I don't recharge NiCads until they're 80-90% discharged. (Definitely
don't want to discuss the pros/cons of that!) My question is what is
a reasonable discharge rate to get the batteries down to that level?
For example, for a pack of 2800mah batteries, a bulb pulling 300ma
takes a long time to draw them down. Can I safely up the load to 1 or
1.5A to discharge them faster without causing damage to the batteries?

Why? Typically I'll have usage on a battery pack at the end of the
day, but want to start tomorrow with a fully charged pack.

KC

KC wrote:
I don't recharge NiCads until they're 80-90% discharged. (Definitely
don't want to discuss the pros/cons of that!) My question is what is
a reasonable discharge rate to get the batteries down to that level?
For example, for a pack of 2800mah batteries, a bulb pulling 300ma
takes a long time to draw them down. Can I safely up the load to 1 or
1.5A to discharge them faster without causing damage to the batteries?

Why? Typically I'll have usage on a battery pack at the end of the
day, but want to start tomorrow with a fully charged pack.

KC

Hmmm,
Discharge rate depends of current draw.

KC writes:

Can I safely up the load to 1 or
1.5A to discharge them faster without causing damage to the batteries?

Sure. The RC toy applications draw tens of amps from such batteries.

On Jun 17, 11:41 pm, KC wrote:
I don't recharge NiCads until they're 80-90% discharged. (Definitely
don't want to discuss the pros/cons of that!) My question is what is
a reasonable discharge rate to get the batteries down to that level?
For example, for a pack of 2800mah batteries, a bulb pulling 300ma
takes a long time to draw them down. Can I safely up the load to 1 or
1.5A to discharge them faster without causing damage to the batteries?

Why? Typically I'll have usage on a battery pack at the end of the
day, but want to start tomorrow with a fully charged pack.

Switch to NiMH or Li-ion.

R

Really, only experimentation will tell the story. The higher the discharge
rate, the hotter they will get. You don't want them hot. And when they do
get warm, you'll want them to have a complete cool down before putting them
on the charger.

--
Steve Barker







"KC" wrote in message
ups.com...
I don't recharge NiCads until they're 80-90% discharged. (Definitely
don't want to discuss the pros/cons of that!) My question is what is
a reasonable discharge rate to get the batteries down to that level?
For example, for a pack of 2800mah batteries, a bulb pulling 300ma
takes a long time to draw them down. Can I safely up the load to 1 or
1.5A to discharge them faster without causing damage to the batteries?

Why? Typically I'll have usage on a battery pack at the end of the
day, but want to start tomorrow with a fully charged pack.

KC

On Jun 18, 9:26 am, "Steve Barker"
wrote:
Really, only experimentation will tell the story. The higher the discharge
rate, the hotter they will get. You don't want them hot. And when they do
get warm, you'll want them to have a complete cool down before putting them
on the charger.

Not to be glib, but that's why I asked the question. "Hot" is a
relative term - more than room temp, to hot to touch, etc, etc. So how
hot is too hot? I had hoped there was someone who could point me to a
spec sheet on these things since experimenting at $38 a pop is not
good.
My battery charger somehow senses battery temp since it has a mode
"Charging delayed - battery hot", and I have seen it go into that mode
when the battery case only felt lukewarm in the hand.

KC

KC wrote in
oups.com:

On Jun 18, 9:26 am, "Steve Barker"
wrote:
Really, only experimentation will tell the story. The higher the
discharge rate, the hotter they will get. You don't want them hot.
And when they do get warm, you'll want them to have a complete cool
down before putting them on the charger.

Not to be glib, but that's why I asked the question. "Hot" is a
relative term - more than room temp, to hot to touch, etc, etc. So how
hot is too hot? I had hoped there was someone who could point me to a
spec sheet on these things since experimenting at $38 a pop is not
good.
My battery charger somehow senses battery temp since it has a mode
"Charging delayed - battery hot", and I have seen it go into that mode
when the battery case only felt lukewarm in the hand.

KC



there's a thermoswitch inside the battery pack,the third terminal is the
sense terminal.It opens when the temp goes higher than the switch rating.
IIRC,the NiCds used for RC apps get VERY hot in use(discharging),too hot to
hold.(unless you are into pain)

My 9.6V Makita packs get warm but not "hot" when recharging.
You can hold them without discomfort.

--
Jim Yanik
jyanik
at
kua.net

On 18 Jun 2007 20:30:45 GMT, Jim Yanik wrote:



there's a thermoswitch inside the battery pack,the third terminal is the
sense terminal.It opens when the temp goes higher than the switch rating.
IIRC,the NiCds used for RC apps get VERY hot in use(discharging),too hot to
hold.(unless you are into pain)

My 9.6V Makita packs get warm but not "hot" when recharging.
You can hold them without discomfort.

I sure just mentioning this will bring the battery gods down on me. I
received a Makita drill with NiCds for Christmas 1989. I was flying RC
planes then and marked the date on the batteries as was customary. The
charger crapped out about 5 years ago so I bought a new drill which
was only $50 more than a charger. It came with NiMH batteries. They
died about 2 years ago. I thought, heck I'll try the NiCds which had
been sitting for 3 years. I've been using them for 2 years now.

--Andy Asberry--
------Texas-----

On Jun 18, 3:30 pm, Jim Yanik wrote:

there's a thermoswitch inside the battery pack,the third terminal is the
sense terminal.It opens when the temp goes higher than the switch rating.


I saw that in there but just assumed it was a charging current
limiting resistor. Learn something new every day! Thanks.

KC

On Tue, 19 Jun 2007 06:49:37 -0700, KC wrote:

On Jun 18, 3:30 pm, Jim Yanik wrote:

there's a thermoswitch inside the battery pack,the third terminal is the
sense terminal.It opens when the temp goes higher than the switch rating.


I saw that in there but just assumed it was a charging current
limiting resistor. Learn something new every day! Thanks.

Just about every rechargeable battery pakc, even the seemingly simple
ones, going back for more than a decade has a three pin connector.
Are thyey always a thermoswitch, or what other uses might they have?

KC

mm wrote in
:

On Tue, 19 Jun 2007 06:49:37 -0700, KC wrote:

On Jun 18, 3:30 pm, Jim Yanik wrote:

there's a thermoswitch inside the battery pack,the third terminal is
the sense terminal.It opens when the temp goes higher than the
switch rating.


I saw that in there but just assumed it was a charging current
limiting resistor. Learn something new every day! Thanks.

Just about every rechargeable battery pakc, even the seemingly simple
ones, going back for more than a decade has a three pin connector.
Are thyey always a thermoswitch, or what other uses might they have?

KC




possibly a thermistor;a temp sensitive resistor,it can be either positive
coefficient or negative.

pos thermistor increases resistance(R) with increase in temp,neg decreases
R with increase.

I'd guess that thermistor sensing is rare.It requires a more complex
circuit.

--
Jim Yanik
jyanik
at
kua.net

On 20 Jun 2007 00:15:18 GMT, Jim Yanik wrote:

mm wrote in
:

On Tue, 19 Jun 2007 06:49:37 -0700, KC wrote:

On Jun 18, 3:30 pm, Jim Yanik wrote:

there's a thermoswitch inside the battery pack,the third terminal is
the sense terminal.It opens when the temp goes higher than the
switch rating.


I saw that in there but just assumed it was a charging current
limiting resistor. Learn something new every day! Thanks.

Just about every rechargeable battery pakc, even the seemingly simple
ones, going back for more than a decade has a three pin connector.
Are thyey always a thermoswitch, or what other uses might they have?

KC

possibly a thermistor;a temp sensitive resistor,it can be either positive
coefficient or negative.

pos thermistor increases resistance(R) with increase in temp,neg decreases
R with increase.

I'd guess that thermistor sensing is rare.It requires a more complex
circuit.

Thanks a lot.