Dewalt batteries or charger - kaput?

[gidon]

I bought a Dewalt 14.4v cordless drill, saw combi over a year ago now. It came with two 14.4 batteries and a charger. Just recently the charger won't go to a steady light (to indicate fully charged). After putting the battery on to charge for a short while the charger flashes quickly indicating the batteries are faulty. This happens with both batteries. They really have had very little use - especially considering they are meant for trade use. Could these batts aleady be finished? Or could it be the charger - anyone have any ideas or suggestions.
Thanks
Gidon

 

[Mike.C]

Do you know anyone with the same charger who will let you try charging one of the batteries on their charger to see if it acts the same?

Or could you take your battery to your nearest dealer (may be the one where you purchased the combo from) and ask if he could test the batteries for you?

I really do not know a lot about this sort of thing, but would not using the batteries for say months on end damage them?

Cheers

Mike

 

[gidon]

Thanks for the suggestions Mike.
I checked the charging again - brought the charger and batteries indoors and tried again. This time when I plugged the battery in the charger I heard a soft POP and a smokey smell - smoke then poured out of the charger grill!
Anyway, I truly am gobsmacked at the kindness and generousity shown on this forum (again and again) - two forum members have both offered to send me one of their spare chargers!
Many thanks
Gidon

 

[Woody Alan]

There can be all sorts of reasons for this effect, and maybe some cures if it's the batteries. The problem with this type of kit can sometimes be that the batteries are not "formed" properly (similar to capacitors in flashguns) when the cells are new they would benefit from a couple of slow charge discharge cycles (if possible) before hitting them with the fast charger. If the batteries are not cycled and used a few times from new and left too long between charges they never really get going. NimH cells despite the hype about holding charge longer do not like being left for quite a long time without a charge, if they are stored when new without a charge they sometimes don't work at all. Finally the charge circuits in modern chargers have to be quite sophisticated because of the fast charge, the downside to this is if cell voltage drops below the normal discharged voltage (about 0.9-1 volt) then when it tests the pack prior to charging it thinks it's faulty. It is possible to "wake" the pack up (more on that later perhaps if your other options dont' work) . Start off by measuring the voltage on the packs and see what they are sitting at now. If you have access to a slow charger it might be possible to bring them back to a good state, do you know any radio control modellers/ they will more than likely have a charger that will sort them out...if they can be. Try Mike C's suggestions if possible.

Cheers Alan

 

[Losos]

Gidon,
If you've got smoke comming out of the charger then you've sure got a problem with it

As far as the batteries go, if they are NiCad they should be taken down to zero (Or as near as possible) before re-charging, and they don't much like being left at half charge for long periods.

For a typical home user this makes battery kit a bit of a problem since people might use them intensively for, say, a long weekend, and then not use them for weeks or even months.

I thought the newer types NiMh etc. were better but seems not from above post.

 

[dickm]

Thanks for the suggestions Mike.
I checked the charging again - brought the charger and batteries indoors and tried again. This time when I plugged the battery in the charger I heard a soft POP and a smokey smell - smoke then poured out of the charger grill!
[..]

Sounds pretty familiar - I've bought several of the "cheapo" battery drills/saws, and at the last count, four chargers had gone off pop. I <hope> this is just that the things are really poorly made (and taking them apart supports this idea) and not my incompetence. But I'd be interested to know if anyone with electronic knowledge can suggest a more robust circuit or components compared to the typical "made in China" versions, that is within the competence of an average solderer to build.
There seems now to be a sort of standard for the battery shape among the cheap ones, which looks quite like the Makita batteries. Can anyone confirm this?

 

[Woody Alan]

Yes you can buy a better charger, as I have already said radio control modelers use them you can set the charge current and even do charge discharge cycles. down side of course is you have to make your own connexion to the battery and they run from 12volts . They cost around 60-70 GBP and a mains power unit to run it properly 30GBP from Maplins, so it is a little pricey if you can buy a drill charger and 2 batts from ladles for 20 GBP.

sorry I didn't see the reply about the smoke when I made my previous reply.

none of these things like being stored in damp garages it promotes corrosion etc

Alan

 

[mudman]

As far as the batteries go, if they are NiCad they should be taken down to zero (Or as near as possible) before re-charging, and they don't much like being left at half charge for long periods.

For a typical home user this makes battery kit a bit of a problem since people might use them intensively for, say, a long weekend, and then not use them for weeks or even months.

I thought the newer types NiMh etc. were better but seems not from above post.

Don't take NiCads down to zero, this can be very detrimental to them. The battery pack is a bundle of cells and as they discharge, they won't all reach zero together. This means that when a cell becomes exhausted, the other cells with charge still in them can start to reverse charge it which will ruin it. You should re-charge the pack as soon as the battery shows signs of running out.

 

[Losos]

Barry - Thanks for the advice, I must admit I still get confused about this "Memory effect"

If you don't take them right down to zero do they not tend to "remember" the level at which they were last charged and not go below that.

Likewise I have been told (And read in electronic mags) that a NiCad will not regain its full charge if it gets taken off charge before it has reached full.

 

[gidon]

I'm not sure the Dewalt chargers can be classed as cheapo chargers. I was quoted £70 for a new 9116!
It turns out the charger was faulty - some kind UKW'er has sent me his spare and both batts are now charged to the steady light.
Thanks for all the suggestions. I do tend to use the batts until they start showing early signs of running out and then switch. And they get used pretty reguarly. I think in this case it was just a faulty charger. Sometimes the power gets tripped in the workshop - maybe the charger didn't like that or something. Having said that my bosch charger wasn't affected ...
Cheers
Gidon

 

[Mike.C]

Gidon,

It turns out the charger was faulty - some kind UKW'er has sent me his spare and both batts are now charged to the steady light.

Thats great, i am pleased that you have got the problem sorted out, and well done to the member (who ever you are) whos superb generosity, helped you cure the problem.

Cheers

Mike

 

[gidon]

Thanks Mike -
Cheers
Gidon

 

[mudman]

Barry - Thanks for the advice, I must admit I still get confused about this "Memory effect"

If you don't take them right down to zero do they not tend to "remember" the level at which they were last charged and not go below that.

Likewise I have been told (And read in electronic mags) that a NiCad will not regain its full charge if it gets taken off charge before it has reached full.

It's not actually the memory effect here but the individual cells in a pack having different capacities. Nicads will retain a pretty constant output through the discharge cycle and this will tail off very rapidly as the near a fully discharged state. With a drill you will notice it as the drill slows down. I usually let it run for a bit longer and then put them on charge at this point. Had my batteries for about six years now and still going strong. Don't use them all that often though and they do get left in a semi-charged state quite often. I don't think it does them any harm but they will lose charge over time and again you must make sure they don't fully discharge.

I haven't looked into it for a few years but I believe that the dreaded 'memory effect' was a feature of the early nicads and is a bit of an urban myth.
However I'm not an expert and maybe someone else can confirm or deny this?
May do a bit of digging around on this later and let you know.

 

[dickm]

I'm not sure the Dewalt chargers can be classed as cheapo chargers. I was quoted £70 for a new 9116!
[..]

Sorry, wasn't meaning to suggest the DW was a cheapo (certainly it's too expensive for me ) But when you can buy a cheapo drill plus charger for £20, I'd expect the DW chargers to be a <lot> better - hope your replacement proves to be so!