UPS's are expensive. I have 4 servers (soon to be 6) as well as a switch (with fans). The least I could consider is a 2000VA unit (for only the switch and 2 critical servers).

I know a radio technician, a bit of a tinkerer, who connected a car battery (I'm positive it was 12v) to a UPS to serve as the battery.

Any ideas? Are there any 12v UPS's out there?

My thought was to buy an APC unit, 2000-4000VA, with no batteries, and buy a BIG deep-cycle 12v battery and charger...

He is probalby referring to the 12volt to 110vac inverters you can buy just about anywhere. They very on output capacity. Now the problem is they don't run all the time as normal but can. Requires a charger to continues charging the batteries since the machines will always be running off batteries. This way if power goes for the charger they will not cause a drop in power. The UPS use a feature that engages the batteries when then power is lost in millsecs to prevent power lose. Most power supplies as well motherboards can handle the short lost do to the capacitors in the system.

Now what you maybe referring to is adding addition batteries to the UPS to add longer uptime. That can be done easily. Charging of course will take twice as long with two bateries and longer as more are added. But the issue is the output capacity. A 600vac will deleiver 600vac for what every period of time it is speced at. So if the system needs 1200vac it will more than likely shutdown do to the access pull of power. The ciruitry in the 600vac will not handle that load for long. The circuitry in a 2000vac will handle it fine.

One thing on inverters. Some provide a close somewhat clean sinewave at 60hz which is what current US power is designed at. Many cheap models produce a block type sinewave versus a smooth curve sinewave. They do produce smoothwave inverters. They cost more which is why UPS cost more in this package.

If you wish to try look for a 3000vac to 4000vac inverter that produces smooth sinewave. There are products that can take a raw unclean block wave and convert to smooth sine wave. So you may need to go that route. Now get what number of batteries to run the system and maximum output for for period of power outage. Then a battery charger to charge the batteries to maintain the what the computers are using plus charging power to charge the batteries as well and realitive period of time.

One thing that be able to add is a circuit that can detect the lose of power and make the switch from ac power to inverter power quickly but this also reuires the ability to sync the sinewave from ac to inverter before actually engauging the inverter but before the capacitors discharge to shutdown the computers. Again this is a feature in a UPS and why the cost increases.

One more thought is by several smaller cheaper units and add batteries to them. But you will only be able to connect a few devices to each. But buy the time you add additional batteries then I would say the cost will be close UPS with the same run time. Just my thought.

Brian

No, I saw the unit. It was an APC BackUPS with the rear cover removed, the batteries removed, and the battery leads extended and hooked onto a 12v Deep Cycle truck battery.

The cost issue is what got me thinking about this.

At the moment I have just 2 servers and a switch. Within the next month, It'll end up being 2 BayNetworks switches (with fans), 2 Proliant servers with dual redundant 300W PS's, and 4 Dell desktops running as servers. I'd like a little 'wiggle room' for an additional box...

This all adds up to a BIG UPS load. Looking at the cost of UPS's (around $1000 for 2250W new), it seems much cheaper to buy a unit with no batteries and add something on.

Never seen an APC without batteries. I would say the orignals were remove or went bad. I know what you are talking about. Mentioned a similiar setup above using additional batteries for longer run time. You just are not going to get the capacity of Watts from say a 300W to run a 1200W load no matter how many batteries are added. I would the cost of the batteries in that unit would be around $300 to replace.

I guess try Ebay.

Brian

Brian,

that's exactly what I'm saying.

APC's site suggested a 2200-3000VA model for my setup. They sell new, even on Ebay, for $500-1000.

If I could find one without batteries, I doubt the seller would ask more than $100.

The original battery in the SmartUPS 3000 is a a pair of RBK11's, which are 17AH @ 12v, and cost $177 online.

For about $150, I could get an 850AH deep-cycle car battery. Theoretically, this would give a runtime in the HOURS.

Before I actually try this, I'm not sure about the amperage from the car battery and whether it would damage (maybe blow up) the UPS. If I happen by one, I'll snag an old UPS from the trash and give it a try.

The capacitors in switch-mode power supplies such as computer power supplies are only there to filter the DC. They do not have enough capacity to store a lot of power or volts. Also the inductors can only hold enough current for a few milliseconds.

A true UPS is a flywheel that turns a generator. There is no batteries because the circular forces is keep it at a constant speed until fiction slows it down or something else is keeping it going like a diesel engine or man power.

Using car batteries for a UPS can not be done safely. The UPS uses a special charger that can only be used on the type of battery that it is designed for. During charging there will be hydrogen fumes coming from the battery, so if there is any sparks, there will be a possibility of an explosion. Also car batteries works differently than regular batteries. The energy that it creates is generated a week ago. Again do not use car batteries for UPS.

UPS are expensive, well the good ones that can power computers. UPS contains an inverter, charger, and in addition some brains to provide information to the computer to know when to shut down or when to bitch to the user. If you need 2000 watts or more, it is best to invest in an 24 VDC or 48 VDC inverter (true sine wave) and charge controller. The batteries that I suggest are NiMH or Gel-Acid batteries. Li-ion batteries are also good, but sometimes become unstable, needs a special charger, and they have a memory effect. Fuel cells, wind, water, and solar cells can also be used to generate power if you do not want to use AC from the grid. Look up Xantrex Technology Inc..

BTW, this thread should be in the general forum.

I don't understand the relevance of this... A UPS puts out 120V 60Hz. If it functions correctly, its' action is completely transparent to the devices connected to it.

In terms of the hydrogen gas, I was planning on using a sealed AGM (absorbed glass mat) deep-cycle battery, that doesn't create such hazards.

Huh? I'm confused by this. What do you mean "is generated a week ago"? An AGM that's hooked up to a charger "works" the same as a Li-Ion or NiMH that's hooked up to a charger.

Sorry about the forum, I figured this was a hardware question.

I'm a boat owner, so I know a bit about inverters. Most of the true sine wave ones I've seen that can handle 2kW+ are in the cost range of 2kW UPS's. I just looked online a bit, and 2kW sine wave inverters are in the range of $1700.

I guess it does look like an inverter and charger could do all that a UPS can... and in terms of signalling, I could hook a small, cheap UPS into the mains and let that handle the signalling to the machines.

The only question I have left is whether an inverter could handle the 24x7x365 workload very well...

As it seems I always have to do (perhaps my questions need to be more pointed), let me re-center this post a bit:

Does anyone know, from either experience or plain number-crunching, whether a UPS such as the APC SmartUPS 2200, can handle an input source of 12V from a battery capable of 820 AH? Or is there a possibility that the high current potential could damage the UPS?

In the real world, one UPS is designed differently than the other UPS. A switch-mode power supply complicates things when using an DC/AC inverter.

Does not matter, it still creates a hazard because the built-in charger is not designed for the chemistry of the battery. It is designed for the battery that the UPS came with.

A charger that is used for NiMH batteries can not be used for Li-ion batteries. Again they are different chemistries and the batteries can be damaged when using the wrong charger. Also the charger can be damage.

You can use a cheap UPS to signal the computers, but that will not be very reliable even for 5 or 6 servers. If you have that many servers, spend the money on real UPS setup. If you buy inverters that are for continuous use, then you will not have a problem powering the servers for 24 Hr., 7 days a week, 365 or 366 days a year.


If a device needs 12 volts and it consumes 1 ampere and the battery that it is connected to has a rating of 12 volts and 100 AH (Amp Hours) or 100 A , it will last about 100 hours. This is only when the device consumes this much energy constantly.

Li-ion's are a completely differnet animal. They require special designed chargers based on the number of cell packs involved. A cell when charged is 3.3 volts. When they drop to 3.0v that is considered is maximum drain limit. If you go beyound you run the risk of the li-ions self destroy themselves. This is why devices that use li-ions imploy a monitoring device of the cells so when the discharge limit is reached they are disconnected so as not to discharge any further. I would look into li-ion in the RC planes and Helicopters to get a grasp on them. Same for many manufactors of Power tools like Milwaukee 28volt tools. Not sure on the memory effects as compared to the old Ni-cads of days gone by.

As for the charger of say an APC they are designed for the gel cell type sealed batteries to eliminate the hydrogen gas that results from charger lead acid batteries as Electro mentions. They imploy a charge rated based on the design of battery.

If inverters are $1700 dollars and a UPS of the same size is about $1200 as you mention from an above post #3 then the UPS is the cheaper way to go. I guess you still need to by batteries for the inverter?
The only thing I can say is contact APC or other UPS makers to see if they have any refurbished units without batteries.

Brian

Ok, thinking about the charger, I see what you mean. I would assume that any reputable unit like the APC's is ain all-in-one board design, so it wouldn't be easy to just remove the charger.

$1200 is not an option for me. I'm a college student, and doubt I can go over $300 for the unit.

As I'm sure the next comment will be about servers - the modified desktops I got for free, and the Proliants are under $200 on Ebay.

I guess I'll just have to find a used one and pray for the best.