Diode in NiCd pack - what is it?

"DaveC" schreef in bericht news: snipped-for-privacy@news.individual.net...

You did neither tell the resistor values nor the voltage measured across them. Should be of some help. Can only guess these are old 1N914 or similar. Most likely used for temperature sensing. The temperature itself is not very important. It is the changing of it (dT/dt) that is used to decide whether the batteries are fully charged.

petrus bitbyter

Or it's there as a fuse.(thermally sensitive it blows when the battery starts to overheat. Helps to prevent a battery exploding.)

| So, what diodes should I use if I want to duplicate the pack's circuitry?

Try a couple of 1N4001 and see how it works. You could try a trimmer in place of the resistors and see how the charging is affected.

N

| Sorry: | Resistors: 240 ohm and 120 ohm.

Don't assume that they are just the nominal values. They may have been selected.

N

| Hmm... as in, depending on the vendor of the cells, the end-of-charge | detection circuit needs to be tailor-made?

Not impossible. Cheaper than stocking a large number of precision resistors with various values. There's no other good reason for two resistors, unless this is a short production run.

N

Just to be different, Could the diodes and resistors be used to trickle charge after the batteries are fully charged. The charger output switches from the ( - ) neg of the battery to the resistor diode string connected to ( - ) neg, and allows for long times on the charger without cooking the batteries. Mike

series.

a 0.535v.

would

identify

Yet one more "different"... how about if the voltage drop across the resistor is compared to the breakdown voltage of the diode to determine the state of charge?

Ken

No point. Why put them in the battery? Makes more sense for either

1) Sensing

or

2) Calibrated compensation. N

This has been another of those amusing threads. You've gotten a zillion "answers" each of which could be paraphrased,

1)Stick your finger in the air, or your favorite orifice. 2)Make a GROSS, UNSUBSTANTIATED, SPECULATION based on NO, NONE, NOT ANY information.

I read the thread again. I couldn't even find mention of the polarity of the diodes in the circuit. Heck, one of us might even have relevant information if only we knew the Panasonic model number.

You need to take apart the CHARGER and reverse engineer that. If you published the schematic of the battery and charger, you MIGHT, maybe, get a useful bit of information buried in the inevitable noise. Then your problem would be reduced to deciding which of the conflicting opinions to choose.

IF the charge termination is indeed based on temperature, and IF the unknown elements are involved in temperature sensing, you need to GET IT RIGHT. Did I mention IF???

Nah, who am I kidding. I'm certain the diodes are not diodes at all. They're put there just to add to confusion in internet newsgroups. Leave them out. Bummer, I think I got something on my finger... ;-) mike

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It would have to be temperature sensing for charge termination purposes.

Almost certain to be used as a temperature sensor (relying on the "Diode Equation"), the abrupt rise in temperature indicating when charging is complete.

series.

a 0.535v.

would

identify

The first thing I'd do is take measurements at different temperatures so you can characterize what's happening with the original.

Jeff

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Ah you're over here too.. :)

The circuit in the pack is designed to match the charger. If you can measure the forward voltage under a known current, and match that to some common diode, then you're ok. They probably used cheap diodes, try

1n4001's and see where that gets you. Measure the voltage across the resistors when it's in use, and that will tell you what test current to set up.

charging

They are in series with a combined resistance of 360 Ohms, which is far too high to charge 'C' cells. It would require a charger at 43V to get a charge current of 120mA, and it's only a 2.4V battery pack.

In any case, it has already been established that the circuit in question is connected between the negative terminal and the sense terminal on the battery pack, so it is obviously not carrying the charging current.

To quote the OP-

"The resistors and diodes are not in the path of the charge current. The (+) and (-) cell terms are connected directly to the (+) and (-) terms of the battery pack. The 3rd pack term connects to the (-) cell term via these resistors and diodes."

Dave

These diodes are possibly needed to rectify the ac provided by the charging transformer, so that the batteries recveive dc.Check with your multimeter if the terminals of the charger supply ac.Usually the diodes are silicone, as germanium is more expensive.Do you have a retailer of electronic gear in vicinity that has experience in this kind of parts?The one I buy everything can identify almost anything just with one look.

-- Tzortzakakis Dimitri?s major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr ? "DaveC" ?????? ??? ?????? news: snipped-for-privacy@news.individual.net...

series.

a 0.535v.

would

identify

There are 2 resistors rather than one of higher wattage.These were used extenisevely withtube circuits (I mean high wattage resistors).

-- Tzortzakakis Dimitri?s major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr ? "DaveC" ?????? ??? ?????? news: snipped-for-privacy@news.individual.net...

the

On Wed, 12 Jan 2005 17:51:03 -0800, DaveC put finger to keyboard and composed:

Does current flow into the third terminal or out of it, ie how are the diodes oriented? Are the resistors really resistors? Do they have the usual identifying bands? Does their resistnace change with temperature? If you heat the components with a hair dryer during charging, how does the charger respond? If you disconnect the third terminal, what does the charger do? Is the charger designed to charge battery packs of different voltages and, if so, do the resistors and diodes somehow identify the number of cells???

- Franc Zabkar

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| Nah, who am I kidding. I'm certain the diodes are not diodes at all. | They're put there just to add to confusion in internet newsgroups. | Leave them out. Bummer, I think I got something on my finger... ;-)

Actually, you're right. They're extra parts from the flying saucer used by Kang and Kodos. They were going to build a rectal probe for Homer J, but, as explained in "Treehouse of Horror VII" (1996) - The Halloween episode, they decided against it. "I suppose you want to probe me," says Homer on board the flying saucer and dropping his pants. "Well, you might as well get it over with."

Kang replies, raising a tentacle, and shuddering: "Stop! We have reached the limit of what rectal probing can teach us!"

I suspect we have reached the limit on what speculation on this battery can teach us!

GW

(Always laugh at that one)

| 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?

Because they are hand picked 5% resistors, matched to the battery pack.

N