Hi The resistor and diode in the KBT2 limit the charge current to the internal battery but really do not prevent overcharging. If the input voltage to the K2 id about .2-.3 volts greater than the float charge value of the battery (13.8V) then all is well but if the voltage is higher you may overcharge the battery. The switch off point on my solar controller is set at 14.1 volts. With the duty cycle the average voltage to the battery will be about 13.8 volts or equal to the float charge rating of the battery. If the charge controller is connected to the K2 power input the diode drop in the battery charging circuit would lower the voltage switching point to the battery and the battery will not come up to a full charge. There are two ways to solve this problem. The best way is to install a fused connector on the back of the K2 that connects directly to the battery terminals. The solar controller would connect to this connector when using a solar panel to charge the battery. A power supply will still operate the K2 and charge the battery through the normal power input when not using the solar panel. The other way to solve the problem is to increase the controller switching point to about 14.5 volts by installing a 220K resistor at R9. I have not tried this but should work. The controller would plug directly into the K2 power connector to charge the battery. If you use this method then the controller should not be connected directly to the battery.
Thanks Don Brown KD5NDB ----- Original Message ----- From: "Peter Wollan" <[EMAIL PROTECTED]> To: <elecraft@mailman.qth.net> Sent: Saturday, July 07, 2007 7:33 AM Subject: [Elecraft] K2 - KBT2 and solar power? > After using my K2 for its first Field Day, I now see a reason to install > the KBT2 built-in battery. But, I particularly liked using solar power > -- a 10-watt panel running through Don Brown's solar charge controller > to a gel-cell battery in parallel with the radio while operating. Worked > really well. Can something like that be done with the KBT2? > > The charge controller cuts off the solar panel when the battery gets to > about 14 volts, but it needs to be near the battery to sense the voltage > correctly. The solar panel can generate 20 volts at 1/2 amp -- what > happens if this particular charge controller is plugged in between the > K2+KBT2 and the solar panel? My guess is that the controller would keep > the voltage down to 14 volts, but would never see the battery as fully > charged. Do the diode and resistor in the KBT2 prevent overcharging? > It sounds less controlled than the KBT2 is designed for. Anyone have > experience with this? > > Peter N8MHD > > _______________________________________________ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > 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 > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
