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Rapid charging good or bad for NiMH batteries?

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Anonymous
February 6, 2005 10:41:13 PM

Archived from groups: rec.photo.digital (More info?)

In my research I found that some people say that rapid charging is good
for NiMH batteries and others say it's bad, so I'm confused.

Can anyone shed some light on this matter?

Thanks for your help.
Anonymous
February 6, 2005 10:41:14 PM

Archived from groups: rec.photo.digital (More info?)

"Bruce W.1" <sorry@noDirectEmail.com> wrote in message
news:tpuNd.1884$ng6.153@newssvr17.news.prodigy.com...
> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.

Now that you are confused, you will fit in well here.
Anonymous
February 6, 2005 10:41:14 PM

Archived from groups: rec.photo.digital (More info?)

Bruce W.1 wrote:
> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.

Some batteries, and chargers, are made in a special way for fast
charging. If using those, it probably doesn't cause any harm. Fast
chargers are likely to cause the batteries to warm up more than is good
for them, and may shorten there useful life. But with NIMH batteries
running less than $1 each, why worry about it?


--
Ron Hunter rphunter@charter.net
Related resources
Anonymous
February 6, 2005 10:51:14 PM

Archived from groups: rec.photo.digital (More info?)

"Bruce W.1" <sorry@noDirectEmail.com> wrote in message
news:tpuNd.1884$ng6.153@newssvr17.news.prodigy.com...
> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.

I've used the same twelve AAA no-name NiMH batteries in my wireless
headphones for over two years, charging a pair of them every other day on a
one-hour Ray-O-Vac quick charger and I've never had a battery fail yet. I
also use the same charger for my digital camera AA's and have never had a
battery failure or apparent weaking over the same two years of very hard
service.

Seems to work OK for me, but even had I experienced some failures, the
convenience would have been worth it.
February 6, 2005 11:19:41 PM

Archived from groups: rec.photo.digital (More info?)

Bruce W.1 wrote:
> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.

The conventional wisdom is that it's bad, but at less than $2.50 for 2300 mah
AA's, why use a slow charger? There may be a definitive analysis of the number
of recharges using fast vs. slow charging out there, but I haven't seen it.
Anonymous
February 6, 2005 11:20:40 PM

Archived from groups: rec.photo.digital (More info?)

In article <tpuNd.1884$ng6.153@newssvr17.news.prodigy.com>,
"Bruce W.1" <sorry@noDirectEmail.com> wrote:

> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.

There's a sweet spot in the charging rate. While the physical effects
of fast charging versus slow charging are debatable, 3-hour to 1-hour
rates are where electrical and thermal indicators of a complete charge
are the strongest. Outside of that, the signs are vague and the
batteries are likely to be over charged or under charged.

Unused batteries don't always show electrical signs of a full charge.
It's best to put them in a trickle charger for the first couple of
cycles. They can become very hot before a 1-hour charger detects the
heating.

The ultra-fast chargers use a pressure sensor because gassing is the
best sign of overcharging at higher currents.
Anonymous
February 6, 2005 11:38:19 PM

Archived from groups: rec.photo.digital (More info?)

That is what I say. When most cams take either 2 or 4 of the AA size and
you can get them and a charger for about$ 15 why worry about it. Not sure
about all the cams but even the non AA batteries cost about $ 20 for a new
one and usually last atleast a year.


"deacon" <db@notaol.com> wrote in message
news:xZuNd.2205$aW6.1305@newssvr22.news.prodigy.net...
> Bruce W.1 wrote:
> > In my research I found that some people say that rapid charging is good
> > for NiMH batteries and others say it's bad, so I'm confused.
> >
> > Can anyone shed some light on this matter?
> >
> > Thanks for your help.
>
> The conventional wisdom is that it's bad, but at less than $2.50 for 2300
mah
> AA's, why use a slow charger? There may be a definitive analysis of the
number
> of recharges using fast vs. slow charging out there, but I haven't seen
it.
Anonymous
February 6, 2005 11:41:00 PM

Archived from groups: rec.photo.digital (More info?)

Bruce W.1 wrote:

> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.

It reduces the number of cycles that the battery will last. I'd get the
Maha MH-C401FS which has a selectable charge rate. You can slow charge
overnight, or do a fast charge when needed. Then there are the
"ultra-fast" chargers, which should be avoided. These are like 3.4A
charging rate.

See: http://nordicgroup.us/chargers/
Anonymous
February 6, 2005 11:50:33 PM

Archived from groups: rec.photo.digital (More info?)

Dave Martindale wrote:
> ...
> ...
> There are 14-hour chargers that also overcharge the cells, but at a
> lower rate that won't cause much damage. Still, you don't want to
leave
> cells in these for more than 24 hours or so.
> ...

I've got one of those. I've used it to charge the AAA batteries
for my ancient Palm VIIx and, after about 2.5 years, the
batteries seem to last about as long as ever.

Alan
Anonymous
February 7, 2005 12:10:14 AM

Archived from groups: rec.photo.digital (More info?)

Bruce W.1 wrote:
> In my research I found that some people say that rapid charging is
> good for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.

I don't have the facts on it, but I work under the expectation that slow
is better but fast is not a problem IF they don't overheat. I don't expect
either to be a real problem and I have never lost any sleep over it.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math
Anonymous
February 7, 2005 12:25:16 AM

Archived from groups: rec.photo.digital (More info?)

"Bruce W.1" <sorry@noDirectEmail.com> wrote in message
news:tpuNd.1884$ng6.153@newssvr17.news.prodigy.com...
> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.

Rapid charging, while convenient, is not good for any battery. Rapid
charging is accomplished by increasing the average current flow into the
battery in order to save time. Increased current flow means increased heat.
The increased heat will tend to boil off more of the chemicals in the
battery than slow charging. For every 18 degrees F increase in the
battery's temperature, the reaction doubles. This boiling off of the
chemicals in the battery will eventually lead to a decline in the battery's
storage capacity. That all being said many people do not care if they get
only 100 cycles versus 500 cycles of a Ni-MH battery and are willing to make
the trade off.
Anonymous
February 7, 2005 12:25:17 AM

Archived from groups: rec.photo.digital (More info?)

In article <0XvNd.3851$%M3.3382@news02.roc.ny>,
"Harvey" <hcohenREMOVE@frontiernetTHIS.net> wrote:

> Rapid
> charging is accomplished by increasing the average current flow into the
> battery in order to save time. Increased current flow means increased heat.
> The increased heat will tend to boil off more of the chemicals in the
> battery than slow charging. For every 18 degrees F increase in the
> battery's temperature, the reaction doubles.

Which is why the fast Ansmann chargers have an automatic fan that comes
on automatically to maintain the optimal temperature in the cell while
charging a 2500 mAh NiMh cell in 10 to 40 minutes. Naturally, being a
smart charger, it switches each sell to trickle charge mode as that cell
reaches full charge.

http://www.ansmann.de/en/index.htm?view=detail&pid=614&...
2id=&appid=

--
To reply no_ HPMarketing Corp.
Anonymous
February 7, 2005 2:07:52 AM

Archived from groups: rec.photo.digital (More info?)

"Bob Salomon" <bob_salomon@mindspring.com> wrote in message
news:bob_salomon-43B8B0.16462306022005@news.isp.giganews.com...
> In article <0XvNd.3851$%M3.3382@news02.roc.ny>,
> "Harvey" <hcohenREMOVE@frontiernetTHIS.net> wrote:
>
> > Rapid
> > charging is accomplished by increasing the average current flow into the
> > battery in order to save time. Increased current flow means increased
heat.
> > The increased heat will tend to boil off more of the chemicals in the
> > battery than slow charging. For every 18 degrees F increase in the
> > battery's temperature, the reaction doubles.
>
> Which is why the fast Ansmann chargers have an automatic fan that comes
> on automatically to maintain the optimal temperature in the cell while
> charging a 2500 mAh NiMh cell in 10 to 40 minutes. Naturally, being a
> smart charger, it switches each sell to trickle charge mode as that cell
> reaches full charge.
>
> http://www.ansmann.de/en/index.htm?view=detail&pid=614&...
> 2id=&appid=
>

Interesting. You need to use special fast charge batteries with that unit.
Anonymous
February 7, 2005 2:07:53 AM

Archived from groups: rec.photo.digital (More info?)

In article <crxNd.3865$XP3.2127@news02.roc.ny>,
"Harvey" <hcohenREMOVE@frontiernetTHIS.net> wrote:

> You need to use special fast charge batteries with that unit.

No you can use any NiMh or NiCd cell. These are smart chargers not dumb
ones charging with brute force.

--
To reply no_ HPMarketing Corp.
Anonymous
February 7, 2005 4:41:53 AM

Archived from groups: rec.photo.digital (More info?)

"Bruce W.1" <sorry@noDirectEmail.com> writes:
>In my research I found that some people say that rapid charging is good
>for NiMH batteries and others say it's bad, so I'm confused.

>Can anyone shed some light on this matter?

There are multiple ways to charge a NiMH cell, not just two.

Fast chargers, that charge in 3 hours or less, are *good* - compared to
most other chargers. They detect when the cells have reached full
charge, and stop charging at the high rate. (They may continue trickle
charging at a very low rate).

There are timed chargers that simply charged for a fixed amount of
time, and if the cell wasn't fully discharged before starting, it may
be badly overcharged. These are probably the worst for the batteries.

There are 14-hour chargers that also overcharge the cells, but at a
lower rate that won't cause much damage. Still, you don't want to leave
cells in these for more than 24 hours or so.

So, among these types, fast chargers are best.

On the other hand, if you compare fast chargers only, there are
differences. Ones that monitor each cell individually are better than
ones that charge multiple cells in series or parallel. And one-hour or
faster chargers are likely to give you fewer charge cycles than the
slower 2- or 3-hours chargers, so *when comparing fast chargers* faster
may not be better. On the other hand, faster is convenient, and the
cells are cheap, so you have to balance the convenience against longer
life.

Dave
Anonymous
February 7, 2005 9:18:16 AM

Archived from groups: rec.photo.digital (More info?)

Bruce W.1 wrote:
> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.

I've always been told heat is the enemy of rechargeable batteries, so if
that's true, it makes sense the cooler you can keep them when charging
the better.
Anonymous
February 7, 2005 10:39:03 AM

Archived from groups: rec.photo.digital (More info?)

Bob Salomon wrote:
> In article <crxNd.3865$XP3.2127@news02.roc.ny>,
> "Harvey" <hcohenREMOVE@frontiernetTHIS.net> wrote:
>
>
>>You need to use special fast charge batteries with that unit.
>
>
> No you can use any NiMh or NiCd cell. These are smart chargers not dumb
> ones charging with brute force.
>
You need special batteries for chargers that work in less than 1 hour.
If they aren't properly vented, fast charging could be dangerous. Note
that smart chargers can detect what kind of battery you are using, and
adjust their charging approach automatically. Buy a good charger!


--
Ron Hunter rphunter@charter.net
Anonymous
February 7, 2005 10:43:32 AM

Archived from groups: rec.photo.digital (More info?)

Don B wrote:
>
>
> Bruce W.1 wrote:
>
>> In my research I found that some people say that rapid charging is
>> good for NiMH batteries and others say it's bad, so I'm confused.
>>
>> Can anyone shed some light on this matter?
>>
>> Thanks for your help.
>
>
> I've always been told heat is the enemy of rechargeable batteries, so if
> that's true, it makes sense the cooler you can keep them when charging
> the better.
>
Yes, and no. Most batteries are designed to withstand some heat during
charging. If your charger heats them to a point where you can't stand
to have your finger on them, then it probably isn't doing the batteries
any good.


--
Ron Hunter rphunter@charter.net
February 7, 2005 12:05:24 PM

Archived from groups: rec.photo.digital (More info?)

I've been using the Rayovac 1 hour charger since it was introduced and
have not noticed any significant deterioration of batteries -- nor has
my voltage meter. When I do think they are not peforming up to speed I
discharge them fully a couple of times using my MP3 player and then
recharge overnight in a slow charger. I am very, very battery intensive
and though I have several chargers (including very portable ones for
travel) it is the one I have come to rely on. Now and then batteries
feel warm (not hot). Givent he cost of batteries these days this is a
risk worth taking.

Bruce W.1 wrote:

> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.
Anonymous
February 7, 2005 3:07:15 PM

Archived from groups: rec.photo.digital (More info?)

"Bob Salomon" <bob_salomon@mindspring.com> wrote in message
news:bob_salomon-692245.18161106022005@news.isp.giganews.com...
> In article <crxNd.3865$XP3.2127@news02.roc.ny>,
> "Harvey" <hcohenREMOVE@frontiernetTHIS.net> wrote:
>
> > You need to use special fast charge batteries with that unit.
>
> No you can use any NiMh or NiCd cell. These are smart chargers not dumb
> ones charging with brute force.
>
> --
> To reply no_ HPMarketing Corp.

Perhaps but that is not what the manual says, for what that is worth.
Anonymous
February 7, 2005 3:10:03 PM

Archived from groups: rec.photo.digital (More info?)

>
> The ultra-fast chargers use a pressure sensor because gassing is the
> best sign of overcharging at higher currents.

Gassing? Surely you jest.
February 7, 2005 9:32:35 PM

Archived from groups: rec.photo.digital (More info?)

99% of smart rapid chargers that charge in 1hr or less only charge the
batteries up to about 80% capacity. 2-3 hours of smart charging is about
optimum for best capacity (90-95%), and even then the full capacity is most
likely only reached with a follow up trickle charge.


"Ron" <rgood@netzero.com> wrote in message
news:XEKNd.33183$pq5.1043@fe06.lga...
> I've been using the Rayovac 1 hour charger since it was introduced and
> have not noticed any significant deterioration of batteries -- nor has my
> voltage meter. When I do think they are not peforming up to speed I
> discharge them fully a couple of times using my MP3 player and then
> recharge overnight in a slow charger. I am very, very battery intensive
> and though I have several chargers (including very portable ones for
> travel) it is the one I have come to rely on. Now and then batteries feel
> warm (not hot). Givent he cost of batteries these days this is a risk
> worth taking.
>
> Bruce W.1 wrote:
>
>> In my research I found that some people say that rapid charging is good
>> for NiMH batteries and others say it's bad, so I'm confused.
>>
>> Can anyone shed some light on this matter?
>>
>> Thanks for your help.
>
Anonymous
February 8, 2005 11:30:54 PM

Archived from groups: rec.photo.digital (More info?)

"Harvey" <hcohenREMOVE@frontiernetTHIS.net> writes:

>> The ultra-fast chargers use a pressure sensor because gassing is the
>> best sign of overcharging at higher currents.

>Gassing? Surely you jest.

Nope. The 15 minute Rayovac batteries apparently have a pressure sensor
inside the cell. At the end of charge, the charge current starts
converting water into hydrogen and oxygen instead of changing the
chemical state of the plates. The increase in gas pressure opens a
switch and stops the fast charge.

Because the sensor is inside the cell, the cell doesn't necessarily
vent and lose electrolyte.

Dave
Anonymous
February 9, 2005 12:47:50 AM

Archived from groups: rec.photo.digital (More info?)

Bruce W.1 wrote:
> In my research I found that some people say that rapid charging is good
> for NiMH batteries and others say it's bad, so I'm confused.
>
> Can anyone shed some light on this matter?
>
> Thanks for your help.
My daughter has a 15 minute Ray-O-Vac charger. She cannot get more that
a couple of days out of a charge. I say it is bad because it will reduce
the number of cycles

I have a 13 hour charger and I am using 4 year old Nimh batteries and
have managed to get at least a couple of hundred cycles out of them and
the charge will last upwards of three weeks.

My advice to have both kinds; a slow and a fast charger. The slow one
for sustainability and the fast one for emergencies.

Ron
!