APC+120amp hours battery=insane uptime?

touser

Junior Member
Jun 15, 2002
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Hi all, i have a 120 Amp Hour/850MCA deep cycle marine battery lying around, and i was thinking to myself "isn't there a way to hook this thing up to my APC for some insane uptime in a power outtage?" My question is, can i do this? The battery is brand new, but i don't know if it is going to overload my apc or if there are any other problems with doing this? Thanks in advance!
 

arcas

Platinum Member
Apr 10, 2001
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It depends on the particular APC model. Some of the small APCs might use a single 12V battery in which case you're in pretty good shape (careful, some really small ones might use 6V batteries!). I know the SmartUPS 1000s and 1400s, though, are based on 24V DC input (a pair of 12V batteries). If this is what you have, then you're going to have two problems using a single battery: 1) you'd need a voltage doubler to boost the battery voltage when running on battery backup and 2) you'd need to decrease the charging voltage from around 25-26 volts down to around 13V.

In any case, you'll want to make sure you have adequate air circulation since your deep cycle battery is most likely not sealed (similarly, you'll probably not want to locate it on carpet or in the liveable part of your house...sulfuric acid spills suck).

 

touser

Junior Member
Jun 15, 2002
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Thank you for the reply arcas i appreciate it! my ups only has one battery, so it seems ok in that area, and no the battery is not sealed..one question comes to mind though, i do not want the fumes from the battery in my room, and as you said, i dont want to place it on the carpet, so would it be a good idea to put it in some kind of air tight plastic container? that way i can still have the battery under my desk, but not on the carpet, and not letting the fumes escape into the rest of the house?
 

Justin218

Platinum Member
Jan 21, 2001
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I would not mess with it. Those fumes can be nasty. Isn't worth it, get some SLA batteries if you really want to do it.
 

touser

Junior Member
Jun 15, 2002
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well, since the fumes seem to be the biggest concern, what if i where to put the battery itself outside my bedroom window in a shady area and run a line from it to my ups? my window is less then 5 feet away :).
 

cot

Member
Apr 14, 2000
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If you put the battery outside, you have to worry about it getting wet!

If you're going to try that, I'd get a marine battery box, put fuses on both leads INSIDE the battery box (you want the fuses close to the battery, because if anything goes wrong after the fuses, they'll blow, but if its between the fuses and the battery, the fuses do no good whatsoever)

And then I'd feel relatively safe about running the leads inside.

But it's still pretty hokey, YMMV, do it at your own risk, etc.
 

touser

Junior Member
Jun 15, 2002
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Thanks for that info cot, one question though, where would i get one of these marine battery boxes with fuses? thanks again everyone for the help!
 

cot

Member
Apr 14, 2000
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No problem. I'd look someplace like this for a box



Though you can't quite tell from the picture if it's exactly what you'd want. I think the best would be a box that had a lid that didn't let water in, but then maybe some downlooking vents around the edges or something to let the gas (hydrogen I think) out that is generated during charging.

They'd also likely have the fuse holders and battery terminals if you needed em, but a hardware and/or car parts place might be cheaper sources for those, not sure.

good luck, be careful!
 

arcas

Platinum Member
Apr 10, 2001
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I tend to agree with Justin218. If you were a small business looking to rig up an online UPS solution for your NOC similar to what you'd find in a telecom's basement, then going with big marine batteries makes sense. But for a typical home computer or even home lan, 120Ah is overkill and the details of how and where to store a non-sealed battery probably make it not worth the trouble unless your area is prone to extended blackouts.

Now, if you were going to be running something critical off your power invertor like, say, a sump pump then yeah, a big deep cycle marine battery is a good idea.

You might check your local jet-ski shop for some SLA batteries. I've read that 36AH jet ski batteries will fit in a SmartUPS 1400, for instance (the 1400 normally takes a pair of 17AH batteries).

 

KMurphy

Golden Member
May 16, 2000
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Marine batteries are not designed for float or standby duty. They are designed for deep discharge as are motive power batteries. They would not last long in that application.

The fumes are hydrogen and oxygen. As long as you have proper ventilation (HVAC system), you can not build up sufficient quantities of hydrogen to flash. One or two battery cells would never emit that much hydrogen even if continously overcharged.

Are you sure the battery inside the UPS is not sealed? Can you add water to it? For indoor use, you should stick to gel-cell or AGM type batteries intended for standby use. The best way to get additional capacity is to parallel several batteries together of the same type you have in there now. Let me know what you have, how much backup time you want and how much space you have and I can specify exactly what you should use
 

touser

Junior Member
Jun 15, 2002
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Thank you for all the reply's everyone, it is appreciated. arcas, the reason for me that this is not overkill is the ups doesn't just backup one system, it backs up 3 of them, and my main rig is watercooled so it has to run a 317gph pump and has 8 fans, 4 80mm,4 120mm, and a 19" monitor, in my area we have very bad power and it goes out alot. Another thing i am not worried about is the battery not being used, and on standbye all the time, i am into R/C airplanes and i go flying every weekend and i bring this battery with me to charge all my other batteries up with from, so the battery would not be sitting in a room 24/7 slowly disscharging. Also, i am now not worried about the gasses being produced by the battery because the ups simply doesn't have enough current to charge the battery at a high enough rate to create enough gas to be worried about. Like i stated above, the battery will be getting recharged every weekend by a real charger i have for it outside after i am done using it out on the flying field :). And all in all, if it does fry my ups, so be it hehe, it would have been a fun experiment and the ups was only $40. Thank you all again for all the help and advice! :)
 

Jerboy

Banned
Oct 27, 2001
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How many VA is your UPS?

You have two problems:

1. The UPS charging circuit probably don't have enough charging current to charge up a 120Ah battery after use.

2. Deep cycle doesn't mean it is designed for standby use. Continuous trickle charging might damage such battery.


Other than that, you need to take the UPS outside and put it right next to the battery and pull extension cord on 120V side. Pulling 12V extension puts too much voltage drop on low voltage side.

 

touser

Junior Member
Jun 15, 2002
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Thanks for the reply's again everyone, Jerboy, my ups is only 350va, but i think what i may end up doing is also having my normal battery charger that i have for it always connected to it on a trickle charge, thus taking all the load off of the ups.., and since it would only be a trickle charge there wont be enough hydrogen released to cause a problem.
 

Jerboy

Banned
Oct 27, 2001
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Originally posted by: touser
Thanks for the reply's again everyone, Jerboy, my ups is only 350va, but i think what i may end up doing is also having my normal battery charger that i have for it always connected to it on a trickle charge, thus taking all the load off of the ups.., and since it would only be a trickle charge there wont be enough hydrogen released to cause a problem.


My UPS is 350VA, 180W(this is because PF of most computer periph is ~0.5-0.6)

Let's say your UPS is 350VA/200W. 200W at 12V is 16 2/3A. Say your UPS is 80% efficient. 200/0.8= 250W input. 250/12=21 amperes input.

Voltage drop in cable is always absolute. There is no relative. At given current, it subtracts set amount of voltage regardles of main voltage. The lower the voltage, greater the influence, because that absolute value means greater percentage of total voltage.

21A at 120V AC requires 12AWG to 10AWG for 50ft run to maintain less than 5 or 10% sag(6-12V). I'm not too sure on the numbers, but there are current vs. voltage drop charts made for electricians. You need to go 8 or 6 AWG on 12V, because you cannot afford 6V of voltage drop on 12V system. This is why extending the low voltage side is a BAD idea.

 

touser

Junior Member
Jun 15, 2002
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Thank you for the info Jerboy, I appreciate it, but i have decided not to put the battery outside, it will be sitting under my desk in a plastic box. I have determined that the gasses being released by it on only a trickle charge will not be enough to cause any harm to anything, and if the power does go out, after the outage i will simply disconnect the battery from the ups and take it outside for a quick recharge on the appropriate charger. Also as I stated above, I will always have the appropriate charger connected to it at all times as a trickle charger to take the strain off of the ups's charging unit. :) I sure hope this works hehe :)
 

pm

Elite Member Mobile Devices
Jan 25, 2000
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Just make sure that box is well vented. You are right that the gases emitted won't hurt anything - unless they can't go anywhere and build up. A box full of a oxygen/hydrogen mix could make a reasonably big bomb that could be touched off by static electricity.
 

touser

Junior Member
Jun 15, 2002
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Welp, today was the test, and it failed miserably! I hooked it all up, with the bare minimum, pc+monitor+waterpump, unplugged the unit from the wall, and with a volt meter watched the battery voltage. With no load the battery was at 12.48v, but as soon as the ups was switched over it dropped to 12.08v, the system staid on for all of 30 seconds, and then decided to just shut off completely. The ups "over load" light never came on, the voltage never dropped below 12.08v and staid contant at that under the load, then it just decided to turn off.. So i do not know what to do, the bare minmum it has to be able to run is my monitor,my pc, and my waterpump, and it couldn't even do that!
 

Jerboy

Banned
Oct 27, 2001
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Originally posted by: touser
Welp, today was the test, and it failed miserably! I hooked it all up, with the bare minimum, pc+monitor+waterpump, unplugged the unit from the wall, and with a volt meter watched the battery voltage. With no load the battery was at 12.48v, but as soon as the ups was switched over it dropped to 12.08v, the system staid on for all of 30 seconds, and then decided to just shut off completely. The ups "over load" light never came on, the voltage never dropped below 12.08v and staid contant at that under the load, then it just decided to turn off.. So i do not know what to do, the bare minmum it has to be able to run is my monitor,my pc, and my waterpump, and it couldn't even do that!

I wouldn't be surprised if 350VA PSU couldn't run a monitor and PC together. Mine couldn't do it. My UPS won't even run fluorescent lighting, because it's power factor corrector doesn't agree with UPS output.


 

element

Diamond Member
Oct 9, 1999
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Jerboy you have no idea what you are talking about. A 6V voltage drop on a 12V line? wth are you running extremely thin wires to another state? lol! oh and also stop calling the UPS (uninteruptible power supply) a PSU (power supply unit).

Touser, you don't have to put the UPS outside, just the battery. You can safely run normal cable outside your window to the UPS.

Also i wouldn't use a marine battery if i were you, I would use an automotive battery, they love to be constantly charged. not sure if the same is true for marine batteries, are they lead acid? if so then it is ok. I have a UPS that came with its own lead acid battery, same technology as an automotive battery essentially.

Its true tho that a 350VA UPS is pretty weak. Get yourself a bigger UPS, then when its internal battery dies and can no longer be charged (5 years more or less) you can replace with an automotive battery or 2 depending on if it is 12V or 24 V
 

nemo160

Senior member
Jul 16, 2001
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for the battery box you might try an autoparts store, you can get a good solid plastic battery box designed for relocating the battery from the engine bay to the trunk
by going with a box designed for it you wouldn't have to worry about venting or if the battry will corrodethe box material
 

Jerboy

Banned
Oct 27, 2001
5,190
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Jerboy you have no idea what you are talking about. A 6V voltage drop on a 12V line?

Excuse me? you're the one who has no freaking clue. First look at the resistance for 12AWG copper wire. http://www.epanorama.net/documents/wiring/wire_resistance.html

I was not quite right on this particular calculation, but you didn't even make a calculation to before making a judgement against me. It all depends on the current draw, because I guessed on wire resistance.

A 12AWG copper wire has 1.87x10^-3 ohms per foot. Say he runs 50ft of cord from his battery to UPS and his UPS draws 20A(which is what fully loaded 350VA should draw more or less)

1.87x10^-3ohms per foot x 50foot =0.0935ohms x 2(wire goes two ways, therefore 50 x 2)=0.187ohms. Ohm's law states that V=I x R. We know R is 0.187ohms and I is 20A. So voltage drop is 3.74V, which is 31% of 12V and this is totally unacceptable. When you push 20A of current through this set of cords, it will always take away 3.74V. It doesn't matter if the power source is 12V, 120V, 277V, 480V or etc. Low voltage wiring is a hell because small drop in voltage means great percentage of total voltage.


What if he use a pair of 12AWG 2.5ft wires to connect the battery outside and used a 50ft of 18AWG extension cord to pull the 120V into his house?

battery side:

0.00187ohms per foot x 2.5 x 2 x 20=187mV, 1.6% voltage drop between the battery and the UPS. Acceptable


output side:
since 350VA is about 3A at 120V, let's say output current is 120V 3A.

18AWG cord has a constant of 7.51ohms/ft

0.00751ohms per foot per one direction x 50ft x round trip=0.751ohms. 0.751 ohms x 3A=2.25V lost on 120V side. 1.8% voltage loss. No problem at all.



wth are you running extremely thin wires to another state? lol!

12AWG is considered a relatively thick cable by most people. Do you have any idea how much 50ft of jumper cable size wires would cost?

oh and also stop calling the UPS (uninteruptible power supply) a PSU (power supply unit).

Oops my bad.

Touser, you don't have to put the UPS outside, just the battery. You can safely run normal cable outside your window to the UPS.

You nor I are in the position to make a conclusion yet. He did not specify length of run or cable gauge. You have to use the copper wire resistance factor, ohm's law, length and current draw to figure out the voltage drop.

Also i wouldn't use a marine battery if i were you, I would use an automotive battery, they love to be constantly charged. not sure if the same is true for marine batteries, are they lead acid? if so then it is ok. I have a UPS that came with its own lead acid battery, same technology as an automotive battery essentially.

Automotive batteries are not designed to be drained beyond 20% depth of discharge. Discharging them further will significantly shorten their lives. They're designed for high current short duration load such as starting an engine.


Its true tho that a 350VA UPS is pretty weak. Get yourself a bigger UPS, then when its internal battery dies and can no longer be charged (5 years more or less) you can replace with an automotive battery or 2 depending on if it is 12V or 24 V

Yes you can physically, but it is not proper for the reason I described above.