Posted on 11/08/2012 12:50:14 AM PST by djf
First, a brief bit of intro info. I bought a used UPS at a Goodwill for 20 bucks. They had 3 there, a 300 watter, a 1500 watter, and an APC Back-UPS 900 watter. I tried them all on the outlet, the first 2 the battery light came on immediately, so I got the 900.
I get it home and it worked fine as long as it's plugged in, but shuts down as soon as I unplug it. Well, that ain't good. So I do a bunch of Googling, find that the unit has a heating problem, a few holes drilled and an old computer fan and that problem is fixed.
Still fails. The battery(s) are two SLA (Sealed Lead acid) 12V batteries in series. I determine that one of them is bad, won't take a charge, can't handle any kind of load. The second one seems good.
So a trip to the HW store and I get a replacement for 34 bucks. Now I'm into the unit for about 60 bucks. Not a biggie IF IT WORKS, because its a 200 dollar item new.
I plug the new battery in and SUCCESS!
So the braggin part is over, here's the question.
These SLA batteries are fairly small, this one measures (each, individually) 6 in long, 2 1/2 inches deep, and 4 inches tall. One (the original still in the unit) is rated at 12V 7AH. The dead one was rated the same. The new one I put in (in series with the original) is 12V 8AH.
Is it possible to use this unit with actual auto-type lead acid batteries? I don't know how to convert CCA's (cold cranking amps) to AH (amp hours). Also, does anybody know if the trickle type charging used in UPS units could handle a full auto-type battery(s)? I guess I would need 2 because the actual operating voltage of the unit is 24V.
Thanks in advance for answers. I'm just in general contemplating and thinking about power systems and what is/is not possible.
As long as the voltage is the same, bigger batteries should work fine. The trickle charger will probably work too since it’s designed to push juice into a 24v system and voltage is what matters, not amps, though it will take the entire Christian age to recharge a pair of car batteries.
The biggest difference between the UPS and a lead acid battery is that UPS generates instantaneous power supply as soon as there is a power drop. The unit simultaneously powers up and supplies electricity without any delay, whereas a lead acid battery does not have such provision of uninterruptible power supply. Also, lead acid batteries generate direct current but UPS generates alternating current because, even though batteries in UPS also generate DC, but that is converted into AC by the inverter fitted in the UPS.
An uninterruptible power supply is mainly used where we require absolutely no delay in power cut and the backup supply. In lead acid batteries, there is a predetermined delay that can be afforded at that time. A lead acid battery is used where we need instant increase at the initial stage. Lead acid batteries are typically used in automobiles, but UPS can power whole buildings and institutions. UPS is also valuable when it comes to immediate surges in power or fluctuations in electricity because UPS filters the electricity and passes through only the consistent, conditioned electricity.
Thanks. Thats kinda what I was thinking, but wasn’t sure.
I have a 200W inverter and used to have a couple old car batteries that would take a charge, so that worked for about 6 years. But of course that meant if the juice went out, I had to actually physically plug things in and break out the power strips, extension cords, etc.
It’d be alot nicer if I can just use the UPS setup!
This unit has a surge protector on it but the instructions specifically say basically, “Hey! If you want sine wave power, this probably ain’t your best meow!”
So, smoothed out square wave, which I hear is brutal on electric motors. Anybody know more about this subject please post.
NO.
Auto batteries are not designed to take a “Trickle Charge” and will fail fairly quick.
I deal with UPS in our Data Centers and you need a Marine Battery that will take a trickle charge.
Short answer and I’m not an engineer. That’s what my smart guys tell me and since they are engineers I go with what they say.
The UPS you described isn’t designed for continuous use, but will supply the rated wattage for about 10-15 minutes. Basically this is to give you time to save your work and shut down the equipment or bridge short power outages(brownouts).
To convert from CCA to AH:
(CCA/10)+16 = AH
So a 1000 CCA battery should = 116 AH
This will take over 16 times the amount of time to charge at the charge rate of your UPS. Theoretically, you should be able to get about 150 minutes of power out.
With your cooling fan it might do it, but my bet would be about 30 minutes and it will blow the fuses or the circuit breaker, particularly if you are driving it at or near the rated load.
Also, remember that your larger batteries will off gas as they are charged/discharged.
That is very true, car batteries are more like a capacitor than a battery. Slow charge/discharge sulfates them quickly, and they don’t like being discharged to below 10 volts very many times.
No! NO!....don’t even consider a lead-acid battery....lead acid batteries give off hydrogen gas when charging...need I say; explosive hydrogen gas....never use any other battery than the original model....
Thanks! Xlent info, just what I was looking for. Not the answer I wanted, but hey, gotta have a little whine with that cheese!
Looks like I will be searching for some bigger inverters. Maybe I can figure out a way to have the UPS trip the inverters.
Correct. CCA is the opposite of deep cycle. Lots of power up front but not good for continuous load.
If longer power output is needed, the deep cycle battery is the way to go.
Thanks! These are exactly the kinds of questions and answers I need.
I knew, for example, that CCA is a very limited measurement, almost an instantaneous rating, because after ten seconds of your starter turning, if your rig ain’t started, your battery is getting close to dead.
So what you want is high capacity, that can deliver on a low load for a long time without burning out the unit, and can be trickle charged
I guess a battery used for things like solar setup would be best. In fact what I am doing now is part of the way towards getting into solar.
No matter what, if the juice goes out, we will all have to learn about doing with alot less, and a lifestyle change like we never could even imagine!
regards,
djf
Zactly!
I have four batteries setup with a solar charger to keep em charged.
I could just leave them plugged in to a socket but, since I wanted solar backup I had the whole shebang setup.
Although it is coming up on 5 years. I should have one of my guys check their viability.
In data centers those things are replaced like clock work, whether they are good or not at 5 and 7 year intervals.
“In fact what I am doing now is part of the way towards getting into solar.”
After the last hurricane, I wanted alternative lighting. I bought two deep-cycle golf cart batteries at Interstate batteries and a 400 watt inverter from Harbor Freight. I can light up four rooms for a week using 16-watt CFL’s and yet only discharge the batteries 50%. I have multiple options to recharge the batteries, including an automotive charger, a gasoline generator and also solar panels.
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