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How to calculate Energizer NiMH Charging Times

 
 
SMS
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      05-03-2006
http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:
> Thanks everyone. What's a good charger that can keep up with
> increasing capacity of the batteries? I recall the Energizer has (at
> least in the past) capped the maximum mAh in their larger chargers?


Technically, they have a timer that times out, after what used to be
sufficient time to charge even the highest capacity batteries. I'm sure
that they'll come out with updated models that don't have this
limitation. The timer is supposed to be a fail-safe way of terminating
charging, if the other detection methods don't work for some reason.

The charger makers may want to put a switch on the charger for high
capacity batteries, to increase the duration of the timer from three
hours to maybe six hours.
 
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ASAAR
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      05-03-2006
On 2 May 2006 21:51:21 -0700, (E-Mail Removed) wrote:

> Thanks again. Curious though, quick or rapid chargers are
> recommended. I was under the impression it's better for the
> batteries to be slow charged?


Yes, if you're using an old timer based charger, since there were
many ways that the charger could end up charging the batteries well
beyond the point where they reached a full charge. If a fast
charger was used, the batteries could be severely overheated,
shortening their lives. With "smart" chargers, even if the very
fast ones aren't quite as gentle as the slower chargers, significant
damage won't occur, and you'll get long life (many charge cycles)
whether a fast or a slow charger is used. I use a slower charger
more often, but only because it's smaller and more convenient. I
rarely need to quickly charge a large number of batteries, but that
need arises, I've got several fast (30 and 60 minute) chargers
available. More important than whether you get a fast or slow
charger, is to get one that charges each cell independently. If you
find a charger that only charges batteries in pairs, skip it.

 
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Thomas T. Veldhouse
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      05-03-2006
(E-Mail Removed) wrote:
>
> Thanks again. Curious though, quick or rapid chargers are recommended.
> I was under the impression it's better for the batteries to be slow
> charged?
>


It is better to charge slow, mostly because of the fact that a battery will
take a charge more efficiently and take more of a charge when it is cool in
temperature. Fast charging raises the temperature of a battery. There are
other reasons I believe, but that is a large one.

--
Thomas T. Veldhouse
Key Fingerprint: 2DB9 813F F510 82C2 E1AE 34D0 D69D 1EDC D5EC AED1

 
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Bob Salomon
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      05-03-2006
In article <44589d85$0$277$(E-Mail Removed)> ,
"Thomas T. Veldhouse" <(E-Mail Removed)> wrote:

> It is better to charge slow, mostly because of the fact that a battery will
> take a charge more efficiently and take more of a charge when it is cool in
> temperature.


Some chargers, like the Ansmann Digispeed and Digispeed Ultra have a
temperature controlled exhaust fan in the charger to draw heat off from
the cells when the temperature rises during charging. These automatic
fans keep the batteries at the proper temperature even in the Digispeed
Ultra which charges most cells in 10 minutes to full charge.

--
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Thomas T. Veldhouse
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      05-03-2006
Bob Salomon <(E-Mail Removed)> wrote:
> In article <44589d85$0$277$(E-Mail Removed)> ,
> "Thomas T. Veldhouse" <(E-Mail Removed)> wrote:
>
>> It is better to charge slow, mostly because of the fact that a battery will
>> take a charge more efficiently and take more of a charge when it is cool in
>> temperature.

>
> Some chargers, like the Ansmann Digispeed and Digispeed Ultra have a
> temperature controlled exhaust fan in the charger to draw heat off from
> the cells when the temperature rises during charging. These automatic
> fans keep the batteries at the proper temperature even in the Digispeed
> Ultra which charges most cells in 10 minutes to full charge.
>


I'll tell you what. If a fan is required, then the core of that battery is
going to be hot ... and it will not charge efficiently. Also, heat is not the
only fact, resistance is another, and of course, how the battery has been
conditioned (the better Maha chargers claim to have an algorithm they use to
charge the battery that eliminates the need to condition a battery).

10 minutes ... I suspect the charger is manufacturer is figuring that its
users would prefer to replace batteries more often then to charge slowly. I
find it a rare case that I actually need to quick charge. I keep a couple of
batteries charged as spares and then charge at slow speeds for most charges.
There are cases I want power fast and I will use the fast charge (like a
spontaneous photo opportunity and I need to power my flash), but they are few
and far between.

--
Thomas T. Veldhouse
Key Fingerprint: 2DB9 813F F510 82C2 E1AE 34D0 D69D 1EDC D5EC AED1

 
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SMS
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      05-04-2006
Thomas T. Veldhouse wrote:

> I'll tell you what. If a fan is required, then the core of that battery is
> going to be hot ... and it will not charge efficiently. Also, heat is not the
> only fact, resistance is another, and of course, how the battery has been
> conditioned (the better Maha chargers claim to have an algorithm they use to
> charge the battery that eliminates the need to condition a battery).


The ultra high-rate chargers such as the Ansmann Digispeed and Digispeed
Ultra should be avoided. There is rarely a need to charge the batteries
that fast, and the high charging current and high heat has a very
negative effect on battery life. The fan will dissipate the heat into
the air, but it doesn't help the battery life.

 
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Bob Salomon
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      05-04-2006
In article <4459726d$0$96921$(E-Mail Removed)>,
SMS <(E-Mail Removed)> wrote:

> The fan will dissipate the heat into
> the air, but it doesn't help the battery life.


Certainly has not hurt the cells to date.

--
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Bart van der Wolf
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      05-04-2006

"Bob Salomon" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> In article <4459726d$0$96921$(E-Mail Removed)>,
> SMS <(E-Mail Removed)> wrote:
>
>> The fan will dissipate the heat into
>> the air, but it doesn't help the battery life.

>
> Certainly has not hurt the cells to date.


Is there any evidence for that, e.g. a link to some research? I'm
serious, all I've ever heard/read over the years is that rapid
charging reduces useful life of NiCd/NiMH batteries. It's to do with
the heat generated when the cells reach approx. 80% of their capacity,
more heat changes the chemical ability to recharge. I'd love to see a
good study on that subject.

Bart

 
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Paul Rubin
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      05-04-2006
"Bart van der Wolf" <(E-Mail Removed)> writes:
> Is there any evidence for that, e.g. a link to some research? I'm
> serious, all I've ever heard/read over the years is that rapid
> charging reduces useful life of NiCd/NiMH batteries. It's to do with
> the heat generated when the cells reach approx. 80% of their capacity,
> more heat changes the chemical ability to recharge. I'd love to see a
> good study on that subject.


The rapid chargers that I know of stop charging when that happens.
They switch over to a slow charge, so to get a complete charge takes
several hours. But being able to get the cells up to 80% in 15
minutes is very useful.
 
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SMS
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      05-04-2006
Bart van der Wolf wrote:
>
> "Bob Salomon" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> In article <4459726d$0$96921$(E-Mail Removed)>,
>> SMS <(E-Mail Removed)> wrote:
>>
>>> The fan will dissipate the heat into
>>> the air, but it doesn't help the battery life.

>>
>> Certainly has not hurt the cells to date.

>
> Is there any evidence for that, e.g. a link to some research? I'm
> serious, all I've ever heard/read over the years is that rapid charging
> reduces useful life of NiCd/NiMH batteries. It's to do with the heat
> generated when the cells reach approx. 80% of their capacity, more heat
> changes the chemical ability to recharge. I'd love to see a good study
> on that subject.


Remember, Bob Salomon is the distributer for the Ansmann chargers. So of
course he's going to say what he says.

The fact is that high rate charging, which raises the temperature of the
batteries considerable, reduces the number of charge cycles.

As Isidor Buchmann writes "High temperature during charge and standby
kills batteries."

It'd be interesting to test the number of cycles of the same battery
type using both a normal rate and a high rate charger to see just what
the difference in the number of cycles would be.

It's not usually necessary to charge batteries at such a high rate, so
those very high rate chargers should be avoided unless someone really
needs a super-fast charge.
 
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