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Old May 25, 2007, 10:02 PM   #1
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Can someone tell me does the CTA charger on the left only has two contacts and the Canon has three contacts. The chargers are for the Canon NB-2LH battery packs. the CTA I got from B&H.
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Old May 26, 2007, 1:21 PM   #2
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Hello Imacer,

Sony uses a similar set up. The battery pack has 2 cells. To charge the cells, you need a + and a - connection. The middle connection on my Sony pack is labeled C.

Measuring the voltage at this center connection indicates that it is connected to one of the two cells. There seems to be a diode which makes the voltage reading of the other cell not possible.

Two connections are all that is needed to charge the battery pack. The middle connection may be used to monitor the balance of the two cells within the pack. Theoretically, you could measure the pack voltage, subtract from it the one cells voltage and derive the other cells voltage. You could then compare the voltages of the two cells to see if they are in balance. In a really smart system, you could adjust the charge to each cell to bring them into balance at the end of the charge, but I don't think any of these chargers are up to that level of sophistication. I think the look for an imbalance and shut the charger down.

Tom
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Old May 26, 2007, 2:51 PM   #3
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Thanks silver. I will not use it than.
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Old May 26, 2007, 5:27 PM   #4
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Hello Imacer,

Well, there must be some other circuitry in there. I just charged up my Sony pack and the center connection showed 3.5 volts when the pack was fully charged to 8.3 volts. This means that my original guess was wrong.

I have a charger that only has a + and - connection and have been using it to charge my Sony packs for years. Yours may work fine too.

Tom
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