I'm considering buying another drill as my current one has no working batteries. However, I've just seen a method online to 'recover' a nicd battery by zapping it with a higher voltage. Apparently it destroys the crystal formation that prevents the cells from working, the so-called memory effect.

Has anyone ever done this to recover a nicd battery? If it does work, anyone got any ideas how I could find/create a 36 volt power source (given that the batteries are 18v).

I'm not overly worried if it doesn't work, they were destined for the bin but if they can be recovered then it's a good thing.

I looked into this but eventually bought a new drill so I can't say if it works.

The article I read suggested using two 12 volt batteries in series so they were presumably using 24 volts to recover an 18 volt NICD battery.

I used to work in the model industry, was pretty common place.

best way (by far!) is to open the pack up and look at each cell in isolation. if its 18v pack there will be 15 cells (1.2v nominal per cell).

put a small load across the pack terminals, such as a 5w bulb (two in series if theres still some charge in the pack).

then check each cells voltage with a multimeter. In all likelihood you will find most of the cells are OK, with one or a couple either dead or reversed polarity. If this is the case, only 'flash' the dead/reversed cells. I used a 12v battery or battery charger, so a couple of seconds. Then re-check the duff cells to see if they are alive/positive voltage. If they are, recharge the whole pack using the proper charger, but don't reassemble the case.

once recharged, stick a decent load across the pack terminals (id suggest a couple of headlamp bulbs in series (18v pack needs a 24v load, one bulb will blow). with that load (approx. 42watts) check each cells voltage individually. so long as the duff cells aren't weak, then you may have got away with it. if they immediately show a poor voltage or reverse polarity, then they need to be pulled out and replaced with new (couple of quid each).

if you do replace a cell(s) with new, try to charge them individually before assembling into a part charged pack, or you will create a charge imbalance across the cells again.

NiCd are as tough as old boots, and generally recover, but if not replacing the offending cells is cheap and easy.

one last thing, try not to run the drill dead flat in future, certainly for the first few use cycles after the repair/replacement, just to give them a chance to all get along again.

above doesn't apply to NiMh ( nickel metal hydride) or LiPo or LiOn cells (lithium polymer or lithium ion), double check they are old skool nicads first!

any queries, just holla

CNH

doing the 'flash' across the pack doesn't single out the poorly cells and can bugger the good cells, must be done at cell level and not pack level imho

Thanks for the pointers. Cell by cell makes sense, I've already opened the pack and can see the individual cells. They're a bit of an odd physical size though so I'll have to look into where to get replacements from. And it does mean I don't have to mess about with higher voltages.

A bit of experiment time tonight then!

without pics I cant be sure, but I suspect they will be 'sub C' size, a little smaller than the normal C size domestic batteries. These are probably the widest used in industrial tool applications and one of the more common in RC models.
approx. 22mm diameter and approx. 43mm long

Hi
Having run a partitioning & suspended ceilings business since 1982
We have used every make of cordless drill , the only fault being the batteries
and nearly always cheaper to buy a new drill.
so you are left with a good drill which is unusable.
For the kit car builder , I have come up with a good idea to make use of the these
Take the battery pack apart & remove the batteries, drill a hole in the back of the pack
fit a 3m length of flex soldered to the internal terminals , re-stick the two halves together
Fit crocodile clips to other end of flex, and you have a very powerful 12V reversible
Drill which can be used out & about or if you have no power in your garage with a 12v Battery.
good luck

"flashing" does/can work but there is a small risk of exploding cells. from using batterys in rc cars for 20+ years nicads are tough old things but do slowly loose capacity nimh are more powerful but need very careful looking after to last more than a year LIPO are brilliant loads of power, keep a charge when stored for a few months and last a long time, but do take care of them misuse can make them scrap! i'd get a new lipo drill and take good care of the batterys

Might be worth sticking it in a freezer overnight works for most batteries before a re-charge

Nick N

I have recovered quite a few NiCd cells like this. However, in my experience cells that have been recovered like this are prone to fail again in the not too distant future.

quote:

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Originally posted by CNHSS1
without pics I cant be sure, but I suspect they will be 'sub C' size, a little smaller than the normal C size domestic batteries. These are probably the widest used in industrial tool applications and one of the more common in RC models.
approx. 22mm diameter and approx. 43mm long

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quote:

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Originally posted by renetom
Hi
Having run a partitioning & suspended ceilings business since 1982
We have used every make of cordless drill , the only fault being the batteries
and nearly always cheaper to buy a new drill.
so you are left with a good drill which is unusable.
For the kit car builder , I have come up with a good idea to make use of the these
Take the battery pack apart & remove the batteries, drill a hole in the back of the pack
fit a 3m length of flex soldered to the internal terminals , re-stick the two halves together
Fit crocodile clips to other end of flex, and you have a very powerful 12V reversible
Drill which can be used out & about or if you have no power in your garage with a 12v Battery.
good luck

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Hi
One of our 18v I converted runs fine on 12v
try it , what to loose.

quote:

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Originally posted by renetom
Hi
One of our 18v I converted runs fine on 12v
try it , what to loose.

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