Battery drill connections

The charger for my old battery drill has died and I'm trying to
resurrect it. There are three connections to the battery, two larger
connections labeled "+" and "-" and a third connect, smaller and
labeled "T". The plus and minus connections are easy enough but what
is the "T" connection.
As some of the components in the charger are unmarked I have been
thinking of just connecting a 12 volt charger to the battery
connections and am wondering about what to do about the "T"
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T = temperature
Those battery packs have temperature sensors to allow the charger to charge at high rates without destroying the battery.
Reply to
Pete C.
T for Temperature to monitor the charging temp would be my educated guess.
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Temperature. Keeps track of the internal temp of the battery while charging. Least..some do.
Reply to
Gunner Asch
DO NOT CONNECT A RANDOM CHARGER TO THE BATTERY PACK. If you want to build a charger, you need to know a LOT more about batteries than you appear to know.
The T connection is probably related to temperature and can be configured to operate in several different ways. And it MUST be connected as designed for that system.
What usually happens is that one or more of the cells short. That increases the current and overheats the transformer and the thermal fuse inside the transformer opens up.
It's likely that you need a new transformer and a new battery. Even if you get a new charger of the proper type, your battery may kill it too.
I have a lot to say on the subject, but unless you want to become a battery engineer, you're better off buying a new drill.
Reply to
If by "Transformer" you are referring to the charger it is a bit more than a thermal fuse, it was several capacitors that died and leaked all over the circuit board, a resister that apparently overheated physically broke and two three legged devices one of which is a transistor, the other is unmarked.
I charged one of the two batteries, using an automotive 12 volt charger and once charged the battery appears to have normal capacity, at least measured by number of holes it can drill.
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What Mike said. Your term "old drill battery" is likely to be the problem, and could've caused the charger to fail. NICD cells generally fail shorted when left sitting around for months at a time, then only charged when needed.
Charging batteries with chargers intended for different battery chemistries is a bad idea. NICD and NIMH tool battery packs don't charge safely or properly by the same methods used for car lead/acid batteries.
And I knew a guy that was so cheap he'd "recharge" non-rechargeable batteries with a car battery, claiming that it worked perfectly, good as new (just a quick zap with a jumper wire). He could've lost his eyes for less than a couple bucks for new batteries.
In some tool battery packs, the T terminal is the (-) charging terminal connected thru a self-resetting thermal protector. Many packs use different methods.
There are many ways to approach power tool battery needs.. some companies specialize in rebuilding packs with higher capacity cells. Empty used pack cases are available on eBay, which can be "good as new" or better, when refilled with fresh new cells. Universal NICD-NIMH, original OEM and other suitable chargers are also available on eBag and elsewhere.
The best quality cells, IMO, are made in Japan.. Sanyo, Panasonic and FDK are some examples. IME, new NIMH cells perform better after the first 6 or so uses, so their performance is considerably better than it seems for the first couple of uses.
By buying new cells with tabs attached, they're ready to be connected safely without soldering directly on the cells.. overheating will typically damage cells and likely cause leaking.
Reply to
You asked a question. You got an answer. You ignored it.
Suggest you learn braille. It's easier while you can still see. Maybe practice typing with one hand. Make sure you've got good disability insurance.
Getting hurt is extremely least that's what I was thinking half a second after I got a face full of hot battery juice when the pack exploded. If I hadn't been wearing glasses, I'd likely be typing this on a braille typewriter.
Maybe you'll have better luck.
Reply to
Look on ebay for another charger.
Remove 333 to reply. Randy
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Partially correct. I asked a question and I got an answer and so far I haven't ignored it.
You, on the other hand leaped into the fray and started nattering on about "transformers" and a lot of other garbage which weren't germane to the conversation and now you relate a story about how you exploded a battery.
Well, good on you, but so far, and I've been at it for a while, I haven't been stupid enough to blow up a battery so your tirade might better be entitled, "Stupid things I've done"
>Suggest you learn braille. It's easier while you can still see. >Maybe practice typing with one hand. >Make sure you've got good disability insurance. > >Getting hurt is extremely least that's what I was >thinking half a second after I got a face full of hot battery juice >when the pack exploded. If I hadn't been wearing glasses, I'd likely >be typing this on a braille typewriter. > >Maybe you'll have better luck.
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That is a thought although the key-less chuck is about on its last legs and the drill must be nearly 10 years old so I might use this as an excuse to buy a new one :-) ("See Honey, I can't charge the batteries so I need to get a new drill if you want that shelf in the kitchen :-)
Reply to
Ages ago I worked at a tool store. We got Makita charges in all the time that, "didn't work." I took one apart one day and found they had a fuse hidden inside the case. If you plugged in a battery hot from continuous use it would blow the fuse. I started "fixing" them in house for customers. Certainly worth a look.

Reply to
Bob La Londe
The 'T' connection is sometimes a thermally-protected charging input. If the battery heats beyond it's acceptable maximum, the thermal breaker opens, stopping the charge until the battery cools again.
Reply to
Lloyd E. Sponenburgh
Interesting. I have the charger in pieces and (while I wasn't looking for one) didn't see a fuse. All of the capacitors were leaking and one resister (I think) was burned black to the extent that one end connection was loose on the body of the resister. More to the point there were two three legged gizzies with heat sinks, neither of which had any markings, that may or may not be damaged.
I had about decided that a new drill might well be the best answer until I priced a few.... they certainly have gone up in the last ten years since I bought my no-name Chinese drill :-)
My final (at least for now) solution was to hook up a small 12 VDC power supply and use it for a charger. I hooked up a DC amp meter to monitor the charge rate and am getting about 1 amp into a nearly flat battery and about a 90% charge after an all night charge, so for now that is good enough.
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