How to replace failed NiMH batteries in a siemens C35?

[Manco Marzio]

I tried to replace old 500mAh NiMH batteries into my old siemens C35
by cutting off the 3 original batteries inside their plastic box
(there were 3 cells in series), and wiring in place 3 new AAA NiMH
batteries. I kept the small chip welded between the "-" contact
and the central contact, thus just replacing the cells.
Eventually a left the original battery pack in place, just removed
old cells and rewired the new AAA outside the cell to try if works.

But the phone does not work: it lights up for just seven seconds
the turns off, like with discarged batteries.
It however does charge the new AAA batteries such wired,
and i think it really recharges them fully at least (it needs 4 hours)

There is only one difference between new and old cells (alongside the
shape of course the new are 750mAh and not 500mAh.

What it's wrong?

bye!!!

 

[Mark W. Lund, PhD]

The only thing that I can imagine is that there is more
wrong with the phone than just the battery. You thought
that the batteries were worn, but something else is wrong.

Best regards
mark

I tried to replace old 500mAh NiMH batteries into my old siemens C35
by cutting off the 3 original batteries inside their plastic box
(there were 3 cells in series), and wiring in place 3 new AAA NiMH
batteries. I kept the small chip welded between the "-" contact
and the central contact, thus just replacing the cells.
Eventually a left the original battery pack in place, just removed
old cells and rewired the new AAA outside the cell to try if works.

But the phone does not work: it lights up for just seven seconds
the turns off, like with discarged batteries.
It however does charge the new AAA batteries such wired,
and i think it really recharges them fully at least (it needs 4 hours)

There is only one difference between new and old cells (alongside the
shape of course the new are 750mAh and not 500mAh.

What it's wrong?

bye!!!

--
----------------------------------------------------------------------
Mark W. Lund, PhD ** Battery Chargers
CEO ** Bulk Cells and Custom Battery Packs
PowerStream Technology ** Custom Power Supplies
140 S. Mountainway Drive ** DC/DC Converters
Orem Utah 84058 ** Custom UPS
http://www.PowerStream.com ** Engineering, manufacturing, consulting

 

[Manco Marzio]

The only thing that I can imagine is that there is more
wrong with the phone than just the battery. You thought
that the batteries were worn, but something else is wrong.

but the phone works ok with another old battery that hold
the charge for just a hour or two!

So you think that it should work with external batteries?

Bye!

 

[Mark W. Lund, PhD]

If a NiCad pack will work in this application, so will
a NiMH. If the phone works with another pack, then
there must be something wrong with the NiMH pack.

If possible, look at the pack voltage as the phone is
turning on. It is possible that one of the cells is
dead, shorted, or inserted the wrong way in the pack.

To troubleshoot batteries with a voltmeter it helps to
put them under load.

One easy way to do this is to set your volt meter on the
highest amperage (10+ amps) range, and put the test leads
directly across a single cell (don't try this with
C or D cells!!!!). Compare the amperage reading of each
of the cells, and it will be obvious which one is bad.
If none of the can put out more than a few hundred milliamps
either they are all bad or they are not being charged.

Best regards
mark

but the phone works ok with another old battery that hold
the charge for just a hour or two!

So you think that it should work with external batteries?

Bye!

--
----------------------------------------------------------------------
Mark W. Lund, PhD ** Battery Chargers
CEO ** Bulk Cells and Custom Battery Packs
PowerStream Technology ** Custom Power Supplies
140 S. Mountainway Drive ** DC/DC Converters
Orem Utah 84058 ** Custom UPS
http://www.PowerStream.com ** Engineering, manufacturing, consulting

 

[NSM]

But the phone does not work: it lights up for just seven seconds
the turns off, like with discarged batteries.

What voltage on the battery pack when charging and when not charging?

 

[Ivor Floppy]

[..]

One easy way to do this is to set your volt meter on the
highest amperage (10+ amps) range, and put the test leads
directly across a single cell (don't try this with
C or D cells!!!!).

I wouldn't try it with AAA's or AA's either, unless you fancy changing the
fuse in your multimeter.

Compare the amperage reading of each
of the cells, and it will be obvious which one is bad.

Comparing the voltage is an even easier way, and less likely to end up
frying your meter leads when you discover your multimeter isn't fused on the
top range.

 

[Mark W. Lund, PhD]

I am speaking from experience. Of course my meter reads
20 amps full scale, so I should have said that, but he
has 750 mAH cells, not likely to put out enough current
to blow the fuse. So use a 20 amp + meter.

Measuring the open circuit
voltage is not usually very useful, because it doesn't
take much active chemistry to show the full voltage. It takes
a lot of active chemistry to put out a few amps.

I routinely test AA alkalines using this method.

Best regards
mark

[..]

One easy way to do this is to set your volt meter on the
highest amperage (10+ amps) range, and put the test leads
directly across a single cell (don't try this with
C or D cells!!!!).

I wouldn't try it with AAA's or AA's either, unless you fancy changing the
fuse in your multimeter.

Compare the amperage reading of each
of the cells, and it will be obvious which one is bad.

Comparing the voltage is an even easier way, and less likely to end up
frying your meter leads when you discover your multimeter isn't fused on the
top range.

--
----------------------------------------------------------------------
Mark W. Lund, PhD ** Battery Chargers
CEO ** Bulk Cells and Custom Battery Packs
PowerStream Technology ** Custom Power Supplies
140 S. Mountainway Drive ** DC/DC Converters
Orem Utah 84058 ** Custom UPS
http://www.PowerStream.com ** Engineering, manufacturing, consulting

 

[Dave Plowman (News)]

Measuring the open circuit
voltage is not usually very useful, because it doesn't
take much active chemistry to show the full voltage. It takes
a lot of active chemistry to put out a few amps.

I routinely test AA alkalines using this method.

Alkalines have a much higher internal resistance so can't deliver much
current.

What sort of current would you expect to see from a fully charged NiMH AA
into a 20 amp ammeter?

 

[Bob Shuman]

Mark,

Then you are constantly risking damage to your meter. Suffice it to say
that your meter's precision resistor that it uses to measure amperage by
actually measuring voltage drop across that resistor is probably 0.1 ohm or
greater. This resistor coupled in series with the internal battery
resistance, the leads, and probe contacts is what is limiting your current
to under its fuse rating.

By the way, the 750mAH battery rating has absolutely nothing to do with the
actual maximum instantaneous current that battery can deliver. The AH
number is an energy capacity rating that simply describes how long the
battery will last based on the current it must supply.

Bob

 

[isa --]

What voltage on the battery pack when charging and when not charging?

voltage battery appears to be ok:
4.10V when charged and 3.9 discharged, exactly as
with original battery.

The phone does charge my artificial AAA battery pack:
it takes 4 hours and it is perfectly ok.

I tried to light up a 6volt bike light bulb to check
battery and it lights up and hold it well.
I didn't measure Amps, but the light was fine
for a 6V lamp at only 4.1V

tried just now ddp at phone's contacts removing battery pack
(I plugged in the charger) I measure 4.07V between + and -
and 4.07V between - and center contact. In the battery pack
the mid contact is linked to - contact via a 10K smd resistor,
it's probably a PTC to check battery temp I guess.

bye!

 

[NSM]

tried just now ddp at phone's contacts removing battery pack
(I plugged in the charger) I measure 4.07V between + and -
and 4.07V between - and center contact. In the battery pack
the mid contact is linked to - contact via a 10K smd resistor,
it's probably a PTC to check battery temp I guess.

I'd have guessed a fuse - if it's a PTC it should be almost zero ohms.

 

[isa --]

I'd have guessed a fuse - if it's a PTC it should be almost zero ohms.

a fuse with 10Kohm? I don't know really, but usually cell batteries
have a thermal something to cutoff the charger if heat up.

 

[isa --]

tried just now ddp at phone's contacts removing battery pack
(I plugged in the charger) I measure 4.07V between + and -

*while* charging the battery I measure 4.7V.

bye

 

[Mark W. Lund, PhD]

It is a thermistor, 10 k at 25 degrees is the standard
for battery packs.

Best regards
mark

voltage battery appears to be ok:
4.10V when charged and 3.9 discharged, exactly as
with original battery.

The phone does charge my artificial AAA battery pack:
it takes 4 hours and it is perfectly ok.

I tried to light up a 6volt bike light bulb to check
battery and it lights up and hold it well.
I didn't measure Amps, but the light was fine
for a 6V lamp at only 4.1V

tried just now ddp at phone's contacts removing battery pack
(I plugged in the charger) I measure 4.07V between + and -
and 4.07V between - and center contact. In the battery pack
the mid contact is linked to - contact via a 10K smd resistor,
it's probably a PTC to check battery temp I guess.

bye!

--
----------------------------------------------------------------------
Mark W. Lund, PhD ** Battery Chargers
CEO ** Bulk Cells and Custom Battery Packs
PowerStream Technology ** Custom Power Supplies
140 S. Mountainway Drive ** DC/DC Converters
Orem Utah 84058 ** Custom UPS
http://www.PowerStream.com ** Engineering, manufacturing, consulting

 

[Mark W. Lund, PhD]

Come on, Bob. A small battery is going to put out less current
in a short circuit than a big battery. Batteries are often rated

By the way, the 750mAH battery rating has absolutely nothing to do with the
actual maximum instantaneous current that battery can deliver. The AH
number is an energy capacity rating that simply describes how long the
battery will last based on the current it must supply.

--
----------------------------------------------------------------------
Mark W. Lund, PhD ** Battery Chargers
CEO ** Bulk Cells and Custom Battery Packs
PowerStream Technology ** Custom Power Supplies
140 S. Mountainway Drive ** DC/DC Converters
Orem Utah 84058 ** Custom UPS
http://www.PowerStream.com ** Engineering, manufacturing, consulting

 

[NSM]

It is a thermistor, 10 k at 25 degrees is the standard
for battery packs.

But in series with the cells?

 

[Mark W. Lund, PhD]

One side is connected to the negative side of the cells, the
other two a separate terminal, so there should be three
cells coming out the pack, as he described.

Best regards
mark

But in series with the cells?

--
----------------------------------------------------------------------
Mark W. Lund, PhD ** Battery Chargers
CEO ** Bulk Cells and Custom Battery Packs
PowerStream Technology ** Custom Power Supplies
140 S. Mountainway Drive ** DC/DC Converters
Orem Utah 84058 ** Custom UPS
http://www.PowerStream.com ** Engineering, manufacturing, consulting