Scrap SLA's-Minimum voltage for OK

[domwild]

Friends,

From this forum I know that a flooded lead-acid batt. with an at-rest voltage of 10.5V at a scap yard is worthwhile to use again, but what sort of a minimum acceptable voltage is considered for experimenting with SLAs?

I need three 12V SLA batts. for a 36V UPS to experiment with and therefore need three equally "bad" ones.

As an aside our telco in Oz is sending pallets of batts. via scrapyards to China and there is a prohibition on selling batts. ex exchanges to the public. One Telecom technician told me via the net some Telecom batts. were found dumped in the bush with Telstra (Telecom) markings on them leading to this ban.

Thanks.

[ghurd]

I would not haul one home if it was under about 12.3V.

SLAs hold their voltage for a long time.

I left 7AHs sit for 6 or 12 months and had the voltage on some at 12.5V.

I bought some old 12V 7AH at under 12V that were fine, while others at 12.2V seemed to have a dead cell.

Rolling the dice.

G-

[Flux]

I agree with Ghurd.

Sealed batteries hold their charge for a long time. You may be able to rescue them form a lower voltage but any battery below 12v may have issues.

If it is in a scrap yard it may be there because it is no longer wanted or it may be there because it is scrap.

From voltage alone you can't tell much. Something showing 10.5v may be well discharged but could be recovered. It could more probably be well charged and have one duff cell and be scrap. Unless you can measure individual cell volts it really ought to be over 12v to be worth having unless you can get it on a take it back if no good basis.

Flux

[GlutealCleft]

Look for a spark when you short them.  I've seen a LOT of SLAs which would measure fine on the voltage, but ANY load would instantly drop them.

[Junkie]

Yeah I've hauled a few back that read 12.7 only to find  them completely wasted. Voltage isn't a great indicator.

[Nothing40]

Get an old turn-signal bulb or something from a car,and solder some wire tails onto it to use as a rough 'life checker' for the batteries..I'd probably bring a DMM with me too,and check the voltage with/without the lightbulb load.

[domwild]

Thaks for the many good answers. I have no experience at all with SLAs. I hope some end up in scrap yards because they were exchanged on a strict time basis like in telephone exchanges and not because they failed.

Cheers,

[zap]

Have a look at this post http://www.fieldlines.com/story/2009/4/6/161139/6278

It may be of interest.