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
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.
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
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.
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.
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.
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.
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.
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.
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
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.
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
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.
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?
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?
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.
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.
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
Are you saying that I was lying about the 340 micro amp trickle
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