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Originally Posted by Shu Song
That brings up a very interesting point. Why aren't the camera and servos just powered by the main battery? It wouldn't make sense to call something a "back-up" battery if it provides essential power systems when the "main" battery isn't dying. I hate to be cynical, but I think someone was cutting corners by doing it this way, but I hope I'm wrong.
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Shu,
A number of years ago, we did not have a backup battery. As the number of motors and their power increased (the small CIM can draw 133A each at stall), we started to have problems with the main battery power.
Every battery has an internal resistance. As you draw more and more current, the battery voltage drops (Ohm's Law). Also, a rapid discharge can temporarily deplete the reactant chemicals at the battery plates.
The end result was that, when robots got into shoving matches, the main battery voltage would collapse to the point that the RC controller would reset. This was not viewed as a feature by those of us using the controls...
Thus, the backup battery was added 3 (or was it 4) years ago.
If you were to power the camera off the 12V bus, the CPU on the camera would reset in the middle of a match. You would loose all calibration information and the camera would be useless for the remainder of the match... Most of us would not enjoy this either...
Therefore, we power the camera off of the backup battery...
I hope this explains why things are done this way.
Regards,
Mike