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Question on Recharging Time for AA NiMH batteries

 
 
eb
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      04-12-2004
I bought a very inexpensive Sakar Digital Concepts mini charger with 2
AA 1800ma NiMH batteries from Microcenter. The charger and batteries
work very well, and I figure I will buy new 2200 or 2400ma batteries
separately.

I did have a question on charging time - the charger does not give the
recommended time. It is an "overnight" charger, not a rapid one. It
lists output as "2x(3.2V---60mA)." How can I figure full charging time
on 2 AA 1800ma batteries (or 2200 or 2400ma) with this charger? Thanks
 
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David J Taylor
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      04-12-2004
"eb" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) m...
> I bought a very inexpensive Sakar Digital Concepts mini charger with 2
> AA 1800ma NiMH batteries from Microcenter. The charger and batteries
> work very well, and I figure I will buy new 2200 or 2400ma batteries
> separately.
>
> I did have a question on charging time - the charger does not give the
> recommended time. It is an "overnight" charger, not a rapid one. It
> lists output as "2x(3.2V---60mA)." How can I figure full charging time
> on 2 AA 1800ma batteries (or 2200 or 2400ma) with this charger? Thanks


In theory at least 2400mAH divided by 60mA - 40 hours. In practice, give
it another 10- 20%. You have a 2-day charger for that capavity of
battery!

David


 
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Bob Salomon
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      04-12-2004
In article <(E-Mail Removed)> ,
http://www.velocityreviews.com/forums/(E-Mail Removed) (eb) wrote:

> I bought a very inexpensive Sakar Digital Concepts mini charger with 2
> AA 1800ma NiMH batteries from Microcenter. The charger and batteries
> work very well, and I figure I will buy new 2200 or 2400ma batteries
> separately.
>
> I did have a question on charging time - the charger does not give the
> recommended time. It is an "overnight" charger, not a rapid one. It
> lists output as "2x(3.2V---60mA)." How can I figure full charging time
> on 2 AA 1800ma batteries (or 2200 or 2400ma) with this charger? Thanks


The rule is to take the battery, add 40% to the capacity and divide that
by the output to find the required time to recharge the battery.

For example your charger will fully charge a 2200 mAh cell would take
51.3 hours to fully charge them. However you have a charger that
requires pairs of batteries to charge. If the batteries are at different
states of discharge then it may stop charging the weaker one when the
stronger one is fully charged.

In comparison the Ansmann Digispeed charger has a charge current of 1700
mAh on AC or DC. It takes about 1.8 hours to fully charge a 2200 cell.
As this is a "smart charger" each cell is charged individually so one
cell will not stop charging when another one is fully charged, and any
number of cells can be inserted without resorting to pairs of cells.
Further when a cell reaches full charger that cell is then switched to a
delta V trickle charge mode so the cell does not have to be removed from
the charger to prevent overcharging. And, as the charger uses such a
high current for charging the charger employs an automatic fan to keep
heat build-up to a minimum.

The difference? Fully charged batteries and not inexpensive.

--
To reply no_ HPMarketing Corp.
 
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Dave Cohen
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      04-12-2004
That rating doesn't sound correct. I have two overnight chargers (that I no
longer use - see below). The Rinpoche is rated 2.8v 130 ma. The Quest is
less clear, says 3v 240 ma. I believe they mean 120 ma for each bank of two
cells.
I later purchased a Sakar made charger with 4 cells from Walmart, still
available for $17. They call this Ultra-Fast, has a 700 ma rating and
switches from fast to trickle in under 3 hrs. Comes with auto cord. While
not the best you can't beat that price.
As far as charge times, the overnight type will not harm cells if left on
somewhat longer than needed. The fast charger swiches to trickle which
should be quite safe.
Dave Cohen

"Bob Salomon" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> In article <(E-Mail Removed)> ,
> (E-Mail Removed) (eb) wrote:
>
> > I bought a very inexpensive Sakar Digital Concepts mini charger with 2
> > AA 1800ma NiMH batteries from Microcenter. The charger and batteries
> > work very well, and I figure I will buy new 2200 or 2400ma batteries
> > separately.
> >
> > I did have a question on charging time - the charger does not give the
> > recommended time. It is an "overnight" charger, not a rapid one. It
> > lists output as "2x(3.2V---60mA)." How can I figure full charging time
> > on 2 AA 1800ma batteries (or 2200 or 2400ma) with this charger? Thanks

>
> The rule is to take the battery, add 40% to the capacity and divide that
> by the output to find the required time to recharge the battery.
>
> For example your charger will fully charge a 2200 mAh cell would take
> 51.3 hours to fully charge them. However you have a charger that
> requires pairs of batteries to charge. If the batteries are at different
> states of discharge then it may stop charging the weaker one when the
> stronger one is fully charged.
>
> In comparison the Ansmann Digispeed charger has a charge current of 1700
> mAh on AC or DC. It takes about 1.8 hours to fully charge a 2200 cell.
> As this is a "smart charger" each cell is charged individually so one
> cell will not stop charging when another one is fully charged, and any
> number of cells can be inserted without resorting to pairs of cells.
> Further when a cell reaches full charger that cell is then switched to a
> delta V trickle charge mode so the cell does not have to be removed from
> the charger to prevent overcharging. And, as the charger uses such a
> high current for charging the charger employs an automatic fan to keep
> heat build-up to a minimum.
>
> The difference? Fully charged batteries and not inexpensive.
>
> --
> To reply no_ HPMarketing Corp.



 
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Joseph Meehan
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      04-12-2004
eb wrote:
> I bought a very inexpensive Sakar Digital Concepts mini charger with 2
> AA 1800ma NiMH batteries from Microcenter. The charger and batteries
> work very well, and I figure I will buy new 2200 or 2400ma batteries
> separately.
>
> I did have a question on charging time - the charger does not give the
> recommended time. It is an "overnight" charger, not a rapid one. It
> lists output as "2x(3.2V---60mA)." How can I figure full charging time
> on 2 AA 1800ma batteries (or 2200 or 2400ma) with this charger? Thanks


I strongly suggest you invest a little money now for a good "smart"
charger. You will save more in longer battery life and trouble than the
cost of the charger. You also will no longer need concern yourself with
questions like this, the charger takes care of it.

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math



 
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MarkH
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      04-13-2004
"Dave Cohen" <(E-Mail Removed)> wrote in
news:(E-Mail Removed) s.com:

> That rating doesn't sound correct. I have two overnight chargers (that
> I no longer use - see below). The Rinpoche is rated 2.8v 130 ma.


That would be slow on the higher capacity NiMH cells

> The Quest is less clear, says 3v 240 ma. I believe they mean 120 ma for
> each bank of two cells.


240mA sounds normal. 2000mAh cells would take about 12 hours to charge
from dead at 240mA. Remember that 240mA for a bank of 2 cells equals 240mA
for each cell, 3V for 2 is about right, 1.5V on each battery (remember that
while charging the cell it might be 1.5v, while draining it will be the
1.2v written on the cell).


--
Mark Heyes (New Zealand)
See my pics at http://homepages.ihug.co.nz/~markh/
"There are 10 types of people, those that
understand binary and those that don't"

 
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Daniel Prince
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      04-13-2004
Bob Salomon <(E-Mail Removed)> wrote:

>In comparison the Ansmann Digispeed charger has a charge current of 1700
>mAh on AC or DC. It takes about 1.8 hours to fully charge a 2200 cell.
>As this is a "smart charger" each cell is charged individually so one
>cell will not stop charging when another one is fully charged, and any
>number of cells can be inserted without resorting to pairs of cells.
>Further when a cell reaches full charger that cell is then switched to a
>delta V trickle charge mode so the cell does not have to be removed from
>the charger to prevent overcharging.


What happens if after the cell is fully charged, the AC power goes out
for a few minutes?
--
Whenever I hear or think of the song "Great green gobs of greasy
grimey gopher guts" I imagine my cat saying; "That sounds REALLY,
REALLY good. I'll have some of that!"
 
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Bob Salomon
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      04-13-2004
In article <(E-Mail Removed)>,
Daniel Prince <(E-Mail Removed)> wrote:

> Bob Salomon <(E-Mail Removed)> wrote:
>
> >In comparison the Ansmann Digispeed charger has a charge current of 1700
> >mAh on AC or DC. It takes about 1.8 hours to fully charge a 2200 cell.
> >As this is a "smart charger" each cell is charged individually so one
> >cell will not stop charging when another one is fully charged, and any
> >number of cells can be inserted without resorting to pairs of cells.
> >Further when a cell reaches full charger that cell is then switched to a
> >delta V trickle charge mode so the cell does not have to be removed from
> >the charger to prevent overcharging.

>
> What happens if after the cell is fully charged, the AC power goes out
> for a few minutes?


The charger is a smart charger so it checks the condition of the battery
before charging. It then switches from rapid to delta V mode as required
so it could briefly start to rapid charge it but it would almost
immediately begin the delta V mode.

With the more sophisticated Ansmann chargers like the Energy 8 and the
Energy 16 the chargers actually indicates the state of charge as each
cell is inserted into a chamber. A red LED would be less then 25% of
full charger. If the LED is yellow then it has between 25 and 80% of
full charge and if it is green it has 80% or more of full charge. As
these are slower chargers it allows you to closely estimate the time the
cell will take to reach full charge.

--
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