On Sat, Sep 21, 2013 at 11:03 PM, Hal Murray <[email protected]> wrote: >
> We are talking about running computers and radio gear rather than motors. > > I can see running motors in bursts from batteries, but computers and radios > generally run continuously so they shouldn't need a battery when the sun is > up. > > Am I missing something? Can't the computers and radios run off solar power > when the batteries are dead? Does the receiver take more than (ballpark) > peak solar-cell output under nasty conditions? > I jst looked up some specs. The electronic is housed in a heated box. Apparently if the heat goes away some parts fail. Also it is a close call if the radio and computer could run under solar power alone. It can if the communications path uses a Mars orbiting relay but it takes 55W to transmit directly to Earth and the computer burns 15W. The computer can't run full time. It uses to much power so the solar charger has a built-in timer that can wake the computer. I looks like normal operation is to let the battery charge while the computer and everything thing else of powered down, then after so much time the charger wakes the computer so it can do something, then back to charging. This lets them do work with very degraded solar cells. But at some point the battery freeze and the heated electronics box can't be kept warm any more. This was a reasonable design for a system that had a 90 day planned operational lifetime. There are a lot of things they could have done. For example why not push the arm into the ground hard enough to left the front wheels and tilt the panels square to the sun? I guess the added weight of the more robust arm was not worth it. They had a weight, volume and cost and time budget to work with. -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
