Is anyone running their UPS(Battery Backup) on car batteries?

Never have done it before, but a word of caution on wiring new batteries as a back up to the internal batteries: You shouldn't wire batteries of different capacities or different ages together. This is coming from experience with 24V trolling motor systems for boats. If you have batteries of different capacities or age together, one battery will end up doing more work than the other. In the case of attaching new batteries to the old ones, it is likely that the old batteries will draw power from the new ones, and with no regulation system between the two, you don't have control of what could happen.

Logically, you should be ok to replace the two older batteries with two newer batteries of larger capacity, as long as both new batteries are the same capacity. It will take longer for your UPS to charge them though.

Good luck!

Good thread. I want to try that with my UPS (disconnecting the internal batteries of the UPS and connecting the car batteries to it). Only question for me is will the charging circuit in the UPS handle the larger capacity batteries?

skrypj said:

What I would like to do is grab a pair of deep cycle marine batteries from Wal-Mart($58 each! what a steal) and wire them in series as either a backup to the internal batteries or as the primary battery bank.

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Reading the link that BB provided (Thanks BrotherBart!), you should not plan on using a standard marine deep cycle battery. That would be a flooded lead battery and the UPS will likely over-charge it, causing either the battery to die out quickly, or even worse, a buildup of explosive hydrogen gas. Additionally, the UPS itself may not be designed to handle the longer run time provided by larger capacity batteries.

Safest bet would be to replace the existing batteries with new versions that are the same technology and capacity.

Good Luck!

BrotherBart said:

Conversation about what you want to do. http://forums.anandtech.com/showthread.php?t=2026013

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A 24 minute video that said: Yes, you can wire 1 or 2 automotive batteries to replace your UPS battery for extended run time. Safety, Safety, Safety, attempt at your own risk, Safety, Safety, Safety!

I currently have my old car battery hooked to a 45watt solar charger to keep ham radios operating if needed.
Plus, I have the UPS is in the garage not UPS'ing anything!

Bill

Any battery that has not been on a charger for two years or more should be treated as a door stop. The cells are by then so sulphated that they will never recover. There are extreme measures that may bring them back, but they are not worth the effort.

A new battery for indoor use must be of sealed construction. It should be either gelled electrolyte or AGM ( absorptive glass mat/starved electrolyte) construction in order to be compatible with the charging system of the UPS.
There should be a fuse already built into the UPS to protect against excessive current. If there isn't one add one to your wiring. The best place to put the fuse is right at the battery terminal. That way a clumsy moment is only an inconvenience and not a catastropy.

kofkorn said:

Reading the link that BB provided (Thanks BrotherBart!), you should not plan on using a standard marine deep cycle battery. That would be a flooded lead battery and the UPS will likely over-charge it, causing either the battery to die out quickly, or even worse, a buildup of explosive hydrogen gas. Additionally, the UPS itself may not be designed to handle the longer run time provided by larger capacity batteries.

Safest bet would be to replace the existing batteries with new versions that are the same technology and capacity.

Good Luck!

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If the UPS really is designed to run for two hours it can run as long as any battery will last. In most cases by the end of about one half hour the circuitry is at the highest temperature it can achieve. Thermal time constants for heating of electronics tends to be measured in minutes not hours. Likewise the charging circuitry should have no problem with a larger cell.
Of course, not having seen the design, this is strictly my opinion and there are no guaranties.

One note.
Some UPS' need to have the batteries in place and charged, and the 120 hooked up, then lost before the "backup" will fire up..

Hi,
How long would a pellet stove last on these batteries?

Thanks

sam5 said:

Hi,
How long would a pellet stove last on these batteries?

Thanks

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That depends... What stove?, What batteries, What UPS? What stove settings? What weather?

Yes I do it, after MUCH research, years of experience with electricity and electronics, an ability to calculate wire sizes and wire in the proper fusing, a healthy respect for what happens if you short those batteries (it's just plain deadly), and ready access to a master electrician. Would I advise a regular home owner to do it? No. But if you are willing to learn there are many great links online. If you are willing to MAINTAIN those batteries (e.g., trickle / float charge them), the solution can work, but you need to monitor and maintain that system much like the maintenance required of an off grid homeowner. It is NOT something you should do casually.

My site says it all.. Goes about 10 hours...
If you turn off a UPS, most won't turn on without AC power. Even with fresh batteries.

http://www.butkus.org/ups/ups.htm
P.S It'll run the 52" LED TV too... shortens the run time though.
I check the water every 4 months.

I would never charge a larger battery with the built in charge controller. Consider an outboard controller for that.

I would never charge a larger battery with the built in charge controller. Consider an outboard controller for that. and at that point, you might as well just get a pure sine invertor too.
and at that point, you might as well just buy a generator, because it will be cheaper. lol

skrypj said:

That is the conclusion I am starting to come too. Why spend $150,$200 or more on batteries if i could just get a generator and not worry about it.

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My reason is that I can save about $35/day in fuel costs by turning the gen off for 12 hours/day, plus it allows me to keep less fuel on hand. We don't have natural gas near our home, a large propane tank is much more expensive (with large fuel costs), and the battery system will handle what we need to power and keep us running for several days even in a very bad storm with "rationed" gen use.

But this is well beyond the skills of many homeowners, and the dangers are significant. You're not dealing with a few cells in a flashlight - these are very powerful batteries. When someone thinks they can just use a car battery, it's a tipoff that their knowledge is insufficient.

The UPS is older. I would contact the manufacturer and get replacement batteries. Then everything is within spec and works the way it was designed to by a smarter than me engineer.

If the UPS is very old I would buy an inverter and batteries for a backup. Then you can use the inverter on trips for charging laptops and such. If the you buy batteries that match your vehicle batteries then you can interchange them and top them off with your vehicle during an extended power outage.

flhpi said:

you buy batteries that match your vehicle batteries then you can interchange them and top them off with your vehicle during an extended power outage.

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A bit risky for most batteries. Vehicle batteries are not designed to supply power for extended periods. Their plates are much thinner, and they do not respond well after a few deep discharge cycles. You can ruin a regular "car" battery in just a single storm if you discharge it enough. Not trying to argue, but my concern is for those who try to build these systems "on the cheap" and find their strategy isn't workable right when they really need it.

I thought a vehicle battery would work. I see plenty of inverters that are used hooked up to car batteries. Your requirements for power output might be beyond a Northern Tool inverter.

Good luck getting the setup the works best for you. Last summer I got my parents house setup for a power outage and it is a load off my mind knowing they are not dependent on the power company during storms.

I didn't know about the plates being thin on car batts. Good info. This is why I spent too much time on the Internet and this website. The information that I learn might save my butt one day.

flhpi said:

I didn't know about the plates being thin on car batts.

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I could be mistaken, but I thought it was the other way around. Car batteries are designed for short duration, high current surges for engine starting and need thicker plates to survive those surges. They do not survive deep discharge. So called Marine batteries aka deep discharge batteries don't handle the high currents because of their thinner plates, but are designed for high capacity in a smaller volume and can recover from deep discharge if they aren't allowed to sit discharged for too long. For indoor use, a sealed AGM battery or a sealed, gelled electrolyte battery are the only two safe technologies to use.

On another note. Anyone who is planning on keeping a bank of lead acid batteries for backup should look into a desulfating charger. These chargers put current pulses into the battery that dislodge sulphate plaque that builds on the plates. Without that, a good battery can go dead in just a few years even though it has been kept fully charged.

On second thought, don't play around with lead acid batteries unless you plan on spending a few weeks learning about the technology in order to do it safely.

With batteries, it's the surface of the plates that generates the power. So the more surface area you have, the more surge power you are able to get. Thinner plates means that you can fit more plates in the same volume, equaling more surface area. However, when you discharge the battery, the surface of the plates sulfate. So thinner plates get destroyed faster. On a car, you rarely discharge more than 10% of the total energy out of the battery, so there is very little sulfation happening. On a deep cycle battery the thicker plates can withstand the sulfation much better, so they are not damaged quickly.

Deep cycles are made to discharge down much further, but can still be easily damaged if you discharge more than 50% of the energy out too often. That's why the recommended cut-off voltage on a deep cycle is usually 10.5-11V. If you stay above that, you should be able to keep your battery in good condition for quite a while.