How to identify cell phone battery terminals?"

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Luhan

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Bitch

If it reads 0 volts, my first guess is that it is not be rechargeable at all. The terminals with the 10K resistance reading are probably a temperature sensor. There may be a fuse inside the battery pack which is blown.

I'm not sure what kind of charger you have in mind other than the original one. Li-Ion charging requirements are rather exacting, and batteries can explode if mistreated.

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I agree, most always I can measure the voltage at some terminals and then apply a very controlled charging current. I like constant current at about 200-300 ma. for not more than a couple hours to be safe. gs

That may not always be safe. LiIon batterys can not be treated like nicad or NiMH. You need a special charger for them. I made one myself...

So far, I'm still around to talk about it.

Luhan

That may not always be safe. LiIon batterys can not be treated like nicad or NiMH. You need a special charger for them. I made one myself...

So far, I'm still around to talk about it.

Luhan

In charging my boss's phone, I also monitored voltage as well as current. A basic lab supply.

greg

I think the reason it reads 0 volts is because there is a FET transistor inside the package that disconnects the battery if the voltage falls below 2.5 volts. They can be damaged if allowed to discharge below 2 volts. So, I don't think there is anything wrong with the pack, just needs a charge.

I have a homemade charger that limits the voltage to 4.1 which is near full charge for Lithium cells, so charging is not a problem, just the polarity is unknown. But I took a look at another cellphone battery with polarity markings. It has the same configuration with 2 (shorted) terminals close together marked (-) and a single terminal on the opposite side marked (+). So, if I assume this is a standard way of doing it, it should work with the singlae terminal as positive. But no one seems to know, I asked at a computer store and a electronics store, but they didn't have any ideas.

I don't know what the results will be with reverse polarity. I may just give it a short charge of a few seconds to see if it takes any charge.

-Bill

As others have said already, don't mess with Lithium batteries. Use the charger you already have (built into the cell phone) and spend $30 on this:

We are now in the qualification testing phase of a military power supply and battery charging system. It charges and manages a pair of big custom Lithium smart batteries. 1/3 of the engineering cost was for the power supply and charger. 2/3 of the engineering cost was for designing and building a suitable tester, including battery emulators.

That 10K bit you found is almost certainly a thermistor. It is used as a safety sensor to prevent overheating of the battery.

Personally, I would never buy Lithium batteries or chargers from anyone other than the manufacturer of the cell phone. It's not worth the risk.

================================

Greg Neff VP Engineering

Well, I managed to charge the battery with trial and error. Nothing happened one way, so I reversed the polarity and the voltage jumped up to 2.5 volts. I left it on the power supply for a couple hours at 250mA and the voltage went up to 3.8. Seems to work well now, but the cell phone is dead. I bought the cell phone and battery at a swap meet for fifty cents, so I didn't expect the phone to work. But the battery is good and worth the fifty cents.

-Bill