# Roasted Drill Battery?



## Les (Feb 11, 2008)

I picked up a DeWalt electric drill at a garage sale for a couple of bucks. No charger included. The battery was almost flat. I took it home and hooked it to a 7.2V charger that I'd brought out a couple of alligator clips off the +/- leads. I've been using this lashup successfully on other batteries for a good while, with pleasing success, by putting them on to charge one hour as my high-class new HF instruction manual advises. (The DeW. was 7.2V, too).

The thing is, the DeWalt had a third lug besides the two above. I figured it was for some sort of sensor circuit to shut off the charger when full charge was reached. Well, I forgot and left it on about six hours. When I went down there the battery was so hot I couldn't (or declined to) hold it in my hand. The charger was pretty toasty, too.

The next morning I put it on the DeWalt, and it spun it up just fine. 'Another winner,' thinks I. A couple of days later I grabbed it to drill a hole (naturally) and after about a minute it started sagging, then died. Probably not two full minutes of run time.

I suspect I creamed it. Here's my questions:

1) what is the third lug on those batteries and chargers all about? I think as I explained above.

2) Any way to revive that thing?

Chances are the battery was dead before I got it, though the drill looked very good--still in plastic case. I'd hate to think I done it in. Now I have the charger on a one-hour timer. I'd been meaning to do that.

Les


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## Semper Vaporo (Jan 2, 2008)

I have a Makita drill/driver (9.6V I think) and the batteries and charger often don't like each other. I mark the date of purchase (or close to it) on my batteries so I can tell them apart and determine which ones have been causing problems.

Some batteries charge normally.

But with some batteries the charger will shut off within a few seconds of a "Reset" and "Start". I put a couple of screws in a metal block at the spacing of the Reset and Start buttons and clamp it on the charger so both buttons are continually pressed. Eventually the charger will stop clicking off and back on. and the charger seems to complete the charge. I place he charger in the middle of a concrete floor while charging. Sometimes they do get "warm" but I have never had one really hot.

Some batteries then seem to have taken a good charge as evidenced by the drill working at full speed. Others don't... the drill will not run for more than a few seconds. I throw the bad ones away (recycle bin!)

The ones that seem to take a charge will work for anywhere from just a couple of minutes to the usual 1/2 hour or so of hard use. The ones that don't last, I still keep and charge them just before I think I will need them and they help be get through the job at hand.

The really good ones soon become bad ones all on their own. Seems like I have to purchase a new battery once a year on average... and they (the model I use) are getting hard to find.

I think the only thing you can do is just wait and see how it recharges and how long it works after being charged and how long it will hold a charge on the shelf. Some of the Makita batteries seem to have healed themselves and will hold the charge a long time, AFTER I have been ready to toss it and decided to keep it just a wee bit longer.


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## izzy0855 (Sep 30, 2008)

Les, 

The third off set copper pin is the temperature thermistor, the thermistor tells the charger when your battery-pack is fully charged and tells the charger when to shut-off. Yes, you have over cooked your battery-pack and the electroliltes within each cell have fallin to the bottom of the cylinder and can no longer to recharged. My company, "Cordless Renovations" manufactures DeWalt battery-pack inserts that you can easily insert into your existing case without having to rebuild or buy a hole new battery. Go to www.cordlessrenovations.com . . . click on Battery-Pack Inserts / DeWalt. There you will see inserts for all different models of DeWalt batteries. If you have any questions, please give me a call. 

Rick Isard 
Cordless Renovations


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