UPS and battery

S

secure.boy

Limp Gawd
Joined
Oct 22, 2007
Messages
474
HI
i have 4x500 VA UPS all of the are the same brand/model
the battery inside is 12V 7A
i want to buy a car battery i mean one example 12V 100A
and all of the ups to use that battery

how should i connect all of them
what i mean is this


[BATTERY 12v 100A]
| | | |
[ups1][ups2][ups3][ups4]

i think only one ups should recharge the battery
and overs only should use the electricity on that battery
 
I think this is a bad idea. First off the 500 VA UPS was not designed to charge such a large battery. It might take days for it to charge and it might not be designed to handle that type of thermal dissipation.

Second point how are you going to control which UPS will charge the battery. I haven't seen a UPS that small with charging controls.

Are you sure it's just 1 x 12 V 7.5 Ah inside of it. Usually there will be 2 x 12 V 7.5 Ah batteries in series to give you 24 V 7.5 Ah. The current draw on just one 12 V battery is double that of 24 V. The other problem I can see with this is that the 500 VA UPS was not designed to run for hours and hours. It will generate a lot of heat while being on and could cause internal damage.
 
i think just one ups to connect directly
other i think to connect with "diode" so the electricity will go only in one way
Diode_symbol.svg

what do you think?

the ups's some Chinese brand no name for me
i would like to sell but no one does not want to buy
 
You can't use a car battery. You will have to get a deep-cycle battery. A marine battery, advertised as deep-cycle is marginal. You could use an electric golf cart battery.

You'd have to rig up a proper charger for this and have it triggered by one of the UPSes. I doubt a 500VA UPS can handle a 100AH battery.

Given that such a battery will set you back around $200 and four replacement UPS batteries will be around $120-$150, why bother?
 
Michael Daly said:
You can't use a car battery. You will have to get a deep-cycle battery. A marine battery, advertised as deep-cycle is marginal. You could use an electric golf cart battery.

You'd have to rig up a proper charger for this and have it triggered by one of the UPSes. I doubt a 500VA UPS can handle a 100AH battery.

Given that such a battery will set you back around $200 and four replacement UPS batteries will be around $120-$150, why bother?
Click to expand...

i will use 55Ah battery
 
55AHr still run about $150. Add to that the cost of a charge controller.

You will need a charge controller since it takes 7.8 times the current to charge a 55AHr battery than a 7AHr at the same voltage (according to my Yuasa battery manual). The UPS controller won't be able to handle that.

You'll also have to figure out how to convince the UPS to control the charge controller and have the UPS figure out what the battery's state of charge is.

For so little gain, the 55 is not a great idea unless you're an electrical engineer and are going to design and test your own UPS.
 
today i just received e-mail
a friend of mine wants to buy all of them

thanks for your replays

i will get one "big" apc 3000va
 
secure.boy said:
today i just received e-mail
a friend of mine wants to buy all of them

thanks for your replays

i will get one "big" apc 3000va
Click to expand...

That is going to require a L5-30P outlet which most people do not have at home available in the locations that you would have a PC.
 
Sounds like a fun project if you have a crap UPS laying around. All three of mine were
given to me, so no big loss if one of them dies.
 
Gillbot said:
It works fine with 1 ups and 1 car battery.
Click to expand...

"Fine" is relative. The car battery will not last as many charge-discharge cycles as a true deep cycle under the kind of loads that UPSes are designed for. Car batteries deliver a very high current for a few seconds, not steady low current for a long period. That's why they have thin, sometimes porous plates. Deep-cycle batteries have thick plates that will last longer.

The UPS will only charge with a low current and the charge time will be considerably longer than a proper UPS battery. For a car battery, the UPS would be somewhere between a trickle charger and a proper charger. That doesn't make for a useful UPS if ordinary reliability is required - even though it can handle a longer outage, it will take a long time to recharge and be ready for the next cycle.

If the UPS and car battery are really cheap or free, that's an alternative. But I wouldn't recommend such a setup for anything you'd want to trust in the long run.
 
In the past i have used a car battery charger, 2 car batterys connected in paralell and one of those 230v step up box's.

It worked but it wasnt ideal.
 
i have seen people are using inverter DC to AC
2x100AH battery; inverter 5kVA
for under 600$
 
The difference s whether you want a standby power supply or uninterruptible power supply. Any battery can be set up to provide standby power. However, it you want to create a system that automatically provides uninterrupted power, you need a sophisticated assembly of battery, charger, inverter, and computer-connected controller.
 
Michael Daly said:
"Fine" is relative. The car battery will not last as many charge-discharge cycles as a true deep cycle under the kind of loads that UPSes are designed for. Car batteries deliver a very high current for a few seconds, not steady low current for a long period. That's why they have thin, sometimes porous plates. Deep-cycle batteries have thick plates that will last longer.

The UPS will only charge with a low current and the charge time will be considerably longer than a proper UPS battery. For a car battery, the UPS would be somewhere between a trickle charger and a proper charger. That doesn't make for a useful UPS if ordinary reliability is required - even though it can handle a longer outage, it will take a long time to recharge and be ready for the next cycle.

If the UPS and car battery are really cheap or free, that's an alternative. But I wouldn't recommend such a setup for anything you'd want to trust in the long run.
Click to expand...

Why not include the whole quote?
Gillbot said:
It works fine with 1 ups and 1 car battery.
http://www.ocforums.com/showthread.php?t=502584

Though I HIGHLY recommend getting a sealed deep cycle battery.
Click to expand...
;) And the only reason that car battery was used was because it was free and the UPS was only $2.50 from a local thrift store.
 
Gillbot said:
Why not include the whole quote?
Click to expand...

Sorry, I wasn't intending to criticize you, I just wanted to clarify what "fine" might mean. A free car battery with a cheap UPS will work; it just isn't a reliable replacement for a real, uninterruptible power source for a computer.
 
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