mach7 Posted January 8, 2013 Report Share Posted January 8, 2013 Hello everyone!I am trying to charge 4 AAA NiMh rechargeable batteries with this simple circuit. Do you have any suggestions for better results? The resistor is getting really hot during charging. Is that normal? I use a 12V, 2A transformer.Thank you. Quote Link to comment Share on other sites More sharing options...
Relayer110 Posted January 13, 2013 Report Share Posted January 13, 2013 What is the voltage of the NiMh batteries? I hope not 1.5V each...Regards,Relayer Quote Link to comment Share on other sites More sharing options...
Hero999 Posted January 15, 2013 Report Share Posted January 15, 2013 The battery voltage is not the problem. The main issue is the charge current is too high. Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted January 17, 2013 Report Share Posted January 17, 2013 The circuit shows a wall transformer and not a rectified AC power adaptor. So the resistor would need to be in series with the batteries. A half wave rectifier has more ripple, but the 1000uF capacitor with a 1Kohm resistor may charge the batteries slow enough. You probably have a regulated AC power adaptor. So change the resistor to a 2Kohm. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted January 17, 2013 Report Share Posted January 17, 2013 The resistor is in series with the batteries.A capacitor is not necessary because the battery doesn't care about the ripple current.I agree, increase the resistor to 1k to 2k to limit the current to something more sensible. Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted January 17, 2013 Report Share Posted January 17, 2013 The resistor in this half wave rectified circuit is in series with the capacitor and battery. If you change the resistor to reduce the charging current, the battery could take a week to charge. If the resistor is in series with only the battery, it will charge in a fraction of the time. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted January 18, 2013 Report Share Posted January 18, 2013 You're wrong, whether the resistor is in series with both the capacitor and battery or just the battery will make little difference to the charging time. Quote Link to comment Share on other sites More sharing options...
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