[Elecraft] KX1 battery

[Dick Harms PA2DW]

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