# Emergency 120v Battery Backup Power Supply



## ddawg16 (Aug 15, 2011)

jburd964 said:


> I have several appliances, stove, hot water heater, telephone, that could be used in a power outage with a small 120 volt back up battery supply. Does anyone have any experiences with something like this? What would be the best way to approach this? What would be the best type of self charging supply?


Do an internet search on UPS (Uninteruptable Power Supply)

I'm assuming all the above are electric....Except for the phone, forget about putting any of those devices on a UPS. A UPS to keep those devices alive for even a short period of time would cost several thousand dollars.....and you would need a whole closet just to hold the batteries..

You would be better off with a generator.

Your phone..if hard wired, is self powered by the phone line. Yes...your wireless handsets will not work. But any of the new wireless setups, at least the base station will let you use the phone without power.


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## wkearney99 (Apr 8, 2009)

High drain devices like the stove and water heater are not suitable for running off batteries. They pull FAR too much current. You cannot realistically power them from batteries. Bear in mind, batteries don't last forever and have to be changed out, sometimes as often as 2 years. And they have the potential to emit combustible gasses. So the number of batteries you'd need, the cost to replace them and the risk of fumes make it an astoundingly BAD idea to use them for stuff like stoves or water heaters.

Get a generator. But be aware of their risks too. Portable ones are quite often involved in deaths from people misusing them. Like operating one in a closed space (as in, keep it in the garage to keep is 'safe' but end up dying from carbon monoxide poisoning as a result). Or setting themselves on fire trying to refill the small tank while it's running or still hot. Portable ones are not designed for extended duty cycles. They're meant to run for a few hours and then cool down before being used again. A built-in one driven off natural gas, propane or tank-fed diesel are a much, much safer solution.

I went with a 20kw unit running off natural gas. It has a whole house automatic transfer switch. It turns itself on automatically within 30 seconds of losing utility power. It's capable of running for many days straight. I do still have a few small battery UPS units around to support electronic gear during the 30 second cut-over. Cost around $10k installed, absolutely well worth it.


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## Yoyizit (Jul 11, 2008)

jburd964 said:


> a power outage


How long, average time and max time, do you think you'll need backup?


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## jburd964 (May 4, 2009)

The thought came to mind the other night when I'd been working outside all day and came in to take a shower and the power went out. I thought well if I had a battery back up for our on demand water heater, that would be sweet as I climbed in for a cold shower. Just thought there could be something that would work in a reasonable price range without a lot of head ache. I have a generator for the long hauls.


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## k_buz (Mar 22, 2012)

Just for my own curiosity, is the on-demand water heater gas or electric?


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## mpoulton (Jul 23, 2009)

Backing up gas appliances that only have electronic controls is easy since they hardly use any power. But providing backup power for huge loads like electric stoves, dryers, or (worst of all) an electric on-demand water heater definitely requires a generator. A huge generator, in the case of a whole-house on-demand water heater.


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## wkearney99 (Apr 8, 2009)

jburd964 said:


> The thought came to mind the other night when I'd been working outside all day and came in to take a shower and the power went out. I thought well if I had a battery back up for our on demand water heater, that would be sweet as I climbed in for a cold shower. Just thought there could be something that would work in a reasonable price range without a lot of head ache. I have a generator for the long hauls.


So if you have a generator then what's the issue? Or are you dealing with a portable unit or a manual transfer switch? One with an automatic transfer makes the transition painless. Just wait 30 seconds, it starts itself automatically and cuts power over to it. It also cuts back over to utility power and turns itself off when power resumes. This alone, beyond the safety and setup hassles of a portable, more than justified getting a fixed unit for us.


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## wkearney99 (Apr 8, 2009)

mpoulton said:


> A huge generator, in the case of a whole-house on-demand water heater.


Define huge. I've got a 20kw unit and even with EVERYTHING in the house fired up it still only peaked at 85% load. This included the AC (compressor and blower), microwave, electric oven, hot tub (220vac; heater on and pumps running), electric dryer, plasma tv, computers, washer and every possible light. Just how much draw does this heater you mention require?

This was a $10k investment, installed, and it's a bit smaller than the size of 3 drawer file cabinet laid on the side. From what I've gathered it costs about 20% to generate electric this way over the local utility. So while it's 'more expensive' it's not enough that I'm worried about what it'll cost me should the power go out for a few days.


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## mpoulton (Jul 23, 2009)

wkearney99 said:


> Define huge. I've got a 20kw unit and even with EVERYTHING in the house fired up it still only peaked at 85% load. This included the AC (compressor and blower), microwave, electric oven, hot tub (220vac; heater on and pumps running), electric dryer, plasma tv, computers, washer and every possible light. Just how much draw does this heater you mention require?
> 
> This was a $10k investment, installed, and it's a bit smaller than the size of 3 drawer file cabinet laid on the side. From what I've gathered it costs about 20% to generate electric this way over the local utility. So while it's 'more expensive' it's not enough that I'm worried about what it'll cost me should the power go out for a few days.



An electric on-demand water heater typically requires more power than the entire rest of the house combined. They come in many different sizes so it's hard to generalize, but they are usually 12-48kW.


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## jburd964 (May 4, 2009)

Incomplete post removed.


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## jburd964 (May 4, 2009)

Everything in my new house is gas except for the dryer an it's piped for when this one goes out. All I want to do is to have hot water and stove for the short outages, instead of hooking up my 20kw PTO drive generator. As for as the stand by generators they're a pile of **** unless you send around 20k for the air cooled ones and then I'd do some serious questioning. I had a 15kw Generac Guardian at around 10k investment that went to sh** around 13 months old with expired warranty. To sell them they cut all corners an sacrifice reliability by using aluminum windings over copper. Aluminum is to unstable and expands under the heat of normal operation either coming in contact with stator and pulling itself apart. The engines run constantly at ex-streamly high 3500 RPM's. If ran as needed in emergency conditions it's engine used a quart of oil in a 24 hour period, I call manufacture and the said this was typical. Everything that glitters isn't gold. Sometimes its the light reflecting off the moisture in a pile of sh**.

I'm not a professional., But I did stay at Holiday Inn Express last night.


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## curiousB (Jan 16, 2012)

Any backup scheme typically relies on batteries for brief dropouts, generator for longer periods. Typically battery backup is for just a couple minutes until the generator kicks in. 

Your upset about the generator random failure you had. Think how upset you'll be when you have to change out a $3,000+ bank of lead acid batteries every 3-5 years because they get sulfated and are no longer usable....

Battery backup for an entire residence isn't practical. I wouldn't dismiss all the worlds generators because you had a bad experience. Lots of people have car failures just out of warranty. Does that make cars terrible across the board.... Random failures happen, you just got the unfortunate occurrence.


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## zappa (Nov 25, 2011)

k_buz said:


> Just for my own curiosity, is the on-demand water heater gas or electric?


Yeah, since they all run on gas except the phone :laughing: your idea of battery backup is doable.


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## Red Squirrel (Jun 29, 2009)

I recently setup a UPS using an inverter-charger. All UPSes that you buy at the store only have a short run time. 5-10 minutes at most with an actual load on it. I wanted a couple hours. 

An inverter-charger is basically a UPS, except you can connect any amount of batteries you please and normally the batteries you'd buy for this will be much bigger, marine batteries. The little ones in an off the shelf UPS are maybe 7 amp hour while big ones you buy (for about the same price) are 100amp hour. You can even pay more and get higher end AGM batteries meant for solar systems and some of them can be 150 or even 200ah. Only downside is most inverter-chargers are 12vdc and not 24vdc so there's a bit more efficiency loss there. The more amps you draw from a single battery, the lower it's AH rating is. When a battery is 100AH, it means it is 100AH at a specific amperage. At a higher amperage it may be 80AH or even lower. I'm no expert on this so I wont really go too technical but you can find more online on this subject. 

This is the UPS I setup:



I still need to setup voltage monitoring and a hydrogen sensor but otherwise it works. Yes, hydrogen sensor. If you start adding big batteries like this in your house it's something to keep in mind. they do produce hydrogen. Hydrogen dissipates pretty quick so it's usually not a concern but better safe than sorry. 

My setup will run a 300w load for about 5 hours according to my testing. It will NOT run things like you mentioned though, stove or hot water heater. For that you're looking at a much bigger and expensive setup. 3000w+ capacity and tons of big batteries. You would not want to run this off a 12v system either, more like 48v. A stove is also split 120/240 so you'd need an inverter that can do that. 

A UPS like my setup is good for loads up to around 1000w. Mine specifically is rated at 750w. I would not want to put more than 700w on it. So it will do a bunch of computers, lights, TV, that kind of stuff. 

For anything big you'll want a generator. A UPS is good for stuff that cannot be momentarily turned off such as computers. Things like a stove or hot water heater can be turned off momentarily by the time you hook up the generator, not a huge deal. You can always look at a standby generator too if you get lot of outages that way everything turns off and a minute or even less later the generator kicks in. Also a good idea to test the generator once and a while, and have it run for an hour or two just to get the parts moving.


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## jburd964 (May 4, 2009)

Let me get this straight, the only thing the back up would be powering is the igniter and a small digital display on natural gas on demand hot water heater and stove top igniter.

I'm not a professional., But I did stay at Holiday Inn Express last night.


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## Red Squirrel (Jun 29, 2009)

Ohh ok so it's a gas water heater? Then yeah a UPS could work to power the electronics and power vent fan if any.

Use an amp meter to find out how many amps the devices use, times by the voltage (120 or 240) and that will give you about how many watts it uses. Divide this by the DC voltage of whatever UPS you'll use, then divide the amp hours of the battery by this value. Will give you a rough estimate of how long you'll have. You can probably times by 0.8 to get a more accurate number as it will always be lower.


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## ddawg16 (Aug 15, 2011)

jburd964 said:


> I have several appliances, stove, hot water heater, telephone, that could be used in a power outage with a small 120 volt back up battery supply. Does anyone have any experiences with something like this? What would be the best way to approach this? What would be the best type of self charging supply?_* Let me get this straight, the only thing the back up would be powering is the igniter and a small digital display on natural gas on demand hot water heater and stove top igniter*_.


So it took 16 posts for yo to realize that you didn't give us all the information that we needed to give you an accurate answer?

Your initial post illuded to you have all electric devices....only now do we find out your stove is gas and you 'on demand' water heater is gas...with electric controls.....that information up front would have saved a lot of time.

Ok...stove...you don't need electric for it...just use one of those hand ignighters...

For the gas water heater....use an extension cord.

A UPS for those devices is not a big deal....your big issue is how you segregate them from your house power. If your willing to run separate circuits from those devices to the UPS....yea...it would work. 

TBH....not sure why you are worried aobut taking a shower during a power outage.....I would be more worried about the fridge....


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## Red Squirrel (Jun 29, 2009)

I guess I can see the concern since it's on demand so as soon as it stops, the hot water is no longer hot, unlike a tank. Sucks if you're in the middle of a shower and the power goes out. 

What I'd do is add a dedicated UPS for that one, I'm guessing it's wired straight into the panel, so what you'd have to do is change it so there is a power outlet near it, and add a plug to it. So plug the UPS in the outlet and the heater in the UPS. If it's only powering a gas valve and a few electronics, it probably does not use much power so you may actually get a good 30 minutes out of it. You're not going to be getting multiple hours unless you do a bigger setup like I did though. The only purpose would be to give you a chance to finish up your shower if you happen to be taking one and the power goes out.


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## 71turbobmw (Mar 29, 2013)

Hello i would like to know what kind of ups you are useing for the build you have? I need something that can power a 220 watt fan 1.9 amps 60 hz for about 5 hrs would your setup be able to handle that? also i'm not great with all this electrical stuff i am a car mechanic and can install typical house electrical repairs but not familiar with ups systems can you help me out? Thanks


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## Shellback (Apr 21, 2015)

Get a small engine and an automotive alternator. visit Epicenter dot Com, and see how to put together a means to keep everything running. 

If you use an engine with electric start, you can cobble together an automatic system to start your engine when the power fails. 

The battery, like a flywheel, will keep the system running while the engine starts and comes up to speed.


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## danpik (Sep 11, 2011)

You do realize the original posting on this thread is almost 3 years old


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