Battery Question...
Archiver
Posts: 46,084
This is kind of a more generic electronics question, but since I know you
all are pretty smart from previous stamp questions I have asked, I thought
you could give me a good answer:
I bought a stereo boom box that takes 6 "D" size batteries (1.5v). Can I
modify it to use a 9.6v R/C Car battery like you find at radio shack? I
know that with the batteries it would be 9 volt and with the car battery
it would be 9.6v but does .6 really matter? also, is there anything I
would have to worry about regarding amperage? is it true that amperage
doesnt matter because the device will always pull whatever it needs so you
cant burn it out? what other issues may be a problem in doing this
conversion?
- Matt
all are pretty smart from previous stamp questions I have asked, I thought
you could give me a good answer:
I bought a stereo boom box that takes 6 "D" size batteries (1.5v). Can I
modify it to use a 9.6v R/C Car battery like you find at radio shack? I
know that with the batteries it would be 9 volt and with the car battery
it would be 9.6v but does .6 really matter? also, is there anything I
would have to worry about regarding amperage? is it true that amperage
doesnt matter because the device will always pull whatever it needs so you
cant burn it out? what other issues may be a problem in doing this
conversion?
- Matt
Comments
rechargable D batteries and I already have a 9.6 battery and charger out
at the flying field (where the boom box will be). It doesnt matter if it
runs down sooner because those packs take 15 minutes to charge.
- Matt
On Sun, 24 Mar 2002, Leroy Hall wrote:
> I don't think the .6 volt will give you a problem. Actually your idea
> is a very good one. The 'D' size batteries have a higher amperage
> rating, than the 'C' or 'A' size that you will find in the rechargeable
> packs, but that's OK. The smaller size will run down faster, never the
> less they in my opinion will work fine. The ability to recharge will
> bring many benefits.
>
> leroy
>
> Matt Johnson wrote:
> >
> > This is kind of a more generic electronics question, but since I know you
> > all are pretty smart from previous stamp questions I have asked, I thought
> > you could give me a good answer:
> >
> > I bought a stereo boom box that takes 6 "D" size batteries (1.5v). Can I
> > modify it to use a 9.6v R/C Car battery like you find at radio shack? I
> > know that with the batteries it would be 9 volt and with the car battery
> > it would be 9.6v but does .6 really matter? also, is there anything I
> > would have to worry about regarding amperage? is it true that amperage
> > doesnt matter because the device will always pull whatever it needs so you
> > cant burn it out? what other issues may be a problem in doing this
> > conversion?
> >
> > - Matt
> >
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Body of the message will be ignored.
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is a very good one. The 'D' size batteries have a higher amperage
rating, than the 'C' or 'A' size that you will find in the rechargeable
packs, but that's OK. The smaller size will run down faster, never the
less they in my opinion will work fine. The ability to recharge will
bring many benefits.
leroy
Matt Johnson wrote:
>
> This is kind of a more generic electronics question, but since I know you
> all are pretty smart from previous stamp questions I have asked, I thought
> you could give me a good answer:
>
> I bought a stereo boom box that takes 6 "D" size batteries (1.5v). Can I
> modify it to use a 9.6v R/C Car battery like you find at radio shack? I
> know that with the batteries it would be 9 volt and with the car battery
> it would be 9.6v but does .6 really matter? also, is there anything I
> would have to worry about regarding amperage? is it true that amperage
> doesnt matter because the device will always pull whatever it needs so you
> cant burn it out? what other issues may be a problem in doing this
> conversion?
>
> - Matt
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
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with the 9.6 v R/C battery as long as it provides enough current for your
application. The Amp hour rating is listed on the 9.6 v battery and should be
compared to the rating of the D cells. The worst thing that may happen is
that you may have to recharge the 9.6 v battery more often.
On Fri, 29 Mar 2002 azeasi@a... wrote:
> You are generally correct in your statements. You should have no problems
> with the 9.6 v R/C battery as long as it provides enough current for your
> application. The Amp hour rating is listed on the 9.6 v battery and should be
> compared to the rating of the D cells. The worst thing that may happen is
> that you may have to recharge the 9.6 v battery more often.
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
Rob
Original Message
From: Matt Johnson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=1ff0WmHZKZLky4kNSXMPgfFLJ3SOzr76Y8UtxnXv-CyX7Z1I0wT7rZvv7h9m31_uQIFvgV8]matt@m...[/url
Sent: 30 March 2002 06:05
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Battery Question...
What is the amp rating of a D cell?
On Fri, 29 Mar 2002 azeasi@a... wrote:
> You are generally correct in your statements. You should have no
problems
> with the 9.6 v R/C battery as long as it provides enough current for
your
> application. The Amp hour rating is listed on the 9.6 v battery and
should be
> compared to the rating of the D cells. The worst thing that may happen
is
> that you may have to recharge the 9.6 v battery more often.
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject
and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
>
>
>
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Ben
Matt Johnson <matt@m...> wrote: What is the amp rating of a D cell?
On Fri, 29 Mar 2002 azeasi@a... wrote:
> You are generally correct in your statements. You should have no problems
> with the 9.6 v R/C battery as long as it provides enough current for your
> application. The Amp hour rating is listed on the 9.6 v battery and should be
> compared to the rating of the D cells. The worst thing that may happen is
> that you may have to recharge the 9.6 v battery more often.
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
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>
>
>
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BEN (TEAM DBR)
http://www.geocities.com/temdbr
Do You Yahoo!?
Get personalised at My Yahoo!.
[noparse][[/noparse]Non-text portions of this message have been removed]
> What is the amp rating of a D cell?
http://www.swssec.com/bat2.html
and see if that answers your question..
regards,
Leroy
Matt Johnson wrote:
>
> What is the amp rating of a D cell?
>
http://www.swssec.com/bat2.html
and see if that answers your question..
regards,
Leroy
Matt Johnson wrote:
>
> What is the amp rating of a D cell?
>
the conversion to see how long it will last compared to 6 "D" size
batteries?
I dont know the consumtion rate of the radio, its a boom box.
- Matt
On Sat, 30 Mar 2002, Rob wrote:
> Can be from 1.2Ahrs - 4Ahrs (1.2v nominal cell voltage) .
>
> Rob
>
>
Original Message
> From: Matt Johnson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=HqywVRrNvUEnhQi4tl9RYUHPvy1RFBBzJgtN9O-m_mzpEiHwjWfI63X9i1KNwswkrDAUrA]matt@m...[/url
> Sent: 30 March 2002 06:05
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] Battery Question...
>
> What is the amp rating of a D cell?
>
>
> On Fri, 29 Mar 2002 azeasi@a... wrote:
>
> > You are generally correct in your statements. You should have no
> problems
> > with the 9.6 v R/C battery as long as it provides enough current for
> your
> > application. The Amp hour rating is listed on the 9.6 v battery and
> should be
> > compared to the rating of the D cells. The worst thing that may happen
> is
> > that you may have to recharge the 9.6 v battery more often.
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the Subject
> and Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> >
> >
> >
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject
> and Body of the message will be ignored.
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>
>
>
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>
is 14.25 Ahrs and your NiCad is 1.7Ahrs. This equates to 1.7 / 14.25 =
0.119 Therefore the NiCad will only last about a 1/10 of the time the
alkaline will. The above is using generalizations about discharge rates
etc, but will give you some idea. One point to bear in mind is that
NiCad's "self discharge" in relatively short space of time. A few days
of non use and capacity is starting to drop. The major (can be
dangerous) characteristic of NiCad's, is that you can source extremely
high currents over a short duration. So proper fusing needs to be used
in case a short circuit occurs.
Rob
Original Message
From: Matt Johnson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=tSoFtpi4q5U-XBgTaaomxoeoIl4yRxMBefQlOT5Chs7TIEk-h5PdAoXaZAFlq6RsCD5VoT_U]matt@m...[/url
Sent: 30 March 2002 20:33
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Battery Question...
Well if my 9.6v battery pack from radio shack is 1700 mah. How do you do
the conversion to see how long it will last compared to 6 "D" size
batteries?
I dont know the consumtion rate of the radio, its a boom box.
- Matt
On Sat, 30 Mar 2002, Rob wrote:
> Can be from 1.2Ahrs - 4Ahrs (1.2v nominal cell voltage) .
>
> Rob
>
>
Original Message
> From: Matt Johnson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=tSoFtpi4q5U-XBgTaaomxoeoIl4yRxMBefQlOT5Chs7TIEk-h5PdAoXaZAFlq6RsCD5VoT_U]matt@m...[/url
> Sent: 30 March 2002 06:05
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] Battery Question...
>
> What is the amp rating of a D cell?
>
>
> On Fri, 29 Mar 2002 azeasi@a... wrote:
>
> > You are generally correct in your statements. You should have no
> problems
> > with the 9.6 v R/C battery as long as it provides enough current for
> your
> > application. The Amp hour rating is listed on the 9.6 v battery and
> should be
> > compared to the rating of the D cells. The worst thing that may
happen
> is
> > that you may have to recharge the 9.6 v battery more often.
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
Subject
> and Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> >
> >
> >
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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>
>
>
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>If as stated by one the links, the Ah capacity of a "D" alkaline battery
>is 14.25 Ahrs and your NiCad is 1.7Ahrs. This equates to 1.7 / 14.25 =
>0.119 Therefore the NiCad will only last about a 1/10 of the time the
>alkaline will. The above is using generalizations about discharge rates
>etc, but will give you some idea. One point to bear in mind is that
>NiCad's "self discharge" in relatively short space of time. A few days
>of non use and capacity is starting to drop. The major (can be
>dangerous) characteristic of NiCad's, is that you can source extremely
>high currents over a short duration. So proper fusing needs to be used
>in case a short circuit occurs.
I've not been paying much attention to this thread because I was confused
from the start about what battery types were being mixed, etc., but I can
comment on the point involving capacity - from a position of 30 years in
the lead-acid battery industry.
The capacity of a battery is dependent on the rate at which it is
discharged. Assuming for a moment a "D" cell alkaline cell has a
manufacturer's rated capacity of 14.25 Amp-hours and the NiCd in question
has a capacity of 1.7 Amp-hours.... at a discharge rate of say 10 ma, the
"D" alkaline cell will far outperform the NiCd. But in an application that
demands a high current you could well find that the NiCd outperforms the
alkaline. Why? The reasons relate to two things - the basic chemistry
involved and that the alkaline cell has a higher internal resistance.
When you pull a heavy current from the NiCd cell it's voltage drops very
little as it delivers current until it's capacity is nearly exhausted, then
the voltage drops like a rock tossed off a cliff. When you pull a heavy
current from an alkaline cell the voltage drops immediately and then
proceeds on a steady downhill slope as the discharge continues. At some
point in the discharge of each cell the voltage will fall below the voltage
needed to keep the device running and that's the end for both. Generally
speaking, alkaline cells deliver more capacity then NiCds at low discharge
rates and Ni-Cd outperforms alkaline at high discharge rates.
Some of the battery manufacturers publish characteristic curves for their
cells. These will allow you to predict performance at any discharge
rate. You *CANNOT* just pick one capacity rating, say 14.25 AH for an
alkaline "D" cell and apply that to assorted conditions involving varying
discharge rates. You can't do it with Ni-Cd either, but Ni-Cd does come
closer than alkaline to delivering a more consistent capacity at varying rates.
An example of the characteristic curves that relate voltage to discharge
rate over time are shown at
http://data.energizer.com/batteryinfo/application_manuals/cylindrical_alkaline.h\
tm
The main site URL is http://data.energizer.com/ . Other manufacturer's
sites are easy enough to find with a search at http://www.google.com
This is what you need to use to predict performance. Don't forget to
determine the minimum voltage for the device you're powering first - and be
aware that a device that averages a draw of 100 ma, but has peaks of 500 ma
can stop working suddenly when the battery is low and a peak load is placed
on it that crashes the voltage. Also note that NiCd manufacturers tend to
rate their cells down to 0.9 or 1.0 volts (minor difference since NiCds are
failing fast at 1.0 volts), while Alkaline manufacturers seem to rate down
to 0.8 or 0.9 volts. All that matters is your needs, and then compare
those to the characteristic curves. The curves let you pick the cutoff
voltage your device needs and predict capacity to that cutoff voltage.
Jim H
it inline with the red or black wire?
- Matt
On Sun, 31 Mar 2002, Rob wrote:
> If as stated by one the links, the Ah capacity of a "D" alkaline battery
> is 14.25 Ahrs and your NiCad is 1.7Ahrs. This equates to 1.7 / 14.25 =
> 0.119 Therefore the NiCad will only last about a 1/10 of the time the
> alkaline will. The above is using generalizations about discharge rates
> etc, but will give you some idea. One point to bear in mind is that
> NiCad's "self discharge" in relatively short space of time. A few days
> of non use and capacity is starting to drop. The major (can be
> dangerous) characteristic of NiCad's, is that you can source extremely
> high currents over a short duration. So proper fusing needs to be used
> in case a short circuit occurs.
>
> Rob
>
>
Original Message
> From: Matt Johnson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=-y7Y5NvGlKZM7wPgL5IcdJs_Ru2HNFDGJ5_8zpbt_azZhafOW6Z1QbkqPPskVVjffNCy6OR1nA]matt@m...[/url
> Sent: 30 March 2002 20:33
> To: basicstamps@yahoogroups.com
> Subject: RE: [noparse][[/noparse]basicstamps] Battery Question...
>
>
> Well if my 9.6v battery pack from radio shack is 1700 mah. How do you do
> the conversion to see how long it will last compared to 6 "D" size
> batteries?
> I dont know the consumtion rate of the radio, its a boom box.
>
> - Matt
>
> On Sat, 30 Mar 2002, Rob wrote:
>
> > Can be from 1.2Ahrs - 4Ahrs (1.2v nominal cell voltage) .
> >
> > Rob
> >
> >
Original Message
> > From: Matt Johnson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=-y7Y5NvGlKZM7wPgL5IcdJs_Ru2HNFDGJ5_8zpbt_azZhafOW6Z1QbkqPPskVVjffNCy6OR1nA]matt@m...[/url
> > Sent: 30 March 2002 06:05
> > To: basicstamps@yahoogroups.com
> > Subject: Re: [noparse][[/noparse]basicstamps] Battery Question...
> >
> > What is the amp rating of a D cell?
> >
> >
> > On Fri, 29 Mar 2002 azeasi@a... wrote:
> >
> > > You are generally correct in your statements. You should have no
> > problems
> > > with the 9.6 v R/C battery as long as it provides enough current for
> > your
> > > application. The Amp hour rating is listed on the 9.6 v battery and
> > should be
> > > compared to the rating of the D cells. The worst thing that may
> happen
> > is
> > > that you may have to recharge the 9.6 v battery more often.
> > >
> > > To UNSUBSCRIBE, just send mail to:
> > > basicstamps-unsubscribe@yahoogroups.com
> > > from the same email address that you subscribed. Text in the
> Subject
> > and Body of the message will be ignored.
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> > >
> > >
> > >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the Subject
> > and Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
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> >
> >
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> >
> >
> >
>
>
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>
the nicads? What can I do to protect the electronics against anyhting that
may happen with the battery?
- Matt
On Sun, 31 Mar 2002, Jim Higgins wrote:
> At 08:42 03/31/02, Rob wrote:
> >If as stated by one the links, the Ah capacity of a "D" alkaline battery
> >is 14.25 Ahrs and your NiCad is 1.7Ahrs. This equates to 1.7 / 14.25 =
> >0.119 Therefore the NiCad will only last about a 1/10 of the time the
> >alkaline will. The above is using generalizations about discharge rates
> >etc, but will give you some idea. One point to bear in mind is that
> >NiCad's "self discharge" in relatively short space of time. A few days
> >of non use and capacity is starting to drop. The major (can be
> >dangerous) characteristic of NiCad's, is that you can source extremely
> >high currents over a short duration. So proper fusing needs to be used
> >in case a short circuit occurs.
>
> I've not been paying much attention to this thread because I was confused
> from the start about what battery types were being mixed, etc., but I can
> comment on the point involving capacity - from a position of 30 years in
> the lead-acid battery industry.
>
> The capacity of a battery is dependent on the rate at which it is
> discharged. Assuming for a moment a "D" cell alkaline cell has a
> manufacturer's rated capacity of 14.25 Amp-hours and the NiCd in question
> has a capacity of 1.7 Amp-hours.... at a discharge rate of say 10 ma, the
> "D" alkaline cell will far outperform the NiCd. But in an application that
> demands a high current you could well find that the NiCd outperforms the
> alkaline. Why? The reasons relate to two things - the basic chemistry
> involved and that the alkaline cell has a higher internal resistance.
>
> When you pull a heavy current from the NiCd cell it's voltage drops very
> little as it delivers current until it's capacity is nearly exhausted, then
> the voltage drops like a rock tossed off a cliff. When you pull a heavy
> current from an alkaline cell the voltage drops immediately and then
> proceeds on a steady downhill slope as the discharge continues. At some
> point in the discharge of each cell the voltage will fall below the voltage
> needed to keep the device running and that's the end for both. Generally
> speaking, alkaline cells deliver more capacity then NiCds at low discharge
> rates and Ni-Cd outperforms alkaline at high discharge rates.
>
> Some of the battery manufacturers publish characteristic curves for their
> cells. These will allow you to predict performance at any discharge
> rate. You *CANNOT* just pick one capacity rating, say 14.25 AH for an
> alkaline "D" cell and apply that to assorted conditions involving varying
> discharge rates. You can't do it with Ni-Cd either, but Ni-Cd does come
> closer than alkaline to delivering a more consistent capacity at varying
rates.
>
> An example of the characteristic curves that relate voltage to discharge
> rate over time are shown at
>
http://data.energizer.com/batteryinfo/application_manuals/cylindrical_alkaline.h\
tm
>
> The main site URL is http://data.energizer.com/ . Other manufacturer's
> sites are easy enough to find with a search at http://www.google.com
>
> This is what you need to use to predict performance. Don't forget to
> determine the minimum voltage for the device you're powering first - and be
> aware that a device that averages a draw of 100 ma, but has peaks of 500 ma
> can stop working suddenly when the battery is low and a peak load is placed
> on it that crashes the voltage. Also note that NiCd manufacturers tend to
> rate their cells down to 0.9 or 1.0 volts (minor difference since NiCds are
> failing fast at 1.0 volts), while Alkaline manufacturers seem to rate down
> to 0.8 or 0.9 volts. All that matters is your needs, and then compare
> those to the characteristic curves. The curves let you pick the cutoff
> voltage your device needs and predict capacity to that cutoff voltage.
>
>
> Jim H
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and Body
of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
Just connect a fuse in line with the positive NiCad lead. A car stereo
in-line fuse holder with a 2amp fuse should be OK.
Rob
Original Message
From: Matt Johnson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=rR3oiVPV4OYikwi-oPZ0T67Y0t3gazVZwhKnjmM7Us10DEpBH9-EWp8I_UxgrhSa426Mn7cNwlc]matt@m...[/url
Sent: 31 March 2002 19:33
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Battery Question...
In your last paragraph are you saying that I can ruin the boom box with
the nicads? What can I do to protect the electronics against anyhting
that
may happen with the battery?
- Matt
On Sun, 31 Mar 2002, Jim Higgins wrote:
> At 08:42 03/31/02, Rob wrote:
> >If as stated by one the links, the Ah capacity of a "D" alkaline
battery
> >is 14.25 Ahrs and your NiCad is 1.7Ahrs. This equates to 1.7 / 14.25
=
> >0.119 Therefore the NiCad will only last about a 1/10 of the time the
> >alkaline will. The above is using generalizations about discharge
rates
> >etc, but will give you some idea. One point to bear in mind is that
> >NiCad's "self discharge" in relatively short space of time. A few
days
> >of non use and capacity is starting to drop. The major (can be
> >dangerous) characteristic of NiCad's, is that you can source
extremely
> >high currents over a short duration. So proper fusing needs to be
used
> >in case a short circuit occurs.
>
> I've not been paying much attention to this thread because I was
confused
> from the start about what battery types were being mixed, etc., but I
can
> comment on the point involving capacity - from a position of 30 years
in
> the lead-acid battery industry.
>
> The capacity of a battery is dependent on the rate at which it is
> discharged. Assuming for a moment a "D" cell alkaline cell has a
> manufacturer's rated capacity of 14.25 Amp-hours and the NiCd in
question
> has a capacity of 1.7 Amp-hours.... at a discharge rate of say 10 ma,
the
> "D" alkaline cell will far outperform the NiCd. But in an application
that
> demands a high current you could well find that the NiCd outperforms
the
> alkaline. Why? The reasons relate to two things - the basic
chemistry
> involved and that the alkaline cell has a higher internal resistance.
>
> When you pull a heavy current from the NiCd cell it's voltage drops
very
> little as it delivers current until it's capacity is nearly exhausted,
then
> the voltage drops like a rock tossed off a cliff. When you pull a
heavy
> current from an alkaline cell the voltage drops immediately and then
> proceeds on a steady downhill slope as the discharge continues. At
some
> point in the discharge of each cell the voltage will fall below the
voltage
> needed to keep the device running and that's the end for both.
Generally
> speaking, alkaline cells deliver more capacity then NiCds at low
discharge
> rates and Ni-Cd outperforms alkaline at high discharge rates.
>
> Some of the battery manufacturers publish characteristic curves for
their
> cells. These will allow you to predict performance at any discharge
> rate. You *CANNOT* just pick one capacity rating, say 14.25 AH for an
> alkaline "D" cell and apply that to assorted conditions involving
varying
> discharge rates. You can't do it with Ni-Cd either, but Ni-Cd does
come
> closer than alkaline to delivering a more consistent capacity at
varying rates.
>
> An example of the characteristic curves that relate voltage to
discharge
> rate over time are shown at
>
http://data.energizer.com/batteryinfo/application_manuals/cylindrical_al
kaline.htm
>
> The main site URL is http://data.energizer.com/ . Other
manufacturer's
> sites are easy enough to find with a search at http://www.google.com
>
> This is what you need to use to predict performance. Don't forget to
> determine the minimum voltage for the device you're powering first -
and be
> aware that a device that averages a draw of 100 ma, but has peaks of
500 ma
> can stop working suddenly when the battery is low and a peak load is
placed
> on it that crashes the voltage. Also note that NiCd manufacturers
tend to
> rate their cells down to 0.9 or 1.0 volts (minor difference since
NiCds are
> failing fast at 1.0 volts), while Alkaline manufacturers seem to rate
down
> to 0.8 or 0.9 volts. All that matters is your needs, and then compare
> those to the characteristic curves. The curves let you pick the
cutoff
> voltage your device needs and predict capacity to that cutoff voltage.
>
>
> Jim H
>
>
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>On Sun, 31 Mar 2002, Jim Higgins wrote:
>
> > At 08:42 03/31/02, Rob wrote:
> > >If as stated by one the links, the Ah capacity of a "D" alkaline battery
> > >is 14.25 Ahrs and your NiCad is 1.7Ahrs. This equates to 1.7 / 14.25 =
> > >0.119 Therefore the NiCad will only last about a 1/10 of the time the
> > >alkaline will. The above is using generalizations about discharge rates
> > >etc, but will give you some idea. One point to bear in mind is that
> > >NiCad's "self discharge" in relatively short space of time. A few days
> > >of non use and capacity is starting to drop. The major (can be
> > >dangerous) characteristic of NiCad's, is that you can source extremely
> > >high currents over a short duration. So proper fusing needs to be used
> > >in case a short circuit occurs.
> >
> > I've not been paying much attention to this thread because I was confused
> > from the start about what battery types were being mixed, etc., but I can
> > comment on the point involving capacity - from a position of 30 years in
> > the lead-acid battery industry.
> >
> > The capacity of a battery is dependent on the rate at which it is
> > discharged. Assuming for a moment a "D" cell alkaline cell has a
> > manufacturer's rated capacity of 14.25 Amp-hours and the NiCd in question
> > has a capacity of 1.7 Amp-hours.... at a discharge rate of say 10 ma, the
> > "D" alkaline cell will far outperform the NiCd. But in an application
> that
> > demands a high current you could well find that the NiCd outperforms the
> > alkaline. Why? The reasons relate to two things - the basic chemistry
> > involved and that the alkaline cell has a higher internal resistance.
> >
> > When you pull a heavy current from the NiCd cell it's voltage drops very
> > little as it delivers current until it's capacity is nearly exhausted,
> then
> > the voltage drops like a rock tossed off a cliff. When you pull a heavy
> > current from an alkaline cell the voltage drops immediately and then
> > proceeds on a steady downhill slope as the discharge continues. At some
> > point in the discharge of each cell the voltage will fall below the
> voltage
> > needed to keep the device running and that's the end for both. Generally
> > speaking, alkaline cells deliver more capacity then NiCds at low discharge
> > rates and Ni-Cd outperforms alkaline at high discharge rates.
> >
> > Some of the battery manufacturers publish characteristic curves for their
> > cells. These will allow you to predict performance at any discharge
> > rate. You *CANNOT* just pick one capacity rating, say 14.25 AH for an
> > alkaline "D" cell and apply that to assorted conditions involving varying
> > discharge rates. You can't do it with Ni-Cd either, but Ni-Cd does come
> > closer than alkaline to delivering a more consistent capacity at
> varying rates.
> >
> > An example of the characteristic curves that relate voltage to discharge
> > rate over time are shown at
> >
>
http://data.energizer.com/batteryinfo/application_manuals/cylindrical_alkaline.h\
tm
> >
> > The main site URL is http://data.energizer.com/ . Other manufacturer's
> > sites are easy enough to find with a search at http://www.google.com
> >
> > This is what you need to use to predict performance. Don't forget to
> > determine the minimum voltage for the device you're powering first -
> and be
> > aware that a device that averages a draw of 100 ma, but has peaks of
> 500 ma
> > can stop working suddenly when the battery is low and a peak load is
> placed
> > on it that crashes the voltage. Also note that NiCd manufacturers tend to
> > rate their cells down to 0.9 or 1.0 volts (minor difference since NiCds
> are
> > failing fast at 1.0 volts), while Alkaline manufacturers seem to rate down
> > to 0.8 or 0.9 volts. All that matters is your needs, and then compare
> > those to the characteristic curves. The curves let you pick the cutoff
> > voltage your device needs and predict capacity to that cutoff voltage.
>In your last paragraph are you saying that I can ruin the boom box with
>the nicads? What can I do to protect the electronics against anyhting that
>may happen with the battery?
No, and I don't see any likelihood of damage to your boom box from using NiCds.
Just understand that alkaline cells have a nominal voltage of 1.5 volts per
cell and NiCds have a nominal voltage of 1.2 volts per cell, so you get
less voltage from the NiCds from the start. But as you use the boom box,
the NiCds will probably tend to hold their voltage over time better than
the alkaline cells - especially if this is a big boom box that really eats
batteries. The NiCds perform better under heavy loads. If I knew exactly
how much current the boom box draws, and the brand of batteries you're were
using, I could probably dig up the battery performance curves from the
manufacturer's web site and make a more informed prediction. One catch - a
lot of "D" sized NiCds are really only "C" sized NiCds in a "D" sized
shell. If you think you need the real "D" cells, then compare the weight
of the "D" NiCds to the same brand of "C" NiCd and if they're about the
same, then they're really "C" cells hiding inside a "D" cell casing. Mfgrs
do this because most folks don't need the extra capacity (and expense) of a
true "D" NiCd.
Like I said, I missed out on the beginning of this discussion so I may have
missed something.
Back to NiCds causing damage to some devices - yes this can happen. The
circumstances under which it happens is when the performance of the battery
in the device is limited by the internal resistance of the battery rather
than the resistance of the device. This can be the case with some cheaper
electronic flash units where the charging electronics can overheat because
NiCds can deliver more current under heavy load than alkaline cells
can. If you fire off a lot of shots one after another you could damage
some cheap flash units. If this is likely, the directions will probably
warn not to use NiCds. You can also damage a DC motor running on NiCds if
you stall the motor. An alkaline cell may not be able to continue
delivering all the current a stalled motor calls for, but a NiCd is able
and it can burn out a stalled motor. If you don't stall the motor though,
it's not a problem, though lower voltage could make the motor run slightly
slower when it's lightly loaded.
I hope that helps. Feel free to ask more questions if you want to, but
beware I might have to ask for whatever earlier specifics I missed to
answer them.
Jim H
http://www.srbatteries.com/
They make excellent batteries at reasonable prices. I'm not affiliated,
just constantly amazed at the quality of the packs.
Steve
On Sat, 30 Mar 2002, Rob wrote:
> Can be from 1.2Ahrs - 4Ahrs (1.2v nominal cell voltage) .
>
> Rob
>
>
Original Message
> From: Matt Johnson [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=Xi6m1QrUIM4JpMpdro7rVXMO94C8qGT-Q3FHXXhzhZFqNE3Dgrk14W7E7BTw9pg3TuSEjqEs]matt@m...[/url
> Sent: 30 March 2002 06:05
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps] Battery Question...
>
> What is the amp rating of a D cell?
>
>
> On Fri, 29 Mar 2002 azeasi@a... wrote:
>
> > You are generally correct in your statements. You should have no
> problems
> > with the 9.6 v R/C battery as long as it provides enough current for
> your
> > application. The Amp hour rating is listed on the 9.6 v battery and
> should be
> > compared to the rating of the D cells. The worst thing that may happen
> is
> > that you may have to recharge the 9.6 v battery more often.
> >
> > To UNSUBSCRIBE, just send mail to:
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> and Body of the message will be ignored.
> >
> >
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> >
> >
> >
>
>
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>
>
Sean T. Lamont, CTO / Chief NetNerd, Abstract Software, Inc. (ServNet)
Seattle - Bellingham - Vancouver - Portland - Everett - Tacoma - Bremerton
email: lamont@a... WWW: http://www.serv.net
"Do not fear mistakes, There Are None" - Miles Davis