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Rechargeable batteries Question

K

KLM

Jan 1, 1970
0
Question. What is the difference between NiCads and rechargeable
alkaline cells?

I have about two dozen rechargeable AA cells. The older DYNACHHARGE
NiCad batteries came with a wall cube charger (with a red LED
indicator) and a 4 cell battery in-series holder that plugs into the
wall cube. There used to be a time when the LED indicator would light
up when the batteries were fully charged. The LED never comes on now
even though the batteries do seem to be charged.

Then I bought a set of rechargeable Alkaline batteries (Grandcell, a
China made generic) that came with a neat charger with 4 docks to
charge the batteries in parallel . When charging the red LED shows it
is on. When fully charged a green LED also comes on.

I could not use the DYNACHARGE wall cube to charge the Grandcell
alkaline cells although the cell voltage (NiCad 1.2V, alkalines 1.5 V)
are close enough.

When I put the DYNACHARGE NiCads into the Grandcell charger the NiCad
became hot and charged faster. But the green LED never came on to
show the full charge condition. Heat from charging is of course bad
for the NiCads as it boils off the electrolyte. But surely the
fraction of a volt difference should not cause thr NiCad to heat up.
 
M

mike

Jan 1, 1970
0
KLM said:
Question. What is the difference between NiCads and rechargeable
alkaline cells?

I have about two dozen rechargeable AA cells. The older DYNACHHARGE
NiCad batteries came with a wall cube charger (with a red LED
indicator) and a 4 cell battery in-series holder that plugs into the
wall cube. There used to be a time when the LED indicator would light
up when the batteries were fully charged. The LED never comes on now
even though the batteries do seem to be charged.

Then I bought a set of rechargeable Alkaline batteries (Grandcell, a
China made generic) that came with a neat charger with 4 docks to
charge the batteries in parallel . When charging the red LED shows it
is on. When fully charged a green LED also comes on.

I could not use the DYNACHARGE wall cube to charge the Grandcell
alkaline cells although the cell voltage (NiCad 1.2V, alkalines 1.5 V)
are close enough.

NO IT'S NOT. THE CHARGE TERMINATION PROCESS IS COMPLETELY DIFFERENT.
When I put the DYNACHARGE NiCads into the Grandcell charger the NiCad
became hot and charged faster. But the green LED never came on to
show the full charge condition. Heat from charging is of course bad
for the NiCads as it boils off the electrolyte. But surely the
fraction of a volt difference should not cause thr NiCad to heat up.


Yes, that's excatly what's causing them to heat up.
Use a charger designed for the battery technology.
mike



--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/
 
K

KLM

Jan 1, 1970
0
NO IT'S NOT. THE CHARGE TERMINATION PROCESS IS COMPLETELY DIFFERENT.



Yes, that's excatly what's causing them to heat up.
Use a charger designed for the battery technology.


Thanks for the information. Can you ldescribe the technology
involved? I would have thought that charging any battery is just
supplying a small DC overvoltage to the battery.
 
M

mike

Jan 1, 1970
0
KLM said:
Thanks for the information. Can you ldescribe the technology
involved?

Probably, but that would start a firestorm of "no that's not the way
it is." Google is your friend.
mike

I would have thought that charging any battery is just
supplying a small DC overvoltage to the battery.

You would have thought wrong...




--
Return address is VALID.
Bunch of stuff For Sale and Wanted at the link below.
Toshiba & Compaq LiIon Batteries, Test Equipment
Yaesu FTV901R Transverter, 30pS pulser
Tektronix Concept Books, spot welding head...
http://www.geocities.com/SiliconValley/Monitor/4710/
 
A

Asimov

Jan 1, 1970
0
"KLM" bravely wrote to "All" (02 Jun 04 21:09:45)
--- on the heady topic of "Rechargeable batteries Question"

KL> From: KLM <[email protected]>
KL> Reply-To: [email protected]

KL> Question. What is the difference between NiCads and rechargeable
KL> alkaline cells?

Different chemistry of both the metals and electrolytes used for each.


KL> I have about two dozen rechargeable AA cells. The older DYNACHHARGE
KL> NiCad batteries came with a wall cube charger (with a red LED
KL> indicator) and a 4 cell battery in-series holder that plugs into the
KL> wall cube. There used to be a time when the LED indicator would light
KL> up when the batteries were fully charged. The LED never comes on now
KL> even though the batteries do seem to be charged.

It might be a defective LED or the voltage sensing.


KL> Then I bought a set of rechargeable Alkaline batteries (Grandcell, a
KL> China made generic) that came with a neat charger with 4 docks to
KL> charge the batteries in parallel . When charging the red LED shows it
KL> is on. When fully charged a green LED also comes on.

KL> I could not use the DYNACHARGE wall cube to charge the Grandcell
KL> alkaline cells although the cell voltage (NiCad 1.2V, alkalines 1.5 V)
KL> are close enough.

KL> When I put the DYNACHARGE NiCads into the Grandcell charger the NiCad
KL> became hot and charged faster. But the green LED never came on to
KL> show the full charge condition. Heat from charging is of course bad
KL> for the NiCads as it boils off the electrolyte. But surely the
KL> fraction of a volt difference should not cause thr NiCad to heat up.

It is really a matter of chemistry. A fraction of a volt difference is
a very big deal in primary cells. A fully charged Nicad measures 1.25
volts while a fully charged alkaline measures 1.56 volts. The alkaline
charger expects to see 1.56 volts to signal a full charge and stop. It
will overcharge the nicads and make them heat up because they will
resist rising above 1.25 volts. Each type needs its specific charger.

A*s*i*m*o*v

.... I worked hard to attach the electrodes to it.
 
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