Ni-Cd batteries

[orvillefpike]

What is the idea voltage per cell to "slow charge" a Ni-Cd battery. I
know that for a lead-acid battery, it is 2.3 Volts per cell at 25°C.
Ni-Cd "fast chargers" pump in current until the battery gets hot and
then shuts off the current. I think that this is the perfect recipe to
ruin the battery quickly. I know that if you leave a lead-acid battery
connected to a charger that delivers 2.3 Volts per cell, you can leave
it on forever and it won't ruin the battery. That's the way it's done
with alarm system and good quality batteries can last up to 15 years.
I assume it could be the same with Ni-Cd batteries if they where "slow
charge".

Thanks

 

[Charles]

What is the idea voltage per cell to "slow charge" a Ni-Cd battery. I
know that for a lead-acid battery, it is 2.3 Volts per cell at 25°C.
Ni-Cd "fast chargers" pump in current until the battery gets hot and
then shuts off the current. I think that this is the perfect recipe to
ruin the battery quickly. I know that if you leave a lead-acid battery
connected to a charger that delivers 2.3 Volts per cell, you can leave
it on forever and it won't ruin the battery. That's the way it's done
with alarm system and good quality batteries can last up to 15 years.
I assume it could be the same with Ni-Cd batteries if they where "slow
charge".


Constant voltage chargers used to place a stiff voltage across a cell or
battery for charging. Stiff means that the voltage changes little under
load. True, or ideal, constant voltage means no change in voltage
regardless of the load (not attainable in practice).

I said "used to" as these are not popular these days. Now, you find more
constant current current chargers with temperature and voltage sensors to
cut the charge back at an appropriate time.

A constant voltage charger is also called a taper charger as the charging
current tapers off as the cell or battery charges up. The charging current
tapers off with time ... again, not much used these days.

The ideal charger does not exist but the modern units come close. They use
a constant current or a pulsed current and measure temperature and voltage
as they do their thing. The little beasts often have computer chips built
in.

A trickle charger is a very slow (low current) charger, and that might be
what you are interested in?

 

[Jim Yanik]

What is the idea voltage per cell to "slow charge" a Ni-Cd battery. I
know that for a lead-acid battery, it is 2.3 Volts per cell at 25°C.
Ni-Cd "fast chargers" pump in current until the battery gets hot and
then shuts off the current. I think that this is the perfect recipe to
ruin the battery quickly. I know that if you leave a lead-acid battery
connected to a charger that delivers 2.3 Volts per cell, you can leave
it on forever and it won't ruin the battery. That's the way it's done
with alarm system and good quality batteries can last up to 15 years.
I assume it could be the same with Ni-Cd batteries if they where "slow
charge".

Thanks

NiCds get charged by CURRENT,not voltage;for a 1000mAH cell, a slow charge
would be C/10,or 100 ma. NiCds last longer with fast charges,IMO.

 

[Christopher Ott]

What is the idea voltage per cell to "slow charge" a Ni-Cd battery. I
know that for a lead-acid battery, it is 2.3 Volts per cell at 25°C.
Ni-Cd "fast chargers" pump in current until the battery gets hot and
then shuts off the current. I think that this is the perfect recipe to
ruin the battery quickly. I know that if you leave a lead-acid battery
connected to a charger that delivers 2.3 Volts per cell, you can leave
it on forever and it won't ruin the battery. That's the way it's done
with alarm system and good quality batteries can last up to 15 years.
I assume it could be the same with Ni-Cd batteries if they where "slow
charge".

Thanks

--

Panasonic used to have a really good Application Note on battery charger
circuits for various chemistries. I just looked and couldn't find it
anymore. You may want to do some more thorough digging on their website. If
I recall correctly, Ni-Cd batteries were the only ones which would decrease
in temperature (approx 10degrees) while charging, and increase if charged
while full. This made it really easy to detect when the charge was done.
Ni-Cd is very sensitive to over temperature and according to the A.N. heat
was the #1 cause of premature failure. As far as fast charging, it depends
on the Ni-Cd chemistry. Some can be quick charged and some not.

It was actually an interesting read, wish I could find it again...

Chris

 

[Phil Allison]

** Groper Alert !!

What is the ideal voltage per cell to "slow charge" a Ni-Cd battery.

** There is no such thing with Ni-Cd cells.

I know that for a lead-acid battery, it is 2.3 Volts per cell at 25°C.

** Different animal.


Ni-Cd "fast chargers" pump in current until the battery gets hot and
then shuts off the current. I think that this is the perfect recipe to
ruin the battery quickly. I know that if you leave a lead-acid battery
connected to a charger that delivers 2.3 Volts per cell, you can leave
it on forever and it won't ruin the battery. That's the way it's done
with alarm system and good quality batteries can last up to 15 years.
I assume it could be the same with Ni-Cd batteries if they where "slow
charge".


** You assume too much.



........ Phil

 

[John Tserkezis]

** Groper Alert !!

** There is no such thing with Ni-Cd cells.

You know, you could have said that consant-voltage charging is unideal for
NiCds, but of course you HAD to put in a groper in there somewhere...

Ni-Cd "fast chargers" pump in current until the battery gets hot and
then shuts off the current.

In the greater scheme of things, this is relatively rare. Very few use
Delta-t to detect end-of-charge. Shame actually, it's the more reliable and
safe (albeit more expensive and inconvenient) way of doing it.

I think that this is the perfect recipe to ruin the battery quickly.

Shame actually, it's the more reliable and safe way of doing it.

I know that if you leave a lead-acid battery connected to a charger that
delivers 2.3 Volts per cell, you can leave it on forever and it won't
ruin the battery.

Yes, they're pretty much all constant voltage type chargers.

That's the way it's done with alarm system and good quality batteries
can last up to 15 years.

Yes, with Lead/Acid, or SLA, that's pretty much the ONLY way it's done.
With a few exceptions on certain time-critical applications, there are at
least temporary exceptions to the "rule", but for the most part, they're all
constant-voltage chargers.

I assume it could be the same with Ni-Cd batteries if they where "slow
charge".

Sorta kinda, but not really. On the El-Cheapo (TM) NiCd chargers. After
the primary charge cycle, they use a constant voltage source via a current
limiting resistor to feed each cell. (or each cell block if they're really
cheap). The resistor is chosen as a best compromise over the selection of
NiCd sizes that fit in that slot that will overcome natural NiCd discharge and
not overly heat the cell(s) via wasted energy. It is deemed the heating and
overcharging is insignificant to the overall life of the cell/battery.

** You assume too much.

Sheez, he's just asking a question.

 

[Brian MW0GKX]

What is the idea voltage per cell to "slow charge" a Ni-Cd battery.
<snip>

See:

http://homepage.ntlworld.com/denise.wilkinson3/beginner/battery.htm

For battery info.

 

[Eeyore]

What is the idea voltage per cell to "slow charge" a Ni-Cd battery.

You charge nicads with a current controlled supply, not a voltage contolled one.

Graham

 

[Eeyore]

You know, you could have said that consant-voltage charging is unideal for
NiCds,

I believe that 'un-ideal' is something of a understatement.

Graham

 

[Phil Allison]

"Eeysore"

I believe that 'un-ideal' is something of a understatement.

** " Will grossly overheat & blow the shit out of the things "

....... is somewhat more appropriate.




........ Phil

 

[PeteS]

What is the idea voltage per cell to "slow charge" a Ni-Cd battery. I
know that for a lead-acid battery, it is 2.3 Volts per cell at 25°C.
Ni-Cd "fast chargers" pump in current until the battery gets hot and
then shuts off the current. I think that this is the perfect recipe to
ruin the battery quickly. I know that if you leave a lead-acid battery
connected to a charger that delivers 2.3 Volts per cell, you can leave
it on forever and it won't ruin the battery. That's the way it's done
with alarm system and good quality batteries can last up to 15 years.
I assume it could be the same with Ni-Cd batteries if they where "slow
charge".

Thanks

NiCad chargers come in a variety of flavours, and they are virtually all
constant current (or close to it).

Slow charge on a NiCad is C/10 or lower, but my preference is C/20 where
C is the nominal capacity. Some high temperature batteries will get
destroyed eventually at the C/10 rate. You can approximate this with a
resistive feed from a voltage source, of course.

The terminal voltage of a NiCd is nominally about 1.2V, but can range
from 1V to 1.5V depending on it's internal temp and state of charge.
Don't let the terminal voltage exceed 1.5V, by the way, unless you are
interested in pyrotechnic displays.

Cheers

PeteS

 

[orvillefpike]

My question comes from the fact that, according to what I read, heat
is the enemy of lead-acid batteries. If you charge them at more than
2.3 Volts per cell, they overheat and die quickly. I have a charger
for a Makita drill that charges the 8 cell battery (8 x 1.2V = 9.6V)
at around 15 volts and the battery have a thermistor in them, so when
they "overheat" the charger shuts off. I thought that heat would also
be detrimental to NiCd batteries also. I guess I'm wrong, that's why I
am asking on this forum.

Thanks

 

[Eeyore]

I thought that heat would also be detrimental to NiCd batteries also.

It is.

I guess I'm wrong, that's why I am asking on this forum.

You need to understand that lead-acid and NiCd are completely different
'chemistries' and there's no reason they should be even remotely similar in
their characteristics.


Graham

 

[PeteS]

My question comes from the fact that, according to what I read, heat
is the enemy of lead-acid batteries. If you charge them at more than
2.3 Volts per cell, they overheat and die quickly. I have a charger
for a Makita drill that charges the 8 cell battery (8 x 1.2V = 9.6V)
at around 15 volts and the battery have a thermistor in them, so when
they "overheat" the charger shuts off. I thought that heat would also
be detrimental to NiCd batteries also. I guess I'm wrong, that's why I
am asking on this forum.

Thanks

Heat is detrimental in the sense of self leakage, particularly in
NiCads, and also in the sense of overheating.

NiCads have a constant current charge regime, and at C/30 (in the
correct ambient conditions) you can trickle charge them indefinitely,
which is not true of other chemistries.

The most efficient charge controllers for NiCads depends on the
chemistry involved (which varies widely for various manufacturers)

Cheers

PeteS

 

[Phil Allison]

"orvillefpike"

My question comes from the fact that, according to what I read, heat
is the enemy of lead-acid batteries. If you charge them at more than
2.3 Volts per cell, they overheat and die quickly.

** They can be damaged even at 2.3 volts per cell, unless the charge
includes current limiting.

You have not read nearly enough to hold an opinion on the mater.

I have a charger
for a Makita drill that charges the 8 cell battery (8 x 1.2V = 9.6V)
at around 15 volts

** Nonsense - it does no such thing.

With flat pack, the voltage will commence at around 10 volts, then rise over
the charging period to around 12 volts.

Once all the cells are charged THEN they produce heat instead of storing
the electrical energy as charge.


........ Phil

 

[orvillefpike]

"orvillefpike"




** They can be damaged even at 2.3 volts per cell, unless the charge
includes current limiting.

You have not read nearly enough to hold an opinion on the mater.


** Nonsense - it does no such thing.

With flat pack, the voltage will commence at around 10 volts, then rise over
the charging period to around 12 volts.

Once all the cells are charged THEN they produce heat instead of storing
the electrical energy as charge.

....... Phil

If the charger is regulated at 2.3 V and the cell is charged to 2.3 V,
there is no current in one direction or the other, so how can it
damage the cell.
My NiCd charger has a transformer, a diode bridge, a relay and a
capacitor so how can it go to 10 V then go up to 12 V when there is no
electronics to regulate anything.

Thanks

 

[Phil Allison]

"orvillefpike"

If the charger is regulated at 2.3 V and the cell is charged to 2.3 V,
there is no current in one direction or the other, so how can it
damage the cell.

** ROTFL !!

Go away - IDIOT

My NiCd charger has a transformer, a diode bridge, a relay and a
capacitor so how can it go to 10 V then go up to 12 V when there is no
electronics to regulate anything.

** Gotta be a desperate attempt at a TROLL.

No one born is that stupid.

So maybe it wasn't.



....... Phil