Hi all, Some days ago I posted a message regarding the charging of NiMh battery's. I got only one reaction, so I guess many are wondering what is a good way! I decided to go for the experimental way and did the following: - Measure the supply voltage, we call that U1; - Measure the battery voltage in charged situation, we call that U2; - Take U1-U2 and devide that over the charging current you want to use. In case of my 2400 mA/h cells I decided for a "conservative" 200 mA; - The result is the resistor value, in my case about 33 Ohm; - Take the square of U1-U2 and devide over R and you have the power, in my case between one and 2W. I had a 33 Ohm resistor of 5W in stock which was only 0,3 inch, so it fits very nicely. I have mounted it on the component side of the pcb, otherwise it gets in the way of the battery!
The result is very positive, it charges nicely. I have mounted a timer in line with the charging supply, an old Nokia 12V GSM supply, to avoid overcharging as I read that NiMh cells dont like that. Have fun! Oh and by the way; modifying is at your own risk and will probably violate the warranty. Or perhaps Wayne and Eric find it such a good idea that they will allow it ;) 73, Dick PA2DW _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
