Putting the spark back in NiCd batteries.

[Shannow]

Have posted before that Mrs Shannow's solar garden lights stop working after a while, and I replace them with regular alkalines after they've served a life in a TV remote or some greater necessity like the WII.

The used alkalines go for at least as long as the NiCd, and the solar lights don't push them as hard as my Rezap battery charger does, so no leaks to date (don't use Duracells, as they DO leak after a single charge on the Rezap).

So I've had NiCd that won't charge, the Rezap calls a fault on them...I ditch them at ALDI, but had one on the weekend.

But I had heard of people giving NiCd a bit of a belt with an arc welder to destroy the "crystals" that "short it out internally"...Don't know batteries that well, have made some solid salt zinc/epsom toys for play things.

Not wanting to pump arc welded current through a AA sized battery (yet), I thought my spark maker, made from a weedwhacker motor/magneto would be a low current high impact type fix.



First day out back in the sun, and it's back to being a solar powered light, with the original, sparked up NiCd...

 

[spasm3]

How would replacing them with nimh work? I don't they they develop a memory like nicad batteries.

 

[JHZR2]

Originally Posted By: spasm3
How would replacing them with nimh work? I don't they they develop a memory like nicad batteries.


They are both 1.2V cells, though the charging scheme optimally can be slightly different for these applications, its probably all the same. That would be my choice. NiCd is good, but Cd is not something Id want to mess with any more.

 

[Rand]

AND.... NIMH are very inexpensive now.

I saw a 12pack of eneloop AAA for 9.99$ the other day..

 

[Brad_C]

A couple of things...

A) Yeah, what's with bloody Duracells leaking? I swapped everything over to Sanyo Eneloops a couple of years ago.. sick of having to repair or replace alkaline damaged products..

B) Dendrites (the crystals that short NiCd/MH) puncture the separator as they grow. When you zap them and smash the dendrite the little hole in the separator remains and increases the self-discharge on the cell. Also the dendrites tend to grow back.

C) NiCD are better in solar lights than NiMH. NiCD respond much better to very low charge currents whereas NiMH don't tend to retain as much. Also, they're more resistant to abuse than NiMH, and so tend to last longer in devices with inadequate charge characteristics and subject to summer solar temperatures.

I spent a *lot* of time experimenting with replacement cells for solar lamps. On the whole NiMH die fast. I never tried alkaline however. Or expensive NiMH for that matter. Quality NiCD's last a *lot* longer than the NiCD that come in the from the factory. In fact after replacing the solar light cells with quality NiCD, the cells outlasted the lamps (an even split between UV disintegrating them and the dog chewing them up).

For dendrite blasting, just a crack with jumper leads to a car battery will do a nice job.

 

[HerrStig]

I use a 0 to 15 volt current and voltage limited power supply to zap them, but that's overkill I suspect. NiCads have a limited number of discharge cycles before they begin to degrade. There is some charge replaced in an alkaline when in the charging circuit of a solar light but the chemistry is not designed for that purpose.

 

[redbone3]

Originally Posted By: HerrStig
I use a 0 to 15 volt current and voltage limited power supply to zap them, but that's overkill I suspect. NiCads have a limited number of discharge cycles before they begin to degrade. There is some charge replaced in an alkaline when in the charging circuit of a solar light but the chemistry is not designed for that purpose.


I have used the same technique. For someone without a supply, I suspect a very quick attachment to a car battery would do the trick.

 

[JHZR2]

Originally Posted By: Brad_C


C) NiCD are better in solar lights than NiMH. NiCD respond much better to very low charge currents whereas NiMH don't tend to retain as much. Also, they're more resistant to abuse than NiMH, and so tend to last longer in devices with inadequate charge characteristics and subject to summer solar temperatures.


yes, NiMH has higher self-discharge, but the "precharged" and "eneloop" types have overcome these issues. Selection of the right ones makes this less of an issue.

 

[Brad_C]

Originally Posted By: JHZR2
Originally Posted By: Brad_C


C) NiCD are better in solar lights than NiMH. NiCD respond much better to very low charge currents whereas NiMH don't tend to retain as much. Also, they're more resistant to abuse than NiMH, and so tend to last longer in devices with inadequate charge characteristics and subject to summer solar temperatures.


yes, NiMH has higher self-discharge, but the "precharged" and "eneloop" types have overcome these issues. Selection of the right ones makes this less of an issue.


I love my eneloops, however misuse will very quickly damage the low self discharge characteristic. Like I said before, NiMH don't cope well with tiny charge currents and don't retain much of the charge they are presented with. This alone makes them a bad fit for solar lights. The reality is most people won't notice the difference, but NiCD will last longer in both life and runtime in that particular application.

Like I said before, I've replaced every alkaline battery in the house with either eneloops or Powerex Imedion (even the 9V PP3s). No more leaks and only require a top up charge every year or two for low drain devices.

Fast charging, super high current discharge and simple charge cycles will degrade the LSD characteristics however. The more you cycle them, the higher the self discharge becomes. In things like remotes, clocks and low drain kit it's a non-issue, because by the time you've put enough cycles on them to notice the damage to the LSD characteristics the world will have moved on, but things like solar lights where they are cycled 364.25 times a year will be a different kettle of fish.

Pack cells (like the PP3s) like to be equalized every couple of charges. The Imedion 9.6v PP3's are spectacular though. I reckon in the years I've been using them in my Guitar wireless alone I've saved about 400 alkaline batteries from landfill.

I'm hanging out for the LiIon PP3s to become commodity. I think they are the answer to a maidens prayer for test equipment and wireless kit.

 

[Shannow]

Pretty happy I started the thread, as there's great discussion...

Brad_C, what do you charge with ?

I've got an older Rezap, which has saved me a fortune over the decade of ownership

 

[Brad_C]

I use a maha c9000 for aa & aaa and a c490f for pp3s. I charge aa at 1A and aaa at 300ma. Have had great results so far.

Prior to switching to the maha stuff 4+ years ago I used energiser chargers and could never make the batteries last.

I got burned a couple of years ago with some eBay fake eneloops, but the genuine stuff has been great.