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Oemtech · 09-15-2005, 04:18 AM

How many of you have a cordless battery that the charger says is bad. Well today I brought 2 batteries back to life.

I had a Craftsman 15.6 cordless that had a bad battery (over 2 years ago) according to the charger. But, the other one worked fine. So, I figured that I would get a replacement battery from Sears. I figured I could get a deal as my daughter worked for Sears. Wrong, $49.95 for 1 battery. She bought me a new cordless with 2 batteries for about the same money after the discounts and coupons. The store does not carry all the batteries and you have to order them via parts and there is not much discount on parts.

Today I needed a cordless and decided to use the old one as the new one was in the new RV building just up the road. Needless to say it was dead. I put it on the charger and it was not only dead but bad. I went looking for new batteries on the net and found a site that advertised a method for "resurrecting" NiCad/Nimh batteries for $12.95. This got me thinking... Back in the "day" when I was wrenching in the back room of the service station we use to "shock" old batteries with high charge off the battery charger.

So, I got to looking at the cordless battery and "assumed" the center tap was for the charger to figure out if the battery needed charging or was dead. Figuring I had nothing to loose I hit the battery with my 12 volt car battery charger. The charge went off the scale and came back to almost 0 in about 3 to 5 secs. I then put it on the cordless charger, it showed good and in about an hour it was as fully charged. I gave the same treatment to the 2nd battery and it is also fully charged.

I was a bit surprised when I checked the batteries with a VOM and it showed 18.75 volts for a 15.6 battery. So, I checked my 16.8 battery that I just charged for the other cordless and it was also 18+ volts.

I figured I just saved myself $80 for new and maybe $40 for 2 off Ebay.

Lastly, if the battery is very warm to hot set it in the refrigerator for awhile before you charge it. Most have a "thermistor" and will not charge a hot battery. Also, run the battery until it is almost dead before recharging as It helps remove the "charge memory".

WARNING - Applying "high voltage/amperage" to any kind of battery can cause it to explode. What is "high voltage/amperage" - anything that it wasn't designed for. In my case 12 volts at about 6+ amps.

<span class="ev_code_RED">Update</span> - Both my 15.6 and 16.8 Craftsman batteries charge to over 18 volts... But the real surprise is my 18 volt Ryobi charges to 20 volts.

Oemtech · 09-15-2005, 04:18 AM

How many of you have a cordless battery that the charger says is bad. Well today I brought 2 batteries back to life.

I had a Craftsman 15.6 cordless that had a bad battery (over 2 years ago) according to the charger. But, the other one worked fine. So, I figured that I would get a replacement battery from Sears. I figured I could get a deal as my daughter worked for Sears. Wrong, $49.95 for 1 battery. She bought me a new cordless with 2 batteries for about the same money after the discounts and coupons. The store does not carry all the batteries and you have to order them via parts and there is not much discount on parts.

Today I needed a cordless and decided to use the old one as the new one was in the new RV building just up the road. Needless to say it was dead. I put it on the charger and it was not only dead but bad. I went looking for new batteries on the net and found a site that advertised a method for "resurrecting" NiCad/Nimh batteries for $12.95. This got me thinking... Back in the "day" when I was wrenching in the back room of the service station we use to "shock" old batteries with high charge off the battery charger.

So, I got to looking at the cordless battery and "assumed" the center tap was for the charger to figure out if the battery needed charging or was dead. Figuring I had nothing to loose I hit the battery with my 12 volt car battery charger. The charge went off the scale and came back to almost 0 in about 3 to 5 secs. I then put it on the cordless charger, it showed good and in about an hour it was as fully charged. I gave the same treatment to the 2nd battery and it is also fully charged.

I was a bit surprised when I checked the batteries with a VOM and it showed 18.75 volts for a 15.6 battery. So, I checked my 16.8 battery that I just charged for the other cordless and it was also 18+ volts.

I figured I just saved myself $80 for new and maybe $40 for 2 off Ebay.

Lastly, if the battery is very warm to hot set it in the refrigerator for awhile before you charge it. Most have a "thermistor" and will not charge a hot battery. Also, run the battery until it is almost dead before recharging as It helps remove the "charge memory".

WARNING - Applying "high voltage/amperage" to any kind of battery can cause it to explode. What is "high voltage/amperage" - anything that it wasn't designed for. In my case 12 volts at about 6+ amps.

<span class="ev_code_RED">Update</span> - Both my 15.6 and 16.8 Craftsman batteries charge to over 18 volts... But the real surprise is my 18 volt Ryobi charges to 20 volts.

RV Wizard · 09-16-2005, 02:04 AM

I have done and I believe posted this trick in the past using a capacitor. Charged cap and discarged across the battery terminals. It sometimes will bring them back to life. Caution is always a good idea, long leads and around a corner.

Eddielee · 09-17-2005, 02:23 PM

Usually, before I throw away my "bad" 1.5vdc rechargables, I short them across a 12vdc car battery. It's amazing how many of them I can resurrect. In a pinch, I've even used this to "recharge" standard flashlight batteries

FatDog · 09-17-2005, 03:35 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Caution is always a good idea, long leads and around a corner. </div></BLOCKQUOTE>

clever idea guys, i had never heard of it before, .... although a number of things i do in my garage require the approach Mike listed above

WAGM · 09-17-2005, 06:09 PM

Hey Dale, That sounds very interesting, I am gonna try it. If anyone knows of a way to do this to a 12volt gel cell let me know, I have several of those laying around that the electric cart eats up. <span class="ev_code_RED">THANKS</span>.

See yall in the funnies, Warren