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Charging NiMH batteries (slightly OT ?)

 
 
Bill Smith
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      09-22-2006
I recently bought a new charger for my camera batteries (it's made by
Energiser and comes with 4 AAs).
The instruction leaflet says "Batteries MUST be completely discharged
before recharging", and the charger itself has a Test button and a
Discharge setting.
Until now, I thought that NiMH batteries could be topped up from any
state of charge. My camcorder has an in-built charger and I've always
topped it up after a day out, ditto my Nikon camera.

Is the Energiser advice right, or wrong?

TIA for any sound advice,
BS.
 
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Andrew MacPherson
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      09-22-2006
http://www.velocityreviews.com/forums/(E-Mail Removed) (Bill Smith) wrote:

> Batteries MUST be completely discharged
> before recharging"


I've had no problems using an "intelligent" charger, but basic models
seem to work on a timed method. So if your batteries aren't drained,
they may suffer due to being overcharged. Better models can tell when
individual batteries are getting indigestion, and switch to trickle
charge instead.

So Energiser are probably right, even if they're also wrong.

Andrew McP

 
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Joseph Meehan
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      09-22-2006
Bill Smith wrote:
> I recently bought a new charger for my camera batteries (it's made by
> Energiser and comes with 4 AAs).
> The instruction leaflet says "Batteries MUST be completely discharged
> before recharging", and the charger itself has a Test button and a
> Discharge setting.
> Until now, I thought that NiMH batteries could be topped up from any
> state of charge.


Unless they have changed the batteries, those instructions must be for a
cheap dumb charger.

> My camcorder has an in-built charger and I've always
> topped it up after a day out, ditto my Nikon camera.
>
> Is the Energiser advice right, or wrong?
>
> TIA for any sound advice,
> BS.




--
Joseph Meehan

Dia duit


 
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bluezfolk
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      09-22-2006

Bill Smith wrote:
> I recently bought a new charger for my camera batteries (it's made by
> Energiser and comes with 4 AAs).
> The instruction leaflet says "Batteries MUST be completely discharged
> before recharging", and the charger itself has a Test button and a
> Discharge setting.
> Until now, I thought that NiMH batteries could be topped up from any
> state of charge. My camcorder has an in-built charger and I've always
> topped it up after a day out, ditto my Nikon camera.
>
> Is the Energiser advice right, or wrong?
>
> TIA for any sound advice,
> BS.


I've been told that NiMH batteries do retain some memory as to
how much of a charge they take, although not nearly as bad a NiCads.
The only batteries that don't have a memory, and therefore will always
take a full charge are the LithIons. I can't swear by the accuracy of
my info, but I do try to run my NiMH batteries down pretty far before
charging rather than topping them off frequently.

Eric

 
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AustinMN
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      09-22-2006
Bill Smith wrote:
> I recently bought a new charger for my camera batteries (it's made by
> Energiser and comes with 4 AAs).
> The instruction leaflet says "Batteries MUST be completely discharged
> before recharging", and the charger itself has a Test button and a
> Discharge setting.
> Until now, I thought that NiMH batteries could be topped up from any
> state of charge. My camcorder has an in-built charger and I've always
> topped it up after a day out, ditto my Nikon camera.
>
> Is the Energiser advice right, or wrong?


Let me guess...it also says ONLY recharge Energizer NiMH batteries, and
probably says not to charge older NiMH batteries (or perhaps only NiMH
batteries with at least xxxx mAH capacity).

That's because it's a timer-based charger. It's going to put a voltage
on the battery of X time, period. If the battery isn't ready to take
it (not discharged) or able to take it (not sufficient capacity), the
poor thing will get cooked.

I believe NiMH have a very slight memory effect, but nothing like NiCd
batteries. I have also heard that repeatedly deep discharging them
shortens their life. I make sure mine are discharged perhaps one in
ten cycles, and that has worked for hundreds of cycles (so far) for me.

I would never use that charger.

But all of this, in my opinion, is mostly academic. Between the cost
of a good charger and NiMH, by the time you've gone through about 15
charge-discharge cycles (usually less) you've made back your
investment. If you only get 25 cycles out of a set of batteries (a
dismal performance), you are still a long ways ahead of disposables.

Austin

 
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Dave Cohen
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      09-22-2006
AustinMN wrote:
> Bill Smith wrote:
>> I recently bought a new charger for my camera batteries (it's made by
>> Energiser and comes with 4 AAs).
>> The instruction leaflet says "Batteries MUST be completely discharged
>> before recharging", and the charger itself has a Test button and a
>> Discharge setting.
>> Until now, I thought that NiMH batteries could be topped up from any
>> state of charge. My camcorder has an in-built charger and I've always
>> topped it up after a day out, ditto my Nikon camera.
>>
>> Is the Energiser advice right, or wrong?

>
> Let me guess...it also says ONLY recharge Energizer NiMH batteries, and
> probably says not to charge older NiMH batteries (or perhaps only NiMH
> batteries with at least xxxx mAH capacity).
>
> That's because it's a timer-based charger. It's going to put a voltage
> on the battery of X time, period. If the battery isn't ready to take
> it (not discharged) or able to take it (not sufficient capacity), the
> poor thing will get cooked.
>
> I believe NiMH have a very slight memory effect, but nothing like NiCd
> batteries. I have also heard that repeatedly deep discharging them
> shortens their life. I make sure mine are discharged perhaps one in
> ten cycles, and that has worked for hundreds of cycles (so far) for me.
>
> I would never use that charger.
>
> But all of this, in my opinion, is mostly academic. Between the cost
> of a good charger and NiMH, by the time you've gone through about 15
> charge-discharge cycles (usually less) you've made back your
> investment. If you only get 25 cycles out of a set of batteries (a
> dismal performance), you are still a long ways ahead of disposables.
>
> Austin
>

I suspect, as others do, that the charger is a timed affair. Not
recommended. The real dumb overnight chargers will charge forever and
are safe, the charge current is fairly low and I've had no qualms about
topping off. The very best chargers monitor each cell but as might be
expected are more expensive. This one isn't:
http://www.greenbatteries.com/nibachwilcdd.html
but I know no more about it than what you can read for yourself, but I
have just ordered one to replace the inexpensive smart charger I've been
using for some time. I also picked up a set of 4 eneloop's from
Ritz(retail), but will be awhile before I know how these work out.
Dave Cohen
 
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~~NoMad~~
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Posts: n/a
 
      09-22-2006
You should have bought the Energizer 15 minute charger, its Great!

Charges each battery individually at up to 7 amps.
Not a timed charger.
Has built-in fan to keep batteries cool.
Will run directly off 12 volts.
Works OK with some off-brand batteries but makes some old ones spew.
Works Best with Energizer 2500 Mah batteries.

Enjoy!

NM


"Bill Smith" <(E-Mail Removed)> wrote in message
news:t3PQg.22928$(E-Mail Removed). uk...
>I recently bought a new charger for my camera batteries (it's made by
>Energiser and comes with 4 AAs).
> The instruction leaflet says "Batteries MUST be completely discharged
> before recharging", and the charger itself has a Test button and a
> Discharge setting.
> Until now, I thought that NiMH batteries could be topped up from any state
> of charge. My camcorder has an in-built charger and I've always topped it
> up after a day out, ditto my Nikon camera.
>
> Is the Energiser advice right, or wrong?
>
> TIA for any sound advice,
> BS.



 
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Dave Cohen
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Posts: n/a
 
      09-22-2006
Dave Cohen wrote:
> AustinMN wrote:
>> Bill Smith wrote:
>>> I recently bought a new charger for my camera batteries (it's made by
>>> Energiser and comes with 4 AAs).
>>> The instruction leaflet says "Batteries MUST be completely discharged
>>> before recharging", and the charger itself has a Test button and a
>>> Discharge setting.
>>> Until now, I thought that NiMH batteries could be topped up from any
>>> state of charge. My camcorder has an in-built charger and I've always
>>> topped it up after a day out, ditto my Nikon camera.
>>>
>>> Is the Energiser advice right, or wrong?

>>
>> Let me guess...it also says ONLY recharge Energizer NiMH batteries, and
>> probably says not to charge older NiMH batteries (or perhaps only NiMH
>> batteries with at least xxxx mAH capacity).
>>
>> That's because it's a timer-based charger. It's going to put a voltage
>> on the battery of X time, period. If the battery isn't ready to take
>> it (not discharged) or able to take it (not sufficient capacity), the
>> poor thing will get cooked.
>>
>> I believe NiMH have a very slight memory effect, but nothing like NiCd
>> batteries. I have also heard that repeatedly deep discharging them
>> shortens their life. I make sure mine are discharged perhaps one in
>> ten cycles, and that has worked for hundreds of cycles (so far) for me.
>>
>> I would never use that charger.
>>
>> But all of this, in my opinion, is mostly academic. Between the cost
>> of a good charger and NiMH, by the time you've gone through about 15
>> charge-discharge cycles (usually less) you've made back your
>> investment. If you only get 25 cycles out of a set of batteries (a
>> dismal performance), you are still a long ways ahead of disposables.
>>
>> Austin
>>

> I suspect, as others do, that the charger is a timed affair. Not
> recommended. The real dumb overnight chargers will charge forever and
> are safe, the charge current is fairly low and I've had no qualms about
> topping off. The very best chargers monitor each cell but as might be
> expected are more expensive. This one isn't:
> http://www.greenbatteries.com/nibachwilcdd.html
> but I know no more about it than what you can read for yourself, but I
> have just ordered one to replace the inexpensive smart charger I've been
> using for some time. I also picked up a set of 4 eneloop's from
> Ritz(retail), but will be awhile before I know how these work out.
> Dave Cohen


Just to clarify, I didn't mean to imply one should charge forever in a
dumb charger, just that it doesn't shut off and isn't critical if you
charge a few more hours after cells are charged which of course you
won't know, hence the preference for a smart charger.
Dave Cohen
 
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Bill Smith
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Posts: n/a
 
      09-25-2006
Bill Smith wrote:
> I recently bought a new charger for my camera batteries (it's made by
> Energiser and comes with 4 AAs).
> The instruction leaflet says "Batteries MUST be completely discharged
> before recharging", and the charger itself has a Test button and a
> Discharge setting.
> Until now, I thought that NiMH batteries could be topped up from any
> state of charge. My camcorder has an in-built charger and I've always
> topped it up after a day out, ditto my Nikon camera.
>
> Is the Energiser advice right, or wrong?
>
> TIA for any sound advice,
> BS.


Thanks to all - the answer seems to be a resounding "Maybe"!

The Energiser didn't specify any brand of battery, though maybe, as they
included their own, they assumed that's all their charger would be used for.

My older charger is Uniross, and its instructions say nothing about
discharging, nor does the charger have a discharge button. I've used it
for 2+ years with Uniross and other makes, often topping up at the end
of a day on holiday whatever the battery charge state, and had no problems.

I'll ignore the Energiser advice meantime, and await developments!

BS
 
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