I have been trying to find a battery charger that doesn't overheat my
AA batteries. The latest one I tried was an Energizer, CH1HR. I tried
topping up a partially depleted set of 2700 AAs. In the short time it
took for them to be fully charged they were so hot I couldm't hold
them. Even the 2500 AAs that came with the charger got very hot. Am I
correct in thinking that if batteries get too hot to handle will be
damaged by the charger?
> I have been trying to find a battery charger that doesn't overheat my
> AA batteries. The latest one I tried was an Energizer, CH1HR. I tried
> topping up a partially depleted set of 2700 AAs. In the short time it
> took for them to be fully charged they were so hot I couldm't hold
> them. Even the 2500 AAs that came with the charger got very hot. Am I
> correct in thinking that if batteries get too hot to handle will be
> damaged by the charger?
Don't know how hot they can get before the heat ruins them, but hands are
a different matter.
I've noticed:
1) Some cells seem to get hotter than others under the same charge
conditions.
2) A lower charge rate will help
3) Most of the high temperature seems to occur during the latter part of
the cycle.
My charger is supposed to shut off for a bad cell or excessive heat. I'm
not sure what their definition of excessive heat might be but I've had
some cells get uncomfortably hot without the charger complaining. The
high temperature doesn't appear to cause any immediate harm, long term who
knows.
Dave Cohen
On a recent 3-month overseas trip I used a Vivitar charger that didn't
charge individual batteries separately, didn't claim to detect
excessive temps or detect dead batteries. When using it the batteries
got very hot, but not as hot as the Energizer charger I got ro replace
it that charged individual batteries, claimed to detect excessive heat
and dead batteries. On the trip I carried 3 sets of spare battreies
for my 2 cameras. By the time I returned home I noticed that most of
my sets of batteries didn't last very long, much shorter time than
when I left on the trip. The Energizer charger detected that there was
at least 1 dead battery in 3 of the sets.
Mike
On Tue, 30 Oct 2007 00:45:37 GMT, Dave Cohen <spam@nowhere.net> wrote:
>On Tue, 30 Oct 2007 00:22:31 +0000, MikeM wrote:
>
>> I have been trying to find a battery charger that doesn't overheat my
>> AA batteries. The latest one I tried was an Energizer, CH1HR. I tried
>> topping up a partially depleted set of 2700 AAs. In the short time it
>> took for them to be fully charged they were so hot I couldm't hold
>> them. Even the 2500 AAs that came with the charger got very hot. Am I
>> correct in thinking that if batteries get too hot to handle will be
>> damaged by the charger?
>
>Don't know how hot they can get before the heat ruins them, but hands are
>a different matter.
>
>I've noticed:
>1) Some cells seem to get hotter than others under the same charge
>conditions.
>2) A lower charge rate will help
>3) Most of the high temperature seems to occur during the latter part of
>the cycle.
>
>My charger is supposed to shut off for a bad cell or excessive heat. I'm
>not sure what their definition of excessive heat might be but I've had
>some cells get uncomfortably hot without the charger complaining. The
>high temperature doesn't appear to cause any immediate harm, long term who
>knows.
>Dave Cohen
MikeM wrote:
> On a recent 3-month overseas trip I used a Vivitar charger that didn't
> charge individual batteries separately, didn't claim to detect
> excessive temps or detect dead batteries. When using it the batteries
> got very hot, but not as hot as the Energizer charger I got ro replace
> it that charged individual batteries, claimed to detect excessive heat
> and dead batteries. On the trip I carried 3 sets of spare battreies
> for my 2 cameras. By the time I returned home I noticed that most of
> my sets of batteries didn't last very long, much shorter time than
> when I left on the trip. The Energizer charger detected that there was
> at least 1 dead battery in 3 of the sets.
>
> Mike
>
The question is how hot? If they get too hot to leave your finger on
them, then that is bad for the batteries, and will shorten their useful
life. You didn't mention how long these chargers take to charge the
batteries. Generally, the faster the charge, the hotter the batteries
will normally get.
Setting the charger in a place with good airflow will certainly help,
but if the batteries get too hot to touch, you might want to investigate
a better charger. I have a MAHA that only gets the batteries warm, and
then only near the end of the 3-4 hour charging cycle.
On Tue, 30 Oct 2007 00:22:31 GMT, MikeM <mmo45018@bigpond.net.au>
wrote:
>I have been trying to find a battery charger that doesn't overheat my
>AA batteries. The latest one I tried was an Energizer, CH1HR. I tried
>topping up a partially depleted set of 2700 AAs. In the short time it
>took for them to be fully charged they were so hot I couldm't hold
>them. Even the 2500 AAs that came with the charger got very hot. Am I
>correct in thinking that if batteries get too hot to handle will be
>damaged by the charger?
Some chargers electronics can't handle topping off mostly charged
batteries without overheating them. If you have one of these, it
sounds like you do, don't use it for topping off.
I think the only way a fast charger knows when to stop is by sensing
the temperature rise, because the voltage across the cells does not
change drastically at end of charge.
On Thu, 01 Nov 2007 07:54:43 -0700, Dave W <davewi11@yahoo.co.uk>
wrote:
>I think the only way a fast charger knows when to stop is by sensing
>the temperature rise, because the voltage across the cells does not
>change drastically at end of charge.
>
>Dave W
Some might but most high tech newer fast chargers sense a voltage
change or dip to shut down. I have seen these type overheat a NIMH
battery if the battery was mostly charged to begin with.
Best bet is to just use a dumb slow charger (130 ma) for topping off.
Another good idea is to use the same cheap dumb chargers hooked
to a timer. Set the timer to turn on just one or two hours a day. It
will never overheat or damage the battery when it is used this way.
I now have all my spare batteries hooked up this way. I am never
without a "topped off" battery. I only use smart chargers when I'm
on the road.
On Nov 1, 2:50 pm, t...@mucks.net wrote:
> On Thu, 01 Nov 2007 07:54:43 -0700, Dave W <davew...@yahoo.co.uk>
> wrote:
>
> >I think the only way a fast charger knows when to stop is by sensing
> >the temperature rise, because the voltage across the cells does not
> >change drastically at end of charge.
>
> >Dave W
>
> Some might but most high tech newer fast chargers sense a voltage
> change or dip to shut down. I have seen these type overheat a NIMH
> battery if the battery was mostly charged to begin with.
>
> Best bet is to just use a dumb slow charger (130 ma) for topping off.
>
> Another good idea is to use the same cheap dumb chargers hooked
> to a timer. Set the timer to turn on just one or two hours a day. It
> will never overheat or damage the battery when it is used this way.
> I now have all my spare batteries hooked up this way. I am never
> without a "topped off" battery. I only use smart chargers when I'm
> on the road.
A battery is fully charged just when its temp starts to rise and volts
drop, at least thats how Nicads are, Are you sure it isnt the charger
itself getting hot. I cant see how fast chargers are safe for the long
run, I use a 3-5 hr sony charger thats given good battery life.
Battery charger & hot batteries 
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