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#1
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NiCAD Memory Effect
Hi all,
I've seen quite a few posts on this subject, and would like to add my $.02. About 10 years ago, I was involved in the design of a telemetry device that used NiCADs for backup (up to 23 hrs.). I was deeply concerned about the charge/discharge of these, so my boss, who was an ex-VP for GE, tracked down the NiCAD guru at Gates. When asked about "memory", this guru stated, unequivocally, that the "memory" effect was somewhat of an urban legend, promulgated by the difficulties NiCADs presented when initially developed somewhere around WW2. Modern battery manufacturing designs and techniques in the last few decades or so have totally eliminated the "memory" effect Last I checked, one of these telemetry devices was still running OK, even though it was installed over 8 years ago. Granted, I have no idea if it's **ever** actually used it's battery backup, but I have to assume that sometime in it's life it has been unplugged for at least a little while. No troll, no flame wars please. I'm just passing on some info. SS |
#2
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NiCAD Memory Effect
Well, here is an item that reinforces the myth: My 18V NiCad drill came
with a charger that has a "Battery Conditioning" button. The instructions say that every 6 to 8 recharges I should press the button to restore the original capacity of the battery pack. My top of the line MaHa NiMh/NiCD charger has a similar button with the same instructions. The MaHa/Powerex instructions go on to say that new NiMH batteries must go through 4 or 5 complete drain cycles before they will store their full capacity and that I could do that by pressing the "condition" button. The charger would then drain the batteries before starting the charge. Sure sounds like a cure for "memory loss" to me. Sir Spamalot wrote: Hi all, I've seen quite a few posts on this subject, and would like to add my $.02. About 10 years ago, I was involved in the design of a telemetry device that used NiCADs for backup (up to 23 hrs.). I was deeply concerned about the charge/discharge of these, so my boss, who was an ex-VP for GE, tracked down the NiCAD guru at Gates. When asked about "memory", this guru stated, unequivocally, that the "memory" effect was somewhat of an urban legend, promulgated by the difficulties NiCADs presented when initially developed somewhere around WW2. Modern battery manufacturing designs and techniques in the last few decades or so have totally eliminated the "memory" effect Last I checked, one of these telemetry devices was still running OK, even though it was installed over 8 years ago. Granted, I have no idea if it's **ever** actually used it's battery backup, but I have to assume that sometime in it's life it has been unplugged for at least a little while. No troll, no flame wars please. I'm just passing on some info. SS -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
#3
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NiCAD Memory Effect
I bought a camcorder several years ago. I asked about the memory
effect of the NiCd batteries. The salesperson said that the memory affect is a myth. During the time I owned the camera I always put it on charge after using it. Never noticed any loss of capacity. Maybe it is just certain brands or types of NiCds. Doug s/v Callista "Glenn Ashmore" wrote in message news:wE7Ac.906$4n.607@lakeread04... Well, here is an item that reinforces the myth: My 18V NiCad drill came with a charger that has a "Battery Conditioning" button. The instructions say that every 6 to 8 recharges I should press the button to restore the original capacity of the battery pack. My top of the line MaHa NiMh/NiCD charger has a similar button with the same instructions. The MaHa/Powerex instructions go on to say that new NiMH batteries must go through 4 or 5 complete drain cycles before they will store their full capacity and that I could do that by pressing the "condition" button. The charger would then drain the batteries before starting the charge. Sure sounds like a cure for "memory loss" to me. Sir Spamalot wrote: Hi all, I've seen quite a few posts on this subject, and would like to add my $.02. About 10 years ago, I was involved in the design of a telemetry device that used NiCADs for backup (up to 23 hrs.). I was deeply concerned about the charge/discharge of these, so my boss, who was an ex-VP for GE, tracked down the NiCAD guru at Gates. When asked about "memory", this guru stated, unequivocally, that the "memory" effect was somewhat of an urban legend, promulgated by the difficulties NiCADs presented when initially developed somewhere around WW2. Modern battery manufacturing designs and techniques in the last few decades or so have totally eliminated the "memory" effect Last I checked, one of these telemetry devices was still running OK, even though it was installed over 8 years ago. Granted, I have no idea if it's **ever** actually used it's battery backup, but I have to assume that sometime in it's life it has been unplugged for at least a little while. No troll, no flame wars please. I'm just passing on some info. SS -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
#4
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NiCAD Memory Effect
OK, so there's no memory effect. But, why do I have to regularly change out
the rechargeable batteries of my cordless phones, dustbuster, laptop, electric toothbrush, flashlight, ect.? 1,000 recharge cycles? ........rubbish! |
#5
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NiCAD Memory Effect
Because you leave them on simple trickle chargers long term, which causes little
whisker crystals called dendrites to form inside the battery and short it out internally. I get a heck of a lot of recharge cycles out my rechargeables. I use smart chargers that just about shutdown (go way below "trickle") when the battery is charged. -- Chuck Tribolet http://www.almaden.ibm.com/cs/people/triblet Silicon Valley: STILL the best day job in the world. "Floyd I Johnson" wrote in message . .. OK, so there's no memory effect. But, why do I have to regularly change out the rechargeable batteries of my cordless phones, dustbuster, laptop, electric toothbrush, flashlight, ect.? 1,000 recharge cycles? ........rubbish! |
#6
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NiCAD Memory Effect
"Chuck Tribolet" wrote in message ... Because you leave them on simple trickle chargers long term, which causes little whisker crystals called dendrites to form inside the battery and short it out internally. I get a heck of a lot of recharge cycles out my rechargeables. I use smart chargers that just about shutdown (go way below "trickle") when the battery is charged. -- Chuck Tribolet I believe that, as the crystalline area grows, it obscures the usable plate area, which is what causes the "memory" effect. I read some recent research (which I now can't find) where new cells were put through a careful charge and then a deep discharge cycle. Then, the cells were deliberately overcharged. Instant loss of capacity; the "memory" effect instantly duplicated. OTOH, another group of new cells were put through many shallow discharge cycles, with careful recharging. Result, no memory effect. Then, with one overcharge cycle, the memory effect was now there. Seems to confirm the concept of "memory", it's just that the culprit is the charge profile, not the discharge portion. And that means that dumb "trickle" chargers are really cell killers; we need to use smart chargers exclusively. I wonder if NiMH chemistry shows the same effect? Ed wb6wsn |
#7
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NiCAD Memory Effect
On Thu, 17 Jun 2004 16:44:50 GMT, "Floyd I Johnson"
wrote: OK, so there's no memory effect. But, why do I have to regularly change out the rechargeable batteries of my cordless phones, dustbuster, laptop, electric toothbrush, flashlight, ect.? 1,000 recharge cycles? ........rubbish! Because the chargers supplied with the consumer grade equipment is improperly charging the batteries from the get-go. If they are charged **correctly**, and discharged **correctly**, no memory. And Larry is also right; the consumer buys into the "rechargable" aspect without verifying if the battery is being charged correctly in the first place. For consumer equipment, I've noticed that overdischarging, which is a major cause of failure for any rechargable battery, is ignored. Does your dustbuster have an overdischarge shutoff? I bet not. SS |
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