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!

"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

,
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?

I have a laptop that I left connected to the charger all the time, and after
about a year the battery capacity dropped to about 2 minutes run time. I
think it has the lithium ion battery. I would have thought that with a $160
battery they would have designed a charger with a tiny trickle, but maybe
not.

"Ed Price" wrote in
news:0CxAc.24993$0z6.18587@fed1read07:


I wonder if NiMH chemistry shows the same effect?

Ed
wb6wsn



Nope. Why anyone would STILL be using NiCd batteries remains a mystery to
me. Even my Garmin VHF HT has 2300 mAH NiMH batteries in it. They'll run
it a whole weekend, now, instead of the 5 hours it would run on the Garmin
cheapy NiCd crap that came with it. I'm using the same drop-in charger
with the 12V charging cord (has a regulator or resistor bauble that has a
green LED and gets warm while it's in the charger. Takes 2 days to recover
these monsters, the biggest NiMH 'AA' cells I could find.

I used to carry around alkaline battery-loaded Garmin packs for when the
rechargeable went dead. No longer an issue, now.

I dumped the batteries in my old Eagle GPS, too. It's running on 4 of the
NiMH 2300 mAH monsters. The battery meter shows about 2/3 of full voltage
because they are only 1.2V cells in a GPS made for alkalines. But, alas,
it reads 2/3 of full voltage for DAYS, not hours, now...(c;

NiCd batteries are always provided because they are DIRT CHEAP....It's
always about the profits.

Larry

They may have done the other BAD thing --- over-discharging.
When you run an NiCD pack DEAD flat, the weakest cell gets
reverse polarized, and that's death to that cell. One dead
cell means the pack is kaput.

--
Chuck Tribolet

http://www.almaden.ibm.com/cs/people/triblet

Silicon Valley: STILL the best day job in the world.


"Ed Price" wrote in message news:0CxAc.24993$0z6.18587@fed1read07...

"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

No, the research was done using single cells, not multi-cell packs. And they
didn't discharge them to "flat", but rather stopped at something like 5%
capacity. They wanted a "deep" cycle, but not a deadly cycle.

Ed
wb6wsn



"Chuck Tribolet" wrote in message
...
They may have done the other BAD thing --- over-discharging.
When you run an NiCD pack DEAD flat, the weakest cell gets
reverse polarized, and that's death to that cell. One dead
cell means the pack is kaput.

--
Chuck Tribolet

http://www.almaden.ibm.com/cs/people/triblet

Silicon Valley: STILL the best day job in the world.


"Ed Price" wrote in message
news:0CxAc.24993$0z6.18587@fed1read07...

"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