nuckollsr(at)cox.net
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 Posted: Mon Feb 19, 2007 6:04 pm Post subject: Battery chargers |
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At 06:36 PM 2/19/2007 -0600, you wrote:
| Quote: | Bob, I am not a normal contributor to your list but read with interest,
when possible, and thought I would offer this for your thoughts. There
seems to be a lot of interest lately on battery chargers.
I have used old small UPS systems for battery chargers and found them to
be pretty good at charging and keeping batteries charged. The type of UPS
systems that I am talking about is normally used for personal computers or
servers. I have done some measuring and they seem to vary a little in
how sophisticated they are. Some of the high end ones also seem to have a
DC pulse of some higher than 12v intensity. I don't have a scope
available so just observed a pulse reading on a meter that looks larger
than 30 volts. I assumed this was some form of attempt at preventing
sulfation. The resting or float voltage varies with units all the way
from 13.2 up to 13.8 using an uncalibrated meter. The nice part is that I
have found a lot of these around that people don't seem to want to bother
with replacing their old or bad batteries and will pass them on or junk
them. Since I am a classic cheap skate, it seemed a shame not to reclaim
them for a useful purpose. Several of these small ups systems originally
had Panasonic sealed lead acid batteries similar in size and shape to the
Odyssey 680 and since I have a 680 in the RV4, I thought this might make a
good battery charger/tender/minder for it.
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| Quote: | My assumption is that UPS manufacturers probably built a pretty good
battery charger/tender in the unit so as not to over charge the internal
battery. I don't have a recording meter system so I am not aware of how
they charge; as in "equalize", versus "float", etc They also seem to
have built in several protection modes, such as turning off the 117 volt
inverters or the load when the battery reaches a certain voltage (not
important when using as a charger) and they also shut down the 12 volt
output when the battery is below a certain starting voltage. In other
words, a completely flat battery will have to be paralleled with another
good battery to use these power supplies as chargers.
For my convenience, I mounted banana plug female jacks on the outside of
the units and made up jumpers with alligator jacks on them. They also
seem to work pretty good at charging up portable jumper batteries too.
In your opinion, am I slowly cooking any battery that I hook up to these
"inexpensive" power supplies.
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What a novel discovery my friend, thank you for sharing this!
Of course, uninterruptible are tasked with maintaining a battery
(that almost never gets cycled) in a high state of readiness.
Unlike vehicular systems that crank engines and supply fill-in
power when engine RPMS are too low, the UPS battery may sit
for years while the owner expects it to keep things running
for a useful period of time during power failures.
As others have observed on the List . . . batteries applied
in this special service may benefit from special treatment
by the charging/maintaining system powered from AC mains.
Which reminds me, the UPS on my desk is about 6 years old
and the last time I had a neighborhood power down, the
battery lasted barely long enough for me to do an orderly
save.
I don't have a battery on hand that fits inside but I do
have some instrumentation batteries as large as 32 AH.
It occurred to me last week that I might bring the battery
wires out and use one of these fat mamas to replace the
internal battery. Your posting has prompted me to revisit
that task with new purpose in mind. I'll take some measurements
on how this particular device treats its battery.
If anyone else has occasion to conduct some similar
investigations into John's idea, please share it with
us here on the List.
Bob . . .
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