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Main
Date: 30 Dec 2006 15:36:27
From: dgk
Subject: When 12 volts is not 9.6 volts
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I like to use rechargable batteries in my lights, and for the most
part using a rechargable AA in place of a regular battery works fine.
But with cold cathode bulbs on my bike, the little transformer thing
needs 12 volts. So I replaced the normal 8 AAs with 8 rechargables.
And it sort of works. But one bulb starts dimming after a half hour or
so. Checking with normal batteries, this doesn't happen.
I looked a bit closer at my rechargables, which are, it turns out, 1.2
volts, not 1.5 like regular batteries. All rechargables that I looked
at are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD players,
work fine on the rechargeables, but the cold cathodes have a bit of a
problem. Obviously, 10 batteries instead of 8 should do the trick, but
I don't have, and can't find, a case that holds 10 batteries.
So, why do some things work fine with 1.2, and others not? And why
aren't rechargeables 1.5?
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Date: 31 Dec 2006 20:42:06
From: Matt O'Toole
Subject: Re: When 12 volts is not 9.6 volts
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On Sat, 30 Dec 2006 15:36:27 -0500, dgk wrote:
> I like to use rechargable batteries in my lights, and for the most part
> using a rechargable AA in place of a regular battery works fine. But
> with cold cathode bulbs on my bike, the little transformer thing needs
> 12 volts. So I replaced the normal 8 AAs with 8 rechargables. And it
> sort of works. But one bulb starts dimming after a half hour or so.
> Checking with normal batteries, this doesn't happen.
>
> I looked a bit closer at my rechargables, which are, it turns out, 1.2
> volts, not 1.5 like regular batteries. All rechargables that I looked at
> are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD players, work
> fine on the rechargeables, but the cold cathodes have a bit of a
> problem. Obviously, 10 batteries instead of 8 should do the trick, but I
> don't have, and can't find, a case that holds 10 batteries.
>
> So, why do some things work fine with 1.2, and others not? And why
> aren't rechargeables 1.5?
Alkaline batteries can't deliver their rated voltage (1.5V) when connected
to a high current device like a bike light. With a bike light,
rechargeables (nicad or NiMH) may actually deliver more voltage, though
nominally rated for less (1.2V).
The "1.5V" of alkaline batteries drops quickly and steadily with use
anyway. Note how bike lights powered by alkalines start out very bright,
but dim steadily as the batteries wear down. With rechargeables, they
stay relatively bright for quite awhile before dimming significantly.
Matt O.
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Date: 01 Jan 2007 08:35:37
From: Bill Baka
Subject: Re: When 12 volts is not 9.6 volts
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Matt O'Toole wrote:
> On Sat, 30 Dec 2006 15:36:27 -0500, dgk wrote:
>
>> I like to use rechargable batteries in my lights, and for the most part
>> using a rechargable AA in place of a regular battery works fine. But
>> with cold cathode bulbs on my bike, the little transformer thing needs
>> 12 volts. So I replaced the normal 8 AAs with 8 rechargables. And it
>> sort of works. But one bulb starts dimming after a half hour or so.
>> Checking with normal batteries, this doesn't happen.
>>
>> I looked a bit closer at my rechargables, which are, it turns out, 1.2
>> volts, not 1.5 like regular batteries. All rechargables that I looked at
>> are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD players, work
>> fine on the rechargeables, but the cold cathodes have a bit of a
>> problem. Obviously, 10 batteries instead of 8 should do the trick, but I
>> don't have, and can't find, a case that holds 10 batteries.
>>
>> So, why do some things work fine with 1.2, and others not? And why
>> aren't rechargeables 1.5?
>
> Alkaline batteries can't deliver their rated voltage (1.5V) when connected
> to a high current device like a bike light. With a bike light,
> rechargeables (nicad or NiMH) may actually deliver more voltage, though
> nominally rated for less (1.2V).
>
> The "1.5V" of alkaline batteries drops quickly and steadily with use
> anyway. Note how bike lights powered by alkalines start out very bright,
> but dim steadily as the batteries wear down. With rechargeables, they
> stay relatively bright for quite awhile before dimming significantly.
>
> Matt O.
I have to agree. My CatEye light is rated for 4 alkalines (6V) and I use
4 NiMH rechargeables at 1.2V for a total of 4.8V. The alkalines do start
out a little brighter but soon run dimmer than the rechargeable. I think
this is because the alkalines sink more under load than the NiMH. So an
alkaline can go from 1.5V no load to <1.2V full load, while a NiMH
pretty much stays at 1.2V, same as a NiCd, at least until you blow one
up from too much current. Just what I heard, except for the observed
results on my CatEye. The LEDs run at 3.4V (driven by 6V) down to 3.2V
(driven by some fried (1.0V) alkalines. The light is not linear with the
voltage since the LEDs are only current limited by some big resistors.
No fancy electronics to start/stop.
Bill Baka
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Date: 31 Dec 2006 08:22:44
From:
Subject: Re: When 12 volts is not 9.6 volts
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dgk wrote:
> I like to use rechargable batteries in my lights, and for the most
> part using a rechargable AA in place of a regular battery works fine.
> But with cold cathode bulbs on my bike, the little transformer thing
> needs 12 volts....
> I looked a bit closer at my rechargables, which are, it turns out, 1.2
> volts, not 1.5 like regular batteries. ...
> So, why do some things work fine with 1.2, and others not? And why
> aren't rechargeables 1.5?
Werehatrack's answer was exactly right.
To put it another way, the voltage measurements that give you 1.5 volts
and 1.2 volts are taken when there's no current flowing. If you took
an ordinary incandescent flashlight and measured the voltage actually
delivered to the bulb while it's shining, you'd find the two types of
batteries delivered pretty similar voltages at the bulb. If, instead,
you were feeding voltage to something that required little current, the
voltage delivered by the two battery types would be different.
But I'm curious about your "cold cathode lights." What are they,
exactly? Sounds like a flourescent or neon-type bulb?
- Frank Krygowski
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Date: 31 Dec 2006 19:30:14
From: Richard B
Subject: Re: When 12 volts is not 9.6 volts
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frkrygow@gmail.com wrote in news:1167582164.367803.326110
@n51g2000cwc.googlegroups.com:
>
> dgk wrote:
>> I like to use rechargable batteries in my lights, and for the most
>> part using a rechargable AA in place of a regular battery works fine.
>> But with cold cathode bulbs on my bike, the little transformer thing
>> needs 12 volts....
SNIP
>
> But I'm curious about your "cold cathode lights." What are they,
> exactly? Sounds like a flourescent or neon-type bulb?
>
> - Frank Krygowski
>
Perhaps he is talking about this...
http://www.elwirecheap.com/pococabili.html
Richard B.
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Date: 01 Jan 2007 20:01:24
From: dgk
Subject: Re: When 12 volts is not 9.6 volts
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On Sun, 31 Dec 2006 19:30:14 -0000, Richard B
<blueSPAMMENOTrandonee@gmail.com > wrote:
>frkrygow@gmail.com wrote in news:1167582164.367803.326110
>@n51g2000cwc.googlegroups.com:
>
>>
>> dgk wrote:
>>> I like to use rechargable batteries in my lights, and for the most
>>> part using a rechargable AA in place of a regular battery works fine.
>>> But with cold cathode bulbs on my bike, the little transformer thing
>>> needs 12 volts....
>
>SNIP
>>
>> But I'm curious about your "cold cathode lights." What are they,
>> exactly? Sounds like a flourescent or neon-type bulb?
>>
>> - Frank Krygowski
>>
>
>Perhaps he is talking about this...
>http://www.elwirecheap.com/pococabili.html
>
> Richard B.
Yes, that is it exactly. In fact, I bought them from that outfit. But
I think they are out of business and instead they come from Vibelights
now.
They are a bit (bit?) ostentatious. On the other hand, they really
make it hard to get hit accidently at night. Deliberately, well,
that's another story.
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Date: 03 Jan 2007 22:28:19
From: Werehatrack
Subject: Re: When 12 volts is not 9.6 volts
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On Mon, 01 Jan 2007 20:01:24 -0500, dgk <sonice@zero-spam-hotmail.com >
may have said:
>On Sun, 31 Dec 2006 19:30:14 -0000, Richard B
><blueSPAMMENOTrandonee@gmail.com> wrote:
>
>>Perhaps he is talking about this...
>>http://www.elwirecheap.com/pococabili.html
>>
>> Richard B.
>
>Yes, that is it exactly. In fact, I bought them from that outfit. But
>I think they are out of business and instead they come from Vibelights
>now.
>
>They are a bit (bit?) ostentatious. On the other hand, they really
>make it hard to get hit accidently at night. Deliberately, well,
>that's another story.
Never underestimate the power of human stupidity.
--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.
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Date: 04 Jan 2007 09:58:08
From: dgk
Subject: Re: When 12 volts is not 9.6 volts
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On Wed, 03 Jan 2007 22:28:19 -0600, Werehatrack
<rault00@earthWEEDSlink.net > wrote:
>On Mon, 01 Jan 2007 20:01:24 -0500, dgk <sonice@zero-spam-hotmail.com>
>may have said:
>
>>On Sun, 31 Dec 2006 19:30:14 -0000, Richard B
>><blueSPAMMENOTrandonee@gmail.com> wrote:
>>
>>>Perhaps he is talking about this...
>>>http://www.elwirecheap.com/pococabili.html
>>>
>>> Richard B.
>>
>>Yes, that is it exactly. In fact, I bought them from that outfit. But
>>I think they are out of business and instead they come from Vibelights
>>now.
>>
>>They are a bit (bit?) ostentatious. On the other hand, they really
>>make it hard to get hit accidently at night. Deliberately, well,
>>that's another story.
>
>Never underestimate the power of human stupidity.
I was just thinking that some folks might be offended by the lights
and aim for me - kidding I think. I have had people stop me to ask
where they can get them; mostly kids who think that they're way cool.
I just think that they're one more element in avoiding getting
clobbered at night.
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Date: 31 Dec 2006 23:59:07
From: Nodey
Subject: Re: When 12 volts is not 9.6 volts
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Richard B <blueSPAMMENOTrandonee@gmail.com > wrote in
news:Xns98AA750566CE1bluerandoneegmailcom@216.168.3.50:
>> But I'm curious about your "cold cathode lights." What are they,
>> exactly? Sounds like a flourescent or neon-type bulb?
Cold cathode lighting is a very encompassing term. I guess keting uses
it because it sounds, uh, cooler. It's basically any type of lighting that
uses excited gas from emitted electrons, without a heater to emit light.
So it includes your average neon lights, but it could also be any other gas
- xenon or argon for different colors, for example. It could even be
vacuum, and then you've got it striking some other glowing material
(phosphor-screen) to make light.
Nodey
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Date: 31 Dec 2006 01:09:13
From: Werehatrack
Subject: Re: When 12 volts is not 9.6 volts
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On Sat, 30 Dec 2006 15:36:27 -0500, dgk <sonice@zero-spam-hotmail.com >
may have said:
>So, why do some things work fine with 1.2, and others not?
An alkaline that delivers 1.5V unloaded may only be supplying 1.3V or
so under load due to internal resistance. The internal resistance of
the typical rechargeable is lower; its output maintains close to rated
voltage farther into the discharge cycle. If the device has a fairly
high drain level, the rechargeable may actually deliver a higher
voltage than the alkaline, but a device which loads alkalines to the
point that their output drops to that of a NiCd will also drain them
in a frustratingly short period of time. As a result, manufacturers
of battery-powered items tend to choose batteries that will maintain
the desired operational characteristics for an acceptable period...and
this means that the load is low enough that the delivered voltage of a
rechargeable typically still will not be as high as that of the
alkaline unit with the same physical form factor. Where the device is
voltage-sensitive, rechargeables may not work in place of alkalines.
>And why
>aren't rechargeables 1.5?
Chemistry.
--
My email address is antispammed; pull WEEDS if replying via e-mail.
Typoes are not a bug, they're a feature.
Words processed in a facility that contains nuts.
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Date: 30 Dec 2006 20:40:46
From: peter
Subject: Re: When 12 volts is not 9.6 volts
|
dgk wrote:
> I looked a bit closer at my rechargables, which are, it turns out, 1.2
> volts, not 1.5 like regular batteries. All rechargables that I looked
> at are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD players,
> work fine on the rechargeables, but the cold cathodes have a bit of a
> problem. Obviously, 10 batteries instead of 8 should do the trick, but
> I don't have, and can't find, a case that holds 10 batteries.
You already have a case that holds 8, so buy a holder for two
additional cells and connect the two battery holders in series so they
deliver a full 12 VDC. However, you should note that rechargeable
cells can be damaged if you discharge them to the point where they're
getting reverse-charged. With 10 cells in series you might have a
situation where one of the cells may have a little less capacity than
the others and therefore it goes dead first. Even if the voltage of
that cells drops to 0, you could still be getting 9 x 1.2 = 10.8 V from
the other cells which may be enough to keep your device operating. But
driving that current through the discharged cell will probably damage
it.
So when using that many cells in series you need to be careful that all
the cells are well-balanced so they discharge at close to the same
time. Keep cells purchased together as a set and always fully charge
them at the same time. Also try to avoid running them to the point
where they're close to fully discharged.
>
> So, why do some things work fine with 1.2, and others not? And why
> aren't rechargeables 1.5?
As already mentioned this boils down to the basic chemistry involved in
each type of cell. The lead-sulfuric acid cells used in car batteries
produce a bit over 2 V/cell and therefore you get 12 V from 6 cells in
series. Rechargeable lithium ion cells produce about 3.7 V/cell while
NiCd and NiMH cells are about 1.25 V/cell. The latter is close enough
for many devices designed to run on the nominal 1.5 V/cell produced by
alkaline cells.
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Date: 01 Jan 2007 20:09:43
From: dgk
Subject: Re: When 12 volts is not 9.6 volts
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On 30 Dec 2006 20:40:46 -0800, "peter" <prathman@comcast.net > wrote:
>dgk wrote:
>> I looked a bit closer at my rechargables, which are, it turns out, 1.2
>> volts, not 1.5 like regular batteries. All rechargables that I looked
>> at are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD players,
>> work fine on the rechargeables, but the cold cathodes have a bit of a
>> problem. Obviously, 10 batteries instead of 8 should do the trick, but
>> I don't have, and can't find, a case that holds 10 batteries.
>
>You already have a case that holds 8, so buy a holder for two
>additional cells and connect the two battery holders in series so they
>deliver a full 12 VDC. However, you should note that rechargeable
>cells can be damaged if you discharge them to the point where they're
>getting reverse-charged. With 10 cells in series you might have a
>situation where one of the cells may have a little less capacity than
>the others and therefore it goes dead first. Even if the voltage of
>that cells drops to 0, you could still be getting 9 x 1.2 = 10.8 V from
>the other cells which may be enough to keep your device operating. But
>driving that current through the discharged cell will probably damage
>it.
>
>So when using that many cells in series you need to be careful that all
>the cells are well-balanced so they discharge at close to the same
>time. Keep cells purchased together as a set and always fully charge
>them at the same time. Also try to avoid running them to the point
>where they're close to fully discharged.
>>
I did exactly that. I went to RadioShack and got a 2 battery holder
and a few of those 9-volt battery connector things, which is what the
current holder uses. Then I just wired them together and velcored them
physically together. The lights look great.
I bought twelve rechargable AA batteries at the start of the cold(er)
weather and have been using eight for the lights and two for a CD
player. So I took the two from the player and am using them with the
eight, so all ten are around the same wear. The two formerly unused
ones are in the CD player.
They never get drained that much during the ride home, and now the
days are supposedly getting longer again so all should be fine. Once
in a while I discharge them all the way just to keep them honest. The
charger does that.
Thanks for the advice.
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Date: 31 Dec 2006 17:43:21
From: Skip
Subject: Re: When 12 volts is not 9.6 volts
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"peter" <prathman@comcast.net > wrote in message
news:1167540046.542659.294810@v33g2000cwv.googlegroups.com...
> The latter is close enough
> for many devices designed to run on the nominal 1.5 V/cell produced by
> alkaline cells.
Um, wasn't it Carbon/Zinc that produced the original 1.5 volts that is also
approximated by Alkaline cells.
- Skip (an old fogey)
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Date: 30 Dec 2006 21:40:25
From: Mike Ellis
Subject: Re: When 12 volts is not 9.6 volts
|
dgk wrote:
> I like to use rechargable batteries in my lights, and for the most
> part using a rechargable AA in place of a regular battery works fine.
> But with cold cathode bulbs on my bike, the little transformer thing
> needs 12 volts. So I replaced the normal 8 AAs with 8 rechargables.
> And it sort of works. But one bulb starts dimming after a half hour or
> so. Checking with normal batteries, this doesn't happen.
>
> I looked a bit closer at my rechargables, which are, it turns out, 1.2
> volts, not 1.5 like regular batteries. All rechargables that I looked
> at are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD players,
> work fine on the rechargeables, but the cold cathodes have a bit of a
> problem. Obviously, 10 batteries instead of 8 should do the trick, but
> I don't have, and can't find, a case that holds 10 batteries.
>
> So, why do some things work fine with 1.2, and others not? And why
> aren't rechargeables 1.5?
Some things work fine whilst others don't because the application isn't
so voltage critical. It could also be that the internal circuitry
reduces the input voltage to a lower value so that lower voltage cells
will work. The reason that rechargeables are only 1.2 volts is because
the chemical reaction only produces 1.2V whereas the chemical reaction
of regular batteries produces 1.5V. I'm afraid its all down to the
chemistry.
Mike
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Date: 31 Dec 2006 19:19:23
From: Richard B
Subject: Re: When 12 volts is not 9.6 volts
|
Mike Ellis <news@mellis.me.uk > wrote in
news:4596dcc2$0$2754$c3e8da3@news.astraweb.com:
> dgk wrote:
>> I like to use rechargable batteries in my lights, and for the most
>> part using a rechargable AA in place of a regular battery works fine.
>> But with cold cathode bulbs on my bike, the little transformer thing
>> needs 12 volts. So I replaced the normal 8 AAs with 8 rechargables.
>> And it sort of works. But one bulb starts dimming after a half hour
>> or so. Checking with normal batteries, this doesn't happen.
>>
>> I looked a bit closer at my rechargables, which are, it turns out,
>> 1.2 volts, not 1.5 like regular batteries. All rechargables that I
>> looked at are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD
>> players, work fine on the rechargeables, but the cold cathodes have a
>> bit of a problem. Obviously, 10 batteries instead of 8 should do the
>> trick, but I don't have, and can't find, a case that holds 10
>> batteries.
>>
>> So, why do some things work fine with 1.2, and others not? And why
>> aren't rechargeables 1.5?
> Some things work fine whilst others don't because the application
> isn't so voltage critical. It could also be that the internal
> circuitry reduces the input voltage to a lower value so that lower
> voltage cells will work. The reason that rechargeables are only 1.2
> volts is because the chemical reaction only produces 1.2V whereas the
> chemical reaction of regular batteries produces 1.5V. I'm afraid its
> all down to the chemistry.
>
> Mike
>
Why not susbtitute a small sealed lead acid battery, AKA a Gel Cell...
Look at this site:
http://www.zbattery.com/sla.html
Or if you really want to get ceative see:
http://www.powerstream.com/SLA.htm
Richard B.
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Date: 01 Jan 2007 20:18:19
From: dgk
Subject: Re: When 12 volts is not 9.6 volts
|
On Sun, 31 Dec 2006 19:19:23 -0000, Richard B
<blueSPAMMENOTrandonee@gmail.com > wrote:
>Mike Ellis <news@mellis.me.uk> wrote in
>news:4596dcc2$0$2754$c3e8da3@news.astraweb.com:
>
>> dgk wrote:
>>> I like to use rechargable batteries in my lights, and for the most
>>> part using a rechargable AA in place of a regular battery works fine.
>>> But with cold cathode bulbs on my bike, the little transformer thing
>>> needs 12 volts. So I replaced the normal 8 AAs with 8 rechargables.
>>> And it sort of works. But one bulb starts dimming after a half hour
>>> or so. Checking with normal batteries, this doesn't happen.
>>>
>>> I looked a bit closer at my rechargables, which are, it turns out,
>>> 1.2 volts, not 1.5 like regular batteries. All rechargables that I
>>> looked at are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD
>>> players, work fine on the rechargeables, but the cold cathodes have a
>>> bit of a problem. Obviously, 10 batteries instead of 8 should do the
>>> trick, but I don't have, and can't find, a case that holds 10
>>> batteries.
>>>
>>> So, why do some things work fine with 1.2, and others not? And why
>>> aren't rechargeables 1.5?
>> Some things work fine whilst others don't because the application
>> isn't so voltage critical. It could also be that the internal
>> circuitry reduces the input voltage to a lower value so that lower
>> voltage cells will work. The reason that rechargeables are only 1.2
>> volts is because the chemical reaction only produces 1.2V whereas the
>> chemical reaction of regular batteries produces 1.5V. I'm afraid its
>> all down to the chemistry.
>>
>> Mike
>>
>
>Why not susbtitute a small sealed lead acid battery, AKA a Gel Cell...
>
>Look at this site:
>http://www.zbattery.com/sla.html
>
>Or if you really want to get ceative see:
>http://www.powerstream.com/SLA.htm
>
> Richard B.
Thanks. I do have a spare SLA battery from an old Nite Hawk bike light
that I don't use much anymore and I considered using that. I thought
it was 12 volt but I just looked and apparently it's only 6 volts.
Anyway, it weighs a lot. It's the type that fits the water bottle
cage.Nah, I think I'll stick to the NiMHs.
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Date: 31 Dec 2006 08:33:48
From: dgk
Subject: Re: When 12 volts is not 9.6 volts
|
On Sat, 30 Dec 2006 21:40:25 +0000, Mike Ellis <news@mellis.me.uk >
wrote:
>dgk wrote:
>> I like to use rechargable batteries in my lights, and for the most
>> part using a rechargable AA in place of a regular battery works fine.
>> But with cold cathode bulbs on my bike, the little transformer thing
>> needs 12 volts. So I replaced the normal 8 AAs with 8 rechargables.
>> And it sort of works. But one bulb starts dimming after a half hour or
>> so. Checking with normal batteries, this doesn't happen.
>>
>> I looked a bit closer at my rechargables, which are, it turns out, 1.2
>> volts, not 1.5 like regular batteries. All rechargables that I looked
>> at are 1.2. So, 8 * 1.2 = 9.6, not 12. Other stuff, like CD players,
>> work fine on the rechargeables, but the cold cathodes have a bit of a
>> problem. Obviously, 10 batteries instead of 8 should do the trick, but
>> I don't have, and can't find, a case that holds 10 batteries.
>>
>> So, why do some things work fine with 1.2, and others not? And why
>> aren't rechargeables 1.5?
>Some things work fine whilst others don't because the application isn't
>so voltage critical. It could also be that the internal circuitry
>reduces the input voltage to a lower value so that lower voltage cells
>will work. The reason that rechargeables are only 1.2 volts is because
>the chemical reaction only produces 1.2V whereas the chemical reaction
>of regular batteries produces 1.5V. I'm afraid its all down to the
>chemistry.
>
>Mike
I was afraid that it was going to be something elemental.
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