Quote:
Originally Posted by harlequin2
First off, you can't use a fet as a load without some form of stabilisation - simply applying some voltage to the gate results in a completely unknown and quite unstable current flowing. "Calibration" as you suggested does not work, it is simply too unstable to be even thought about.
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And a feedback loop would kill the component count gain, so I guess the idea goes down the toilet.
Quote:
Originally Posted by harlequin2
Item 3 - I don't understand how the addressing might work.
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We start with assigning a one or two byte integer to each board as an address and then query them one by one in a loop (M - battery module, C - main controller):
[...]
C: battery no 27, report status
M27: voltage is 4.18V, temperature is 28C, shunt is off
C: battery no 28, report status
M28: voltage is 4.21V, temperature is 28C, shunt is on
[...]
We need a kind of a board -> battery location mapping (to know which cell actually has the problem) anyway.
Address could be assigned over IR during an initial setup phase (a new module would have to be introduced face-to-face to the main controller) and saved in the battery module EEPROM.
Quote:
Originally Posted by harlequin2
The internal oscillator in the PIC is +- 2% from 0 to 60 deg C and only +- 5 % down to -40 deg, so its much better than the AVR R/C oscillator. It is stable enough for the RS232 to work over that temp range.
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That explains a lot
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Thanks for the feedback on the ideas.