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Old 02-17-2011, 11:09 AM   #1
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Just want a simple answer from an electrician about a battery backup.


Hello. Hopefully I am now in the right place where someone can help me.

I have asked around several "hobby" forums about this and people don't have a clue or don't understand what I'm saying and get too technical. So I thought I know I'll find an electrical forum and ask an electriction directly.

I googled this and came accross the forum for "pro electritions" It pretty much said I need to be a pro to join and told me to come here instead... so I HOPE there is someone here that can help me.


Ok this is simple. I want something that will power the heating mats under my snake cages in a power outage. I DON'T WANT a generator that uses propane or gas because I'm afraid of starting a fire - and I'd forget to fill it etc etc.

At one time I rememeber someone using a battery with an AC plug to power their telescope at a dark site - so I went to an astronomy forum to ask this without any luck.

However I DID find this: http://www.walmart.com/ip/DieHard-71...Specifications

That LOOKS kinda like what I'm thinking of. It does have AC plugs on it so you can plug in ac devices. However I have no CLUE if it would really work the way I want to.

It says that : "Two AC outlets power up to 400 watts of household power for small electronic appliances/devices"

However the stuff after that I have no clue what they are talking about.

What I want is a device I can simply plug into the wall, charge, (perfer to leave plugged in without ill effects) then when/if the electric goes out - plug in a power strip with the various heat mats plugged into it (the strip.) I'd have about 100 watts worth. That's it. No buying another device to use with. No hardwireing (that scares me ok?)

I just need someone to tell me

a) would this work.

b) do the math to tell me how long this will power 100 watts. or how many watts it will power over a 24 hour period.

c) provide a simple condenced formula where I can take X watts plug it in the formula and find a result of Y hours - or vice versa.

Everytime I've looked up info on how to convert amp hours or amps to watts I get complex paragraphs of stuff that just goes over my head.

SO PLEASE avoide the long complex technical jargin. I just want a simple answer.


And if this won't work do you have any suggestions that would?

more expensive would be a solar geneartor... but I'd look into that if they would work the way I outlined above AND provide enough power to run stuff even if it's cloudy or snowing!

I Don't TRUST liquid fuel generators btw so please don't bother suggesting thouse.

Thank you for your time. (and I hope I don't have a zillion people rolling their eyes at me now.)

- Sharon

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Old 02-17-2011, 11:28 AM   #2
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Just want a simple answer from an electrician about a battery backup.


well, the DC is 12V and P = VA (Power (Watts) = Voltage X Amperage), you will be running about 8.33 amps (A = P/V = 100W / 12V = 8.33). Since it is a 22Ah battery (Ah = amp hours), divide 22Ah by 8.33A and you get about 2.6 hours.

so, ignoring all the technical jargon, about 2 and a half hours of power at 100 watts.


Last edited by NitroNate; 02-17-2011 at 11:48 AM.
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Old 02-17-2011, 11:30 AM   #3
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Just want a simple answer from an electrician about a battery backup.


What you want is an Uninterruptible Power Supply, available from any computer store. It does exactly what you need; plugs into the wall, stays charged, and provides battery power when the household power fails. You'll probably need a fairly large one to run for 24 hours, though. Or one smaller one for each individual heat mat.

Last edited by McSteve; 02-17-2011 at 11:31 AM. Reason: stupid typo..
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Old 02-17-2011, 11:35 AM   #4
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Just want a simple answer from an electrician about a battery backup.


Now that I've actually looked at that Walmart link, it looks like that could work reasonably well too, as long as you're there to unplug your heat from the wall and plug it into the battery pack. If you get a UPS meant for computer use, you won't have to worry about losing the heat if the power goes out while you're not home.
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Old 02-17-2011, 12:06 PM   #5
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Just want a simple answer from an electrician about a battery backup.


As others have said, an uninterruptible power supply (UPS) does what you want... but you need a very large one to power your heating mats for very long. UPS's are generally only intended to provide power for a few minutes until the equipment can be gracefully shut down or transferred to generator power. A UPS with enough battery capacity to run your heating mats during an extended outage would be prohibitively large and expensive. The other problem with UPS's is that their run time is absolutely limited - there is no way to keep your heating mats running during an extended power outage, because the UPS batteries cannot be "refilled".

The only real solution for long-term operation of a load like yours during a power outage is, in fact, a generator. That's what generators are for.
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Old 02-17-2011, 12:31 PM   #6
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Just want a simple answer from an electrician about a battery backup.


You could also look into an inverter-charger and hook it up to a bank of deep cycle batteries. To get 24 hours you will probably be looking at many batteries. When a standard home grade computer UPS says it can last for hours, that's BS, I have never seen a UPS last more then about 15 minutes with a real load on it.

I would look at pricing for a big UPS setup or a standby generator, and figure out which is more feasible.
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Old 02-17-2011, 12:31 PM   #7
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Just want a simple answer from an electrician about a battery backup.


Quote:
I Don't TRUST liquid fuel generators
!!!! You don't like cars or lawnmowers, then? I am having trouble getting my head around this particular phobia.
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Old 02-17-2011, 01:58 PM   #8
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Just want a simple answer from an electrician about a battery backup.


wow. Wasn't expecting this many replys in so short a time.


First, Thanks Nate - I think I can follow what your saying.

Second - After reading the first few posts I was about to say basicatly what mpoulton and red squirrel said about UPSes designed to provied power for only a few minutes... which means they havn't really made progress in 20 years because that was how the one I had in High school worked. was really annoying too.

What I don't get is to me 100 watts isn't much of a "load" but it is infered by other's posts that it is alot. (each mat is between 10 and 20 wats. so 100 wats is a rough estimate).

oberkc: well I trust the gas tank in my car to be constructed well enough not to cause problems - I don't trust it if I hit something where I feel I damaged it - but then I'd have a mechanic check it out.

I guess what I don't trust is *me* using the fuel... what if I spill it? what if I forget about it? I hear of propane explosions regularly. And I don't want cans of gas sitting around. (IE the only container I do trust is the car).

And I don't own a lawnmower.

I had been thinking about solar generators but are they worth it? (not talking on the roof stuff) If I'm going to spend 1000-2000k then I'd want them to power more then heat matts and for longer times.

Maybe I'm asking too much of technology - I tend to do that.

(I'm still waiting for a battery operated space heater that would be safe to leave on at night...)
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Old 02-17-2011, 02:12 PM   #9
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Just want a simple answer from an electrician about a battery backup.


Well, you are asking a lot. Part of the reason that electric cars are not as broadly accepted is that the amount of energy one can store in a battery that one can carry in a car is not as much as one can store in liquid fuel. It is just tough to beat fossil fuel for energy density. While batteries have improved in 20 years, they are still not as good as gasoline (or just too expensive).
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Old 02-17-2011, 02:36 PM   #10
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Just want a simple answer from an electrician about a battery backup.


i think it is honestly a shock to most people how much energy typical items really consume. 100 Watts is small in terms of household electricity use, but it's all relative to what you are comparing it to. you need a lot of space and a pretty massive array of solar panels to produce even a few hundred watts.

batteries are the Achilles heal when it comes to electric power. they are heavy, expensive and they just don't store that much energy given the weight. when peak performance, efficiency and lifespan are necessary for batteries such as in electric vehicles or hybrids like the prius, complicated electronics are used to maintain the proper charge zone. the prius only uses about 40% of the total capacity of its battery. 60% of the charge is basically useless, just so the battery is able to perform at its best for 10+ years of daily use. that is a lot of added weight and cost for reliability purposes.

we all know how reliable batteries are. we work with them all the time. who has ever had a rechargeable battery that has maintained its full charge under any sort of extended use for very long? shoot, you were either supposed to discharge it fully or not discharge it fully or not leave it on the charger too long or not store it in too cold or too hot of temperatures. batteries just suck, plain and simple.

Last edited by NitroNate; 02-17-2011 at 02:41 PM.
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Old 02-17-2011, 02:57 PM   #11
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Just want a simple answer from an electrician about a battery backup.


A good-sized deep cycle marine battery, along with an inverter could run those mats for several hours.

You'll need a battery with a capacity of about 100 Amp-hours for every 12 hours of operation you want to acheive. The larger the battery, the longer it will be able to power your load.

The inverter does not need to be very large, with a 100 watt load connected to it.

You could make your setup by using an RV inverter/charger. Loss of power would not affect the operation of the mats, as long as the battery holds out.


Here is a link with some useful information on those deep-cycle batteries.

PS: The correct spelling is Electrician
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Last edited by kbsparky; 02-17-2011 at 03:04 PM. Reason: added link
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Old 02-17-2011, 04:07 PM   #12
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Just want a simple answer from an electrician about a battery backup.


Running 100w off an invertor is no problem,
100W from the mains is not much power,
However 100w from a 12v battery is a good solid load.
The only down side of the idea is suppling enough 12v power,
to supply it for 24hrs, you would need minimum 200 amp/hours,
for good practice 400 amp/hours is recommendded.
A typical car battery is only 60 amp/hours.
Although other larger batteries are available,
they will not be cheap.
Maintaining the batteries will be required,
So the idea is do-able,
but not as simple as you might like.
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Old 02-17-2011, 06:26 PM   #13
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Just want a simple answer from an electrician about a battery backup.


Out of curiosity, since snakes are reptiles, wouldn't they tolerate a short span of cool (> freezing) temperature? I assume these are in your house and it should keep fairly warm during an outage?
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Old 02-18-2011, 05:47 AM   #14
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Just want a simple answer from an electrician about a battery backup.


Electrician.
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Old 02-19-2011, 12:10 AM   #15
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Just want a simple answer from an electrician about a battery backup.


Quote:
Originally Posted by McSteve View Post
What you want is an Uninterruptible Power Supply, available from any computer store. It does exactly what you need; plugs into the wall, stays charged, and provides battery power when the household power fails. You'll probably need a fairly large one to run for 24 hours, though. Or one smaller one for each individual heat mat.

Most battery back-ups use a 12V 8AH battery.

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