Recharging these batteries?

[crazyboy25]

We had a security system in our house for a long time but never used it finally my dad took apart the old emergency box ang gave me two batteries they are rechargeable but im not quite sure how to go about it any ideas?

 

http://i179.photobucket.com/albums/w318/crazyboy25/bat1.jpg

http://i179.photobucket.com/albums/w318/crazyboy25/bat2.jpg

[asilentbob]

They look like standard SLA (Sealed Lead Acid) batteries. You can buy chargers for them in many stores. Like harbor freight tools. There are also wall wort style chargers, but I'm not sure how well those work. You could also use a solar panel if it was the right voltage and size and had a blocking diode or whatever they are called so that the battery can't fry the solar panel.

 

I'm actually a bit jealous, I have wanted some SLA batteries to mess around with. I need to go buy some sometime this summer.

[mike_au]

A 12V car battery charger would be fine for topping them up, however if you drain them substantially you will need something to limit the current (a resistor in series or a current limited power supply).

 

I=V/R so say you run them down to 9.8V your charger puts out 13.8V so your difference is 4V. I = 1.75A so you want R > 2.3Ohms. Stick in a 5-10Ohm (charging will be slower but safer). You will probably need to use a wire-wound resistor as you are unlikely to find a carbon film that will handle the power.

[crazyboy25]

A 12V car battery charger would be fine for topping them up, however if you drain them substantially you will need something to limit the current (a resistor in series or a current limited power supply).

 

I=V/R so say you run them down to 9.8V your charger puts out 13.8V so your difference is 4V. I = 1.75A so you want R > 2.3Ohms. Stick in a 5-10Ohm (charging will be slower but safer). You will probably need to use a wire-wound resistor as you are unlikely to find a carbon film that will handle the power.

I have a battery charger. But these things are totally drained not even a tiny spark when I touch the positive and negative wires.

 

Sorry im not so good with electronics, your saying I need a way to limit the current from the battery charge if I plan to use it to charge the batteries? I've seen resistors before. They are really small and have thin wires won't the battery charger fry them? If not how would I go about it? Just attach a 10ohm resistor to each clamp and then each end of the resistor to the batteries?

 

Would the car battery charge straight to these presumably dead batteries totally fry them or cause them to explode?

[mike_au]

Yes, putting more than the 1.75A listed on the side of the battery will likely cause it to start venting and could lead to an explosion.

 

The small resistors you have seen won't handle the amount of power that you would normally use to charge those batteries. You could use them but they would have to have a high resistance and charging would take a long time (days/weeks), or you could get a high power resistor (aka wire wound, if you have some nichrome floating around for e-match you could make your own).

 

Most small resistors are 0.25 or 0.5watt. P=IV so for P=0.5w (assuming 0v in the battery, 13.8v from the charger) you can put a max of 36mA through the circuit. So using I=V/R we get a resistance of ~4kOhm or ~8kOhm if you only have 0.25w resistors. You can use resistors in parallel but lets not worry about that for now.

 

You only need 1 resistor, you would connect charger +ve to resistor, resistor to battery +ve, and charger -ve to battery -ve.

 

If they are that far drained, they might well be stuffed (lead acid batteries don't like to be deep cycled).

 

(Sorry if the equations seem confusing, I'm putting them in mainly so others can point out if I have stuffed up, it has been a while since I have pulled out my soldering iron)

[FrankRizzo]

I have a battery charger. But these things are totally drained not even a tiny spark when I touch the positive and negative wires.

 

Sorry im not so good with electronics, your saying I need a way to limit the current from the battery charge if I plan to use it to charge the batteries? I've seen resistors before. They are really small and have thin wires won't the battery charger fry them? If not how would I go about it? Just attach  a 10ohm resistor to each clamp and then each end of the resistor to the batteries?

 

Would the car battery charge straight to these presumably dead batteries totally fry them or cause them to explode?

If the batteries are completely dead (voltmeter reads less than 12V), they've likely been that way for quite some time. Batteries in that state are *extremely* difficult to recondition to a state where they will take a charge. They are likely destined for recycling (garbage).

[mike_au]

I'm going to hijack the thread a bit here, but on the subject of stuffed LA batteries, would it be possible to salvage the lead for milling media just by draining the battery?

 

Or would it be too dangerous/contaminated/etc?

I would have thought the hardest part would be safely disposing of the acid.

Since it is sulfuric acid, would it make the media unusable with chlorates (and other sulfur sensitive chems)?

[Richtee]

Since it is sulfuric acid, would it make the media unusable with chlorates (and other sulfur sensitive chems)?

Hmm..I'm kind of interested too. I am a licensed security system installer, so I go thru quite a few of these.

 

And as Frank said...once they are discharged to that low a state, or have been float charged for so long, wether cycled..used or not,,they sufate up and are junk. I typically get about 5 years out of these batts before they die.

[tentacles]

You're better off selling the batteries for scrap and seeing if the scrapyard has any lead to sell you. Alternatively go by locally owned car shops and ask if you can have some of their old lead tire weights to make fishing weights out of. It's 3% tin so slightly harder than pure lead and cheeeap. The scrap value is $.26/lb

 

FrankRizzo is right about trying to charge dead LA batteries. To get them to take charge again you need to repolarize the lead plates, and it's unlikely you'd be able to do this even with the correct equipment. If you do try to charge them, do so outside so when they explode (they are sealed!) it won't mess up your house/garage.

[TheSidewinder]

I USED to be a Fire and Security System installer, many years ago.

 

Are you CERTAIN that those are Lead Acid batteries? I don't see the "Corrosive" caution on them, and no International symbol denoting it.

 

In my day we used what were called "Gell Cell's". They weren't your standard Lead Acid battery, that much I do remember, ut they look IDENTICAL to what you've pictured, right down to the plug connectors.

 

You could put them in any position, even upside down, and they were fine with it.

 

But when they went bad, they were BAD... no resurrection was possible.

[oskarchem]

Don't we still use gel cel batteries? Because I have one on my lawn mowor, but they are expensive like shit... Like 90 Euros a piece...

[marks265]

I use these batteries all the time for fishing electrons. The charger for a 7amp/hr battery is a wall mount plug in transformer. It drops the wall voltage to 12 volt DC and has an output of 500ma (or 1/2 amp). If the battery does not charge in a day maybe two I would get rid of it. I would think that Radio Shack or similar electronic store would have one. It may have an end you can't use but you could cut the output end off and add your own aligator clips for battery connection.

The one I have in my hand right now is a

 

"DE" BRAND AC/DC ADAPTOR CLASS 2 TRANSFORMER

MODEL #D41-12-500

INPUT:AC-120V 60HZ 13W

OUTPUT: 12VDC 5OOMA

 

MADE IN SOME PLACE CALLED CHINA

[tentacles]

TS: Newer SLA batteries don't have the warnings on them. I guess the companies figure they're damned hard to bust open (and are). The gel cells are used in situations where there is a lot of vibration or shock (like your mower) where a normal SLA or LA would fail quickly.

[Richtee]

I USED to be a Fire and Security System installer, many years ago.

 

Are you CERTAIN that those are Lead Acid batteries? I don't see the "Corrosive" caution on them, and no International symbol denoting it.

 

In my day ...

I was there in those days...they dropped the warnings. It's STILL H2SO4 in gel form and lead... Had one crack a month ago, and THOUGHT I cleaned my hand up...ouch...what's that stinging? ;{)

[TheSidewinder]

Don't we still use gel cel batteries? Because I have one on my lawn mowor, but they are expensive like shit... Like 90 Euros a piece...

I'm fairly sure they're still used in alarm systems, richtee, but not certain to what degree. I got out of that business years ago.

 

I do know they still EXIST, just not sure where their technology has taken them since the late 70's. Back then, they were the ONLY choice for any "battery-backup" component in a Fire or Security system. (That was partially dictated by the existing Fire Codes, too.)

 

And yeah, they're horribly expensive, and were back then, too.

[Arthur]

Those batteries are available in th UK for about £25 each. So let that temper the amount of work you put into them. If a lead acid cell is left discharged for too long it will not recover its capacity ir peak current supply.

 

 

If you have a suitable PSU, separate the two batteries and try to charge one, Metering the voltage and current, should tell you whether that battery will accept charge and be usefull.

 

If applying 15v the right way round to the terminals causes current to flow into the battery, things are starting to look good! reduce the voltage until a current about half an amp is passing into the battery, and keep that current for a couple of hours. Rest the battery for a few minutes then try a small lamp as a load If it will run a small 12v lamp you are in luck.

 

If you are fortunate the leave the battery on charge at its float voltage for 24 hours.

 

Try the other battery too! Don't expect too much a battery left discharged for 12 months will likely be dead anyway and not recover much capacity.

 

The plate material is lead oxide and lead hydroxide in a serviceable battery. in an unserviceable battery much of the lead is as sulphate. Trying to melt the contents down to get lead will only get you the supporting lead matrix from the plates to get the active materials recovered demands reducing the compounds from salte to metals with heat, flux and carbon. SO weigh the batteries in and buy some second hand lead for casting.

[mike_au]

I think I already know the answer to this ("No, its too hard") but I will ask anyway.

 

If the plate contains large amounts of lead oxide, is there any chance of using it to make a lead dioxide anode for a chlorate cell?

[Richtee]

I think I already know the answer to this ("No, its too hard") but I will ask anyway.

 

If the plate contains large amounts of lead oxide, is there any chance of using it to make a lead dioxide anode for a chlorate cell?

Well- I believe it'll be lead sulfate mainly...

[tentacles]

Lead dioxide used in lead acid batteries is NOT suitable for chlorate/perchlorate. If it was that easy.... Anyways. Wrong type of lead dioxide (alpha) and it's basically a compressed powder/matrix deal.

[Arthur]

Messing with the insides of a battery isn't nice - strong acids and lead compounds.

 

If you are determined then you could perhaps use a cleaned lead plate as the basis for a lead dioxide electrode. It would have a huge area for its weight so may even overheat.

 

Hardly a great project

[Yankie]

I am not quite sure where to post this so move it if nessecary mods.

I would like to build a Electronic firing device that is reletavely portable, would I be able to use 9v batteries, or even a cheaper option a shitload of AA batteries, you can buy like 50 for 10 bucks at supercheap.

[mike_au]

How good are your electronic skills?

 

Your description is a little vague, a nail board with a heap of wire wrapped around it is relatively portable, a wireless remote with the receiver strapped to the mortar stand much more so.

 

I'm working on the latter at the moment, the remote design and code is pretty much sorted, just have to finish designing the receiver and then move them from a breadboard to a PCB. I'd be happy to share the schematics and hex files (PIC 16F series) if you're interested.

 

The $10/50 batteries are going to be pretty lousy, especially if you start taking high current from them, you might find a decent set of energizer or duracell D cells would cost less in the long run than a pile of cheap AAs.

[tentacles]

Why not just get a cheap SLA battery and recharge it as needed? Then you get a battery that can supply big chunky current and is reusable.

[Yankie]

My electronics is pretty good but not fantastic. I am doing electronics at school and the teacher says I can buy components from the school. I would like to make a 12 cue remote system, theres a tutorial in the member tutorial section.

where can you get SLA batteries and roughly how much are they? have a rechargable battery from an old spot light, I'm not sure on the voltage, but I think its either 6 or 12v.

[mike_au]

Personally I would be hesitant to use any off the shelf equipment that wasn't designed to be intrinsically safe. As mentioned in the tutorial, the only thing differentiating your transmitter from someone else's is an 8bit encoder setting. The chances of random radio noise triggering a cue are low, but the more radio noise there is around, the higher your risk.

 

If the battery is from one of the $20 supercheap spotlights then its 12v, it should be printed on the side anyway.