NiCd vs. NiMh

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If left hooked up permanently as most people do then yes, any charger can harm the battery.

Slow charging a battery until it's charged is preferred over a fast charging a battery until it's charged. The heat generated by fast charging degrades the battery over time when compared to slow charging.
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vs: if it's hooked up to a charger and left for days, but only turned on and off for eight hours a day?
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wrote:

At maximum( it will be much, much less) 2/10ths of a watt of heat can be generated. A battery hooked to this for two hours can easily dissipate any heat or withstand any other devastation that such a puny charge system can throw at it.
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snipped-for-privacy@mucks.net wrote:

Slow discharged? I meant I've never slow charged NiMH!

I felt that way until 1987, when I got a cordless drill with a C/2 charger. I thought that would be harmful to the cells, so I built a regulator and set it to 1.4V per cell.
In a couple of months, two cells had severe self-discharge and the other three had greatly reduced capacity. During slow charges of nickel cells, salts accumulate on the plates. These salts can both reduce available plate area and serve as conductors for electrical leakage between plates.
Panasonic explains it in their tech manual for their NiMH batteries.
Nowadays there are chargers that will slow charge nickel batteries without causing salt buildup. These chargers use pulses, like the modern chargers designed to be left connected to lead-acid batteries.
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How can Panasonic explain NIMH batteries when your "Nowadays" explanation is talking about lead acid batteries? Please site the info that says NIHM shouldn't be charged on slow chargers that are also on slow timers. For your convenience here is the start page.
http://www.panasonic.com/industrial/battery/oem/chem/nicmet/
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snipped-for-privacy@mucks.net wrote:

Read it again. I said modern chargers for both types of batteries use pulses instead of trickles.
If you had bothered to look at the page you recommend, you would see that Panasonic says overcharging, even with a trickle charge, will damage NiMH batteries.
If you buy a cheap charger, don't even check the current, and run it 2 hours a day, how can you possibly expect not to overcharge? The page you recommend says a maintenance charger must monitor the voltage of the standby battery. When it self-discharges to a certain point, the charger must come on just long enough to charge it.
I didn't buy hybrid or low-self-discharge batteries. I bought the ordinary NiMH cells available 11 years ago, and they still hold a charge for months. I credit the good results to the use of automatic fast chargers designed for NiMH.
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wrote:

Are you trying to skew what I am saying by leaving out a time constraint on charging????
Then suggest trickle charging with a time limit. So do I.

Because the charger is intentionally so weak that it can't harm the battery in two hours no matter what the state of charge.

A maintenance charge higher in current than what I am talking about without a mechanical timer yes, but by using a charger small enough you can simply time it.

If you want to use this type of charger, yes.

Define months. Non hybrids won't hold a full charge this long without some sort of maintenance charge.

So others success stories must be attributed to "automatic fast chargers designed for NiMH"
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snipped-for-privacy@mucks.net wrote:

Panasonic specifically recommends against trickle charging except on top of a fast charge.

Now I remember why I got a fast charger when I got NiMH cells. My NiCd charger would have been .05 lt for the NiMH I bought, and NiMH may not charge at that current. Panasonic's chart shows that except at cool temperatures, they won't charge fully even at .1 lt.

Lunar months are about 29.5 days. Calendar months are 28-31 days.
Panasonic shows that their ordinary NiMH cells may retain a 90% charge after 4 weeks. That could mean 50% after 6 months. Even after 11 years, I expect that of my NiMH cells. Using a manual .1 lt charger, my NiCds wouldn't hold a charge that long unless they were pretty new.
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Again you are skewing the facts again. Panasonic's talk about overcharging with trickle charging is assuming that the charger stays on. Which I do agree with.

Good try. I said define monthS, with an S......When you speak of non hybrid NIMH batteries and you say "and they still hold a charge for months." What charge, and how many months?

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snipped-for-privacy@mucks.net wrote:

It's a fact that Panasonic simply says not to trickle charge.

The only trickle charge they suggest is on top of a fast charge. You seem to say a trickle charge is whatever you happen to get from a cheap charger. Are you calling .1 lt a trickle charge? Panasonic says that's 2 or 3 times bigger than a trickle charge. They recommend a timed .1 lt charge only for standby batteries and they recommend that the charger turn on only when the voltage falls below what they specify.

Since 1980, if I wondered about the condition of my nickel cells, I'd charge each one and use it to power an analog clock while shunted with 2 ohms. That would tell me a cell's capacity. Then I'd try it again after letting a charged cell sit on the shelf a week. That would allow me to calculate self-discharge.
How about you? Have you tested the capacity and self-discharge of cells exposed to current from a cheap charger two hours a day over a period of months or years?
You don't seem to be a reader. I said I expect my old NiMH to hold a charge 6 months. I've been using wireless keyboards 40 months. I've recharged batteries 5 times. That would mean a pair of NiMH 10 years old holds enough charge for a wireless keyboard about 8 months.
I've also done very well with NiCds after going to fast charging. Either type of battery will probably power my 800ma flashlight after several months on the shelf.

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I've been charging Ni-Cads since 1983, NIMH AA's since 1996.
I've used fast chargers, medium chargers, slow chargers, smart fast chargers, smart medium rate chargers, and just plain dumb slow chargers. Then I started using the most inexpensive slow dumb chargers I could find along with the cheapest mechanical timer I could find. That reduced the rate of charge so slow that I could keep the setup plugged into the wall continuously.
I've tossed AA NIMH batteries from fast smart chargers. I have never had any AA NIMH battery go bad from the 8 day charge method.
What I have learned is this. When comparing much more expensive smart chargers to my setup the only advantage to fast or mediums rate smart chargers is time to charge. That's it.
The advantage of my 8 day to charge setup is it's impossible to harm the batteries. I'll always have fully charged batteries on hand. The price of the setup is ridiculously low.
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Two hours a day, every day.
Well, if a smart charger is smart enough to go into trickle charge, and stay there, then just how is it that my trickle charger which trickles considerably less can somehow become dumb and harm the battery?

It actually was/is more useful with batteries that have a high self discharge rate. The batteries are topped off each day.

Again, all this is only pertaining to chargers that charge at a higher rate. Chargers less than C/10 don't apply. Mine is C/15 at absolute max, but in reality is more like C/50 once charged.

I found the mechanical timer at garage sale for 50 cents. The dumb slow chargers were given to me by not so smart people that discarded them when they made what they thought was a smart purchase. The purchase of an expensive smart charger.
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snipped-for-privacy@mucks.net wrote:

Panasonic says a timer should terminate the C/20 - C/30 trickle. I think a top-off trickle is foolish. Sometimes an automatic charger can shut off before a cell is fully charged. So what? If sometimes I have to swap batteries after running a device 9 hours instead of 10, I won't notice. I will notice if I put charged cells on the shelf and they're dead two weeks later because trickle charging has damaged them.

Before I bought my first NiMH, I read that their self-discharge was higher than NiCd. I've been pleasantly surprised.

1973. On a ship's mast, it was a great advantage to be able to solder without an electrical cord. The Wahl unit was intended to be kept in its charger so it would always be charged. In a few weeks, the battery was shorted. At the time, I thought the current was too high for extended charging.
My second experience was with walkie-talkies in 1975. The old ones used several alkalines. The new ones used NiCd battery packs. The walkie-talkies were kept in chargers designed to fast charge and switch to a trickle. Before long, these batteries would short. Back to alkalines.
I started using AA NiCds in 1981. They were supposed to be good for 500 charges. I'd read that the capacity would gradually diminish. Instead, the self-discharge increased while the capacity showed little change. My first set shorted completely within 100 charges.
In 1986, I made a regulated charger for a cordless drill. I thought that would make the cells last longer. They went bad very quickly.
In my experience with AA NiCds, timed charging at C/10 causes cumulative damage that increases self-discharge. In my experience with walkie-talkies and a drill, regulated trickle charging is worse.
For me, automatic fast charging has worked much better. My chargers measure only voltage change, and that's not foolproof. Panasonic says an ideal charger should monitor voltage, temperature, voltage change, temperature change, and time.
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snip

Just for you I measured the trickle charge using my method on AA's that are already charged. 340 micro amps......for two hours a day.
Panasonic says- Panasonic says- Panasonic says- Panasonic says - Panasonic says. Are you a parrot???????? What do you think? Do you really think that a 340 micro amp trickle charge for two hours a day will harm a battery?
snip

Panasonic says- Panasonic says- Panasonic says- Panasonic says
By the way 340 micro amps represents a c/6000 charge rate. Do you still think this is harmful?
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snipped-for-privacy@mucks.net wrote:

I've told you what Panasonic says and what I think from my own experience.
How did you get a plain dumb charger to cut back that far? I've seen it with regulated chargers built in the early 1970s and with one I built in the 1980s. Both ruined batteries pretty quickly. So I understand why Panasonic recommends against trickle charging.

Yes I do.
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snip

It's called electrical theory. Even the dumbest of dumb chargers have to abide by it.
snip

If that is what you think then it's pointless. Do you think near by lightning strikes will harm the battery too?
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snipped-for-privacy@mucks.net wrote:

The dumbest of dumb chargers use rectified sine waves. Without a voltage regulator, the state of charge will have little effect on current.
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Really? The state of charge has a direct effect on the output of the charger. Just what world do you live in?
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snipped-for-privacy@mucks.net wrote:

You're talking about capacitors. If you charged a capacitor with a regulated 1.4V, the current would taper toward nothing at 1.4. With an unregulated charger, current would taper toward nothing at about 2V.
Chemical batteries are different. Voltage-regulated chargers have been used for lead-acid batteries but never worked for nickel batteries. Terminal voltage on NiMH drops when it's fully charged, which means a voltage-regulated or unregulated charger would speed up.
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wrote:

I can't believe how ignorant one can be. Regulated or not, battery or not, when for example a source puts out one volt and a load holds a 1 volt charge just what kind of current will flow from a 1000 amp source?
Are you saying that I was lying about the 340 micro amp trickle charge?
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