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Dave Liquorice[_2_] · 01-12-2012, 05:26 PM posted to uk.rec.gardening

On Sat, 1 Dec 2012 02:51:46 -0800 (PST), wrote:

I bought a hedge trimmer and a cutter both battery operated. Didnt
use (medical reason) for 2 years. Now cant get batteries to take a
charge. Have checked charger and engines, all okay. Is this normal?

Afraid so.

Any solution?

Depends a bit of the technology used by the battery.

If theyre NiCd or NiMH they should have survived no problem.

If they have been charged the self discharge over that period of time
knackers them in my experience. If they had been discharged when going
into storage they would have stood a better chance.

Its unlikely they're lead acid, but if they were they wouldnt be
expected to survive 2 years flat.

Lead acid are the oppsite to NiCd/NiMH they prefer to be stored charged,
so yes stored flat wouldn't do 'em any good. I'd expect a lead acid
battery to not worry unduly about 2 years, it will have self discharged a
bit (maybe 50%) but should still be functional.

Resurection is a varies with the technology. In NiCd/NiMH cells the self
discharge produces "whiskers" in the cell that short it out. It's
sometime possible to fuse these whiskers by *briefly* applying a higher
voltage and hefty current to the cell(*). Then doing a normal C/10
(capacity divided by ten) charge for 16 hours or so. Then cycle the
battery a few times at the C/10 rate. It'll never be as goood again but
maybe good enough.

I find that once a sealed lead acid battery has a dead cell that's it.
With wet lead acid I think you can add chemicals to remove the sulphation
and/or flush out and change the acid but that all a bit messy and battery
acid isn't very skin or surface friendly. A wet lead acid battery that
still has its nominal 12v terminal voltage will probably recover if
trickle charged for a day or two. Keep and eye on the cells and stop when
most are gassing a bit.

I doubt power tools have lead acid batteries though almost certainly
NiCd/NiMH. It might possible to recell the packs for less than new packs,
assuming that new packs are still available...

(*) Connect the cell (note cell not battery) directly across a 12v car
battery for a couple of seconds.

--
Cheers
Dave.