SLA

[Robert Murphy]

Hi,

I have a bunch of 12V SLA batteries (from a couple of aquired UPSs) that I'd
like to test. I'd guess that putting say 12V across them for a few hours
(while monitoring the current draw), then discharging them with a light bulb
a few times would tell whether they're still viable. Would that be an
acceptable method? Sorry I don't have the exact Ah ratings for them at the
moment. Also, using a regulated power supply it's going to be 12V across
their terminals, I remember from somewhere that monitoring the terminal
voltage across a SLA is the way to tell when it's fully charged - I may be
better off with an unregulated supply (assuming that I can't just find a
battery charger from soemwhere).

Robert

 

[atec]

you local battery shop should test then for free , make sure they are
charged though as the loading and test is tough on the batteries.

Robert Murphy wrote:

Hi,

I have a bunch of 12V SLA batteries (from a couple of aquired UPSs) that I'd
like to test. I'd guess that putting say 12V across them for a few hours
(while monitoring the current draw), then discharging them with a light bulb
a few times would tell whether they're still viable. Would that be an
acceptable method? Sorry I don't have the exact Ah ratings for them at the
moment. Also, using a regulated power supply it's going to be 12V across
their terminals, I remember from somewhere that monitoring the terminal
voltage across a SLA is the way to tell when it's fully charged - I may be
better off with an unregulated supply (assuming that I can't just find a
battery charger from soemwhere).

Robert

 

[Phil Allison]

"Robert Murphy" <selectmax@hotmail.com>

I have a bunch of 12V SLA batteries (from a couple of aquired UPSs) that
I'd
like to test. I'd guess that putting say 12V across them for a few hours..

** That will not charge a nominal 12V SLA - the correct voltage is 13
..7.

(while monitoring the current draw),

** When the current draw settles to a low value - the job is done.


then discharging them with a light bulb a few times would tell whether
they're still viable.


** Once would do.

Would that be an acceptable method?

** If the bulb has a similar current draw to you application.

Also, using a regulated power supply it's going to be 12V across
their terminals,

** You need a 13.7 volt *regulated* and ** CURRENT LIMITED ** supply to
do the job.

I remember from somewhere that monitoring the terminal
voltage across a SLA is the way to tell when it's fully charged

** Nope.

I may be> better off with an unregulated supply

** Even worse that your first idea.


(assuming that I can't just find a

battery charger from somewhere).

** There is a glimmer at the end of the tunnel ;-)




............ Phil

 

[Franc Zabkar]

On Fri, 7 May 2004 22:36:22 +1000, "Robert Murphy"
<selectmax@hotmail.com> put finger to keyboard and composed:

I have a bunch of 12V SLA batteries (from a couple of aquired UPSs) that I'd
like to test. I'd guess that putting say 12V across them for a few hours
(while monitoring the current draw), then discharging them with a light bulb
a few times would tell whether they're still viable. Would that be an
acceptable method? Sorry I don't have the exact Ah ratings for them at the
moment.

WES have an intelligent, 1A current limited SLA charger for $20 (code
LAC1201). It is recommended for SLA batteries up to 12Ah.


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

 

[Russ]

"Franc Zabkar" <fzabkar@optussnet.com.au> wrote in message
news:41pq90poi6ccq4n01phrabi9rb2pr2buqv@4ax.com...

On Fri, 7 May 2004 22:36:22 +1000, "Robert Murphy"
selectmax@hotmail.com> put finger to keyboard and composed:

I have a bunch of 12V SLA batteries (from a couple of aquired UPSs) that
I'd
like to test. I'd guess that putting say 12V across them for a few hours
(while monitoring the current draw), then discharging them with a light
bulb
a few times would tell whether they're still viable. Would that be an
acceptable method? Sorry I don't have the exact Ah ratings for them at
the
moment.

WES have an intelligent, 1A current limited SLA charger for $20 (code
LAC1201). It is recommended for SLA batteries up to 12Ah.

Note that if SLAs have been left uncharged for a long period of time (>1
year) then the chances are they are buggered and you won't be able to get
them to take a charge.

One trick I'd heard of in this case is to try high-voltage DC for a short
period of time, which I tried with a couple of old batteries, but even at
90v almost no current was flowing.

Russell.

 

[budgie]

On Sun, 9 May 2004 10:04:02 +1000, "Russ" <russell_UnSpamMe_@thehovel.net>
wrote:

"Franc Zabkar" <fzabkar@optussnet.com.au> wrote in message
news:41pq90poi6ccq4n01phrabi9rb2pr2buqv@4ax.com...
On Fri, 7 May 2004 22:36:22 +1000, "Robert Murphy"
selectmax@hotmail.com> put finger to keyboard and composed:

I have a bunch of 12V SLA batteries (from a couple of aquired UPSs) that
I'd
like to test. I'd guess that putting say 12V across them for a few hours
(while monitoring the current draw), then discharging them with a light
bulb
a few times would tell whether they're still viable. Would that be an
acceptable method? Sorry I don't have the exact Ah ratings for them at
the
moment.

WES have an intelligent, 1A current limited SLA charger for $20 (code
LAC1201). It is recommended for SLA batteries up to 12Ah.

Note that if SLAs have been left uncharged for a long period of time (>1
year) then the chances are they are buggered and you won't be able to get
them to take a charge.

Often the case, but I've had some interesting "recovery" cases here.

One trick I'd heard of in this case is to try high-voltage DC for a short
period of time, which I tried with a couple of old batteries, but even at
90v almost no current was flowing.

Try a current-limited supply at or maybe a tad above the nominal float charge
voltage. Watch the current. It may take many hours, or even days, but the
current will often rise to respectable levels and charge will accumulate
properly.

I use a charger based on the Unitrode/TI UC3906, and it has recovered some very
old SLA's, including one Yuasa dated 8703 which had been inside an unused NCR
computer frame for over_seven_years.

Don't abandon hope, but don't bank on them powering your critical life support
systems either.

 

[Alan Peake]

One trick I'd heard of in this case is to try high-voltage DC for a short
period of time, which I tried with a couple of old batteries, but even at
90v almost no current was flowing.

Russell.

I found that some SLAs would respond if you give the high voltage
treatment for anout an hour or so then let the batteries "rest" for
another few hours then put them on mormal charge. As you say, intitilly,
they won't take much current at the high voltage but after "resting",
they would then charge at the normal rate.
Alan

 

[Robert Murphy]

Umm, OK. So what do I do then? Trickle charge, or zap them? There's a bunch
of them, (2 UPSs) so if I can get one working set I'd be very happy.

I don't know that much about this (guess I've made that obvious by now) -
what would be an appropriate charge current through a 7VA 12V SLA (a
Powerblock PB1270) for different types of charging?


"Alan Peake" <adpeake@killspam.internode.on.net> wrote in message
news:409DC43C.1010706@killspam.internode.on.net...

One trick I'd heard of in this case is to try high-voltage DC for a
short
period of time, which I tried with a couple of old batteries, but even
at
90v almost no current was flowing.

Russell.

I found that some SLAs would respond if you give the high voltage
treatment for anout an hour or so then let the batteries "rest" for
another few hours then put them on mormal charge. As you say, intitilly,
they won't take much current at the high voltage but after "resting",
they would then charge at the normal rate.
Alan

 

[Russ]

"Robert Murphy" <selectmax@hotmail.com> wrote in message
news:409e521f$0$16596$5a62ac22@freenews.iinet.net.au...

Umm, OK. So what do I do then? Trickle charge, or zap them? There's a
bunch
of them, (2 UPSs) so if I can get one working set I'd be very happy.

I don't know that much about this (guess I've made that obvious by now) -
what would be an appropriate charge current through a 7VA 12V SLA (a
Powerblock PB1270) for different types of charging?

The cheap intelligent charger that was mentioned that WES and Jaycar sells
doas a max charge rate of 1 amp, winding back to trickle once the battery is
charged. I'd guess that a trickle rate would be around 200-300mA. Charging
or discharging SLAs at any any great rate is not regarded as god for their
health.

Russ.

"Alan Peake" <adpeake@killspam.internode.on.net> wrote in message
news:409DC43C.1010706@killspam.internode.on.net...

One trick I'd heard of in this case is to try high-voltage DC for a
short
period of time, which I tried with a couple of old batteries, but even
at
90v almost no current was flowing.

Russell.

I found that some SLAs would respond if you give the high voltage
treatment for anout an hour or so then let the batteries "rest" for
another few hours then put them on mormal charge. As you say, intitilly,
they won't take much current at the high voltage but after "resting",
they would then charge at the normal rate.
Alan

 

[Terry Collins]

Robert Murphy wrote:

Hi,

I have a bunch of 12V SLA batteries (from a couple of aquired UPSs) that I'd
like to test. I'd guess that putting say 12V across them for a few hours

I will add my weight to getting a trickle charger and leaving it for a
month or two. I've had a similar experience and I found that I could
revive the SLA by just leaving them plugged in for weeks. Eventually
they came back to some degree.

I was using the Powertech regluated SLA charger from Jaycar.