Posts: 147
Threads: 19
Joined: Aug 2007
i agree with andres. if you just take an electrolytic capacitor *alone* to do the job, this can be hazardous to the electronics. however, if you put a proper zener diode in parallel with the cap, there should be nothing wrong with taking it as a accumulator replacment.
what is a proper zener diode?
1) the voltage rating of the diode should match the accu voltage: if the accu was rated 4.8 volts, then take a zener diode of 5.1 volts. (this 'odd' value is most likely in stock of any electronics vendor)
2) the power rating of the diode must be high enough, so that the diode is able to absorb the incoming charger energy without damage. example: if your charger can deliver 8 volts with a power of 3VA, then it can deliver (roughly) a current of 3VA/8V = 0.375A. the power rating of the diode should then be at least 5.1V * 0.375A = 2Watts. (some of you may state, that the current of the transformer is rms, and that the current through the diode has a form factor, and that there must be a current limiting resistor etc, etc...: let's keep it simple!)
3) when parallelling diode and capacitor, check proper polarity: the *cathode* of the zener goes to the *plus*- pole of the capacitor.
happy soldering