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N707 charger, how smart is it?

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How does the charger in the MZ-N707 know when the battery is fully loaded? I wanna replace the 700 mAh NiCD battery with a 1800 mAh NiMH one, to boost playing time by 250% smile.gif But is this a good idea, or will the charger constantly undercharge the battery, decreasing it's capacity to 700 mAh?

Edit: Of course, the 1800mAh battery is supposed to be NiMH and nothing else.

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Guest Anonymous

From personal experience, the charger doesn't know shit. My charger just charges the battery for a few hours then stops. If I push charge again, it charges again for the same time length. SO, if you charge the battery multiple times, you might get more than 700 mah

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I did some try with different NiMH batteries. With up to 1400 mAh all is ok. With greater mAh values (i.e. 1700 or 1850) there is a great heat production so I guess that the stop charge detect system does not properly work.

I belive that the charger is "tuned" for NiMH batteries very similar to Sony NH-WM2AA that is 1400 mAh

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That's too bad... Generally a NiMH charger decides when to stop by noticing that the cell has reached a peak voltage. E.g., the battery has a nominal voltage of 1.2V but a fresh fully charged cell will actually be up at 1.3 or 1.4V. As such, a typical NiMH charger should be able to fully charge any NiMH cell, no matter what its capacity, given enough time.

Some chargers have a failsafe timer built in, to cut themselves off after a set time limit, no matter what the voltage reads. I guess you're running into this limit. But it should be perfectly OK to restart the charging process multiple times, because it should still cut off when it reaches the final voltage.

However, with a charger designed for a 700mAh battery, it's always going to take a much longer time to charge a 1800mAh battery, because the charger is putting out much less current than it could. (Generally a slow charger charges at C/10 rate, to achieve full charge in 10 hours. So for a 700mAh battery the charger would be designed to put out 70mA. But for an 1800mAh battery it should be charging at 180mA instead. It would take the 70mA charger almost 26 hours to bring the 1800mAH battery up to full charge. Faster chargers may charge at C/2 or C or higher rates, but still the 1800mAh battery will take 2.57 times longer than the 700mAh battery.)

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