John Robertson wrote:

Jeff Liebermann wrote:
On 03 Feb 2009 01:34:13 GMT, Warren Post wrote:

I just replaced the battery in my UPS, and notice that the old one was
swollen and hard to remove. Searching this NG and elsewhere on the net,
I see this means that the battery had reached the end of its life some
time ago and should have been replaced sooner. Okay, replacing the
battery when it reaches the end of its life cycle instead of waiting
until it obviously fails is fine by me.

So how do I know when to replace a UPS battery? This particular UPS has
no self test feature and no com port with which to communicate with the
computer, and I don't want to toss perfectly working equipment into the
landfill just because it lacks bells and whistles to make my life a
little easier.

I have several ways to test batteries. The easiest is to install one
or two 100 watt incandescent lamps into the UPS output, unplug the UPS
from AC power, and see how long it will run. I do this when the UPS
is brand new, and again at erratic intervals. I also measure the
charging current to the battery, which is sometimes higher than I
would consider acceptable. These are also the ones that suffer from
premature battery death from overcharging and/or overheating.

You can also test the batteries outside of the UPS by using a 12v
automobile headlight or similar load. Again, compare operating time
with a new battery.

I recently purchased a West Mountain Radio CBA-II battery tester:
http://www.westmountainradio.com/CBA_ham.htm
Charge the battery and then run it through the tester. Compare with
a new battery of the same type. The problem is that the basic unit
does not work well with large batteries yielding odd results due to
connector contact and cable losses. The voltage is measured at the
tester end, not the battery.

I also plan to use the CBA-II to match UPS batteries. I tend to
purchase a fair number of "used" lead acid UPS batteries. The savings
is substantial but there are hazards. One is installing two
mismatched batteries in series.




I have used an ESR meter to check the condition of lead-acid batteries,
but haven't kept up with the practice. Was thinking an easy test would
be to have test points mounted outside of the UPS that one could use to
access each battery for an in-circuit ESR reading. Charting the results
would probably tellone when to replace the battery(eis).

http://flippers.com/esrkthnt.html (bottom of page)

Using the Bob Parker ESR (Blue - Anatek!) kit of course! Available from
us and others...

But beware, if like me you have installed a pair of fat antiparallel diodes
across the test terminals inside the meter (in an attempt to protect the
meter against charged caps) then for goodness sake put a low ESR
electrolytic in series with the test leads before you connect a lead acid
battery, or there will be melted wire everywhere. I don't know what Bob's
ESR meter thinks of DC if the diodes are not fitted - I have never tried it
and I can't remember the schematic.

Chris