Use dummy cell in two cell battery charger?

[Alex Coleman]

At home I use an "intelligent battery charger" which charges cells
two at a time and both must be present for the charger to work.

--------------------

THE PROBLEM .....
Sometimes I want to charge just one cell on its own.

Maybe that one cell is an AA or AAA from a single-cell MP3 player.
Or maybe I have to recharge cells which have very different
capacities or charge levels.

--------------------

To charge only one cell, can I put a resistor in the place of the
second cell as a sort of dummy cell? If so then what values might I
use?

I figure the Negative Delta V sensor would still trip correctly with
one cell as it's unlikely that two cells would reach their voltage
drop simultaneously.

Tech details are below. Thank you for any info.

Alex



--------------------- TECHNICAL DETAILS -------------------
INFO ABOUT CHARGER ...

The charger is a Vanson V-1000 charger which uses Negative Delta V.

The spec says AA cells are charged at 350mA and AA cells at 750mA.
I read 1.45 volts across one 900mAh AAA whilst charging 2 of them.
I read 1.35 volts across one 2000mAh AA whilst charging 2 of them.

Manufacturers info: http://www.vanson.com.hk/details/p3001.html
Wholesaler's info: http://preview.tinyurl.com/22jdld


INFO ABOUT CELLS ....

Use mainly NiMH with some NiCd
AAA cell capacity ranges from 300mAh to 900mAh.
AA cell capacity ranges from 1000mAh to 2800mAh.
-------------------- END OF TECH DETAILS -------------------

 

[Mike S.]

At home I use an "intelligent battery charger" which charges cells
two at a time and both must be present for the charger to work.

--------------------

THE PROBLEM .....
Sometimes I want to charge just one cell on its own.

Maybe that one cell is an AA or AAA from a single-cell MP3 player.
Or maybe I have to recharge cells which have very different
capacities or charge levels.

Buy a charger that charges and monitors each cell individually.

Try www.thomasdistributing.com for a huge selection (no relationship with
them; just a longtime customer). The Maha/Powerex chargers are
particularly well regarded.

 

[Archimedes' Lever]

Well, you "intelligent" charger isn't quite so smart, is it.

They are hard to find but it's still possible to buy chargers that can
charge single cells or any number of cells up to 4 or whatever. I got one
from Wally World a few years ago. Radio Shack might still stock one that
can handle C's and D'c along with the AA's and AAA's. Get one.

Carbon Zinc is a dead form factor.

When you charge cells in series one cell will be undercharged and/or the
other cell will be overcharged.

Not on modern chargers.

That said, if you routinely use cells in pairs, you can make a case for
ALWAYS charging them in series.

"Battery" chargers charge individually. Even the old ones like that
which you mentioned charged in parallel.

When you discharge the "weaker" cell might
actually be "reversed" charge when it runs out of juice while the "strong"
cell is doing just fine, thank you.

You should look into modern cell charging systems.

 

[Archimedes' Lever]

To charge only one cell, can I put a resistor in the place of the
second cell as a sort of dummy cell? If so then what values might I
use?

Take a cell, and measure its internal resistance when fully charged and
when ready to avalanche over to "deadness".

 

[Lostgallifreyan]

Carbon Zinc is a dead form factor.

Why do you think xinc carbon cells were implied? Those cell formats
(AAA,AA,B,C,D) are also used for alkaline and NiCD and NiMH.

Not on modern chargers.

Only true if they charge each cell independently. Otherwise the risk is
there.

"Battery" chargers charge individually. Even the old ones like that
which you mentioned charged in parallel.

Not true. Many charge in pairs, two series pairs in parallel for charging
two or four cells at once. That's a widely standardised form, and it DOES
cause charging imbalances after a while, I've got NiMH cells with this
problem, and they've only been charged in one charger.

You should look into modern cell charging systems.

Probably true, but without carefull assessment of the problem, it's just as
easy to choose a new charger with problems, as an old one. It costs more to
monitor and charge each cell on its own, so unless governments enforce it
to avoid waste going into landfill, there will always be chargers that
offer less effective methods, and many of them will come with misleading
claims to persuade people to buy them.

 

[Lostgallifreyan]

Take a cell, and measure its internal resistance when fully charged and
when ready to avalanche over to "deadness".

I don't get it... What is 'deadness'? It's not a state than any cell
capable of taking a full charge is likely to 'avalanche' into.

Testing the internal resistance, perhaps by short timed pulses of high
drain through known tiny resistance and montoring chages in voltage might
be revealing, but I don't know enough about them to know if it's more
useful than other methods.

Alex, does your charger only use NDV to detect full charge? If so, be wary
because NiMH doesn't drop voltage as gas begins to be produced, as much as
NiCd. One NiMH cell could be too difficult to detect to be trusted, unless
the charger also monitors temperature.

 

[Lostgallifreyan]

Do you mean the sharp drop in NiCd at full charge? If so, bear in mind that
NiMH doesn't drop so sharply, and either way you can't make the test
without NDV detection telling you when to test, so you must test frequently
until you detect NDV. That might need microcontrollers or other major
increases in cost and complexity.

 

[Arthur]

At home I use an "intelligent battery charger" which charges cells

two at a time and both must be present for the charger to work.

--------------------

THE PROBLEM .....
Sometimes I want to charge just one cell on its own.

Maybe that one cell is an AA or AAA from a single-cell MP3 player.
Or maybe I have to recharge cells which have very different
capacities or charge levels.

Make a cell out of a bit of wooden dowel.

Drill a hole through the wooden cell

Connect two 1N4001 diodes in series

Pass the diodes through the hole in the wooden cell

Coil the ends of the connection to the two diodes so
that they lay flat on the ends of the wooden cell.

Fit the wooden cell in place of one cell, the diode "cathode" is the minus
terminal.

Arthur

 

[Archimedes' Lever]

Why do you think xinc carbon cells were implied? Those cell formats
(AAA,AA,B,C,D) are also used for alkaline and NiCD and NiMH.

However, the Rat Shack charger that was mentioned IS NOT. They are the
last vestige of folks still pushing Carbon Zinc cells. Do try to keep
up.

 

[Archimedes' Lever]

I don't get it... What is 'deadness'? It's not a state than any cell
capable of taking a full charge is likely to 'avalanche' into.

Know much about cells, boy?

There is a useful life curve they all have. It varies from one cell
technology to another.

Alkalines keep their full voltage (FAIAP) right up until they AVALANCHE
down to near zero volts.

Other cell types have different curves.

ALL cells exhibit a different internal resistance when fully charged
than they do when discharged, and beginning a charge cycle, and also at
the point at which they avalanche.

The sentence was quite simple, and it takes a real dipshit not to see
what was meant by it.

 

[Archimedes' Lever]

, but I don't know enough about them to know if it's more
useful than other methods.

This is obvious.

 

[Lostgallifreyan]

However, the Rat Shack charger that was mentioned IS NOT. They are the
last vestige of folks still pushing Carbon Zinc cells. Do try to keep
up.

Are you dense or what? Talking like a teacher while prating spastically of
xinc carbon being a dead format, then talking of a charger in the same
discussion. What is this guff of assiciation of one firm's habits? You
won't solve technical problems with weird innuendos about one firm's
selling habits. If you can't address the specific point raised meaninfully,
don't post.

 

[Lostgallifreyan]

The sentence was quite simple, and it takes a real dipshit not to see
what was meant by it.

Troll. That's all I need to know, you're a troll, and unlike Phil Allison,
who writes things worth reading despite his invective, you don't because
unlike him, you don't have the clarity needed to stick to the point.

 

[Lostgallifreyan]

This is obvious.

Yep, a troll. Thought so.

 

[Lostgallifreyan]

Know much about cells, boy?

There is a useful life curve they all have. It varies from one cell
technology to another.

Alkalines keep their full voltage (FAIAP) right up until they AVALANCHE
down to near zero volts.

Other cell types have different curves.

ALL cells exhibit a different internal resistance when fully charged
than they do when discharged, and beginning a charge cycle, and also at
the point at which they avalanche.

The sentence was quite simple, and it takes a real dipshit not to see
what was meant by it.

The original poster asked about the reaching of full charge, so one cell
could be charged. He said his charger uses NDV to detect full charge. That
has nothing to do with the cell resistance at discharge. Focus on what was
asked, and be a bit more explanatory too, if you want to justify your
asshat attitude. Talking like a teacher slapping a pupil fopr innattention,
saying as little as possible, strining in unrelated issues the moment you
do speak of more. You're no teacher. Any teacher who was that bad at it
wouldn't last long in a class.

 

[Archimedes' Lever]

Are you dense or what? Talking like a teacher while prating spastically of
xinc carbon being a dead format, then talking of a charger in the same
discussion. What is this guff of assiciation of one firm's habits? You
won't solve technical problems with weird innuendos about one firm's
selling habits. If you can't address the specific point raised meaninfully,
don't post.

**** you, trying to tell me what to do or how to post.

**** off, jackass.

 

[Archimedes' Lever]

Troll. That's all I need to know, you're a troll, and unlike Phil Allison,
who writes things worth reading despite his invective, you don't because
unlike him, you don't have the clarity needed to stick to the point.

**** you, LostGalliRetard. Go find a tall bridge, you retarded twit.

 

[Lostgallifreyan]

**** you, LostGalliRetard. Go find a tall bridge, you retarded
twit.

Like I said, a troll. At least that's settled. *Plonk*.

 

[Lostgallifreyan]

Looks like IT has morphed, again.

Interesting... should I have recognised this one as another? I guess I'm
not that attentive.

 

[Lostgallifreyan]

I'd like to hear more about that. The alkalines I use all gradually
ramp downward in voltage. I could ship you all sorts of alkaline AA
batteries with voltages between 0.8 and 1.5 volts.

I remember them being preferred in Psion Organiser XP's and LZ's for field
use (those are still used on aircraft carriers, I read somewhere), because
rechargeables (NiCd, NiMH) didn't give enough warning when power was about
to fail. I put a Duracell alkaline in one of mine a while back, and I'd do
that again considering how well it's done so far. I'd have recharged the
NiMH 5 to 8 times since that time if I'd still been using it. I read
somewhere that Duracells can also be recharged safely. If that's true I
really ought to look into that.