Festool cordless drill not working

[petek]

I have a Festool cordless drill, about 10 yrs old which has had only occasional use (model CDD 9.6v). I won it at a corporate golf day - there is no way I could have justified buying such an expensive drill just for DIY use!

I recently came to use it and even though I have charged both batteries it is completely dead with either of them - not even the slightest movement of the chuck. The drill and the batteries were fine the last time I used it.

I have put my AVO across the battery terminals and can detect no voltage at all (again not even the slightest flicker of the needle) on either battery. Could the batteries "die" in this way, so suddenly? They're 9.6v, 1.7Ah, NiCd. They have been stored in the unheated garage recently in this cold weather but I have now brought them in the house to charge them. Is there any way I can test them before I go to great expense to buy new ones?

TIA Pete K

[John Rumm]

The charger will probably be "smart", and some of these can have difficulty if the cell voltage has fallen too far - they can't detect the presence of a battery and hence start the charge. Using some cruder form of charger to get the battery voltage up a bit first might fix the problem. An adjustable wall wart and your avo in series to set a charge current of 100mA or similar ought to do. Give them an hour of that, then try again in the proper charger.

[petek]

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Sorry for my ignorance John - what's an "adjustable wall wart". Also I don't understand the logic of connecting in series with my AVO.

[John Rumm]

Basically some form of plug in power supply brick - the sort you get with lots of bits of electronic equipment. It does not have to be adjustable, but that would make life a little easier since you could tweak the voltage up or down to get enough charge current flowing through the battery.

So you can measure the charge current. Set the AVO to a DC current measurement range, and place it in series with the battery and power supply. You can then see exactly how much current is flowing (if any).

You will probably find a 12V plug in PSU will charge a 9.6V pack at a relatively low rate.

[Tabby]

Agree that the way to go is to precharge them, but I'd be more careful about use of a wallwart. Doing it as described can start a fire. If you use an ordinary wart, pick one with as low as possible current output, and voltage similar to that of the battery, and jsut give it 5 mins, making sure nothing overheats.

NT

[petek]

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Thanks John, I'll give that a try, I've got one or two old PSUs lying about somewhere. I'll just have to chop off the jack plug and rig up some temporary connections to the battery. Is the charge rate significant? You mentioned 100mA - is that max or min?

Pete

[Tabby]

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1.3Ah with a 3hr recommended charge would be about 0.5A recommended charge. Best not to exceed that, except for very brief periods

NT

[dom]

You have checked the charger is producing an appropriate voltage?

[John Rumm]

If you go with a fairly slow rate like 50 to 100mA then there is no danger of overcharging the cells in the battery - you can charge indefinitely at that rate without risk. Lower rates are ok, might just take longer to get the pack reading a voltage. Higher is ok, but I would not push it much over say 500mA for this purpose. Once the pack reads say 7V or more, you will probably find the real charger will handle them from there.

[John Rumm]

Not always easy or safe on smart chargers - some won't output anything without an appropriate battery in place, and some use a high voltage and PWM to control the charge current when working, and hence could give a shock you might not be expecting.

[petek]

I put the AVO across the charger, and funny enough no volts at the terminals but I note John's comment that some chargers won't output unless a suitable battery is in place.

Pete

[chrisj.doran]

quoted text -

Just in case it's something silly... I'm not familiar with your model, but my charger has a button you have to press to start charging. If you haven't used yours for a while, could it be you've forgotten this?

Chris

[F Murtz]

Stick them across your car battery for a short time)correct polarity) Don't let them get too hot.