NiMH battery compatibility with NiCd chargers

[Wild Bill]

Hi.. I don't have any experience with NiMH batteries, and I never much cared
for the problems associated with NiCd cells, so I'd like to know if using
NiMH will be less problematic than NiCd.

Will NiMH cells charge and last perfectly well in NiCd chargers, or will
NiMH chargers be required for best results?
When I use the term NiCd charger, I mean the more sophisticated commercial
chargers, not just the transformer & diode types.

Ideally, I'd like to find a trouble-free, rechargeable battery (if possible)
for a few applications.
I'd like to avoid any type of battery that will short if it's not being
charged or used.. which always seems to happen with any of the NiCd types
I've had.

Thanks
Cheers
WB

 

[Allodoxaphobia]

Hi.. I don't have any experience with NiMH batteries, and I never much cared
for the problems associated with NiCd cells, so I'd like to know if using
NiMH will be less problematic than NiCd.

Will NiMH cells charge and last perfectly well in NiCd chargers,
No.

... or will NiMH chargers be required for best results?

Yes.
Tho', there are what claim to be NiCad/NiMH combo-chargers. Not many
folks in rec.photo.digital (see below) speak well about them.

When I use the term NiCd charger, I mean the more sophisticated
commercial chargers, not just the transformer & diode types.

Mox-Nix. NiMH have different charging characteristics/curves
than NiCad's. You want to get a "smart" NiMH charger, versus
a "timed" NiMH charger.

Using Google Groups, look back in just the last 6 months or
so for "NiMH". The digital camera folks are *anal* about
battery performance: charging, storage, use, capacity, etc. -- and
they all, in general, swear by NiMH's.
(I say "6 months" because these are all FAQ's that come
up every few days or so. You won't live long enough to
read _all_ of them.

HTH
Jonesy

 

[Andy Cuffe]

Hi.. I don't have any experience with NiMH batteries, and I never much cared
for the problems associated with NiCd cells, so I'd like to know if using
NiMH will be less problematic than NiCd.

Will NiMH cells charge and last perfectly well in NiCd chargers, or will
NiMH chargers be required for best results?
When I use the term NiCd charger, I mean the more sophisticated commercial
chargers, not just the transformer & diode types.

Ideally, I'd like to find a trouble-free, rechargeable battery (if possible)
for a few applications.
I'd like to avoid any type of battery that will short if it's not being
charged or used.. which always seems to happen with any of the NiCd types
I've had.

Thanks
Cheers
WB

For best results, you need a charger designed for Ni-MH, but they seem
to be more tolerant than many people would have you believe. I
rebuilt the Ni-Cd battery pack in my cordless phone using some Ni-MH
cells I had on hand and it still works well after 3 or 4 years of
almost constant charging. I would think you would have more trouble
with a 'smart' Ni-Cd charger than a simple charger because it's hard
to say how the smart charger will handle the wrong type of battery. I
have no seen any shorted Ni-HM cells yet. What I have seen is a very
high self discharge rate in old Ni-MH laptop batteries. It's not
unusual to see a laptop battery that will run for 2 hours when freshly
charged, but if it's left sitting for even a few hours it becomes
mostly discharged.
Andy Cuffe
[email protected]

 

[Wild Bill]

Thanks, since most digital cameras are just about the hardest service for
batteries in consumer gear (maybe second to RC vehicles), they are probably
a major improvement over NiCd, which is what I've been hearing rumors of.

Cheers
WB
.................

 

[Wild Bill]

Thanks for the additional info Andy. While the phone example you mentioned
isn't a highly scientific analysis, it's just the sort of example I was
hoping to see. I'm confident from reading your posts for years, that you're
prone to practical solutions, and don't think too much of half-assed
fixes/solutions.

I've got some handheld test gear that use sub-C cells and they have too
little space to install full-sized C cells (even alkaline would be fine for
them, though). These instruments use the simple rectifier, filter, resistor
components for charging from a wall wart.

I haven't bought much rechargeable stuff like most consumers do because of
the poor characteristic experiences I've had with NiCd cells. I'm sure I
never got enough use out of any NiCds to say that they were worn out..
instead, they just failed before any useful life was gotten from them.

I'm drawn to the extra capacity of NiMh, and hope they can provide a much
better service life for some equipment that will primarily be used in remote
locations.

Cheers
WB
.............

 

[Jeff]

Hi.. I don't have any experience with NiMH batteries, and I never much cared
for the problems associated with NiCd cells, so I'd like to know if using
NiMH will be less problematic than NiCd.

Will NiMH cells charge and last perfectly well in NiCd chargers,

Slow chargers YES, (just extend the charge time to cope with the,
probably, larger capacity of the NiMH cell), fast 'intelligent' chargers
NO.

NiMH cell have different end point voltage characteristics, so
'intelligent'
chargers do not detect full charge correctly, with the possibility of
over-charging.

NiMH cell do not suffer as badly as NiCs's with memory effect and are
generally
higher capacity, the only downside is that their self-discharge rate is
quite high. This means that they must be recharge frequently, and are
not
very good in equipment that is not used very often.

Regards
Jeff

 

[H. Dziardziel]

snip

For best results, you need a charger designed for Ni-MH, but they seem
to be more tolerant than many people would have you believe. I
rebuilt the Ni-Cd battery pack in my cordless phone using some Ni-MH
cells I had on hand and it still works well after 3 or 4 years of
almost constant charging.

Unless you made any modifications to the charging current I
suspect the NiMhs, being about double the original NiCad's
capacity, are gently warming themselves at a continous C/20-C/10
rate.

Good qualty recent manufacture NiMh cells can handle that
overcharge for short periods but nevertheless gradually
deterioate. That may not have been noticed since their
original capacity was about double the NICads.

They will last about 4-5 years in a low load like the phone but
far less with high loads due to their internal resistance buildup
as a result of the continous overcharge. .

For maximum life Nimh must not be overcharged, nor trickle charged
and maintenance charged with care. They also die quickly with
heat yet are exothermic during charging especially so towards the
end of charge. Tricky buggers..

The NiCads are more rugged and handle overcharging better but were
also most likely being slowly cooked at about a C/10-C/5 rate in
the phone. Continous C/20-C/10 is generally fine for them (but
not for NiMh).

 

[H. Dziardziel]

Hi.. I don't have any experience with NiMH batteries, and I never much cared
for the problems associated with NiCd cells, so I'd like to know if using
NiMH will be less problematic than NiCd.

Will NiMH cells charge and last perfectly well in NiCd chargers, or will
NiMH chargers be required for best results?
When I use the term NiCd charger, I mean the more sophisticated commercial
chargers, not just the transformer & diode types.

Ideally, I'd like to find a trouble-free, rechargeable battery (if possible)
for a few applications.
I'd like to avoid any type of battery that will short if it's not being
charged or used.. which always seems to happen with any of the NiCd types
I've had.

Thanks
Cheers
WB

Trickle charging NiCads and not using them after is what causes
them to short out. Continous charging at too high a rate (>C/10
as in many phones etc) ) also causes them to deterioate quickly.
But they do handle sloppy recharging well -- if used soon
after.. They are rugged.

NiCads thrive on regular use and thus can't be beat for high
charge-discharge current applications like power tools.

NiMh should not be trickle charged -- they deterioate. New
quality maker NiMhs only weakness is the somewhat higher self
discharge rate and need for careful charging because they are
exothermic and,perversely, their life, very heat sensitive...
They very rarely short out.

Qualty cells and made for NIMh quality chargers will give
excellent results The key points are keeping them cool during
charge and no overcharging (which heats them up more)..

 

[Peter Duck]

In message <[email protected]>

... NiMH cell do not suffer as badly as NiCs's with memory effect and
are generally higher capacity, the only downside is that their
self-discharge rate is quite high. This means that they must be
recharge frequently, and are not very good in equipment that is not
used very often.

I understand that this 'downside' was true only (mostly?) of early NiMHs.

I've had a mobile phone ('cellphone' to USians) with the same batteries
for three or four years: it's only for occsional/emergency use, i.e.
mostly in glove-compartment or coat-pocket without being switched on for
incoming calls.

The need for recharge (when battery-state reaches a notch or two above
'empty') still only arises two or three times a year ...

That seems to be a common experience, and much better than nicads were (are?).

 

[Eric R Snow]

Hi.. I don't have any experience with NiMH batteries, and I never much cared
for the problems associated with NiCd cells, so I'd like to know if using
NiMH will be less problematic than NiCd.

Will NiMH cells charge and last perfectly well in NiCd chargers, or will
NiMH chargers be required for best results?
When I use the term NiCd charger, I mean the more sophisticated commercial
chargers, not just the transformer & diode types.

Ideally, I'd like to find a trouble-free, rechargeable battery (if possible)
for a few applications.
I'd like to avoid any type of battery that will short if it's not being
charged or used.. which always seems to happen with any of the NiCd types
I've had.

Thanks
Cheers
WB

Greetings Bill,
This must be the day for batteries. When shopping for my first digital
camera last year I did tons of research on-line. The upshot of the
battery question was to use NiMH batteries. For reasons like lasting a
long time between charges, no "memory effect", price, etc.. Powerex
batteries made by Maha got the best overall reviews. Thomas
Distributing sell them and has good package deals on batteries and
chargers. I love being able to recharge batteries when they are not
nearly dead and not having to worry about degrading the battery
performance. I use the 1800 mAh AA size. Last year these were the best
value. These batteries last three times longer in my Pentax digital
camera than Duracell batteries. I have no connection with anybody
selling batteries but I am a great advocate for NiMH rechargables and
Thomas Distributing. The batteries work great and Thomas has great
prices and service.
Cheers,
Eric R Snow,
E T Precision Machine

 

[Engineer]

( snip)

For maximum life Nimh must not be overcharged, nor trickle charged
and maintenance charged with care.

Can you explain why NiMH's do not like being trickle charged?

Tks and cheers,

Roger

 

[Wild Bill]

Thanks for the additional info and your experience with actual usage.

Cheers
WB
...............

 

[Wild Bill]

Thanks, I found this lengthy article about analyzing batteries and includes
info about exercising & reconditioning NiCd and SLA types
http://www.buchmann.ca/chap10-page1.asp

The above site was linked from this site which covers desulfating lead/acid
batteries, and includes circuit examples that can be built
http://www.shaka.com/~kalepa/desulf.htm

Cheers
WB
..................

 

[H. Dziardziel]

( snip)


Can you explain why NiMH's do not like being trickle charged?

NiMH degrade (any cell chemistry does since at the very least
reactants are being used up) when over charged and are more
sensitive than NiCad to that. Some kind of end of charge
mechanism is needed such as the common timer for 1/10C range
charge rates or a delta voltage or temperature sense method for
faster rates.

Timed trickle charging is inaccurate and nearly an oxymoron.
It's very close to maintenance level (compensating self discharge
which is high for NiMh) charging. That makes charge state
unpredictable so not used. On the otherhand continuous trickle
charging overcharges eventually
..
Being so close to maintenance charging levels the sense methods
e.g. the last two, are inaccurate. And anyway if one is using
such methods simple trickle charging is cost incongrous.