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Class D Switching Power Amplifiers and Power D/A conversion

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Old 1st April 2013, 07:30 PM   #81
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IIRC, you can apply 10% of the battery's capacity indefinitely with no ill effects.

For a 2000mAh battery, you could put 200mA through forever, and it'll survive. It'll also charge (taking 10 hours from dead).

I'd try to set the voltage for that.

You can charge batteries faster (I've gone to 6A charge current for some R/C car batteries. They're probably knackered now, but it was a 20 minute charge at the time ), but high currents will begin to reduce the battery's capacity - not good.
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Old 10th April 2013, 07:30 AM   #82
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Mooly and Chris again thank you for your expert advice.

Sorry for my delay in responding, I went and visited my auntie on the mainland.

I am trying to wrap my brain around the wiring for the rechargeable battery. I started drawing up a diagram but failed miserably. LOL

I am sure if I read your directions another 50 times I will get it figured out. haha
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Old 10th April 2013, 07:32 AM   #83
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I also was wondering, I know these are cheap little amps, but I am getting a high pitched noise. It starts out a little louder when it is first turned on, and gradually gets lower but you can still hear it if the volume is lower then half.

Is this a power supply problem? Or the amp itself? Any remedies or action I could take to get rid of it?

Thanks
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Old 10th April 2013, 10:42 AM   #84
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Something like this. The wall wart voltage minus 0.7 volts (diode drop) give the voltage you have available to charge a battery. Divide that voltage by the charge current required.

The high pitched noise could be one of a number of things and very hard to pin down without having the unit to work on.

Is the noise coming from the amp itself or from the speaker ?

If the former, then it may well be normal and due to any inductive components (coils in the Class D output filter for example) "singing" due to harmonics of the class D output waveform.
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