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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Battery Capacity
Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but
the 'use once' sort don't? mark |
#2
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Battery Capacity
mark wrote:
Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? becaue..they dont actually HAVE a capacity in tesame sense. A rechargeable is generally rated at a 10 hour discharge rate: with decent cells that capacity is broadly constant across anything from 10 minutes to about 100 hours. Dry cells are not like that. They rapidly polarize under high currents, but then 'recover' if left alone. mark |
#3
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Battery Capacity
The Natural Philosopher wrote:
mark wrote: Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? becaue..they dont actually HAVE a capacity in tesame sense. A rechargeable is generally rated at a 10 hour discharge rate: with decent cells that capacity is broadly constant across anything from 10 minutes to about 100 hours. Dry cells are not like that. They rapidly polarize under high currents, but then 'recover' if left alone. mark If you look in the technical data on the manufacturers sites you will find mAh data. ie http://www.duracell.com/oem/Pdf/new/MX1500_US_UL.pdf |
#4
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Battery Capacity
mark wrote:
Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? I suppose its a selling point and also indirectly an indication of quality on a rechargeable - they are probably also bought by more clued up users. Dry batteries also have a stated capacity - but often only on the makers data sheets rather than boasted on the side of the battery. Note the discharge characteristics will be different - you may not be able to draw the full capacity from a dry cell in quite such as linear was as you can from a rechargeable. Some of the figures are available though: http://cpc.farnell.com/BT03888/batte...acell-15070555 -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#5
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Battery Capacity
In article ,
mark wrote: Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? Probably because it's not in their interest. Better to show bunnies going on and on... But some pro suppliers do give these details. -- *How do they get the deer to cross at that yellow road sign? Dave Plowman London SW To e-mail, change noise into sound. |
#6
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Battery Capacity
Why is it that rechargeable batteries state the capacity,eg., 2500 mAh
but the 'use once' sort don't? Probably because it's not in their interest. Better to show bunnies going on and on... Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. NT |
#7
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Battery Capacity
Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. NT Often I would suspect because some devices cease working before the terminal voltage used in the capacity calculations is reached. |
#8
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Battery Capacity
On Dec 10, 7:08*pm, robert wrote:
The Natural Philosopher wrote: mark wrote: Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? becaue..they dont actually HAVE a capacity in tesame sense. A rechargeable is generally rated at a 10 hour discharge rate: with decent cells that capacity is broadly constant across anything from 10 minutes to about 100 hours. Dry cells are not like that. They rapidly polarize under high currents, but then 'recover' if left alone. mark If you look in the technical data on the manufacturers sites you will find mAh data. ie http://www.duracell.com/oem/Pdf/new/MX1500_US_UL.pdf It used to be given in (I think) the Rapid catalogue, maybe Maplin but I haven't bothered with theirs for quite a few years. MBQ |
#9
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Battery Capacity
On Dec 11, 8:51*am, robert wrote:
Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. NT Often I would suspect because some devices cease working before the terminal voltage used in the capacity calculations is reached. Time to mention http://bigclive.com/joule.htm again? MBQ |
#10
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Battery Capacity
On Dec 11, 1:45*am, wrote:
Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? Probably because it's not in their interest. Better to show bunnies going on and on... Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. Is it really true that a primary cell takes more energy to manufacture than you'll get out of it, or just an urban myth? MBQ |
#11
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Battery Capacity
Man at B&Q wrote:
Is it really true that a primary cell takes more energy to manufacture than you'll get out of it, or just an urban myth? If it was false, wouldn't it best to power the factory making them, from lots of them? |
#12
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Battery Capacity
In article
, Man at B&Q wrote: On Dec 11, 1:45 am, wrote: Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? Probably because it's not in their interest. Better to show bunnies going on and on... Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. Is it really true that a primary cell takes more energy to manufacture than you'll get out of it, or just an urban myth? I'd bet it is true - and by a factor of many. Then there's the energy used to transport it etc. -- *Stable Relationships Are For Horses. * Dave Plowman London SW To e-mail, change noise into sound. |
#13
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Battery Capacity
"Dave Plowman (News)" wrote in message
... In article , Man at B&Q wrote: On Dec 11, 1:45 am, wrote: Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? Probably because it's not in their interest. Better to show bunnies going on and on... Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. Is it really true that a primary cell takes more energy to manufacture than you'll get out of it, or just an urban myth? I'd bet it is true - and by a factor of many. Then there's the energy used to transport it etc. Of course it's true, otherwise the laws of thermodynamics would be in a pickle and the universe would probably explode fairly quickly as entropy would be reversed! -- Bob Mannix (anti-spam is as easy as 1-2-3 - not) |
#14
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Battery Capacity
On Thu, 11 Dec 2008 01:01:10 -0800 (PST), "Man at B&Q"
wrote: On Dec 11, 1:45*am, wrote: Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? Probably because it's not in their interest. Better to show bunnies going on and on... Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. Is it really true that a primary cell takes more energy to manufacture than you'll get out of it, or just an urban myth? No. My perpetual motion machine runs off them. ;-) -- (\__/) M. (='.'=) Owing to the amount of spam posted via googlegroups and (")_(") their inaction to the problem. I am blocking most articles posted from there. If you wish your postings to be seen by everyone you will need use a different method of posting. See http://improve-usenet.org |
#15
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Battery Capacity
Man at B&Q wrote:
It used to be given in (I think) the Rapid catalogue, maybe Maplin but I haven't bothered with theirs for quite a few years. I still have a 1995 Maplin catalog on the shelf - kept because it was the last one to include lots of technical information and device pinouts etc. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#16
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Battery Capacity
robert wrote:
Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. NT Often I would suspect because some devices cease working before the terminal voltage used in the capacity calculations is reached. I have recently had a set of Energiser Lithium AA cells in a camera. They lasted *far* longer than 'ordinary' alkalines which I usually use. Maybe they are sufficiently good to be worth paying their hefty premium? But I do wonder how much is simply loss of voltage rather than actual energy content. -- Rod Hypothyroidism is a seriously debilitating condition with an insidious onset. Although common it frequently goes undiagnosed. www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org |
#17
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Battery Capacity
Rod wrote:
robert wrote: Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. NT Often I would suspect because some devices cease working before the terminal voltage used in the capacity calculations is reached. I have recently had a set of Energiser Lithium AA cells in a camera. They lasted *far* longer than 'ordinary' alkalines which I usually use. Maybe they are sufficiently good to be worth paying their hefty premium? But I do wonder how much is simply loss of voltage rather than actual energy content. Quite - if the camera or device's battery life detector can't be set up for the different discharge characteristics of the available batteries then there is a good chance that the device will close down while there is usable energy in the battery. However looking at the Ultimate Lithium discharge curves - they seem flatter than alkalines and thus shouldnt suffer from early close down. http://data.energizer.com/PDFs/L91ULT_EU.pdf |
#18
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Battery Capacity
robert wrote:
Rod wrote: robert wrote: Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. NT Often I would suspect because some devices cease working before the terminal voltage used in the capacity calculations is reached. I have recently had a set of Energiser Lithium AA cells in a camera. They lasted *far* longer than 'ordinary' alkalines which I usually use. Maybe they are sufficiently good to be worth paying their hefty premium? But I do wonder how much is simply loss of voltage rather than actual energy content. Quite - if the camera or device's battery life detector can't be set up for the different discharge characteristics of the available batteries then there is a good chance that the device will close down while there is usable energy in the battery. However looking at the Ultimate Lithium discharge curves - they seem flatter than alkalines and thus shouldnt suffer from early close down. http://data.energizer.com/PDFs/L91ULT_EU.pdf Thanks. -- Rod Hypothyroidism is a seriously debilitating condition with an insidious onset. Although common it frequently goes undiagnosed. www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org |
#19
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Battery Capacity
"Man at B&Q" wrote in message ... Is it really true that a primary cell takes more energy to manufacture than you'll get out of it, Now that explains what was before the big bang. Have you suggested it to that Hawkins fellow? |
#20
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Battery Capacity
Is it really true that a primary cell takes more energy to manufacture
than you'll get out of it, or just an urban myth? No. My perpetual motion machine runs off them. ;-) There was a supposed perpetual machine that did. It used 2 battery piles disguised as just supporting pillars to electrostatically attract a clock pendulum, and this slight force was enough to keep the clock running. NT |
#21
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Battery Capacity
On Dec 11, 9:45*am, "Bob Mannix" wrote:
"Dave Plowman (News)" wrote in ... In article , * Man at B&Q wrote: On Dec 11, 1:45 am, wrote: Why is it that rechargeable batteries state the capacity,eg., 2500 mAh but the 'use once' sort don't? Probably because it's not in their interest. Better to show bunnies going on and on... Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. Is it really true that a primary cell takes more energy to manufacture than you'll get out of it, or just an urban myth? I'd bet it is true - and by a factor of many. Then there's the energy used to transport it etc. Of course it's true, otherwise the laws of thermodynamics would be in a pickle and the universe would probably explode fairly quickly as entropy would be reversed! Does it take more energy to process Uranium ore than can we get from using the resulting compound in a nuclear reactor? Does it take more energy to pick a few lumps of coal off the floor at an open cast mine than you get from burning it? If so, these would also seem to put the laws of thermodynamics in a pickle. Due to natural processes (or divine providence in the words of the Polish guy on R4 describing his country's abundance of coal) these substances are able to yield energy to us that was locked up millenia ago. It boils down to how much of the energy of a primary cell is put there by the processing of the constituent chemicals versus the potential energy in the raw materials. Is it all due to the processing? MBQ |
#22
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Battery Capacity
"Rod" wrote in message ... robert wrote: Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. NT Often I would suspect because some devices cease working before the terminal voltage used in the capacity calculations is reached. I have recently had a set of Energiser Lithium AA cells in a camera. They lasted *far* longer than 'ordinary' alkalines which I usually use. Maybe they are sufficiently good to be worth paying their hefty premium? But I do wonder how much is simply loss of voltage rather than actual energy content. You should be using NiMh rechargeable in most cameras. The cameras have high discharge currents and alkalines can't keep it up. |
#23
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Battery Capacity
On Dec 12, 9:40*am, "dennis@home"
wrote: "Rod" wrote in message ... robert wrote: Also when one question is answered, the next one is raised. And the next one would be why do so many one shot batteries give only a fraction of their rated capacity in real life apps. Some questions are better left unasked. NT Often I would suspect because some devices cease working before the terminal voltage used in the capacity calculations is reached. I have recently had a set of Energiser Lithium AA cells in a camera. They lasted *far* longer than 'ordinary' alkalines which I usually use. Maybe they are sufficiently good to be worth paying their hefty premium? But I do wonder how much is simply loss of voltage rather than actual energy content. You should be using NiMh rechargeable in most cameras. The cameras have high discharge currents and alkalines can't keep it up. You need to put new batteries in your reading glasses. He said "Lithium". The problem in cameras is the high peak currents that can be required. These can no longer be satisfied without excessive voltage drop as the batteries discharge. A neat solution (which has been proposed if not actually implemented by some manufacturers) is to use an intermediate supercapacitor that can be charged at a lower average current and thus get longer battery life. Much the same principle as charging a capacitor to power the flash. MBQ |
#24
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Battery Capacity
On 12 Dec, 07:18, wrote:
There was a supposed perpetual machine that did. It used 2 battery piles disguised as just supporting pillars to electrostatically attract a clock pendulum, and this slight force was enough to keep the clock running. "Hidden batteries" is one of the 4 classes of perpetual motion machine, (really works, doesn't even start to work, deceitful hidden power source, natural power source like an Atmos clock). However the electrostatic pendulum is a fairly well-known bit of honest physics demonstration kit (Glasgow University has one in an entrance hall?) but I don't think they've been "passed off" like this. |
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