I've seen the technique on youtube to revive NiCad batteries.
Can I use the same technique to revive MiMH?

Cheers.

On 06/07/2014 17:54, wrote:
I've seen the technique on youtube to revive NiCad batteries.
Can I use the same technique to revive MiMH?

Cheers.


I don't know about you, but I have a Nicad and NiMH rechargeable battery
charger. I just switch from one to the other accordingly.

On 06/07/14 17:54, wrote:
I've seen the technique on youtube to revive NiCad batteries.
Can I use the same technique to revive MiMH?

Cheers.

no. Nothing really works. Bin em


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

In message , The Natural Philosopher
writes
On 06/07/14 17:54, wrote:
I've seen the technique on youtube to revive NiCad batteries.
Can I use the same technique to revive MiMH?

Cheers.

no. Nothing really works. Bin em

Nevertheless, I'd try a quick nicad-style zap first.


--
Ian

On Sunday, July 6, 2014 8:31:22 PM UTC+1, Ian Jackson wrote:
In message , The Natural Philosopher
writes
On 06/07/14 17:54, artbag10 wrote:

I've seen the technique on youtube to revive NiCad batteries.
Can I use the same technique to revive MiMH?

no. Nothing really works. Bin em

Nevertheless, I'd try a quick nicad-style zap first.

I've heard that a 'reconditioning' charging pattern after zapping makes it last - never tried it meself tho


NT

I doubt it. Is this the one involving the freezer or the high current one?
Brian

--
From the Sofa of Brian Gaff Reply address is active
wrote in message
...
I've seen the technique on youtube to revive NiCad batteries.
Can I use the same technique to revive MiMH?

Cheers.

Really the only way to fix dodgy battery packs is to go inside, weed out the
cells which are duff and replace them with the same types. However it might
just be that when you look inside you decide to change them all. From the
standpoint of replacing them with anything other than what was there before,
I'd be very wary as chargers will be set up for the type originally
supplied.
Normally I find battery packs go due to one r more cells being lower
capacity than the others and thus tend to get reverse charged by the rest
when they go down. You can detect this when the speed or power of the
appliance gets weaker after a while running.

Even fixing the duff cells will not match them up as others will fail one by
one. depends on how lucky you feel.
Brian

--
From the Sofa of Brian Gaff Reply address is active
"Bob H" wrote in message
...
On 06/07/2014 17:54, wrote:
I've seen the technique on youtube to revive NiCad batteries.
Can I use the same technique to revive MiMH?

Cheers.


I don't know about you, but I have a Nicad and NiMH rechargeable battery
charger. I just switch from one to the other accordingly.

I'd not say never, but it is less likely it will work. I have found some
triple A cells can be reclaimed for a while by keeping in a freezer for a
week and then charging them, but the success rate is less than one in 3, and
even then they do self discharge faster than the rest do.

Brian

--
From the Sofa of Brian Gaff Reply address is active
"The Natural Philosopher" wrote in message
...
On 06/07/14 17:54, wrote:
I've seen the technique on youtube to revive NiCad batteries.
Can I use the same technique to revive MiMH?

Cheers.

no. Nothing really works. Bin em


--
Ineptocracy

(in-ep-toc'-ra-cy) - a system of government where the least capable to
lead are elected by the least capable of producing, and where the members
of society least likely to sustain themselves or succeed, are rewarded
with goods and services paid for by the confiscated wealth of a
diminishing number of producers.

On Sun, 6 Jul 2014 09:54:10 -0700 (PDT), wrote:

I've seen the technique on youtube to revive NiCad batteries.
Can I use the same technique to revive MiMH?

Cheers.

Since no one else has offered you any worthwhile advice and
(especially!) the 1st 4 video hits on googling "revive NiCad
batteries" fail to show the optimum/correct method to 'unstick' NiCad
cells that have been left unused for protracted enough periods
sufficient to allow the dendritic crystal growth which shorts out the
cell, making the unchargable on the standard charger, I've decided to
offer you my advice.

First off, NiCads can, after seeing several charge/recharge cycles,
develop dendritic shorts when left unused for long enough to go flat.
This then shorts out the cell sufficiently to stop most 'fast'
chargers being able to raise the cell voltage more than a few
millivolts above zero.

NiCads, if left on a C/30 slow charge normally mitigate the effect of
dentritic shorts by the act of the newly forming short being 'zapped'
by the existing charge on the cell.

The problem arises when Nicads, which have been subjected to this
C/30 charging regime for a year or so (cordless telephone handsets
being the classic case in point), are then removed from the care of
the charger and allowed to self discharge (usually a matter of a month
or three with part worn cells). The lack of any charge in the cell
allows the dendrite to short the cell without being zapped.

Apart from the fact that this renders them unchargable by
conventional means doesn't actually harm the chemistry of the cell
like it would in the case of a lead acid cell (and lithium is even
_more_ fussy about its care than a lead acid cell!).

The best way to remedy this situation (dendritic shorting) is to use
a large value electrolytic capacitor (10,000 to 100,000 microFarads)
charged up to 3 or 4 times the cell voltage via a current limiting
resistor and literally 'zapping' the cell or battery by connecting it
across the cell/battery terminals either directly or via a heavy duty
contactor switch using short thick leads.

Monitoring the cell/battery voltage will allow you to see when these
dendrites have been blasted away allowing the rapid charge pulse to
instill the initial charge required to allow the cell/battery to be
connect to its normal charger to complete the charging cycle.

The theory is that the dendrites are disrupted by being melted into
cadmium globules dispersed within the electrolyte, removing the short
circuit and allowing the normal standard C/14 or fast rate C/6 to C/2
to electrolytically dissolve the material out of the electrolyte and
plate it back onto the electrode from whence it came (high duty pulse
charging offers the best method of achieveing this condition, as well
as reducing the propensity for dendritic crystal growth in the first
instance).

Unfortunately, NiMH suffers failure from other modes that don't
include dendritic failure as the wiki link below shows:

http://en.wikipedia.org/wiki/Nickel_metal_hydride_battery#Telecommunications

This is the relavent paragraph:

"NiMH batteries do not fail in the same way as NiCd or lead–acid
batteries. NiMH batteries fail in two predominant modes that are
somewhat interrelated. The metal hydride material used for the
negative electrode undergoes gradual corrosion in a strong alkaline
environment. This corrosion results in less negative active material
for hydrogen storage and also consumes water from the electrolyte."

So 'zapping' a NiMH cell/battery pack won't, unlike in the NiCad
case, revive it. The only reason for the treatise on 'zapping' NiCads
is to dispel the mis information shown in all those youtube videos on
reviving dead nicad batteries.

Sadly, it turns out that not all of the advice you were given, as I
initially implied, was worthless. TNP's advice to bin them "Is the
_right_ answer!", to emulate the eponymous Gordon Angus Deayton of
HIGN4U fame. :-(
--
J B Good