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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. |
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#1
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Wall Warts
I've a Skil Mod 2375 3/8" cordless drill (9.6v) thats nearly an antique. The old wall wart outputs dc 11v, 250 mA when functional. It now has a slight bulge and outputs 0v. I rumble thru my box of WW's, find one at rated output of dc 12v, 300 mA, splice the wires, plug it in to see if it will charge. It will, but it heats up a bunch, enough to burn my fingers a little. Are there any guidelines for substituting these things? I'd like to keep the drill, but can hardly afford to burn the house down. :-) Thx, P "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule." |
#2
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Wall Warts
"Puddin' Man" I've a Skil Mod 2375 3/8" cordless drill (9.6v) thats nearly an antique. The old wall wart outputs dc 11v, 250 mA when functional. It now has a slight bulge and outputs 0v. ** Wall warts break up into THREE distinct groups: 1. AC output. 2. DC output. 3. Battery chargers. You cannot exchange units from one group into another. Those in group 3 are the most variable in design and are purpose built to charge a specific type and number of cells. The fact they all look much the same and often have the same plugs attached is very misleading. ..... Phil |
#3
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Wall Warts
The reply from whit is a good suggestion, but I suspect that the cells in
the drill are shorted, which will damage a charging power supply. It seems that the old supply became overheated and failed, which will happen if the cells are shorted. I believe this is the reason for the substitute wall wart getting hot. To find out if the cells are shorted, the cells need to be accessed, and individually checked with an ohm meter or an instrument capable of measuring battery cell impedance or ESR. Also, a reading for individual cells with voltmeter reading of zero volts generally indicates shorted cells. Replacing all of the cells is the most effective solution, and cells with tabs can be soldered together in the original order, and restore full (or even better) operation of the drill (or most cordless tools). If you have the ability to make good solder connections, replacement is usually less costly than paying someone else to do the work. There are numerous online sellers with reasonable prices for replacement cells. -- Cheers, WB .............. "Puddin' Man" wrote in message ... I've a Skil Mod 2375 3/8" cordless drill (9.6v) thats nearly an antique. The old wall wart outputs dc 11v, 250 mA when functional. It now has a slight bulge and outputs 0v. I rumble thru my box of WW's, find one at rated output of dc 12v, 300 mA, splice the wires, plug it in to see if it will charge. It will, but it heats up a bunch, enough to burn my fingers a little. Are there any guidelines for substituting these things? I'd like to keep the drill, but can hardly afford to burn the house down. :-) Thx, P "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule." |
#4
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Wall Warts
On Mon, 23 May 2011 20:24:18 -0400, "Wild_Bill" wrote:
The reply from whit is a good suggestion, but I suspect that the cells in the drill are shorted, which will damage a charging power supply. It seems that the old supply became overheated and failed, which will happen if the cells are shorted. I believe this is the reason for the substitute wall wart getting hot. Certainly possible, for all I know. I shoulda mentioned, I'm not an electronics guy, just a tinker. Limited (make that -very- limited) skills, eqpt. I might've charged with the new supply 20 min. before I noticed the heat. The drill worked a little thereafter. To find out if the cells are shorted, the cells need to be accessed, and individually checked with an ohm meter or an instrument capable of measuring battery cell impedance or ESR. Also, a reading for individual cells with voltmeter reading of zero volts generally indicates shorted cells. The drill still works a little. I measure about 4v aggregate from the battery pack. Replacing all of the cells is the most effective solution, and cells with tabs can be soldered together in the original order, and restore full (or even better) operation of the drill (or most cordless tools). The usual case, not practical. Wierd cell shapes, very old unit. If you have the ability to make good solder connections, replacement is usually less costly than paying someone else to do the work. There are numerous online sellers with reasonable prices for replacement cells. If I can't tinker-fix it, it goes in the trash. Any replacement parts either won't fit or are too expensive or both. I hate to throw potentially useful tools away, but ... Thanks, P "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule." |
#5
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Wall Warts
On May 24, 10:55*am, Puddin' Man wrote:
On Mon, 23 May 2011 20:24:18 -0400, "Wild_Bill" wrote: I shoulda mentioned, I'm not an electronics guy, just a tinker. Limited (make that -very- limited) skills, eqpt. I might've charged with the new supply 20 min. before I noticed the heat. The drill worked a little thereafter. To find out if the cells are shorted, the cells need to be accessed, and individually checked with an ohm meter or an instrument capable of measuring battery cell impedance or ESR. Also, a reading for individual cells with voltmeter reading of zero volts generally indicates shorted cells. The drill still works a little. I measure about 4v aggregate from the battery pack. Replacing all of the cells is the most effective solution, and cells with tabs can be soldered together in the original order, and restore full (or even better) operation of the drill (or most cordless tools). The usual case, not practical. Wierd cell shapes, very old unit. If I can't tinker-fix it, it goes in the trash. Any replacement parts either won't fit or are too expensive or both. I hate to throw potentially useful tools away, but ... If the pack didn't consist of 8 AA-sized NiCds I would be muchly surprised. Anybody who can plug new AAs into a remote control, and knows which end of a soldering pencil to hold, likely has the skill level to rebuild a battery pack. |
#6
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Wall Warts
On Mon, 23 May 2011 15:54:46 -0500, Puddin' Man
wrote: I've a Skil Mod 2375 3/8" cordless drill (9.6v) thats nearly an antique. The charger was involved in a safety recall. I have a similar model with the same problem. The xformer will overheat when trying to charge a dead battery. If you call the 800 number, you might get a free charger. http://www.all-cordless.com/skilrecalls.html However, if it's a later replacement, then all you did is blow the thermal fuse inside the charger. You can crack it open and replace it, but my guess(tm) is you also have some very dead batteries. Are there any guidelines for substituting these things? I'd like to keep the drill, but can hardly afford to burn the house down. :-) Not without knowing where the charge controller (probably just a resistor) is located. If it's inside the wall wart, you'll need to add an identical resistor. If it's inside the drill, you can probably get away with your 12VDC substitute. Measure the current drain at the charger output. My guess(tm) is you should have a mess of AA size NiCd batteries inside the drill, which are usually rated at 750ma-hr. Using the 0.1C rule, that would be a charging current of about 75ma max. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#7
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Wall Warts
On Tue, 24 May 2011 11:35:26 -0700, Jeff Liebermann wrote:
On Mon, 23 May 2011 15:54:46 -0500, Puddin' Man wrote: I've a Skil Mod 2375 3/8" cordless drill (9.6v) thats nearly an antique. The charger was involved in a safety recall. I have a similar model with the same problem. The xformer will overheat when trying to charge a dead battery. If you call the 800 number, you might get a free charger. http://www.all-cordless.com/skilrecalls.html However, if it's a later replacement, then all you did is blow the thermal fuse inside the charger. You can crack it open and replace it, but my guess(tm) is you also have some very dead batteries. Thanks. That was worth checking into. They have no replacement parts for the 2375. They say that they'll send paperwork so, if I send 'em the charger, they'll send more paperwork so, if I buy a new Skil drill, they'll refund $25 or somesuch -if- I send 'em the UPC code -and- the orig. receipt, etc, etc ad nauseum. I don't think they really wanna honor the recall. Are there any guidelines for substituting these things? I'd like to keep the drill, but can hardly afford to burn the house down. :-) Not without knowing where the charge controller (probably just a resistor) is located. If it's inside the wall wart, you'll need to add an identical resistor. If it's inside the drill, you can probably get away with your 12VDC substitute. Measure the current drain at the charger output. Lost me there. Measure the *drain* at the charger output? But I'm pretty sure it is inside the buggered charger. My guess(tm) is you should have a mess of AA size NiCd batteries inside the drill, which are usually rated at 750ma-hr. Using the 0.1C rule, that would be a charging current of about 75ma max. It's evidently all original: charger is 92950, power pack is 92955, and is a *sealed* unit. I see no way to take it apart. Am I missing something here? Thx, P "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule." |
#8
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Wall Warts
On May 24, 3:03*pm, Puddin' Man wrote:
On Tue, 24 May 2011 11:35:26 -0700, Jeff Liebermann wrote: My guess(tm) is you should have a mess of AA size NiCd batteries inside the drill, which are usually rated at 750ma-hr. Using the 0.1C rule, that would be a charging current of about 75ma max. It's evidently all original: charger is 92950, power pack is 92955, and is a *sealed* unit. I see no way to take it apart. Am I missing something here? The battery packs I've repaired consisted of two shells epoxied together. Does this one not look like it could be knifed apart? |
#9
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Wall Warts
On Tue, 24 May 2011 17:03:17 -0500, Puddin' Man
wrote: I don't think they really wanna honor the recall. http://www.cpsc.gov/cpscpub/prerel/prhtml03/03082.html Looks like the $25 rebate is all that they are offering. Maybe calling them back and asking for the name of the company attorney and whether this recall is defacto admission of their responsibility if your garage burns down, might get their attention. Are there any guidelines for substituting these things? I'd like to keep the drill, but can hardly afford to burn the house down. :-) Not without knowing where the charge controller (probably just a resistor) is located. If it's inside the wall wart, you'll need to add an identical resistor. If it's inside the drill, you can probably get away with your 12VDC substitute. Measure the current drain at the charger output. Lost me there. Measure the *drain* at the charger output? But I'm pretty sure it is inside the buggered charger. I guess it might be difficult to measure the current if the charger is dead. The problem is that we don't really know how the charging system works without tearing it apart. If the blown charger has a resistor in series with the output, there's no way to know at this point without cracking it open, or comparing it with another working unit. Start by using an ohms-guesser on the charger base. Cut the cord. Is there DC continuity between the two wires and the contacts on the charger base? If there's a measurable resistance, then the charger base has either a resistor, or complexicated charge controller in the base. I would therefore guess(tm) that the wall wart is just a simple wall wart with nothing more complex than a thermal fuse inside. However, if there is DC continuity between the leads and the battery terminal connections, then the charge controller is inside the wall wart, and a simple replacement isn't going to work. Since the power supply is obviously blown and useless, tearing it apart should reveal if there's anything inside. You'll probably find a thermal fuse. If it's blown, just replace it with a similar thermal fuse, glue the case back together, and continue charging. However, if there's a series resistor inside (which is what I suspect), then use the 12V adapter, add a similar resistor in series, measure the charging current, and see if it's reasonable 0.1C. If not, adjust the resistor value for 0.1C charging current. My guess(tm) is you should have a mess of AA size NiCd batteries inside the drill, which are usually rated at 750ma-hr. Using the 0.1C rule, that would be a charging current of about 75ma max. It's evidently all original: charger is 92950, power pack is 92955, and is a *sealed* unit. I see no way to take it apart. Am I missing something here? Most chargers and charging bases are solvent welded together. They can usually be cracked open with brute force. Place a masons chisel along the glue line, and beat on it with a hammer. The glue line should crack as the plastic bends. If not, just use a hack saw to saw along the glue line. Do the repair, and then glue the case back together. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#10
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Wall Warts
Jeff Liebermann wrote:
Most chargers and charging bases are solvent welded together. They can usually be cracked open with brute force. Place a masons chisel along the glue line, and beat on it with a hammer. The glue line should crack as the plastic bends. If not, just use a hack saw to saw along the glue line. Do the repair, and then glue the case back together. Overnight in a freezer helps. It makes the plastic brittle. If you have a deep freezer (0F or colder) use it instead of a refigerator freezer (around 10F). Geoff. -- Geoffrey S. Mendelson N3OWJ/4X1GM It's amazing how many people have no clue what the word "contiguous" means. :-( |
#11
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Wall Warts
On 5/23/2011 4:54 PM, Puddin' Man wrote:
I've a Skil Mod 2375 3/8" cordless drill (9.6v) thats nearly an antique. The old wall wart outputs dc 11v, 250 mA when functional. It now has a slight bulge and outputs 0v. I rumble thru my box of WW's, find one at rated output of dc 12v, 300 mA, splice the wires, plug it in to see if it will charge. It will, but it heats up a bunch, enough to burn my fingers a little. Are there any guidelines for substituting these things? I'd like to keep the drill, but can hardly afford to burn the house down. :-) Thx, P "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule." Recall on the charger, though not much good if the battery is knackered. http://store.boschpowertoolsource.co...9296vwar1.html JC |
#12
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Wall Warts
On Tue, 24 May 2011 22:36:26 -0700, Jeff Liebermann wrote:
Start by using an ohms-guesser on the charger base. Cut the cord. Is there DC continuity between the two wires and the contacts on the charger base? If there's a measurable resistance, then the charger base has either a resistor, or complexicated charge controller in the base. The + side measures 3 ohms. I would therefore guess(tm) that the wall wart is just a simple wall wart with nothing more complex than a thermal fuse inside. However, if there is DC continuity between the leads and the battery terminal connections, then the charge controller is inside the wall wart, and a simple replacement isn't going to work. Since the power supply is obviously blown and useless, tearing it apart should reveal if there's anything inside. You'll probably find a thermal fuse. If it's blown, just replace it with a similar thermal fuse, glue the case back together, and continue charging. However, if there's a series resistor inside (which is what I suspect), then use the 12V adapter, add a similar resistor in series, measure the charging current, and see if it's reasonable 0.1C. If not, adjust the resistor value for 0.1C charging current. My guess(tm) is you should have a mess of AA size NiCd batteries inside the drill, which are usually rated at 750ma-hr. Using the 0.1C rule, that would be a charging current of about 75ma max. It's evidently all original: charger is 92950, power pack is 92955, and is a *sealed* unit. I see no way to take it apart. Am I missing something here? Most chargers and charging bases are solvent welded together. They can usually be cracked open with brute force. Place a masons chisel along the glue line, and beat on it with a hammer. The glue line should crack as the plastic bends. If not, just use a hack saw to saw along the glue line. Do the repair, and then glue the case back together. Thanks for this opportunity for taking revenge on the offending WW. :-) After freezing, it cracked open easily, but I see no fuse. Apologies for lack of quality of pix: http://imageshack.us/photo/my-images...wallwart1.jpg/ http://imageshack.us/photo/my-images...wallwart2.jpg/ Thanks, P "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule." |
#13
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Wall Warts
On Wed, 25 May 2011 14:07:41 -0500, Puddin' Man
wrote: The + side measures 3 ohms. Ok. There may be a diode inside the base. Try reversing the leads on the ohms-guesser and see if it acts like a diode. Thanks for this opportunity for taking revenge on the offending WW. :-) Learn by Destroying(tm). If you haven't destroyed it and fixed it, you don't understand it. After freezing, it cracked open easily, but I see no fuse. Apologies for lack of quality of pix: http://imageshack.us/photo/my-images...wallwart1.jpg/ http://imageshack.us/photo/my-images...wallwart2.jpg/ Yech. I can't see anything in there. Fix the focus. Is there any manner of diode, resitor, charge controller, PCB, pilot lamp (current regulator), or thermal fuse inside? If not, it's an ordinary AC xformer. Also, no points for covering the xformer with the burned insulating material, so I can't see anything. If AC only, then there's the usual problem of what voltage to get. Peak voltage on a single diode is 1.414 * AC voltage. If there's no series resistor, and just a diode in the base unit, then my guess(tm) is that you should be looking for a 7.5VAC wall wart. Again, you'll need to measure the charging current and check for 0.1C current to be sure you got it right. Of course, make sure you don't have a shorted battery pack. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#14
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Wall Warts
En el artículo , Puddin' Man
escribió: Are there any guidelines for substituting these things? You've done the right thing, substituting one of a slightly higher spec. The fact that you've had one burn out and its replacement gets hot suggests there may be something wrong with the charging circuit in the drill or the battery. -- (\__/) (='.'=) (")_(") |
#15
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Wall Warts
On Wed, 25 May 2011 15:57:21 -0700, Jeff Liebermann wrote:
On Wed, 25 May 2011 14:07:41 -0500, Puddin' Man wrote: The + side measures 3 ohms. Ok. There may be a diode inside the base. Try reversing the leads on the ohms-guesser and see if it acts like a diode. Measures infinite ohms when reversed. ... After freezing, it cracked open easily, but I see no fuse. Apologies for lack of quality of pix: http://imageshack.us/photo/my-images...wallwart1.jpg/ http://imageshack.us/photo/my-images...wallwart2.jpg/ Yech. I can't see anything in there. Fix the focus. Is there any manner of diode, resitor, charge controller, PCB, pilot lamp (current regulator), or thermal fuse inside? If not, it's an ordinary AC xformer. Also, no points for covering the xformer with the burned insulating material, so I can't see anything. There's nothing else in there. If AC only, then there's the usual problem of what voltage to get. Peak voltage on a single diode is 1.414 * AC voltage. If there's no series resistor, and just a diode in the base unit, then my guess(tm) is that you should be looking for a 7.5VAC wall wart. Again, you'll need to measure the charging current and check for 0.1C current to be sure you got it right. I'm 'fraid you'll have to elaborate on this last. And, what is "C" in ..1C? Of course, make sure you don't have a shorted battery pack. So I gotta crack the battery pack open. And test each cell individually? How? Thx, P "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule." |
#16
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Wall Warts
On May 26, 10:51*am, Puddin' Man wrote:
Of course, make sure you don't have a shorted battery pack. So I gotta crack the battery pack open. And test each cell individually? How? A 9.6 V NiCd battery pack should consist of 8 NiCd penlight cells, connected in series. |
#17
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Wall Warts
On Thu, 26 May 2011 12:51:48 -0500, Puddin' Man
wrote: The + side measures 3 ohms. Ok. There may be a diode inside the base. Try reversing the leads on the ohms-guesser and see if it acts like a diode. Measures infinite ohms when reversed. It's a diode, with no series resistor. That presents a problem. Without some form of current limiting, the voltage of the xformer will need to be VERY carefully controlled to keep from overcharging the battery. I will swear there's a resistor or charge controller somewhere in the system, but I can't tell where from here. I'm 'fraid you'll have to elaborate on this last. And, what is "C" in .1C? Sorry. C is the current rating of the battery in ampere-hours. A typical NiCd pack, full of AA cells will have a rating of about 750 ma-hr. NiMH would be around 1200 to 2200 ma-hr. The maximum charge current of the charger should be about 0.1 times this value (i.e. 10%) or 75ma for the NiCd pack. Of course, make sure you don't have a shorted battery pack. So I gotta crack the battery pack open. And test each cell individually? How? You don't need to destroy the battery pack in order to test it. First, just measure the terminal voltage of the battery pack after it's been sitting around for a day without being charged. Even if totally discharged, it should have at least 1.1 volts per cell or about 7.7VDC across the terminals. A fully charged NiCd will have about 1.45VDC per cell or about 10.2VDC across the terminals. Now, if you really want to test you battery packs, I have a West Mtn Radio CBA-IIv1: http://www.westmountainradio.com/product_info.php?products_id=cba3 -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#18
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Wall Warts
On Fri, 27 May 2011 17:37:46 -0700, Jeff Liebermann wrote:
On Thu, 26 May 2011 12:51:48 -0500, Puddin' Man wrote: The + side measures 3 ohms. Ok. There may be a diode inside the base. Try reversing the leads on the ohms-guesser and see if it acts like a diode. Measures infinite ohms when reversed. It's a diode, with no series resistor. That presents a problem. Without some form of current limiting, the voltage of the xformer will need to be VERY carefully controlled to keep from overcharging the battery. I will swear there's a resistor or charge controller somewhere in the system, but I can't tell where from here. I dunno where it would be ... I'm 'fraid you'll have to elaborate on this last. And, what is "C" in .1C? Sorry. C is the current rating of the battery in ampere-hours. A typical NiCd pack, full of AA cells will have a rating of about 750 ma-hr. NiMH would be around 1200 to 2200 ma-hr. The maximum charge current of the charger should be about 0.1 times this value (i.e. 10%) or 75ma for the NiCd pack. Thanks. Of course, make sure you don't have a shorted battery pack. So I gotta crack the battery pack open. And test each cell individually? How? You don't need to destroy the battery pack in order to test it. Good! :-) First, just measure the terminal voltage of the battery pack after it's been sitting around for a day without being charged. Even if totally discharged, it should have at least 1.1 volts per cell or about 7.7VDC across the terminals. A fully charged NiCd will have about 1.45VDC per cell or about 10.2VDC across the terminals. I measure just under 4vdc for the pack. Your opinion is solicited. Now, if you really want to test you battery packs, I have a West Mtn Radio CBA-IIv1: http://www.westmountainradio.com/product_info.php?products_id=cba3 Only $150-300. Lordy mercy! I rambled thru my WW box again and found the following: ATLINKS USA Telephone power supply Input: AC120V 60hz 4.4w Output: DC 9v 200 mA Class 2 transformer UL etc but when I measure, I get about 20vdc from my meter. Any idea why the drastic difference from spec? Thx, P "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule." |
#19
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Wall Warts
Jeff Liebermann wrote in
: On Thu, 26 May 2011 12:51:48 -0500, Puddin' Man wrote: The + side measures 3 ohms. Ok. There may be a diode inside the base. Try reversing the leads on the ohms-guesser and see if it acts like a diode. Measures infinite ohms when reversed. It's a diode, with no series resistor. That presents a problem. Without some form of current limiting, the voltage of the xformer will need to be VERY carefully controlled to keep from overcharging the battery. I will swear there's a resistor or charge controller somewhere in the system, but I can't tell where from here. the internal impedance of the transformer itself may be the current limiter. That's the way it was in a B&D VersaPack NiCd charger I have. I'm 'fraid you'll have to elaborate on this last. And, what is "C" in .1C? Sorry. C is the current rating of the battery in ampere-hours. A typical NiCd pack, full of AA cells will have a rating of about 750 ma-hr. NiMH would be around 1200 to 2200 ma-hr. Just a FYI,I have some Everready NiMH AA cells rated at 2350 mAH(bought at Wal-Mart),and saw some no-name 2800 mAH AA cells for sale on Ebay. -- Jim Yanik jyanik at localnet dot com |
#20
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Wall Warts
On Fri, 27 May 2011 22:10:49 -0500, Puddin' Man
wrote: First, just measure the terminal voltage of the battery pack after it's been sitting around for a day without being charged. Even if totally discharged, it should have at least 1.1 volts per cell or about 7.7VDC across the terminals. A fully charged NiCd will have about 1.45VDC per cell or about 10.2VDC across the terminals. I measure just under 4vdc for the pack. Your opinion is solicited. Your battery pack is dead, kaput, eWaste, gone, shorted, etc. That's what probably killed the wall wart and inspired the recall. Charging a shorted cell is a great way to overheat an unprotected transformer. If you simply replace the transformer, you're likely to fry it again. Now, if you really want to test you battery packs, I have a West Mtn Radio CBA-IIv1: http://www.westmountainradio.com/product_info.php?products_id=cba3 Only $150-300. Lordy mercy! The requisite computer is not included in the price. I use it to characterize Li-Ion mutations for model airplanes, robotics, cell phones, and general havoc. The energy available is basically the area under the discharge curve. ATLINKS USA Telephone power supply Input: AC120V 60hz 4.4w Output: DC 9v 200 mA Class 2 transformer UL etc but when I measure, I get about 20vdc from my meter. Any idea why the drastic difference from spec? Sure. You're measuring the voltage without a load. If you load the xformer with a 200ma load: R = 9V / 0.2A = 45 ohms (47 ohms is close enough) and Power = E*I = 9v * 0.2A = 1.8 Watts (so use 5 watt resistor) you should get around 9V DC. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#21
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Wall Warts
On Sat, 28 May 2011 15:38:14 -0500, Jim Yanik
wrote: Jeff Liebermann wrote in : Sorry. C is the current rating of the battery in ampere-hours. A typical NiCd pack, full of AA cells will have a rating of about 750 ma-hr. NiMH would be around 1200 to 2200 ma-hr. Just a FYI,I have some Everready NiMH AA cells rated at 2350 mAH(bought at Wal-Mart),and saw some no-name 2800 mAH AA cells for sale on Ebay. Amazing. I've run tests on some 2200 ma-hr NiMH AA cells using my CBA-II http://www.westmountainradio.com/product_info.php?products_id=cba3 The results are not very impressive. If I discharge at rediculously low rates, such as 0.01C, I might be able to squeeze 2200 ma-hr out of a cell. I tested one at about twice the estimated self discharge rate, and calculated about 5000 ma-hr out of the cell. I think it took about a week to finish the test. However, when I ran it at a more realistic load of 2C, I was barely able to squeeze out 1000 ma-hr. This was also for a brand new cell, as repeated charge/discharge cycles would also decrease the cell capacity. See the discharge curves at: http://4gdo.com/batfaq.htm#Question%20#4: Note how the area under the curve decreases with increasing load. I keep planning to post some test results, but never seem to have the time to organize anything. Sorry(tm). -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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Wall Warts
Jeff Liebermann wrote:
This was also for a brand new cell, as repeated charge/discharge cycles would also decrease the cell capacity. Funny, I've always read the opposite with Nimh cells, they need to go through several charge/discharge cycles before they reach full capacity. This is especially true of the long discharge ones, which come "pre-charged" at about 80% and then at least in my experience take 5-10 cycles to come up to a useable capacity. It also seems in my experience that the lower the charge rate, the more cycles a cell needs. BTW, if you have any info on charging an Azden HT, please let me know. Thanks, Geoff. -- Geoffrey S. Mendelson N3OWJ/4X1GM Making your enemy reliant on software you support is the best revenge. |
#23
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Wall Warts
"Geoffrey S. Mendelson" wrote in message
... Jeff Liebermann wrote: This was also for a brand new cell, as repeated charge/discharge cycles would also decrease the cell capacity. Funny, I've always read the opposite with NiMH cells. They need to go through several charge/discharge cycles before they reach full capacity. This has always been the "conventional wisdom" about nicads, as well. I wish I knew what the "truth" about rechargeables was. Contrary to the common belief, I've never had problems with rapid self-discharge with NiMHs. |
#24
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Wall Warts
On Sun, 29 May 2011 14:59:03 +0000 (UTC), "Geoffrey S. Mendelson"
wrote: Jeff Liebermann wrote: This was also for a brand new cell, as repeated charge/discharge cycles would also decrease the cell capacity. Funny, I've always read the opposite with Nimh cells, they need to go through several charge/discharge cycles before they reach full capacity. I've never seen that. Nothing similar found with Google or on my favorite sites: http://en.wikipedia.org/wiki/Nickel-metal_hydride_battery http://batteryuniversity.com http://batteryuniversity.com/learn/article/Nickel_based_batteries Where I have seen something like this is with cheap Chinese laptop battery packs. The problem is not the battery. It's the charge controller inside the battery. It has to be run up and down in voltage and "trained" before it knows how the pack is going to act. This is usually done at the factory by reputable battery pack manufacturers, but seems to be avoided by others. I've personally only seen this with Li-Ion battery packs, but am told that it's also a problem with older chemistries. This is especially true of the long discharge ones, which come "pre-charged" at about 80% and then at least in my experience take 5-10 cycles to come up to a useable capacity. It also seems in my experience that the lower the charge rate, the more cycles a cell needs. That's probably because NiMH has a rather high self-discharge rate. They may have been at 100% when they left the factory, but have self-discharged in the box. Also, the ideal storage charge level is about 40% for NiMH. None of the NiMH batteries I've tested (Duracell, Rayovac, Sanyo, Energizer, various no-name, and various OEM) have showed anything other than a slow loss of capacity (area under the curve) for repeated charge/discharge cycles. BTW, if you have any info on charging an Azden HT, please let me know. No experience. This might help if it uses NiMH: http://batteryuniversity.com/learn/article/charging_nickel_metal_hydride Note that most of my experiments have been on single cells, not battery packs. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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Wall Warts
On Sat, 28 May 2011 15:38:14 -0500, Jim Yanik
wrote: Just a FYI,I have some Everready NiMH AA cells rated at 2350 mAH(bought at Wal-Mart),and saw some no-name 2800 mAH AA cells for sale on Ebay. Argh. I haven't been paying attention. Duracell 2650 2650 ma-hr Energizer e2 2500 ma-hr Maha Powerex AA 2700 ma-hr Maybe I'll do some shopping and testing (timer permitting). -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#26
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Wall Warts
On Sun, 29 May 2011 07:46:08 -0700, Jeff Liebermann
wrote: Amazing. I've run tests on some 2200 ma-hr NiMH AA cells using my CBA-II http://www.westmountainradio.com/product_info.php?products_id=cba3 Here's some result from the RC groups on NiMH packs. http://www.rcgroups.com/forums/attachment.php?attachmentid=642246 At 0.5A discharge rate, various manufacturers yielded 1700 to 2000 ma-hr. At 0.25A, this Sanyo battery pack managed to squeeze out 1275 ma-hr: http://www.rcgroups.com/forums/attachment.php?attachmentid=2330249 More of the same for 1900 ma-hr: http://www.rcgroups.com/forums/attachment.php?attachmentid=2328003 This is somewhat better than what I was getting. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#27
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Wall Warts
Many thanks.
S'long, P On Sun, 29 May 2011 07:29:38 -0700, Jeff Liebermann wrote: On Fri, 27 May 2011 22:10:49 -0500, Puddin' Man wrote: First, just measure the terminal voltage of the battery pack after it's been sitting around for a day without being charged. Even if totally discharged, it should have at least 1.1 volts per cell or about 7.7VDC across the terminals. A fully charged NiCd will have about 1.45VDC per cell or about 10.2VDC across the terminals. I measure just under 4vdc for the pack. Your opinion is solicited. Your battery pack is dead, kaput, eWaste, gone, shorted, etc. That's what probably killed the wall wart and inspired the recall. Charging a shorted cell is a great way to overheat an unprotected transformer. If you simply replace the transformer, you're likely to fry it again. Now, if you really want to test you battery packs, I have a West Mtn Radio CBA-IIv1: http://www.westmountainradio.com/product_info.php?products_id=cba3 Only $150-300. Lordy mercy! The requisite computer is not included in the price. I use it to characterize Li-Ion mutations for model airplanes, robotics, cell phones, and general havoc. The energy available is basically the area under the discharge curve. ATLINKS USA Telephone power supply Input: AC120V 60hz 4.4w Output: DC 9v 200 mA Class 2 transformer UL etc but when I measure, I get about 20vdc from my meter. Any idea why the drastic difference from spec? Sure. You're measuring the voltage without a load. If you load the xformer with a 200ma load: R = 9V / 0.2A = 45 ohms (47 ohms is close enough) and Power = E*I = 9v * 0.2A = 1.8 Watts (so use 5 watt resistor) you should get around 9V DC. "Law Without Equity Is No Law At All. It Is A Form Of Jungle Rule." |
#28
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Wall Warts
In article ,
Jeff Liebermann wrote: Amazing. I've run tests on some 2200 ma-hr NiMH AA cells using my CBA-II http://www.westmountainradio.com/product_info.php?products_id=cba3 The results are not very impressive. If I discharge at rediculously low rates, such as 0.01C, I might be able to squeeze 2200 ma-hr out of a cell. I tested one at about twice the estimated self discharge rate, and calculated about 5000 ma-hr out of the cell. I think it took about a week to finish the test. However, when I ran it at a more realistic load of 2C, I was barely able to squeeze out 1000 ma-hr. Most NiMH/NiCd battery manufacturers seem to rate their cells at a discharge rate of 0.05C (20 hour rate) - that would be around 100 mA for those AA cells. Sanyo's charts for their "Eneloop" show about a 10% reduction in useful capacity at a discharge rate of 0.5C (1000 mA). If you're actually pulling over 4 amps from them (2C discharge rate) I'd expect a significant further loss of capacity. For comparison, the same Sanyo charts seem to show that an alkaline battery loses about 75% of its useful capacity when you go from 100 mA rates to 1000 mA rates. I gather that the loss of useful capacity is due in part to the series resistance of the battery, and in part due to inefficiencies in the chemistry under high rates of discharge. This was also for a brand new cell, as repeated charge/discharge cycles would also decrease the cell capacity. Had these cells been "formed" properly prior to your test (via several slow-charge / slow-discharge cycles)? There seems to be a general agreement that NiMH cells don't achieve their maximum storage capacity unless they've gone through several cycles like this, and that many manufacturers don't take the time to do this during the manufacturing process. I've seen some indication of this in my own testing (using a smart-charger which can cycle the batteries and report the capacities for each cycle). -- 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! |
#29
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Wall Warts
Argh. I haven't been paying attention.
Duracell 2650 2650 ma-hr Energizer e2 2500 ma-hr Maha Powerex AA 2700 ma-hr Maybe I'll do some shopping and testing (timer permitting). There seems to be a real tradeoff. In general, the very-high- capacity NiMH cells seem to have a more rapid rate of self-discharge; they're good for "use immediately after charge" applications, but not so good for "charge and store" standby uses. The low-self-discharge cells (e.g. Sanyo Eneloop, PowerEx Imedion, and similar) seem to run around 10% lower in rated capacity. For comparison, the Maha Powerex AA are rated at 2700 mAh, while the Maha Powerex "Imedion" AA are rated at 2400 mAh. I've read that this is due to difference the structure/alloy of the metal hydride used for the electrodes... varities which can bind more hydrogen, also tend to suffer from more spontaneous de-binding and leakage (or so my crude understanding goes... I probably have the details wrong). I've had reasonably good results with the Imedion and Eleloop types for my radio go-kit... I can charge them up after use, and depend on finding plenty of power available even six months later. Never could do that with standard NiMH types, when I tried a few years ago... I couldn't trust them to be useful even 3 months after charging. -- 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! |
#30
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"Dave Platt" wrote in message
... Had these cells been "formed" properly prior to your test (via several slow-charge / slow-discharge cycles)? There seems to be a general agreement that NiMH cells don't achieve their maximum storage capacity unless they've gone through several cycles like this, and that many manufacturers don't take the time to do this during the manufacturing process. Why should they, when it would add to the cells' cost? Given the relatively low price of uP-controlleed chargers, there's no point. |
#31
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Wall Warts
"Dave Platt" wrote in message
... There seems to be a real tradeoff. In general, the very-high- capacity NiMH cells seem to have a more rapid rate of self-discharge; they're good for "use immediately after charge" applications, but not so good for "charge and store" standby uses. That hasn't been my experience. My 2200mAh and 2700mAh MAHAs hold up very well -- months, in fact. I've never made a study of the actual capacity, but they /do not/ "fall flat" shortly after being put into use. |
#33
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Wall Warts
On Mon, 30 May 2011 11:35:45 -0700, (Dave Platt)
wrote: Argh. I haven't been paying attention. Duracell 2650 2650 ma-hr Energizer e2 2500 ma-hr Maha Powerex AA 2700 ma-hr Maybe I'll do some shopping and testing (timer permitting). There seems to be a real tradeoff. In general, the very-high- capacity NiMH cells seem to have a more rapid rate of self-discharge; they're good for "use immediately after charge" applications, but not so good for "charge and store" standby uses. The low-self-discharge cells (e.g. Sanyo Eneloop, PowerEx Imedion, and similar) seem to run around 10% lower in rated capacity. Sanyo Eneloop. http://www.eneloop.info/home/performance-details/capacity.html http://www.costco.com/Browse/Product.aspx?Prodid=11504514 http://www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/HR-3UTGA_data_sheet.pdf http://www.rcgroups.com/forums/showthread.php?t=630534 LSD doesn't have lower capacity. It's roughly the same as other NiMH. LSD NiMH batteries have a higher terminal voltage. The energy capacity is the area under the discharge curve, which is close to identical for types with the same chemistry. However, the higher terminal voltage will cause the curve to drop earlier for the LSD NiMH, so they appear to not last as long. Lots of vendors of LSD batteries: http://en.wikipedia.org/wiki/Low_self-discharge_NiMH_battery I've read that this is due to difference the structure/alloy of the metal hydride used for the electrodes... varities which can bind more hydrogen, also tend to suffer from more spontaneous de-binding and leakage (or so my crude understanding goes... I probably have the details wrong). Dunno. I've read some on battery chemistry, but have generally ignored NiMH as a marginal idea. Sorry(tm). I've had reasonably good results with the Imedion and Eleloop types for my radio go-kit... I can charge them up after use, and depend on finding plenty of power available even six months later. Never could do that with standard NiMH types, when I tried a few years ago... I couldn't trust them to be useful even 3 months after charging. Are you running an electric airplane, using the battery pack to run a glow plug, igniting a squib, or running telemetry electronics? All would benefit from a switch to Li-Ion. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#34
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Wall Warts
On Mon, 30 May 2011 12:02:45 -0700, "William Sommerwerck"
wrote: "Dave Platt" wrote in message ... There seems to be a real tradeoff. In general, the very-high- capacity NiMH cells seem to have a more rapid rate of self-discharge; they're good for "use immediately after charge" applications, but not so good for "charge and store" standby uses. That hasn't been my experience. My 2200mAh and 2700mAh MAHAs hold up very well -- months, in fact. I've never made a study of the actual capacity, but they /do not/ "fall flat" shortly after being put into use. The reason I bought a CBA-II battery tester was because of my inability to properly guess actual battery capacity. Most of my experience with NiMH batteries was with Metricom radios and various Motorola and Kenwood handheld radios. It doesn't take much to kill them. For example, you don't even need to discharge them to a NiMH battery pack. The country distributed Motorola MTS2000 radios to all the hospitals as part of the HEARNET (Hospital Emergency Administrative Radio Network) system. The radios were permanently planted in charger with power on 24x7. Some radios were turned on, but most were left off. There would be a short test roughly twice per month. After about a years, not one of the radios were functional because all the NiMH batteries were dead. I'm having a similar experience in my palatial office, where I use a Motorola HT600 and several NTN7016A NiMH battery packs. Unlike the hospital example, I make it a point of not leaving the battery in the charger after it reaches full charge. I also use the radio in a normal manner, charging the battery only when the xmitter craps out. The result is that I charge the battery approximately 3 times per week. Despite this care, I manage to kill about one battery every 2 years (that's after only about 150 charge cycles). I also use NiMH batteries in my various cameras (Canon S5IS etc) all of which use AA cells. I'm seeing the typical 1%/day self-discharge rate. I keep two sets of batteries in the bag. It's not unusual for me to find the spares to be nearly dead after about 2 months. Your NiMH milage may vary, but mine sucks. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#35
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Wall Warts
"Jeff Liebermann" wrote in message
... I also use NiMH batteries in my various cameras (Canon S5IS etc) all of which use AA cells. I'm seeing the typical 1%/day self-discharge rate. I keep two sets of batteries in the bag. It's not unusual for me to find the spares to be nearly dead after about 2 months. Your NiMH milage may vary, but mine sucks. Weird. Which brands do you use? I use mostly MAHA (PowerEx). |
#36
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Wall Warts
In article ,
Jeff Liebermann wrote: Sanyo Eneloop. http://www.eneloop.info/home/performance-details/capacity.html http://www.costco.com/Browse/Product.aspx?Prodid=11504514 http://www.eneloop.info/fileadmin/EDITORS/ENELOOP/DATA_SHEETS/HR-3UTGA_data_sheet.pdf http://www.rcgroups.com/forums/showthread.php?t=630534 LSD doesn't have lower capacity. It's roughly the same as other NiMH. Interesting... one of Sanyo's pages shows different results. See http://www.eneloop.info/home/perform.../capacity.html They compare alkaline, Sanyo Eneloop, and the Sanyo "high capacity" NiMH cells. The latter have a definite advantage in capacity, and the terminal voltages under load look almost identical in the "100 mA discharge" graph. LSD NiMH batteries have a higher terminal voltage. The energy capacity is the area under the discharge curve, which is close to identical for types with the same chemistry. However, the higher terminal voltage will cause the curve to drop earlier for the LSD NiMH, so they appear to not last as long. Hmmm... the graphs on the page cited above seem to suggest differently... what do you think? Are you running an electric airplane, using the battery pack to run a glow plug, igniting a squib, or running telemetry electronics? All would benefit from a switch to Li-Ion. Nope... typical ham-radio handheld radio use (about 80% receive, 20% transmit). I do have several such radios which run on LiIon batteries. My preferred "field assignment" radio is still a NiCd/NiMH type... with the auxiliary six-AA-cell battery pack, and a bunch of charged Imedions and some alkaline AA cells as last-ditch backup, I could be deployed for a couple of days before I'd be in immediate need of a recharge. -- 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! |
#37
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Jeff Liebermann wrote in
: On Mon, 30 May 2011 12:02:45 -0700, "William Sommerwerck" wrote: "Dave Platt" wrote in message ... There seems to be a real tradeoff. In general, the very-high- capacity NiMH cells seem to have a more rapid rate of self-discharge; they're good for "use immediately after charge" applications, but not so good for "charge and store" standby uses. That hasn't been my experience. My 2200mAh and 2700mAh MAHAs hold up very well -- months, in fact. I've never made a study of the actual capacity, but they /do not/ "fall flat" shortly after being put into use. The reason I bought a CBA-II battery tester was because of my inability to properly guess actual battery capacity. Most of my experience with NiMH batteries was with Metricom radios and various Motorola and Kenwood handheld radios. It doesn't take much to kill them. For example, you don't even need to discharge them to a NiMH battery pack. The country distributed Motorola MTS2000 radios to all the hospitals as part of the HEARNET (Hospital Emergency Administrative Radio Network) system. The radios were permanently planted in charger with power on 24x7. Some radios were turned on, but most were left off. There would be a short test roughly twice per month. After about a years, not one of the radios were functional because all the NiMH batteries were dead. I'm having a similar experience in my palatial office, where I use a Motorola HT600 and several NTN7016A NiMH battery packs. Unlike the hospital example, I make it a point of not leaving the battery in the charger after it reaches full charge. I also use the radio in a normal manner, charging the battery only when the xmitter craps out. The result is that I charge the battery approximately 3 times per week. Despite this care, I manage to kill about one battery every 2 years (that's after only about 150 charge cycles). I also use NiMH batteries in my various cameras (Canon S5IS etc) all of which use AA cells. I'm seeing the typical 1%/day self-discharge rate. I keep two sets of batteries in the bag. It's not unusual for me to find the spares to be nearly dead after about 2 months. Your NiMH milage may vary, but mine sucks. The Everready 2350 mAH cells I've been using for my bicycle LED headlight(2 watts draw,homemade) have been very good in regards to low self- discharge,much better than I was led to expect. I also have some "pre-charged" Ray-O-Vac NiMH marked at 2100 mAH that are advertised as holding their charge much longer. -- Jim Yanik jyanik at localnet dot com |
#38
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Wall Warts
On Mon, 30 May 2011 15:14:17 -0700, "William Sommerwerck"
wrote: "Jeff Liebermann" wrote in message .. . I also use NiMH batteries in my various cameras (Canon S5IS etc) all of which use AA cells. I'm seeing the typical 1%/day self-discharge rate. I keep two sets of batteries in the bag. It's not unusual for me to find the spares to be nearly dead after about 2 months. Your NiMH milage may vary, but mine sucks. Weird. Which brands do you use? I use mostly MAHA (PowerEx). Yeah, I know I'm weird. I use a random assortment of whatever I blunder across. Costco has Sanyo Eneloop, so I have a pile of those. I just found several 4 packs of Energizer 2300ma-hr NiMH cells, so I guess I'll use those. I have no idea what's in the camera or in the bottom of the bag, but I'll guess is some no-name brand I picked up at a ham radio flea market. I just found some Duracel 2050ma-hr cells. Oh swell, a pair of Lenmar NoMem Pro 1500 ma-hr cells in my emergency bag. Nice mess (and proud of it). I've been running some battery tests on the new batteries for the last 4 hrs to see if I can find any "conditioning" effects. Stay tunes. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#39
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On Sat, 28 May 2011 15:38:14 -0500, Jim Yanik wrote:
Jeff Liebermann wrote in : On Thu, 26 May 2011 12:51:48 -0500, Puddin' Man wrote: The + side measures 3 ohms. Ok. There may be a diode inside the base. Try reversing the leads on the ohms-guesser and see if it acts like a diode. Measures infinite ohms when reversed. It's a diode, with no series resistor. That presents a problem. Without some form of current limiting, the voltage of the xformer will need to be VERY carefully controlled to keep from overcharging the battery. I will swear there's a resistor or charge controller somewhere in the system, but I can't tell where from here. the internal impedance of the transformer itself may be the current limiter. That's the way it was in a B&D VersaPack NiCd charger I have. I'm 'fraid you'll have to elaborate on this last. And, what is "C" in .1C? Sorry. C is the current rating of the battery in ampere-hours. A typical NiCd pack, full of AA cells will have a rating of about 750 ma-hr. NiMH would be around 1200 to 2200 ma-hr. Just a FYI,I have some Everready NiMH AA cells rated at 2350 mAH(bought at Wal-Mart),and saw some no-name 2800 mAH AA cells for sale on Ebay. I see stuff like that as well. Though i am starting to wonder if it is just printing higher and higher numbers for the capacity without any difference in the cells themselves. |
#40
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josephkk wrote:
I see stuff like that as well. Though i am starting to wonder if it is just printing higher and higher numbers for the capacity without any difference in the cells themselves. All I can say is that I have several AA battery cases for ham radios. The ICOM ones take all AA batteries that I have every put in them, the one off brand one I have that was made in the 1980's won't. It will take AA alkeline batteries and up to 1600mah Nimh batteries, but not the 2500 ones. They really are wider. :-( Geoff. -- Geoffrey S. Mendelson N3OWJ/4X1GM Making your enemy reliant on software you support is the best revenge. |
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