Thursday, October 24, 2013

Posted V0.1.0 of schematic - and Where should we measure current?

Today I posted a revised version of the regulators schematic, and also completed filling in the Hardware Overview.  Some major changes between v0.0.x and v0.0.1.x of the design:

  • Usage of Liner regulators vs. switching regulators for  +5v
  • Elimination of the DUAL port
  • Update of the FET driver chip

For more complete descsiption of the hardware, see the Hardware Overview tab above (or

And to download a .pdf of the whole schematic, click on the Schematic tab above. (

Where to Measure Current?

A comment on elimination of the Dual port, as that is not really talked about anywhere else.  A group of users I am looking at for this design is Marine use, where is is common to have two engines with alternators charging a common house battery.  Given a key goal of this project is to better manage the battery's state of charge - deciding when to exit Absorption phase by MEASURING its state of charge (as indicated by its Acceptance Amps) as opposed to GUESSING its state of charge (by using a length of time), there is the need to know how many Amps are actually going into the Battery.  In a dual engine setup the amounts of amps being delivered would be the sum of each engine.   So my thinking was by measuring the Alternator Amps of each alternator, and sharing that information, the correct decisions would be made.

During trial runs it occurred to me there can easily be even more charging sources.  Generators, Solar Panels, etc..  Combine this with some amps being diverted to directly power house loads we get a situation where the Dual port was a kind of partial solution.  The real solution is:  measure battery the amps AT THE BATTERY, not the Alternator...    So I removed the Dual port and will document Best Practice is to measure the Amps via a whole-battery shunt.   

However, IF one still wants to measure Alternator production (just because they are curious, or perhaps they are using the advanced configuration options to limit the Alternator output - say by managing Watts load for a small engine DC generator), then an Acceptable deployment will be to make some guess on other charging sources and typical house loads.  Down the road there is the ability to add external communications into the regulator via either the serial port (ASCII strings), or an I2C adapter board, to receive information from say an external battery monitor, or even add a 2nd Amp Shunt port...    Will think on this problem a bit more, but for now there is sufficient flexibility in the regulator as-is to accommodate any installation approach.

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