Versapak charger repair

[John Anderton]

Hi all, I wonder if anyone can give me some help here.

I've got an old Black and Decker cordless screwdriver which uses the Versapak system but the charger for said screwdriver no longer charges the batteries. I've opened the charger up and found that no juice is actually getting to the cradle so I assume the "stick it in a socket" transformer has expired.

I've looked into a replacement charger but since they weigh in at about £24 it would be cheaper to replace the screwdriver (since it's the only Versapak tool I've got) so I thought I'd have a rummage through my box of bits to see if I can find a replacement transformer.

The Versapak transformer is marked as "2x4.35V 210mA" but the fount of all knowledge (uk.d-i-y) led me to this

page which states that the output voltage is 7.6 volts.

I've found a similar Netgear transformer with an output of 7.5V 800mA so my question is, can I use this as a substitute ?

(I'm assuming the mismatch in current won't be a problem because :- a) That's the maximum current the transformer can deliver and b) the current drawn will be the same in both cases as the voltage is the same and so is the resistance of the battery.)

Am I correct or am I in danger of starting a small fire ? :-)

Cheers,

John

[Chip]

On Sun, 19 Jun 2005 21:48:47 GMT,it is alleged that John Anderton spake thusly in uk.d-i-y:

From the research you have done it appears 'probably not'. However I would go very very carefully, it may be that the transformer died for a reason, possibly a fault in the charger itself, or, in fact the transformer may not be dead. If you have access to a multimeter, I would 'prove' the transformer dead, then connect it up via the multimeter's current setting [the highest available to begin with], on the low voltage side only, and check the current going in. If all appears well at this point, give the battery 5-10 minutes of charge under supervision, and see if it puts anything into the battery. If it does, let it build up your trust in it gradually :-)

[BigWallop]

Is it 7.5V "DC" 800 mA?

[John Anderton]

Yes,

Cheers,

John

[John Anderton]

Thanks for the tip,

Cheers,

John

[BigWallop]

Then it should be OK. But, a little word of warning here. Don't leave it on to long to begin with. Say 10 to 15 minutes supervised operation to start off with. Keep your hand near the socket switch just in case. Then check that nothing is getting to hot to handle with the battery and charger unit.

It might also be a good idea to check the battery every half hour if all seems well with the first check. And then try the battery in the tool to make sure it is actually charging as well of course.

Good luck with it.

[John Anderton]

Thanks. Fingers crossed and I'll give it a go tomorrow,

Cheers,

John

[bigcat]

absoluetly not. It may be dangerous to do this. Its also possible it may work, but its a very iffy proposition.

it is very much a problem

no, explosion is the risk. I'll overlook the various items that may also be damaged beyond repair.

NT

[John Anderton]

Why ?

Again, why ?

As far as I can see the only things in danger of damage are a redundant Netgear power supply and a useless charger and battery. No great loss at all.

You don't work for the ODPM by any chance, do you ? :-)

You've given out dire warnings without any detail. What exactly is the problem ?

Cheers,

John

[John Anderton]

Just in case anybody cares, that seems to have worked :-)

Cheers,

John

[bigcat]

It depends whether the current control is in the wallwart or the cradle, more often its in the wart. In which case using a standard wart, and one of higher V, would charge the batteries too fast, and overcharge them. With fast charge cells used ni tools this would cause overheating and maybe explosion.

Its the loss of human parts rather than tool parts that is the issue with big bangs.

If it works ok and the batteries dont get hot, and nor does the charger, ok-ish. You may just be shortening batter life, or it may even all be fine.

NT

[Chip]

On Tue, 21 Jun 2005 22:17:49 GMT,it is alleged that John Anderton spake thusly in uk.d-i-y:

Excellent news :-)

Just keep an eye on it for the first few charges to make sure nothing's overheating and then go out and buy beer with the money you saved.