In Car Solar mp3 charger

Nov 06, 2006 2 Replies
S

Hi, I have a cheap mp3 player in my car that runs off a 1.5v aaa battery. I have to change the battery once twice a week as I forget to turn the thing off as it is plugged into the tape slot. My plan is build a circuit that will trickle charge a Ni-MH battery via a solar cell and power the mp3 player during daylight, and the battery will power it in bad light/ darkness.



This is a very cheap mp3 player and the only power connection it will take is off the battery terminals.



I have a 2.5v solar cell on the way from e-bay, and I know I need a a diode to stop the batterry discharging via the solar cell, and possible a voltage regulator so as not to overload the mp3 player.



Any other suggestions to improve on this?



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T

How much current can the solar panel provide? If it's no more than a couple of tens of mA then just the diode should do the trick. The battery will stop the voltage rising too far - solar panels are current rather than voltage sources, so voltage regulation isn't required when charging a battery. If your panel can provide closer to 100mA, you might have to think about something more elaborate as once the battery is full charging it at that kind of rate wouldn't be very good for it.

As the battery would be limiting the voltage to the MP3 player, you need to ensure you can remove it without the risk of the solar panel being connected to the MP3 player without the battery in place to limit the voltage. A switch or connector on the solar panel leads would do fine.

Tim

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