Quote:
Originally Posted by Daox
I'm no electrical engineer (far from it in fact), . . .
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There are electrical engineers at work with less understanding. It is as if upon getting a diploma they decided they had all knowledge and lost any curiosity . . . if they ever had any. <sigh>
Quote:
Originally Posted by Daox
. . . edit: I read the datasheet a bit more (hadn't read much at all) and see what you are doing.
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There are precise, shunt regulator parts but they only sink enough current to operate a power transistor gate and require two bias resistors to set the value. So to make a functional equivalent to a precise Zener, it would take a shunt regulator, two bias resistors, and a third to bias a power transistor.
Although not as precise as I would like, a Zener might be 'close enough' since its thermal profile appears to be 'positive' in a good way for my purpose (aka., thermal runaway in my favor is no vice.) Now you can see why the voltage over 3.3V is so important. The current limiting resistor also raises the effective Zener threshold and hopefully enough to provide the additional voltage needed to achieve peak charge. Designed to handle 1A, it should be precise enough if I tie all of the Zeners to a common, non-shorting, heat sink.
One thing I've learned with the MSP430 is an ADC does not perform a precise, exact metric. Rather, it needs a series of measurements and averaging or weighted-averaging to get a stable value. I'm expecting the LC6803 will have similar characteristics . . . a poorly documented 'feature' of ADCs.
You mentioned the Prius cells are cold-weather, temperature sensitive. I don't see any technical data at A123 that addresses these characteristics. But on Monday I'll send them a letter and using your charts, ask for similar technical data. . . . I'll declare your testing to be at 75F/24C and ask for similar data as a function of temperature. In my case, between 50F/10C and 104F/40C. But I would accept your charts as gospel (assuming your wife doesn't catch the wires running in and out the fridge. <grins>)
One piece of good news, I only need 15A:
I might add some pad and go up to 20A.
Bob Wilson