I have a portable CD player which specifies using either alkaline or
rechargeable NICD batteries .

Should it be acceptable to use NIMH also?

I am wondering whether the charging rates are so different for the two
rechargeable types that the NIMH, or the charging circuit, might be
damaged.

In article ,
wrote:
I have a portable CD player which specifies using either alkaline or
rechargeable NICD batteries .

Should it be acceptable to use NIMH also?

It will work ok on them as they are very similar to Ni-Cad.

I am wondering whether the charging rates are so different for the two
rechargeable types that the NIMH, or the charging circuit, might be
damaged.

The charging systems are different. You could charge them using an
external charger, though, and simply swop them.

High capacity Ni-Cads aren't that much behind standard NiMH, and are
slightly cheaper. They also have a longer service life if charged
correctly.

--
*I used up all my sick days so I called in dead

Dave Plowman London SW 12
RIP Acorn

On Tue, 27 Jan 2004 00:15:02 +0000 (GMT), Dave Plowman
wrote:

SNIP

The charging systems are different. You could charge them using an
external charger, though, and simply swop them.

Do you mean I should't charge NIMH on my NiCd charger?

Peter

"Peter" wrote in message
...
On Tue, 27 Jan 2004 00:15:02 +0000 (GMT), Dave Plowman
wrote:

SNIP

The charging systems are different. You could charge them using an
external charger, though, and simply swop them.

Do you mean I should't charge NIMH on my NiCd charger?

Peter

There shouldn't be any differences between them as long as you aren't using
a higher voltage than the battery needs to take its charge.

"http://www.batteriesplus.co.uk/acatalog/Batteries_Plus_Chargers_and_Power_S
upplies_5.html"

In article ,
Peter wrote:
The charging systems are different. You could charge them using an
external charger, though, and simply swop them.

Do you mean I should't charge NIMH on my NiCd charger?

Correct. Although chargers that do both exist.

That's not to say a Ni-Cad charger won't work *at all* with NiMH - it
will simply shorten their service life.

--
*I didn't drive my husband crazy -- I flew him there -- it was faster

Dave Plowman London SW 12
RIP Acorn

Peter wrote in message . ..

Do you mean I should't charge NIMH on my NiCd charger?


A NiCd charger will work but it may not detect that the NiMH battery
is full and simply continue charging, which is no good.

Quote from

http://www.greenbatteries.com/docume...harger_FAQ.htm

"
Can I use an older NiCd battery charger to charge NiMH batteries?

The answer to this question depends on the type of NiCd charger.
Depending on the type of NiCd charger you have, the older NiCd charger
may undercharge NiMH batteries (most likely), it may overcharge them
(less likely), or it may charge NiMH batteries properly (but it's not
likely to do so automatically and could take a very long time). Let's
take a look at the three cases.

Many of the older NiCd chargers are the simple timed type charger
which will charge batteries for a fixed amount of time and then shut
off. Unfortunately, since NiCd batteries have a much lower capacity
than NiMH batteries, the timer is likely to shut off long before the
NiMH batteries are fully charged. This won't harm the batteries, but
the NiMH batteries won't be fully charged since the timer will have
stopped the charge cycle too soon.

Also common among older NiCd chargers are the so called "overnight"
chargers which charge batteries at a low rate as long as the charger
is plugged in. This type of charger can fully charge NiMH batteries,
but it might take a very long time to do so. It's possible that an
old NiCd charger could take as long as 48 hours to fully charge new
high capacity NiMH batteries! This type of charger is not likely to
damage NiMH batteries unless the batteries are left in the charger for
weeks at a time, but it may not be very convenient to use. If you have
this type of charger you can get an idea of how long you'll need to
charge your batteries by using the calculator found above.

The final possibility is that the older NiCd charger is a rapid
charger that will charge NiMH batteries but will not have the
necessary circuitry to stop the charge cycle once the NiMH batteries
are fully charged. If the NiCd charger is designed to charge
batteries in less than two hours it may be this type. In this case
the risk is that the older charger will overcharge NiMH batteries.
This will be apparent if the batteries get very hot during the charge
cycle. (It is normal for NiMH batteries to get warm as they become
fully charged, especially in a rapid charger). If the NiMH batteries
get too hot to handle and stay that way for more than 20 or 30
minutes, then the NiCd charger is most likely overcharging the NiMH
batteries and may shorten their life. You would be most likely to
encounter this type of charger if the charger was designed for rapid
charging radio control (RC) vehicle batteries. We would recommend
that you not use an NiCD rapid charger to charge NiMH batteries.
"


/Clas-Henrik

One thing that hasn't been said is that NiCd cells retain their life
best if they are discharged almost fully before recharging. They
collect what is known as the memory effect if charged when half
discharged and tend never to have their full capacity thereafter.
NiMH cell do not hav this characteristic and can be recharged at any
time.

rob


(C-H Gustafsson) wrote in message . com...
Peter wrote in message . ..

Do you mean I should't charge NIMH on my NiCd charger?


A NiCd charger will work but it may not detect that the NiMH battery
is full and simply continue charging, which is no good.

Quote from

http://www.greenbatteries.com/docume...harger_FAQ.htm

"
Can I use an older NiCd battery charger to charge NiMH batteries?

The answer to this question depends on the type of NiCd charger.
Depending on the type of NiCd charger you have, the older NiCd charger
may undercharge NiMH batteries (most likely), it may overcharge them
(less likely), or it may charge NiMH batteries properly (but it's not
likely to do so automatically and could take a very long time). Let's
take a look at the three cases.

Many of the older NiCd chargers are the simple timed type charger
which will charge batteries for a fixed amount of time and then shut
off. Unfortunately, since NiCd batteries have a much lower capacity
than NiMH batteries, the timer is likely to shut off long before the
NiMH batteries are fully charged. This won't harm the batteries, but
the NiMH batteries won't be fully charged since the timer will have
stopped the charge cycle too soon.

Also common among older NiCd chargers are the so called "overnight"
chargers which charge batteries at a low rate as long as the charger
is plugged in. This type of charger can fully charge NiMH batteries,
but it might take a very long time to do so. It's possible that an
old NiCd charger could take as long as 48 hours to fully charge new
high capacity NiMH batteries! This type of charger is not likely to
damage NiMH batteries unless the batteries are left in the charger for
weeks at a time, but it may not be very convenient to use. If you have
this type of charger you can get an idea of how long you'll need to
charge your batteries by using the calculator found above.

The final possibility is that the older NiCd charger is a rapid
charger that will charge NiMH batteries but will not have the
necessary circuitry to stop the charge cycle once the NiMH batteries
are fully charged. If the NiCd charger is designed to charge
batteries in less than two hours it may be this type. In this case
the risk is that the older charger will overcharge NiMH batteries.
This will be apparent if the batteries get very hot during the charge
cycle. (It is normal for NiMH batteries to get warm as they become
fully charged, especially in a rapid charger). If the NiMH batteries
get too hot to handle and stay that way for more than 20 or 30
minutes, then the NiCd charger is most likely overcharging the NiMH
batteries and may shorten their life. You would be most likely to
encounter this type of charger if the charger was designed for rapid
charging radio control (RC) vehicle batteries. We would recommend
that you not use an NiCD rapid charger to charge NiMH batteries.
"


/Clas-Henrik

Rob Graham wrote:
One thing that hasn't been said is that NiCd cells retain their life
best if they are discharged almost fully before recharging. They
collect what is known as the memory effect if charged when half
discharged and tend never to have their full capacity thereafter.
NiMH cell do not hav this characteristic and can be recharged at any
time.

Not that old chestnut again, please!!!

The memory effect in NiCd cells is *extremely* unlikely to occur in
normal domestic usage. It only occurs when NiCd cells are repeatedly
(i.e.hundreds of times) recharged and discharged to exactly the same
levels. The effect was noticed in NiCds used on a satellite which got
recharged very regularly each day when the sun rose.

The only reason that dicharging a NiCd completely may help is that a
full charge will not then overcharge it. It's overcharging that makes
most NiCds fail before they should.

--
Chris Green

In uk.d-i-y, wrote:

Not that old chestnut again, please!!!

Indeed, it refuses to die, and as a powerful myth finds its way into
instruction sheets for a fair bit of consumer gear. As you say, one
partial truth is that by telling you to fully discharge your cells
before attaching them to their cheap chargers, and telling you to run
the cheapo for a limited time, mfr's hope to reduce one of the likely
causes of overcooking - leaving an already-charged cell on (non-tiny)
charge. Simpler than incorporating a charge-control IC and switching
tranny into the circuit, and saves valuable component cost ;-)

Stefek

wrote:

I have a portable CD player which specifies using either alkaline or
rechargeable NICD batteries .

Should it be acceptable to use NIMH also?

I am wondering whether the charging rates are so different for the two
rechargeable types that the NIMH, or the charging circuit, might be
damaged.




Its possible. Nimh need slower and more critical charhing on 'fast
charge' (about 1 hr max for NiMh.

But the chances are its a trickle charger anyway. So NiMh will be fine.

Peter wrote:

On Tue, 27 Jan 2004 00:15:02 +0000 (GMT), Dave Plowman
wrote:

SNIP

The charging systems are different. You could charge them using an
external charger, though, and simply swop them.


Do you mean I should't charge NIMH on my NiCd charger?



Not if its a fast charger and doesn't know about NiMh. OK on a trickle tho.


Peter

Rob Graham wrote:

One thing that hasn't been said is that NiCd cells retain their life
best if they are discharged almost fully before recharging. They
collect what is known as the memory effect if charged when half
discharged and tend never to have their full capacity thereafter.
NiMH cell do not hav this characteristic and can be recharged at any
time.

rob



Urban myth Rob.


It happend once with a very regular charge/discharge regme on some
spacecraft. No one has ever really demonstrated it with random charging.

Nicads lose charge anyway over about a year. Or faster. NiMh are dead
within a few months if not charged. They recover tho.

In article ,
wrote:
As you say, one
partial truth is that by telling you to fully discharge your cells
before attaching them to their cheap chargers, and telling you to run
the cheapo for a limited time, mfr's hope to reduce one of the likely
causes of overcooking - leaving an already-charged cell on (non-tiny)
charge.

Trouble with this approach is that if it's a drill etc and you run the
batteries *completely* flat by leaving it on 'till it stops, there's a
very real danger of one or more cells charging in reverse. The best way is
to only run them down until the performance is impaired.

--
*What hair colour do they put on the driver's license of a bald man? *

Dave Plowman London SW 12
RIP Acorn