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How to replace failed NiMH batteries in a siemens C35?

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!!!

Reply to
Manco Marzio
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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

Manco Marzio wrote:

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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
Reply to
Mark W. Lund, PhD

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!

Reply to
Manco Marzio

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

Manco Marzio wrote:

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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
Reply to
Mark W. Lund, PhD

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

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N
Reply to
NSM

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

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.

Reply to
Ivor Floppy

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

Ivor Fl> [..]

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----------------------------------------------------------------------
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
Reply to
Mark W. Lund, PhD

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?

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*Why are they called apartments, when they're all stuck together? *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.
Reply to
Dave Plowman (News)

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

Reply to
Bob Shuman

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!

Reply to
isa -

Reply to
isa -

On Thu, 12 May 2005 18:00:05 GMT, "isa --

Reply to
isa -

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

Best regards mark

isa -- >

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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
Reply to
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 on how many times the capacity they can source in amps (the "C" rating).

Bob Shuman wrote:

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----------------------------------------------------------------------
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
Reply to
Mark W. Lund, PhD

But in series with the cells?

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N
Reply to
NSM

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

NSM wrote:

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---------------------------------------------------------------------- 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
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Reply to
Mark W. Lund, PhD

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