Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
I've never had problems with the supposed rapid self-discharge of NiMH
cells. And now I have proof. Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I took some camera equipment, including freshly charged NiMH cells for the flash. I didn't take any flash pictures, so the cells remained unused in the camera case -- which I just got around to unpacking yesterday. (Really.) Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V, rather lower than the 1.4V NiMH cells commonly charge up to, but close to the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they were not completely discharged. I put them in a Canon 580EX II, and the flash fully charged up in less than two seconds. I fired off some shots. The first few recycled "instantly". The last two took about a half a second. I didn't run down the cells, but it was obvious that two years of sitting on the shelf had no rendered them unusable. The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. -- "We already know the answers -- we just haven't asked the right questions." -- Edwin Land |
#2
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
On Dec 12, 4:26*am, "William Sommerwerck"
wrote: The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. My phone, my wife's phone, my Dremel nail grinder, and the eight Sony AAs I bought before I knew about NiMHs, for a starter. These all are replacements for or successors to products with NiCads, which by comparison held a charge until needed. |
#3
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"spamtrap1888" wrote in message
... On Dec 12, 4:26 am, "William Sommerwerck" wrote: The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. My phone, my wife's phone, my Dremel nail grinder, and the eight Sony AAs I bought before I knew about NiMHs, for a starter. These all are replacements for or successors to products with NiCads, which by comparison held a charge until needed. Then why can four NiMH cells sit for two years and still be able to properly power a high-drain device? |
#4
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
William Sommerwerck wrote:
I've never had problems with the supposed rapid self-discharge of NiMH cells. And now I have proof. Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I took some camera equipment, including freshly charged NiMH cells for the flash. I didn't take any flash pictures, so the cells remained unused in the camera case -- which I just got around to unpacking yesterday. (Really.) Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V, rather lower than the 1.4V NiMH cells commonly charge up to, but close to the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they were not completely discharged. I put them in a Canon 580EX II, and the flash fully charged up in less than two seconds. I fired off some shots. The first few recycled "instantly". The last two took about a half a second. I didn't run down the cells, but it was obvious that two years of sitting on the shelf had no rendered them unusable. The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. so you got dead battery performance and maybe 3 flashes and therefor batteries don't self discharge? |
#5
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
In article ,
William Sommerwerck wrote: The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. You seem to be drawing a sweeping conclusion based on one data point. Not always a reliable approach? Then why can four NiMH cells sit for two years and still be able to properly power a high-drain device? Likely possibility: the NiMH cells that you installed two years ago use an internel chemistry which is superior to that used in early-generation NiMH cells. I definitely did observe the "rapid self-discharge" problem in the first lots of NiMH cells I purchased and used, some years ago. They simply were not reliable for storage times of more than 2-3 months... they'd be down to less than half of their rated capacity after that time. Newer ones are much better. The ones advertised as "low self discharge rate" (e.g Immedions, Eneloops, and the like) have been available for several years, and I believe that the improved low-self-discharge technologies have begun appearing in more "mainstream" NiMH cells which aren't specifically advertised in this way. As I understand it, there's a tradeoff in NiMH cell chemistry: capacity vs. self-discharge. Different metal alloys and structures materials have different hydrogen-bonding characteristics... put crudely, a tightly-binding structure will hold less total hydrogen (i.e. less total charge storage capacity) but self-discharges at a lower rate and thus holds its capacity for a longer time. Cells with higher storage capacity use an alloy/structure which packs in more hydrogen, but doesn't bind it as strongly and thus tends to self-discharge more easily. [Again, this is a crude explanation based on my own in-expert knowledge of the chemistry] In good-quality NiMH AA cells currently on the market, cells down in the 2000-2100 mAh range seem to be representative of the "lower self-discharge rate" variety, and have a useful standby lifetime not terribly different from NiCd cells. NiMH cells up in the 2400-2500 mAh range seem to suffer more self-discharge. At least, that's my own experience over the past year or two. So, my guess is that the batteries you bought two years ago, were ones at the lower-self-discharge end of the design range (even if not explicitly advertised as such). -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#6
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Cydrome Leader" wrote in message
... William Sommerwerck wrote: I've never had problems with the supposed rapid self-discharge of NiMH cells. And now I have proof. Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I took some camera equipment, including freshly charged NiMH cells for the flash. I didn't take any flash pictures, so the cells remained unused in the camera case -- which I just got around to unpacking yesterday. (Really.) Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V, rather lower than the 1.4V NiMH cells commonly charge up to, but close to the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they were not completely discharged. I put them in a Canon 580EX II, and the flash fully charged up in less than two seconds. I fired off some shots. The first few recycled "instantly". The last two took about a half second. I didn't run down the cells, but it was obvious that two years of sitting on the shelf had not rendered them unusable. The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. So you got dead battery performance and maybe 3 flashes and therefore batteries don't self discharge? Where did I say ANY SUCH THING? I'm going to jump down your throat on this one, because I find most people don't understand plain English. If I say "Some people have trouble getting along with their bosses", most readers interpret that as "All people have trouble getting along with their bosses." Really. The cells WERE NOT DEAD. After two years they were at the nominal voltage for a nicad or NiMH cell. Furthermore, they operated the flash without any difficulty. |
#7
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Dave Platt" wrote in message
... In article , William Sommerwerck wrote: The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. You seem to be drawing a sweeping conclusion based on one data point. Not always a reliable approach? It's not the only data point. I've never seen any NiMH cell "rapidly" self-discharge. At least, not over a period of a month or two, which is the general claim. Furthermore, the claim is that ALL NiMH cells "rapidly" self-discharge. I've seen both MAHA and (now) Sanyo cells hold their charge. Then why can four NiMH cells sit for two years and still be able to properly power a high-drain device? Likely possibility: the NiMH cells that you installed two years ago use an internel chemistry which is superior to that used in early-generation NiMH cells. Unlikely. These are not low-discharge-rate cells. Newer ones are much better. The ones advertised as "low self discharge rate" (e.g Immedions, Eneloops, and the like) have been available for several years, and I believe that the improved low-self-discharge technologies have begun appearing in more "mainstream" NiMH cells which aren't specifically advertised in this way. These cells are about three years old. And they're high-capacity -- 2700mAh. To the best of my knowledgte, low-discharge cells have a lower capacity. I think. PS: I will not gainsay anyone's claim to have seen rapid NiMH self-discharge. It's just that I haven't seen it. And I've been using NiMH cells for almost five years. |
#8
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
In article ,
William Sommerwerck wrote: The cells WERE NOT DEAD. After two years they were at the nominal voltage for a nicad or NiMH cell. Furthermore, they operated the flash without any difficulty. To truly know whether (or how much) the cells had self-discharged, you'd need to actually run them down to exhaustion and see how much useful charge had been retained. NiMH cells, like NiCd cells, have a rather flat discharge curve. Their terminal voltage, and their ability to deliver current on demand, don't change very much as they discharge... until they get down to somewhere around the 10% charge level, at which point they "fall off of a cliff" quite rapidly. They tend to work perfectly well, until they die. So, the fact that your batteries had a nominal terminal voltage, and were able to charge the flash quickly and take a few photos, is useful information, but by no means complete enough to diagnose whether (or how much) the cells had discharged during storage. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
#9
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
William Sommerwerck wrote:
"Cydrome Leader" wrote in message ... William Sommerwerck wrote: I've never had problems with the supposed rapid self-discharge of NiMH cells. And now I have proof. Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I took some camera equipment, including freshly charged NiMH cells for the flash. I didn't take any flash pictures, so the cells remained unused in the camera case -- which I just got around to unpacking yesterday. (Really.) Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V, rather lower than the 1.4V NiMH cells commonly charge up to, but close to the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they were not completely discharged. I put them in a Canon 580EX II, and the flash fully charged up in less than two seconds. I fired off some shots. The first few recycled "instantly". The last two took about a half second. I didn't run down the cells, but it was obvious that two years of sitting on the shelf had not rendered them unusable. The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. So you got dead battery performance and maybe 3 flashes and therefore batteries don't self discharge? Where did I say ANY SUCH THING? I'm going to jump down your throat on this one, because I find most people don't understand plain English. If I say "Some people have trouble getting along with their bosses", most readers interpret that as "All people have trouble getting along with their bosses." Really. The cells WERE NOT DEAD. After two years they were at the nominal voltage for a nicad or NiMH cell. Furthermore, they operated the flash without any difficulty. Your test was unscientific, undocumented, anecdotal, incomplete. You are certainly entitled to draw any conclusions you wish and base your personal decisions on those conclusions. Your blanket statement about NiMH based on your sample-of-one anecdote requires extrapolation beyond reason. "Proof" is not a word I'd have used to describe your result. I can say that my personal experience differs from yours. And I get along just fine with my boss. Really!! |
#10
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
William Sommerwerck wrote:
"Cydrome Leader" wrote in message ... William Sommerwerck wrote: I've never had problems with the supposed rapid self-discharge of NiMH cells. And now I have proof. Almost two years ago, I visited a friend in Gold Bar WA for Christmas. I took some camera equipment, including freshly charged NiMH cells for the flash. I didn't take any flash pictures, so the cells remained unused in the camera case -- which I just got around to unpacking yesterday. (Really.) Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V, rather lower than the 1.4V NiMH cells commonly charge up to, but close to the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they were not completely discharged. I put them in a Canon 580EX II, and the flash fully charged up in less than two seconds. I fired off some shots. The first few recycled "instantly". The last two took about a half second. I didn't run down the cells, but it was obvious that two years of sitting on the shelf had not rendered them unusable. The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. So you got dead battery performance and maybe 3 flashes and therefore batteries don't self discharge? Where did I say ANY SUCH THING? sorry you got 100 full power flashes before the batteries died. I'm going to jump down your throat on this one, because I find most people don't understand plain English. If I say "Some people have trouble getting along with their bosses", most readers interpret that as "All people have trouble getting along with their bosses." Really. people that talk about jumping down throats really need to shut the **** up and not be talking about how to get along with a boss. Really. The cells WERE NOT DEAD. After two years they were at the nominal voltage for a nicad or NiMH cell. Furthermore, they operated the flash without any There's nothing quite like the no load battery test. difficulty. yeah, for 3 flashes until the flash was unable to even recycle anymore. |
#11
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"William Sommerwerck" wrote in message ... "Dave Platt" wrote in message ... In article , William Sommerwerck wrote: The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. You seem to be drawing a sweeping conclusion based on one data point. Not always a reliable approach? It's not the only data point. I've never seen any NiMH cell "rapidly" self-discharge. At least, not over a period of a month or two, which is the general claim. The local outlet of the Lidl store chain sometimes has NiMh cells at a very tempting price so I bought loads - unfortunately they're no good for the majority of occasional use items or clocks because they need tediously frequent recharging. As someone else pointed out there are advanced chemistry types - but more expensive and harder to find. |
#12
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Ian Field" wrote in
: "William Sommerwerck" wrote in message ... "Dave Platt" wrote in message ... In article , William Sommerwerck wrote: The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. You seem to be drawing a sweeping conclusion based on one data point. Not always a reliable approach? It's not the only data point. I've never seen any NiMH cell "rapidly" self-discharge. At least, not over a period of a month or two, which is the general claim. The local outlet of the Lidl store chain sometimes has NiMh cells at a very tempting price so I bought loads - unfortunately they're no good for the majority of occasional use items or clocks because they need tediously frequent recharging. As someone else pointed out there are advanced chemistry types - but more expensive and harder to find. I bought a 4 pack of Eveready NiMH cells for my hommade 2 watt bicycle headlight,it outputs 200 lumens for .65A draw,and I go a long time(months) before having to recharge,unless I use the light heavily.Of course,my design does not draw any current when OFF. some items have a draw even when not in use. like my low cost Polaroid digital camera. "Pre-charged" NiMH cells have a lower self-discharge rate,but they don't seem to be all that more expennsive than regular NiMH. they are slightly lower in mAH capacity.(2100mAH vs 2300mAH) I'd ask the OP how many flashes or shots he got from his stored NiMH cells before they needed recharge. seems to me that 1.2V is pretty much "discharged" for NiMH cells. ISTR that 1.1V is the low limit. -- Jim Yanik jyanik at localnet dot com |
#13
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Jim Yanik" wrote in message
4... "Pre-charged" NiMH cells have a lower self-discharge rate,but they don't seem to be all that more expennsive than regular NiMH. they are slightly lower in mAH capacity.(2100mAH vs 2300mAH) I'd ask the OP how many flashes or shots he got from his stored NiMH cells before they needed recharge. seems to me that 1.2V is pretty much "discharged" for NiMH cells. ISTR that 1.1V is the low limit. I didn't run down the flash. I will do so tonight or tomorrow. 1.25V is considered the nominal operating voltage of nicad or NiMH cells. (The point another poster made about the relatively flat discharge was well-taken.) The "discharged" point is, as it is for cells of most chemistries, 1.0V. |
#14
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Cydrome Leader" wrote in message
... yeah, for 3 flashes until the flash was unable to even recycle anymore. You're determined to deliberately misread what I wrote, aren't you? |
#15
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
William Sommerwerck wrote:
"Cydrome Leader" wrote in message ... yeah, for 3 flashes until the flash was unable to even recycle anymore. You're determined to deliberately misread what I wrote, aren't you? Go slam some doors or something, you might be better at that than testing batteries. |
#16
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
William Sommerwerck wrote:
"Jim Yanik" wrote in message 4... "Pre-charged" NiMH cells have a lower self-discharge rate,but they don't seem to be all that more expennsive than regular NiMH. they are slightly lower in mAH capacity.(2100mAH vs 2300mAH) I'd ask the OP how many flashes or shots he got from his stored NiMH cells before they needed recharge. seems to me that 1.2V is pretty much "discharged" for NiMH cells. ISTR that 1.1V is the low limit. I didn't run down the flash. I will do so tonight or tomorrow. 1.25V is considered the nominal operating voltage of nicad or NiMH cells. (The point another poster made about the relatively flat discharge was well-taken.) The "discharged" point is, as it is for cells of most chemistries, 1.0V. What was the load current for your voltage measurement? |
#17
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
On Mon, 12 Dec 2011 10:08:27 -0800, "William Sommerwerck"
wrote: "Dave Platt" wrote in message ... In article , William Sommerwerck wrote: The belief that NiMH cells rapidly self-discharge is utter malarkey. Where it came from, I don't know. You seem to be drawing a sweeping conclusion based on one data point. Not always a reliable approach? It's not the only data point. I've never seen any NiMH cell "rapidly" self-discharge. At least, not over a period of a month or two, which is the general claim. Furthermore, the claim is that ALL NiMH cells "rapidly" self-discharge. I've seen both MAHA and (now) Sanyo cells hold their charge. Then why can four NiMH cells sit for two years and still be able to properly power a high-drain device? Likely possibility: the NiMH cells that you installed two years ago use an internel chemistry which is superior to that used in early-generation NiMH cells. Unlikely. These are not low-discharge-rate cells. Newer ones are much better. The ones advertised as "low self discharge rate" (e.g Immedions, Eneloops, and the like) have been available for several years, and I believe that the improved low-self-discharge technologies have begun appearing in more "mainstream" NiMH cells which aren't specifically advertised in this way. These cells are about three years old. And they're high-capacity -- 2700mAh. To the best of my knowledgte, low-discharge cells have a lower capacity. I think. PS: I will not gainsay anyone's claim to have seen rapid NiMH self-discharge. It's just that I haven't seen it. And I've been using NiMH cells for almost five years. Shall I send you some glorious AA examples that never held enough charge to operate a Canon Powershot A200 a week after a full charge? I have them in both Duracell and no-name. And no, it's *not* due to any shortcomings in the charger or camera. Another brand of cells now delivers, months after charge. |
#18
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
On Mon, 12 Dec 2011 04:26:03 -0800, "William Sommerwerck"
wrote: Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V, rather lower than the 1.4V NiMH cells commonly charge up to, but close to the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they were not completely discharged. NiMH cells do NOT totally discharge themselves. They discharge to about 50% of capacity (by self-discharge) and then just sit there. For example, here are some curves I ran for an Energizer 2300ma-hr cell: http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg and for an Duracell 2050ma-hr cell: http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg There were brand new cells used to test the assertion that NiMH cells need to be charge cycled a few times before they reach full capacity. Basically, that's true. Note the voltages (under 1C load). For the Energizer, it starts off at 1.35v and starts to die at about 1.10v. If you put a load on your Sanyo cells, I'm fairly sure your 1.23v no load voltage will drop to something around 1.18v. In other words, your Sanyo batteries self-discharged until they were almost dead, and stopped. I recently had a similar experience to what you found. I have two old Norelco rotary shavers. I received both with dead batteries and replaced them with NiMH cells of dubious origin. I only charge them when needed, except this time, when a dry squall dropped a few trees through the power lines. http://802.11junk.com/jeffl/pics/2011-12-03-Storm/ When I dug out the shavers, the LCD indicator showed a nearly full charge (about 80%). However, when I tried to use it, both lasted less than 60 seconds. My guess(tm) is that I hadn't charged it since last winter (9 months). That's fairly close to what you observed. There was sufficient voltage for the LCD indicator to proclaim a nearly full charge, but not enough stored energy to do much useful work. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#19
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
On Mon, 12 Dec 2011 18:20:52 -0800, Jeff Liebermann
wrote: For example, here are some curves I ran for an Energizer 2300ma-hr cell: http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg and for an Duracell 2050ma-hr cell: http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg There were brand new cells used to test the assertion that NiMH cells need to be charge cycled a few times before they reach full capacity. Basically, that's true. Hmmm... I haven't done anything with the batteries I used for this test since May 29, 2011. They've just been sitting on the shelf. I recall recharging them after I was done with the test. I'll run the same 1C discharge test again in a few days and see how much capacity is left after 7 months. This should be interesting. 1C is a heavy load, but does yield fast results. Note: I don't have phone or DSL at my house at this time and have dragged my home computah to my office. This test will need to wait until AT&T puts fixes things. Patience. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#20
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Jeff Liebermann" wrote in message
... On Mon, 12 Dec 2011 18:20:52 -0800, Jeff Liebermann wrote: For example, here are some curves I ran for an Energizer 2300ma-hr cell: http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg and for an Duracell 2050ma-hr cell: http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg There were brand new cells used to test the assertion that NiMH cells need to be charge cycled a few times before they reach full capacity. Basically, that's true. Hmmm... I haven't done anything with the batteries I used for this test since May 29, 2011. They've just been sitting on the shelf. I recall recharging them after I was done with the test. I'll run the same 1C discharge test again in a few days and see how much capacity is left after 7 months. This should be interesting. 1C is a heavy load, but does yield fast results. Thanks. That would be interesting. |
#21
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Jeff Liebermann" wrote in message
... NiMH cells do NOT totally discharge themselves. They discharge to about 50% of capacity (by self-discharge) and then just sit there. Then what is the problem? A 50% loss of capacity is hardly disastrous. For example, here are some curves I ran for an Energizer 2300ma-hr cell: http://802.11junk.com/jeffl/NiMH/Energizer-NiMH-2300.jpg and for an Duracell 2050ma-hr cell: http://802.11junk.com/jeffl/NiMH/Duracelll-NiMH-2050.jpg There were brand new cells used to test the assertion that NiMH cells need to be charge cycled a few times before they reach full capacity. Basically, that's true. Note the voltages (under 1C load). For the Energizer, it starts off at 1.35v and starts to die at about 1.10v. If you put a load on your Sanyo cells, I'm fairly sure your 1.23v no load voltage will drop to something around 1.18v. In other words, your Sanyo batteries self-discharged until they were almost dead, and stopped. But they weren't "almost dead". This morning, I did what I should have done before I posted. Over a period of a half-hour, I fired the Canon 580EX II over 100 times AT FULL POWER. The recycling time was 3 to 3.5 seconds (not unreasonable for full-power recycling), and the final cell voltage was about 1.21V (before the cells had time to recover). 100 full-power flashes is not "almost dead". Had I fired on automatic, at a moderate aperture, not using full power, I could easily have gotten 200 or 300 flashes. And had I been willing to tolerate a 5-second recycle, I probably could have gotten another 100 full-power flashes. I recently had a similar experience to what you found. I have two old Norelco rotary shavers. I received both with dead batteries and replaced them with NiMH cells of dubious origin. I only charge them when needed, except this time, when a dry squall dropped a few trees through the power lines. http://802.11junk.com/jeffl/pics/2011-12-03-Storm/ When I dug out the shavers, the LCD indicator showed a nearly full charge (about 80%). However, when I tried to use it, both lasted less than 60 seconds. My guess(tm) is that I hadn't charged it since last winter (9 months). That's fairly close to what you observed. There was sufficient voltage for the LCD indicator to proclaim a nearly full charge, but not enough stored energy to do much useful work. That isn't what I observed this morning. The cells, which had sat for almost two years since being fully charged, were perfectly usable for 100 full-power flashes. I probably have gotten another 100 flashes, but I didn't want to take the chance of abusing the flash. The cells are Sanyo Superlattice Alloy EVO, model HR-3U. They were not shipped pre-charged, and as far as I can tell, they are not slow-self-discharge ("eneloop") cells. The Sanyo USA site has no information about them. However, they are available from Batteries America. (Thomas Distributing doesn't list them.) |
#22
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
|
#23
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Jeff Liebermann" wrote in message ... On Mon, 12 Dec 2011 04:26:03 -0800, "William Sommerwerck" wrote: Four of the cells were 2700mAh Sanyo AAs. They all measured about 1.23V, rather lower than the 1.4V NiMH cells commonly charge up to, but close to the "nominal" 1.25V of NiMH and nicad cells. Contrary to Urban Legend, they were not completely discharged. NiMH cells do NOT totally discharge themselves. They discharge to about 50% of capacity (by self-discharge) and then just sit there. ISTR NiCd cells frequently became shorted if allowed to self discharge too often, but I haven't noticed it with NiMh. |
#24
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
On Tue, 13 Dec 2011 05:13:46 -0800, "William Sommerwerck"
wrote: The cells are Sanyo Superlattice Alloy EVO, model HR-3U. They were not shipped pre-charged, and as far as I can tell, they are not slow-self-discharge ("eneloop") cells. The Sanyo USA site has no information about them. However, they are available from Batteries America. (Thomas Distributing doesn't list them.) http://www.houseofbatteries.com/documents/HR-3U-2500.pdf No mention of low self-discharge. 100 flashes does seem like an almost fully charged battery. However, with such an intermittent load, it would have been nice if you had a more controlled and more measurable way to test charge level. If what you say is true, then you may be correct that there's no self-discharge for a *NEW* NiMH battery. I'm wondering if it might be a phenomenon that appears later as the battery is used. I'll run my little discharge test when I have time and get my computer back home. Incidentally, several people have mentioned that you cannot use the open circuit voltage as an indication of state of charge. I agree. It works with batteries that have sloping discharge curves, such as carbon-zinc and some alkaline. However, batteries that have a flat discharge curve offer such a small change in terminal voltage, that the numbers are difficult to distinguish from tolerance and temperature variations. The only way that seems to work for such batteries are coulomb counter chips, as found in many laptop batteries. More later... bizzeeeeeee -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#25
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Jeff Liebermann" NiMH cells do NOT totally discharge themselves. They discharge to about 50% of capacity (by self-discharge) and then just sit there. ** I have several sets of AA NiMH cells - all Sanyo brand and rated at 1700 to 2500 mAH. Self discharge is a REAL problem, but no worse than with NiCds. In general, charged cells lose 90% of capacity in about 6 to 8 weeks - taking a full 6 hour charge at 400mA to recover. In my Canon A430, the uncharged cells will run the back display for a few minutes, let me take a few shots and maybe one flash before the camera shuts down. .... Phil |
#26
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
On Tue, 13 Dec 2011 05:13:46 -0800, "William Sommerwerck"
wrote: The cells are Sanyo Superlattice Alloy EVO, model HR-3U. They were not shipped pre-charged, and as far as I can tell, they are not slow-self-discharge ("eneloop") cells. The Sanyo USA site has no information about them. However, they are available from Batteries America. (Thomas Distributing doesn't list them.) This might be of interest: http://www.stefanv.com/electronics/sanyo_eneloop.html It's an independent test of the Sanyo Eneloop NiMH batteries including some self-discharge tests. Unfortunately, he doesn't compare the results with the non-LSD batteries. Scroll down to the "Self Discharge" section heading and note the self-discharge tables. 50% charge loss after 1 year. There is also this quote from Sanyo: Storage temperature is of high importance if you measure self-discharge rate. Higher temperatures substantially increase self-discharging. It is best to store Eneloops as cool as possible to keep the charge in the battery. As a rule-of-thumb, every 10°C increase in storage temperature is equivalent to doubling the storage time. Some R/C pilots in Europe put Eneloops in the freezer, with rather good results. So, how were your batteries stored? Presumably, the non-LSD batteries would produce much worse results, making your miraculous Sanyo HR-3U cells better than Eneloop cells, which seems rather dubious. Since the Eneloop batteries tested were brand new, I don't think it's something related to an aging effect. That leaves your test as an oddity. Are you sure someone didn't charge your batteries when nobody was looking? -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#27
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
On Tue, 13 Dec 2011 19:45:07 -0800, Jeff Liebermann
wrote: This might be of interest: http://www.stefanv.com/electronics/sanyo_eneloop.html It's an independent test of the Sanyo Eneloop NiMH batteries including some self-discharge tests. Unfortunately, he doesn't compare the results with the non-LSD batteries. Ok, I lied[1]. There is a comparison. See: http://www.stefanv.com/electronics/sanyo_eneloop.html#compare The graph shows the Eneloop battery to be MUCH better at self-discharge than the conventional NiMH. After 1 year, the Eneloop retained about 50% of charge, while the conventional NiMH retained only 2.6%. [1] I'm suppose to be doing my end of year billing and bookkeeping. I hate doing billing and am therefore easily diverted. If I go broke, it's all your fault for creating an interesting diversion. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#28
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Jeff Liebermann" wrote in message
... 100 flashes does seem like an almost fully charged battery. But it isn't, of course. The voltage was at the nominal 1.25V when I started, but this is well below the end-of-charge voltage for NiMH cells. However, with such an intermittent load, it would have been nice if you had a more controlled and more measurable way to test charge level. If what you say is true, then you may be correct that there's no self-discharge for a *NEW* NiMH battery. I'm wondering if it might be a phenomenon that appears later as the battery is used. I'll run my little discharge test when I have time and get my computer back home. It was "scientific" in the sense of mimicking photographic use. 100+ full-power shots in a half hour, three at a time, is fairly extreme use. Incidentally, several people mentioned that you cannot use the open-circuit voltage as an indication of state of charge. I agree. Of course. That's one of the problems with nicad and NiMH cells. However, the fact that the cells read about 1.25V showed they WERE NOT fully charged. But despite having sat for two years, they were able to give 100+ full-power shots. The point is that their were perfectly usable without having to be recharged. This contradicts belief that NiMH cells rapidly self-discharge. (Rates of 1% or more per day are stated.) I might disable the flash's auto-shutoff and let the cells run down to 1.0V, then see whether it can still fire more than once. (I have no desire to keep popping the flash.) PS: Sanyo says their current eneloop cells (rated at 1500 charge cycles) will hold as much of 75% of their charge for 3 years. |
#29
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Phil Allison" wrote in message
... "Jeff Liebermann" NiMH cells do NOT totally discharge themselves. They discharge to about 50% of capacity (by self-discharge) and then just sit there. ** I have several sets of AA NiMH cells - all Sanyo brand and rated at 1700 to 2500 mAH. Self discharge is a REAL problem, but no worse than with NiCds. In general, charged cells lose 90% of capacity in about 6 to 8 weeks - taking a full 6 hour charge at 400mA to recover. In my Canon A430, the uncharged cells will run the back display for a few minutes, let me take a few shots and maybe one flash before the camera shuts down. I wonder if the "spectacular" behavior of my 2700mAh Sanyos has anything to do with their "superlattice alloy" construction. These appear to be the only Sanyos using this design. (That's life, I guess.) http://en.wikipedia.org/wiki/Superlattice Anyone care to explain this article to me? |
#30
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Jeff Liebermann" wrote in message
... There is also this quote from Sanyo: Storage temperature is of high importance if you measure self-discharge rate. Higher temperatures substantially increase self-discharging. It is best to store Eneloops as cool as possible to keep the charge in the battery. As a rule-of-thumb, every 10°C increase in storage temperature is equivalent to doubling the storage time. Some R/C pilots in Europe put Eneloops in the freezer, with rather good results. So, how were your batteries stored? This is the typical "doubling of chemical reactions with each increase of 10°C" rule. Right before Christmas 2009, I packed up my camera bag for a visit to Gold Bar, WA. Two packs of NiMH cells were in the bag. When I came home, I put the bag on the living room floor, where it has remained for almost two years. The Pacific Northwest is cooler than the rest of the country. The cells were exposed to "high" temperatures only intermittently, during the warmer days of Summer. Presumably, the non-LSD... Hmmm... Is there a purple owl on these cells? ...batteries would produce much worse results, making your miraculous Sanyo HR-3U cells better than Eneloop cells, which seems rather dubious. Agreed, but we don't know whether the "superlattice alloy" has magical powers. Since the Eneloop batteries tested were brand new, I don't think it's something related to an aging effect. That leaves your test as an oddity. Are you sure someone didn't charge your batteries when nobody was looking? Well, it was around Christmas... Elves, perhaps? Brownies? Speaking of which... One of Stan Freberg's less-well-known recordings is "Yulenet", with Joe Friday trying to convince a doubter named Grudge that there really is a Santa Claus. When they visit the North Pole, they're greeted by a brownie from the South Pole (Daws Butler doing a silly mock-Southern voice) who's helping out while Santa is away. I can imagine the flap such a joke would cause today... |
#31
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Jeff Liebermann" wrote in message
... On Tue, 13 Dec 2011 19:45:07 -0800, Jeff Liebermann wrote: This might be of interest: http://www.stefanv.com/electronics/sanyo_eneloop.html It's an independent test of the Sanyo Eneloop NiMH batteries including some self-discharge tests. Unfortunately, he doesn't compare the results with the non-LSD batteries. Ok, I lied[1]. There is a comparison. See: http://www.stefanv.com/electronics/sanyo_eneloop.html#compare The graph shows the Eneloop battery to be MUCH better at self-discharge than the conventional NiMH. After 1 year, the Eneloop retained about 50% of charge, while the conventional NiMH retained only 2.6%. [1] I'm suppose to be doing my end of year billing and bookkeeping. I hate doing billing and am therefore easily diverted. If I go broke, it's all your fault for creating an interesting diversion. Extremely interesting. I'll contact Sanyo and ask them about the self-discharge of my specific cells. |
#32
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
On Tue, 13 Dec 2011 19:45:07 -0800, Jeff Liebermann
wrote: On Tue, 13 Dec 2011 05:13:46 -0800, "William Sommerwerck" wrote: The cells are Sanyo Superlattice Alloy EVO, model HR-3U. They were not shipped pre-charged, and as far as I can tell, they are not slow-self-discharge ("eneloop") cells. The Sanyo USA site has no information about them. However, they are available from Batteries America. (Thomas Distributing doesn't list them.) This might be of interest: http://www.stefanv.com/electronics/sanyo_eneloop.html It's an independent test of the Sanyo Eneloop NiMH batteries including some self-discharge tests. Unfortunately, he doesn't compare the results with the non-LSD batteries. Scroll down to the "Self Discharge" section heading and note the self-discharge tables. 50% charge loss after 1 year. There is also this quote from Sanyo: Storage temperature is of high importance if you measure self-discharge rate. Higher temperatures substantially increase self-discharging. It is best to store Eneloops as cool as possible to keep the charge in the battery. As a rule-of-thumb, every 10°C increase in storage temperature is equivalent to doubling the storage time. Some R/C pilots in Europe put Eneloops in the freezer, with rather good results. So, how were your batteries stored? Presumably, the non-LSD batteries would produce much worse results, making your miraculous Sanyo HR-3U cells better than Eneloop cells, which seems rather dubious. Since the Eneloop batteries tested were brand new, I don't think it's something related to an aging effect. That leaves your test as an oddity. Are you sure someone didn't charge your batteries when nobody was looking? In for a penny's worth; i add that this might be some freaky low self discharge cells for the given process, perhaps at some process corner for the set. ?-) |
#33
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
I'll try to make this quick...
Canon's specs for the 580EX II flash appear to be based on nicad or NiMH cells starting at 1.25 volts. As I explained, when the unloaded voltage was at 1.21V, I had no trouble getting more than 100 full-power flashes, which meets the 100 - 700 flash spec in the book. After letting the flash sit, running, for several hours, the unloaded voltage was about 1.18V. After removing and replacing the cells, the flash charged up once, taking more than 7 seconds. After firing it, it would not recycle. Several points... The cells had sat for two years, but delivered at least the spec'd number of flashes. Some NiMH cells might self-discharge quickly, but these Sanyos did not. (I was surprised that, throughout the discharge, the cells' voltages were virtually identical, never differing by more than about 10mV. This suggests very tight manufacturing tolerances.) It was also interesting that the flash "conked out" well before the cells reached 1.0V. This suggests that this flash is /not/ designed to work down to 1V per cell, the traditional "standard" of battery-operated designs. |
#34
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"William Sommer******" Canon's specs for the 580EX II flash appear to be based on nicad or NiMH cells starting at 1.25 volts. ** The manual clearly states that it is based on Alkaline cells. This implies that the unit will operate with much lower cell voltages and currents than modern digital cameras require. As I explained, when the unloaded voltage was at 1.21V, ** It is totally meaningless to quote unloaded voltages of MiNH, NiCd or alkaline cells. Only when loaded as in the application does terminal voltage become meaningful. .... Phil |
#35
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
On Fri, 16 Dec 2011 05:11:33 -0800, "William Sommerwerck"
wrote: I'll try to make this quick... Canon's specs for the 580EX II flash appear to be based on nicad or NiMH cells starting at 1.25 volts. As I explained, when the unloaded voltage was at 1.21V, I had no trouble getting more than 100 full-power flashes, which meets the 100 - 700 flash spec in the book. After letting the flash sit, running, for several hours, the unloaded voltage was about 1.18V. After removing and replacing the cells, the flash charged up once, taking more than 7 seconds. After firing it, it would not recycle. Several points... The cells had sat for two years, but delivered at least the spec'd number of flashes. " at least the MINIMUM spec'd number of flashes" - which you would expect given (a) the expanse of the range specified (100-700) and (b) the proximity of your cells' voltage to the Canon staring point. Some NiMH cells might self-discharge quickly, but these Sanyos did not. (I was surprised that, throughout the discharge, the cells' voltages were virtually identical, never differing by more than about 10mV. This suggests very tight manufacturing tolerances.) Sanyo is probably the most highly regarded name in both NiCd and NiMH manufacture. You shouldn't be surprised. It was also interesting that the flash "conked out" well before the cells reached 1.0V. This suggests that this flash is /not/ designed to work down to 1V per cell, the traditional "standard" of battery-operated designs. |
#36
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
Several points... The cells had sat for two years, but delivered at least
the spec'd number of flashes. " at least the MINIMUM spec'd number of flashes" - which you would expect given (a) the expanse of the range specified (100-700) and (b) the proximity of your cells' voltage to the Canon staring point. 100 is for a full-power flash. The 700 refers to a partial-power flash, under auto-exposure. |
#37
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"William Sommer****** is Full of **** " 100 is for a full-power flash. ** The flash energy input is probably about 20 Joules, ie 330uF and 350V. Allowing 5 Joules for losses, the energy required for 100 flashes is 2500 Joules. A fully charged, 2500mAH NiMH has a capacity of 11,000 Joules ( 1.2 x 2.5 x 3600 ) Four of them have a capacity of 44,000 Joules So, your "magic" Sanyo cells had under 6% of normal capacity. .... Phil |
#38
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
who where wrote:
On Fri, 16 Dec 2011 05:11:33 -0800, "William Sommerwerck" wrote: I'll try to make this quick... Canon's specs for the 580EX II flash appear to be based on nicad or NiMH cells starting at 1.25 volts. As I explained, when the unloaded voltage was at 1.21V, I had no trouble getting more than 100 full-power flashes, which meets the 100 - 700 flash spec in the book. After letting the flash sit, running, for several hours, the unloaded voltage was about 1.18V. After removing and replacing the cells, the flash charged up once, taking more than 7 seconds. After firing it, it would not recycle. Several points... The cells had sat for two years, but delivered at least the spec'd number of flashes. " at least the MINIMUM spec'd number of flashes" - which you would expect given (a) the expanse of the range specified (100-700) and (b) the proximity of your cells' voltage to the Canon staring point. Some NiMH cells might self-discharge quickly, but these Sanyos did not. (I was surprised that, throughout the discharge, the cells' voltages were virtually identical, never differing by more than about 10mV. This suggests very tight manufacturing tolerances.) Sanyo is probably the most highly regarded name in both NiCd and NiMH manufacture. You shouldn't be surprised. It was also interesting that the flash "conked out" well before the cells reached 1.0V. This suggests that this flash is /not/ designed to work down to 1V per cell, the traditional "standard" of battery-operated designs. Make sure you're comparing apples with apples. The unloaded voltage of a cell is irrelevant. I've found it very difficult to get the unloaded voltage of NiMH below 1.2V. Discharge it down to .8V, remove the load and let it sit and it will creep back up to 1.2V. But it's still dead and can't supply much current. A flash is a VERY high current device. Once the LOADED voltage gets much below 1V, it's too weak for a flash. The ONLY useful voltage measurement is with the intended load. A useful measurement is internal resistance. Use a square-wave load from 1/2A to 1A. Measure the P-P amplitude of the cell voltage and use that to calculate a resistance dV/dI. Try it at different states of charge. Calculate the voltage drop from your load current and the ISR. Multiply that by the number of series cells and it's easy to see why high-current loads quit working long before the open-circuit voltage gets below 1.2V. |
#39
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"Phil Allison" wrote in message
... "William Sommer****** is Full of **** " Phil Allison is a foul-mouthed shmuck. By the way, in German "shmuck" means "jewelry" or "adornment". Billy Wilder gets a funny gag out of this in "One, Two, Three". 100 is for a full-power flash. The flash energy input is probably about 20 joules, ie 330uF and 350V. Allowing 5 joules for losses, the energy required for 100 flashes is 2500 joules. The losses are probably greater than that. When I left the flash running, without firing it, I was surprised that it conked out after about two hours. I suspect this flash provides more than 20Ws output. But the specs are silent on this. A fully charged, 2500mAH NiMH has a capacity of 11,000 joules (1.2 x 2.5 x 3600). Four of them have a capacity of 44,000 joules. So, your "magic" Sanyo cells had under 6% of normal capacity. I can't argue with plausibly-chosen numbers, and I won't. However... You're still missing the point. We have been told that NiMH cells lose several percent of their capacity every week. (Let's say 3%, and assume it's a linear loss, rather than exponential.) After 102 weeks, the cells should have been dead, dead, dead. They were not. They had no trouble powering the flash to its spec'd number of full-power flashes. What do you want, for heaven's sake? The point about "voltage creep" of nicads & NiMH cells was well-taken. However, I measured the cells' voltages within about 15 seconds of shutting off the flash. Furthermore, the under-load voltage is arguably not that important if the DUT works as it's spec'd. Which this flash did. Please note that I actually performed an experiment! I tested cells that should have been useless. They were not. The statement that conventional NiMH cells are generically incapable of holding a charge for extended periods is simply NOT TRUE. Not because "I say so", but because I have empirical evidence. Yesterday I pulled out my Sunpak 622 Super, a "professional" potato-masher flash. It has four 5500mAh NiMH C cells made by CTA, whoever that is. (They came from Overstock.) The last time I charged them was about six months ago. I flicked the power switch, and unit came to full power in 6 seconds. Full-power recycling was 4 seconds -- not great, but not bad, either, especially for "dead" cells.. |
#40
Posted to sci.electronics.repair
|
|||
|
|||
the lie of rapid NiMH self-discharge
"mike" wrote in message
... Make sure you're comparing apples with apples. The unloaded voltage of a cell is irrelevant. I've found it very difficult to get the unloaded voltage of NiMH below 1.2V. Discharge it down to .8V, remove the load and let it sit and it will creep back up to 1.2V. But it's still dead and can't supply much current. A flash is a VERY high current device. Once the LOADED voltage gets much below 1V, it's too weak for a flash. The ONLY useful voltage measurement is with the intended load. A useful measurement is internal resistance. Use a square-wave load from 1/2A to 1A. Measure the P-P amplitude of the cell voltage and use that to calculate a resistance dV/dI. Try it at different states of charge. Calculate the voltage drop from your load current and the ISR. Multiply that by the number of series cells and it's easy to see why high-current loads quit working long before the open-circuit voltage gets below 1.2V. I shouldn't have said anything about the voltage. The point is that the cells "should" have been dead, but weren't. After nearly two years, they powered the flash to its spec's number of flashes. |
Reply |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Rapid and DHL | UK diy | |||
Tek 7904A rapid ticking - no HT... | Electronics Repair | |||
OT? Rapid Prototyping | Metalworking | |||
Is there a difference between dish washer discharge and laundry machine discharge? | Home Repair |