Diode in NiCd pack - what is it?

| The price difference between 5% &1% resistors in production volumes is zero. | The cost of 'hand picked 5% resistors to match the battery pack' - whatever | the latter means- is astronomic even in India or China.

I've worked in production. Using two resistors in series is a dead give away that they are tweaking the system. The other way is to use a 10 turn trimmer. They didn't.

On Thu, 13 Jan 2005 16:52:42 +0200, "Dimitrios Tzortzakakis" put finger to keyboard and composed:

That doesn't explain why the two resistors aren't identical. I would think that 2 x 180 makes more sense than 120 + 240. Could they be NTC resistors?

- Franc Zabkar

| I've encountered a Sansui amp where the main bridge rectifier was | constructed using four parallel pairs of 1A rectifier diodes rather | than four individual 2A or 3A diodes. Placing diodes in parallel is | bad practice because their sharp I-V characteristic almost guarantees | that one will work harder then the other, so my only conclusion is | that the manufacturer wanted to save money by making use of an | existing stock of 1N4004s. Maybe that's what happened in this case???

There is a way to wire them so as to equalize the current somewhat. Also, if they only needed 1.1 A say, the design might get by.

On Fri, 14 Jan 2005 07:32:34 -0800, Jerry G. wrote (in article ):

Yes, you're right, I feel.

In this Panasonic pack, I simply replaced the cells with new ones, and the pack seems to charge and perform as it used to when new.

Another pack, by another manufacturer (Milwaukee), fits this charger, but was never meant to be used with it. This pack has one "diode" and one "resistor" (in quotes, because we're making assumptions, of course). It never performed similarly, because it never charged fully.

I'll go buy another Panasonic pack and when time comes, replace the cells to extend its life.

Thanks for all the comments and suggestions.

Various manufactures may use their own particular designs to match up to whatever they want in correspondence to their chosen designs.

Sometimes they use a diode coming from the battery pack to give a one way isolation to the battery pack for their load testing circuit in their charger. This blocks the load test circuit from feeding back in to the battery pack. They sometimes use a resistor, or combination of resistors with the diode for current limitation of some type, depending again, on what they specifically want to do accomplish in their design.

Sometimes, they may also use a diode that is thermo sensitive, thus being able to also determine if the temperature of the battery pack is going too high. In this case the diode can be serving for several purposes.

If you are replacing this diode you will have to be sure of its specifications before simply using any diode off the shelf. There may be some safety and performance issues here. This is why I prefer to go out and get the original battery packs for my equipment rather than jeopardizing safety and performance for a few dollars saved.

This is almost certainly a diode temperature sensor operating in switched mode. In this mode, temperature is sensed based upon the diode voltage differential at two separate currents: delta Vd= KT/q x Ln( I1/I2), and this also explains why your readings are so low- the meter is averaging- and the sensing may be operating in burst mode. The resistors may serve any number of purposes- cheap current limiting or simply to raise the input voltage level. Two diodes will double the differential- but two resistors?- don't know.

On Thu, 13 Jan 2005 23:29:53 GMT, "NSM" put finger to keyboard and composed:

I've encountered a Sansui amp where the main bridge rectifier was constructed using four parallel pairs of 1A rectifier diodes rather than four individual 2A or 3A diodes. Placing diodes in parallel is bad practice because their sharp I-V characteristic almost guarantees that one will work harder then the other, so my only conclusion is that the manufacturer wanted to save money by making use of an existing stock of 1N4004s. Maybe that's what happened in this case???

- Franc Zabkar