I have just been given a cordless strimmer but after charging the battery overnight there is no life whatsoever. I am assuming that it is because it hadn't been used for 18 months and the battery was completely discharged. I have heard that happens with nicads (they should be periodically charged to stop exactly this happening).
So - are there any tricks to resurrect it?
Cheers
what can happen is that a filament of cadmium (I think, might be the nickel) grows between the plates and shorts the cell. If you measure the voltage on each cell while under charge you should be able to spot the shorted ones. You can then apply say 10 or 20A charging current to the cell using a car battery and some resistance wire to melt the filament. [b]WARNING![/b] If you are too heavy handed the cell will explode - you should stop as soon as you feel it heating up.
I admit I've only ever done it using 4 normal cells to get a high current, having never had access to a car battery.
That sounds a bit tricky - I doubt I could get to individual cells as it is a sealed unit.
Sounds like a bin job to me.
I've recovered a 7.2v pack using a DC power analyser and pumping 20A through it for 10 seconds. However it failed again within 2 charge cycles. On the third normal charge cycle it got very warm and vented 🙁
I doubt I could get to individual cells as it is a sealed unit.
yes, really you need to break the cells out.
If you're disposing, please be aware NiCads are toxic and should be taken the a battery recycling point
🙁
And here was me thinking I had saved the cost of a strimmer. PAH!
Rebuild your own pack with new cells?
Rebuild your own pack with new cells?
To be honest I doubt I have the skills/tools to do that.
Multicell can refurb it for you.
http://www.multicell.co.uk/products/607
It's easier than you think, but woudl require some tools, which if you dont have possibly negates the cash incentive.
You can handbuild a pack with a big soldering iron. It's not recommended by manufacturers, but has been done a lot by modellers etc over the years and it works. You need a BIG HOT iron to make the joints very rapidly (wire between the cells), because too much heat will quickly damage the cell internally. Only apply the iron for one or two seconds, and instantly cool the joint with a cold wet cloth held on tightly for a little while.
Works OK for me and I've built pack for cordless tools and 2M radios etc.
"Zapping" cells to recover them often works for a bit, and is easy enough to do as mentioned. There is honestly no danger of the cell "exploding" if you pump some amps in for only a few seconds. - But once you have to do this to old cells, they tend to rapidly go short again.