Ryan Underwood wrote:
writes:
If they sat for two years and only have 5 V no load, the probability is
high that they are junk.
Hard to believe the longevity is really that bad!
In a UPS that's used constantly in an area that has few power outages (an
average on the order of a few minutes a month or less), the batteries will
last 3 to 5 years or so, and that's about all you will get.
I may be misunderstanding you, but in my experience with a few different
APC UPSes, the UPS doesn't have to be turned on (delivering power to the
outlets) to charge. As soon as you plug the cord into the wall, it
should start charging.
Well, it 'chirps' and the light flickers, but then there is no other sign
of life.
Here is what I have observed of the startup sequence of some different
300-600 VA APC UPSes. This starts with the batteries connected, the UPS
switch off, and the UPS otherwise not connected to anything.
1. Plug UPS cord into wall. UPS may chirp briefly, but will remain off
with no power to battery-backed outlets.
2. UPS will start to charge the batteries. You can see this with a
voltmeter across the batteries or an ammeter in series with the
batteries.
3. Operate the power switch. The UPS will beep and switch on the
battery-backed outlets. After a few seconds, it will do a battery
test. The "on battery" light will come on and you may be able to
hear the transformer humming quietly. If the batteries are good,
this will last for about 10 seconds. If the batteries are bad, it
will last for a second or two, before switching back to line power.
The battery-backed outlets are powered during this entire period.
4. When the battery test is complete, the "on battery" light will go
out and the transformer will stop humming. The UPS should be charging
the batteries again. The battery-backed outlets should still be
powered.
5. Operate the power switch again. The battery-backed outlets will be
shut off, but the batteries should still charge.
Monitor the voltage across the batteries while you plug the UPS in; it
should rise noticeably if the UPS is attempting to charge them.
Interesting. Across one cell, it drops from 5.4V to 2.8V, when initially
plugged in, then after the UPS chirps and dies, it gradually rises again.
Not sure what's going on here.
This _may_ be the self-test failing, then the UPS trying to charge the
battery. It could also be a battery that is so bad that any load
applied by the UPS causes the battery voltage to crater. When the UPS
detects the low voltage, it unloads the battery, which allows the
voltage to rise again.
You might see what each battery does, separate from the UPS, with a load
across it. Something like a 193 (0.5 amp) or 1156 (2 amp) automotive
lamp would be a good load. I suspect that you'll see the same drop in
voltage that you see with the batteries connected to the UPS.
Is it at all possible to buy a long-lasting sealed lead acid battery, or
is it going to be a crapshoot no matter who manufactures it?
In my experience, Panasonic and Power-Sonic make decent SLA (gel-cell)
batteries in the common "small" sizes - 6 V or 12 V, 2 Ah to 15 Ah or
so. Most of the Panasonic gel-cells I have used have been made in
Japan, and most of the Power-Sonic ones have been made in Mexico. I
have never had good luck with any gel cell made in China.
Once you buy a good battery, you have to treat it right. With something
like a UPS, about all you can do is hope that the UPS designer gave you
a good charger, and keep it on charge as much as you can. Batteries
don't like to sit around but they really hate to sit around when
discharged. If you're designing your own charger, READ the technical
notes from the battery vendors first! (Power-Sonic has a fairly good
application note about how to charge their batteries.)
Matt Roberds
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