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Hugh

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Joined: 26/11/2006
Location: Canada
Posts: 41

Posted: 02:38pm 09 Feb 2007

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Hi there
Just acquired a dozen sealed lead acid batt., differnt manufacturers, however al stats are the same 12V 7Ah

charge instructions are
stand-by 13.5v-13.8v / Initial current no limit
cycle use 14.4v-14.7v / initial current 2.1A max.

can I use a charger thats rated @ 19v- 2.2amps
I'm willing to rectify the charger output, preferably without actually canceling its original use. I have a ongoing supply of these batt. and need to keep them topped up.
the charger is regulated & theres a 15 min quick charge built into the system and then it does the slow charge cycle, that eventually charges the 18v nicad in one hr.( the charger is a ryobi 18volt charger). That being said would it be possible to have them charge @ the same time.

I hope this makes a little bit of sense. Any help would be appreciated.
Hugh

thnxs allways

WindChopper
Newbie

Joined: 08/02/2007
Location: United States
Posts: 15

Posted: 07:51pm 09 Feb 2007

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Hi Hugh

Wind Newbie here also - but burning my fingers on a soldering iron for more than I care to remember !

Forget the Ryobi charger - its a NiCad charger as you noted - wrong for SLAs -

I usually use Current Limit + Voltage Limit charging on my SLAs.

PowerOne makes a nice series of single voltage open frame power supplies that show up on the surplus market.

I usually use one of these for my charging .... set the voltage limit to 13.6 ( float voltage ) and set the current limit to C/5 or something like that ....

For the 7ahr SLAs ( sounds like you have someone changing out the batteries in a bunch of computer UPSs ! ) I usually use 13.6 V as the voltage limit and ~1.0 A as the current limit.

Current limits at 1.0 A ( voltage at something less than 13.6 ) until battery gets near 13.6 then voltage limit takes over and you slowly float up to 13.6 V.

This may be a little slower than some use but it treats the batteries nice and gentle.

Great find on the batteries

Have a nice one

Russ

Hugh

Regular Member

Joined: 26/11/2006
Location: Canada
Posts: 41

Posted: 02:13pm 14 Feb 2007

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Hi There Russ
thanks for the info, how would you set it up to charge them all at once and keep them topped up. signed total newbie
Hugh

thnxs allways

WindChopper
Newbie

Joined: 08/02/2007
Location: United States
Posts: 15

Posted: 01:42am 15 Feb 2007

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Hugh

Depends upon what you are going to use them for.

Since these are most likely in various states of health, I would deal with each independently first.

Charge each individually, test it for capacity, tag it, recharge it and shelf it until ready for your project.

Recharge them periodically ( individually ), if you are shelving them for a long period.

When you decide how you are going to use them, series or parallel, match them depending on their test characteristics.   For example creating a pack connected in series, using a low capacity battery, in series with a high capacity battery, will exhibit a pack capacity based on the lowest capacity battery.   ( Weak link in the chain concept. )

With new batteries ( equivilant ratings ) you have more flexibility in creating packs, but with used batteries you need to spend some time matching them.

If these are really pull outs from UPS service you will find a spread from Gold to Garbage.

Not the direct answer you were looking for, but you need to do a little home work to match them up.

If you are not placing them in immediate service, you do not need to continuously charge them.   Letting them sit for a week or a month will let you sample those that have no holding capacity.

Google "Charging SLA Batteries" for more than you really wanted to know about the care and feeding of ....

Now the "short" answer .... surface/trickle/float charge them in parallel from a regulated supply using an isolation diode and series resistor ( maybe 10ohms at 10w ) between each battery and the power supply.   Set the power supply for 13.6vdc + the diode drop (~0.7vdc for your garden variety power diodes ) or ~14.3vdc.   This assumes that you are charging them for storage which is what you indicated.

Later

Russ

Hugh

Regular Member

Joined: 26/11/2006
Location: Canada
Posts: 41

Posted: 01:58am 15 Feb 2007

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thanks russ thats the info i needed
Hugh

thnxs allways

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