (Mar 7, 2014)

I wonder, can you post a pic of your vent from the stove and form out side?  Thanks


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## UpStateNY (Mar 7, 2014)

Very nice,  Which store bough APC did you buy  and what are the specs on it.  Are the the (2) 90AH Marine batteries wired in series (24volt) or parallel (12volt)?


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## chken (Mar 7, 2014)

Great, I've thought of doing that since I have an old UPS that needs new batteries and the replacement ones are barely cheaper than buying a new UPS. Repurposing seems like a good idea.


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## TimfromMA (Mar 7, 2014)

hoverfly said:


> I wonder, can you post a pic of your vent from the stove and form out side?  Thanks




I think I know where you are going with this.

No, my vent has no vertical rise. It exits the back of my stove, has a 45 degree bend then straight out through the wall.


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## TimfromMA (Mar 7, 2014)

UpStateNY said:


> Very nice,  Which store bough APC did you buy  and what are the specs on it.  Are the the (2) 90AH Marine batteries wired in series (24volt) or parallel (12volt)?



Its an APC XS1500

It's a 24V system so the batteries are wired in series.


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## railfanron (Mar 7, 2014)

I'd make sure those batteries don't put out hydrogen when being charged. That could send the battery through the roof if there was a spark of some kind. A friend of mine did that 50 years ago in a gas station and it made a very neat square hole in the ceiling. Glad no one was hurt.
Ron


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## TimfromMA (Mar 8, 2014)

railfanron said:


> I'd make sure those batteries don't put out hydrogen when being charged. That could send the battery through the roof if there was a spark of some kind. A friend of mine did that 50 years ago in a gas station and it made a very neat square hole in the ceiling. Glad no one was hurt.
> Ron



Yes, they do produce hydrogen when charged which is why they are in a completely separate room from the stove.


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## DBCOOPER (Mar 8, 2014)

I'm planning on something similar when the battery in my APC dies. I was wondering if the charging circuit in the APC could handle larger batteries and if it would just take longer to recharge them.


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## TimfromMA (Mar 8, 2014)

The APC will recharge the batteries it just takes several days to do so.


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## hoverfly (Mar 8, 2014)

Tie a solar panel to those batteries!


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## wsar10 (Mar 8, 2014)

chken said:


> Great, I've thought of doing that since I have an old UPS that needs new batteries and the replacement ones are barely cheaper than buying a new UPS. Repurposing seems like a good idea.


 
Check out http://www.batteryspace.com/12vsealedleadacidbatteries.aspx
they have real good prices on batts.


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## TimfromMA (Mar 8, 2014)

hoverfly said:


> Tie a solar panel to those batteries!



I wanted solar but my yard is too shady.


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## wsar10 (Mar 8, 2014)

TimfromMA said:


> I wanted solar but my yard is too shady.


 
roof of your house ,shed or garage ???


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## TimfromMA (Mar 8, 2014)

I had solar a solar guy to my house and he said that I don't get enough direct sunlight for solar to be worthwhile.


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## TimfromMA (Mar 8, 2014)

wsar10 said:


> roof of your house ,shed or garage ???



My garage is under my house and my shed is only an 8' x 10'


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## wsar10 (Mar 8, 2014)

TimfromMA said:


> My garage is under my house and my shed is only an 8' x 10'


 
If the shed location is good though, this sounds like a good excuse to build a bigger shed !! just think _workshop, pellet storage and room for solar panels_ !


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## TimfromMA (Mar 8, 2014)

On a bad month, my electric bill is $120. Most months its in the $70 - $80 range. Solar really isn't economical for me, especially how little I can generate given the lack of direct sunlight.


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## chken (Mar 8, 2014)

wsar10 said:


> Check out http://www.batteryspace.com/12vsealedleadacidbatteries.aspx
> they have real good prices on batts.


Thanks for the link.


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## TimfromMA (Mar 9, 2014)

wsar10 said:


> If the shed location is good though, this sounds like a good excuse to build a bigger shed !! just think _workshop, pellet storage and room for solar panels_ !



The shed sits off to the side of my yard in the trees. It's even shadier than the house is.


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## hoverfly (Mar 9, 2014)

TimfromMA said:


> On a bad month, my electric bill is $120. Most months its in the $70 - $80 range. Solar really isn't economical for me, especially how little I can generate given the lack of direct sunlight.



In this aspect, I'm thinking of long power outage durations when it's cold out.  Unless you got pine trees in the way, having the panels covered up from leaves during the summer  is no big deal.  One or two panels should be enough, would not be bad for a little home project.


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## TimfromMA (Mar 9, 2014)

Every single power failure I've had since I bought my house has been less an hour except for one when Sandy came to town.

This battery system is really only meant to keep the stove running during these short duration outages when the house will fill with smoke if power is cut while the stove is running. After a couple hours, I'm rolling out the backup generator


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## batchman (Mar 9, 2014)

TimfromMA said:


> The APC will recharge the batteries it just takes several days to do so.



That is actually a big testament to your APC UPS.  That is a much bigger charging load than it was shipped with - if the circuit hasn't burnt itself up I give them a big thumbs up.

Cheers,
- Jeff


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## TimfromMA (Mar 10, 2014)

batchman said:


> That is actually a big testament to your APC UPS.  That is a much bigger charging load than it was shipped with - if the circuit hasn't burnt itself up I give them a big thumbs up.
> 
> Cheers,
> - Jeff


Im not sure it works like that.

Think of it like filling up a kiddie pool with a garden hose. The pool will fill up in a few minutes. If you take the same hose and try to fill up an olympic size swimming pool, it doesn't overload the hose, it just takes ALOT longer.


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## hoverfly (Mar 10, 2014)

TimfromMA said:


> Every single power failure I've had since I bought my house has been less an hour except for one when Sandy came to town.
> 
> This battery system is really only meant to keep the stove running during these short duration outages when the house will fill with smoke if power is cut while the stove is running. After a couple hours, I'm rolling out the backup generator



A generator? Oh my back, my back!


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## batchman (Mar 10, 2014)

TimfromMA said:


> Im not sure it works like that.
> 
> Think of it like filling up a kiddie pool with a garden hose. The pool will fill up in a few minutes. If you take the same hose and try to fill up an olympic size swimming pool, it doesn't overload the hose, it just takes ALOT longer.




Except when electronics run at their capacity they get hot,  and if not well designed they get hot enough to damage themselves - especially if run at capacity for a long time.

HTH,
- Jeff


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## TimfromMA (Mar 10, 2014)

batchman said:


> Except when electronics run at their capacity they get hot,  and if not well designed they get hot enough to damage themselves - especially if run at capacity for a long time.
> 
> HTH,
> - Jeff


 
I've only had 1 power failure lasting more than an hour in the 6 years I've owned the house and that one ocurred in the late summer.

Once per year, I like to pull the plug on the APC and let it run on battery for a few hours just to make sure everything is working. Once done, I will disconnect the batteries from the APC and throw them on a proper marine battery charger.

I keep the APC connected to the batteries all summer to trickle charge them.


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## _CY_ (Mar 12, 2014)

TimfromMA said:


> I've only had 1 power failure lasting more than an hour in the 6 years I've owned the house and that one ocurred in the late summer.
> 
> Once per year, I like to pull the plug on the APC and let it run on battery for a few hours just to make sure everything is working. Once done, I will disconnect the batteries from the APC and throw them on a proper marine battery charger.
> 
> I keep the APC connected to the batteries all summer to trickle charge them.



what a killer idea using a UPS for a PC as a 12v to 120v inverter. passed on several large 1,000 watt UPS at garage sales that had dead batteries for less than $20 .. that dead UPS has a 1,000 watt sine wave inverter inside.

400 watt UPS to my PC has an external 12v PB battery much larger than stock.


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## TimfromMA (Mar 12, 2014)

This particular APC is 24V which is why I needed 2 battereis.


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## mass_burner (Mar 12, 2014)

TimfromMA said:


> IThis set up will run my stove for about 8 hours in a power outage.
> 
> View attachment 129158


 

then what? Last year we had a 4-day outtage.


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## TimfromMA (Mar 12, 2014)

mass_burner said:


> then what? Last year we had a 4-day outtage.



Backup generator.


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## Mr. Spock (Mar 12, 2014)

Or this?


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## SwineFlue (Mar 13, 2014)

Mr. Spock said:


> Or this?



What's the capacity of your setup?


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## TimfromMA (Mar 13, 2014)

Wish I had enough direct sunlight.


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## WoodPorn (Mar 13, 2014)

TimfromMA said:


> Im not sure it works like that.
> 
> Think of it like filling up a kiddie pool with a garden hose. The pool will fill up in a few minutes. If you take the same hose and try to fill up an olympic size swimming pool, it doesn't overload the hose, it just takes ALOT longer.


 

Batchman is correct here, maintaining the float charge will not be an issue for the APC, however recharging  a depleted jar wil max out the charging sys,
Now triple or quadrupel that with the added Ah capacity you've created and voila, there will be a failure.

I would look into an added charging sys for this.

Great idea though, and looks to be fairly well done!


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## Mr. Spock (Mar 13, 2014)

SwineFlue said:


> What's the capacity of your setup?


2kw generation. 740 amp/hrs in the 24v bank.


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## SmokeEater (Mar 13, 2014)

Mr. Spock said:


> Or this?
> 
> View attachment 129568
> View attachment 129569



This isn't a battery backup, but I thought an interesting photo of a little hydro plant that my brother and I built.


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## chken (Mar 14, 2014)

Mr. Spock said:


> 2kw generation. 740 amp/hrs in the 24v bank.


Nice install! What incentives/subsidies does Massachusetts offer for solar installs? Is that grid-tied, or a standalone backup?


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## KodiakII (Mar 14, 2014)

I am surprised that UPS runs your stove without damaging it or at least making your motors hum.  It (that particular UPS) is a "stepped approximation to a sine wave" not a pure sine wave model.  Being a St. Croix owner for a number of years I was informed when I bought mine that anything other than pure sine wave would damage the stove.


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## TimfromMA (Mar 14, 2014)

It runs great. You would never know it's running on an APC. 

Before the APC I tried a stove sentry (not the pure sine wave model) and the stove did not like it AT ALL. I was going to upgrade to the pure sine wave stove entry when I got the APC idea. I did alot of experimentation in the middle of my living room floor before moving it downstairs and running an electrical line up inside the wall.


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## SwineFlue (Mar 14, 2014)

Mr. Spock said:


> 2kw generation. 740 amp/hrs in the bank.



Very nice.  So during a long outage, do you think you would average using about 1200 Watts (while it's recharging the batteries) throughout the day and maybe 600 Watts through the night?   Or am I being too optimistic on the battery usage?


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## Mr. Spock (Mar 14, 2014)

SmokeEater said:


> This isn't a battery backup, but I thought an interesting photo of a little hydro plant that my brother and I built.


Technically no. I must physically flip the switch from grid to inverter. But it is a battery bank connected to an inverter. Just happens to be charged by solar panels.


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## Mr. Spock (Mar 14, 2014)

chken said:


> Nice install! What incentives/subsidies does Massachusetts offer for solar installs? Is that grid-tied, or a standalone backup?


Off grid. I believe it was a 20% rebate federal at the time. Do not recall the state incentives.


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## SmokeEater (Mar 14, 2014)

Mr. Spock said:


> Technically no. I must physically flip the switch from grid to inverter. But it is a battery bank connected to an inverter. Just happens to be charged by solar panels.



My thoughts some time ago were similar to your setup.   My electric energy supplier has a day/night rate that differs.  At one time the night rate was about half that of the day rate.  It would make sense to charge batteries during the night and run the home on the bank during the high rate times.  My usage durilng the whole day was about 30 kWhrs so I calculated that if I could store about 60 kWhrs of energy that I would not only cut my energy use in about half, but would have a 2 day backup in case of an outage without the use of a noisy generator.  Sure would work and the inverters I chose were two pure sine wave from Xantrex at 120 volt each.  I could connect them to my panel through a switch and would have my 2 pole single phase 240 v supply.  The batteries i chose were the 2 volt per cell industrial lead acid connected up for a 24 or 48 volt input.  Higher if I could to reduce wire size.  Expensive though.


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## Mr. Spock (Mar 14, 2014)

SwineFlue said:


> Very nice.  So during a long outage, do you think you would average using about 1200 Watts (while it's recharging the batteries) throughout the day and maybe 600 Watts through the night?   Or am I being too optimistic on the battery usage?


In the interest of not totally hijacking this thread, sorry OP, I wil provide the calculation to determine how much runtime you can get from a amp/ hr battery rating vs load.
In my case the XXV draws 120 watts max (no igniter). This is all fans and auger moter running.
So first thing to calculate is the amperage draw for 120 watts on a nominal line voltage of 120v.
Amps=watts/volts. So the XXV is drawing 1 amp.
Next determine the amperage draw when the source voltage differs because the inverter must step up the battery voltage to 120v. The conversion is Batt Amps Draw = Amp draw @ line voltage * ( line voltage/ batt voltage) .
So the in the case of a 1 amp source draw the inverter must pull  5 amps from my 24 bank to supply 120 volts at 1 amp.
To calcuate total run hours ( complete discharge of the bank)  use the equation RunHours=BattAmpHours/DrawAmps.
So  740 amp/hrs  /  Amp draw =  148 run hours.  I would never take the bank down that far. Maybe 50% depth of discharge. So 148 * .5 = 74 hours. 

Now the experienced may note that there are many other variables that come into play here when we start talking discharge rates. These Maths do not take into account battery discharge for different C rates (amp draw)  or battery temperature. But for anything under the C20 rate  they provide conservative values on quality deep cycle batteries.


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## Mr. Spock (Mar 14, 2014)

SmokeEater said:


> This isn't a battery backup, but I thought an interesting photo of a little hydro plant that my brother and I built.





SmokeEater said:


> My thoughts some time ago were similar to your setup.   My electric energy supplier has a day/night rate that differs.  At one time the night rate was about half that of the day rate.  It would make sense to charge batteries during the night and run the home on the bank during the high rate times.  My usage durilng the whole day was about 30 kWhrs so I calculated that if I could store about 60 kWhrs of energy that I would not only cut my energy use in about half, but would have a 2 day backup in case of an outage without the use of a noisy generator.  Sure would work and the inverters I chose were two pure sine wave from Xantrex at 120 volt each.  I could connect them to my panel through a switch and would have my 2 pole single phase 240 v supply.  The batteries i chose were the 2 volt per cell industrial lead acid connected up for a 24 or 48 volt input.  Higher if I could to reduce wire size.  Expensive though.


How much did that hydro build cost?


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## SmokeEater (Mar 14, 2014)

Mr. Spock said:


> How much did that hydro build cost?


I can't give you a price that's accurate.  The dam was existing but we put a lot of time and material into it.  It was an abandonded power plant and the turbine you see was made by BLH of the famed railroad engines.  It weighs about 20 tons and is rated at 750 kw.  There is another newer turbine generator mounted in a vertical position that we bought and installed.  The purchase price alone was about $485,000.  Still had to be installed.  That machine was installed in 1984 and is a 600 kw Francis unit with a 600 kw direct drive Westinghouse generator that you can see the top of in the background inside the red steel railing.  All together the place is on the market for about $2M.  It generates between 5 and 6m kWhrs/year.


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## _CY_ (Mar 15, 2014)

Mr. Spock said:


> 2kw generation. 740 amp/hrs in the 24v bank.



740 AH @ 24v or 12v? 

very nice setup ..


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## Mr. Spock (Mar 17, 2014)

_CY_ said:


> 740 AH @ 24v or 12v?
> 
> very nice setup ..


24v


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## briansol (Oct 14, 2014)

Now i'm paranoid that my ups is too close to my stove.   i actually have it sitting on the left...  you can almost see the corner of it in my avatar, that black line is the start of it.

it's been there 2 years now, now hydrogen bomb.  should i move it?   it's a cyberpower, unmodified.


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## mralias (Oct 14, 2014)

Mr. Spock said:


> Or this?
> 
> View attachment 129568
> View attachment 129569
> ...


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## Wilbur Feral (Oct 16, 2014)

briansol said:


> Now i'm paranoid that my ups is too close to my stove.   i actually have it sitting on the left...  you can almost see the corner of it in my avatar, that black line is the start of it.
> 
> it's been there 2 years now, now hydrogen bomb.  should i move it?   it's a cyberpower, unmodified.


Is your UPS using the factory battery?  If so, it is very likely Absorbed Glass Mat and personally I would not worry as AGM produces very low levels of hydrogen during recharge.  That said, I am no expert and you may wish to consult one.

If you use a standard marine battery that is not AGM, (i.e., you modified a UPS to use one), or if like me you have a stove that can run on battery backup (an MVAE), then do NOT recharge near the stove!  I recharge in a drafty garage with a fan running.


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## briansol (Oct 16, 2014)

I have not modified the unit in any way.   It has stock batteries.   I looked at the manual, and it says 'keep away from fire' but that's most things with batteries.


Battery Size & Type 2x Rechargeable 12V/8.5AH Sealed Lead Acid (User Replaceable)

so they are not AGM.


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## dlehneman (Oct 16, 2014)

TimfromMA said:


> I built this battery backup system for my St Croix Hastings after 1 too many short power outages that caused my house to fill up with smoke.
> 
> It is simply a store bought APC with it's own internal batteries removed. In their place, I wired in (2) 90AH marine batteries. This sits in a room just below the stove. It's wired through the wall directly upstairs to the outlet the stove plugs into.
> 
> ...


Hey Tim,
I've been considering a very similar setup for the past year. I actually bought a UPS missing the battery at a thrift shop hoping to try it out, but unfortunately the UPS wasn't charging at all so I didn't get to try it yet.
Anyway, I know you said it would run your stove about 8 hours, but have you ever tested it that long? If not, what's the longest you've tried? Does the UPS try to estimate run time with those batteries or does it just assume factory battery run time?


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## TimfromMA (Oct 16, 2014)

dlehneman said:


> Hey Tim,
> I've been considering a very similar setup for the past year. I actually bought a UPS missing the battery at a thrift shop hoping to try it out, but unfortunately the UPS wasn't charging at all so I didn't get to try it yet.
> Anyway, I know you said it would run your stove about 8 hours, but have you ever tested it that long? If not, what's the longest you've tried? Does the UPS try to estimate run time with those batteries or does it just assume factory battery run time?



Yes, Ive tried it. I actually measured the voltage on the batteries every 10 minutes for the entire time. After 8 hours, the batteries measured about 11.8V each which represents about 60% discharge. Any further discharge risks damaging the batteries.

The estimated runtime shown on the front of the UPS is based on factory batteries. If you wire in larger batteries like I did, do not rely on it to tell you how much time you have left.


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## dlehneman (Oct 16, 2014)

Thanks!


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