The Raspberry PI was replaced by two Arduino boards.
Arduino #1 is an Arduino Nano clone (£3.50p) which is calculating the grid and solar power. Inputs are two current sensors and a 240V AC to 9V AC power pack which is just used to supply an AC waveform to calculate the power correctly. Outputs are two PWM analog values representing the grid and solar power. 2.5V is 0W, with each 1V = 1KW of power, so configured to measure plus or minus 2.5KW of power.
Arduino #2 is an Arduino Mega clone (£9) plus a 2.2" TFT screen along with the 8 way relay and 2 way relay board I already had, and the 12 line potential divider that all the input voltages are fed through, connected to the battery cells and temperature TDRs.
Software is the software I was running on the R PI with a few changes to accommodate the different hardware.
In it's current state it'll happily charge the battery during the daytime (but it isn't using variable rate charging yet) and feed the house during the evening / night time providing ouput that can be 350/700/1050/1400W.
Things still to add or improve:-
* Build a teeny circuit to control the chargers 'charge rate' input. The output to drive this is already being output from the Arduino Mega, just needs connected up.
* Create a hard coded "Voltage > Capacity" look up table for the battery so I can easily display bettery percentage remaining rather than just voltage as it does at the moment.
* I'll probably play around with a few algorithms to control the three inverters so they will better match the requirements, it's fun trying to control them as they reach full power output anywhere from 20 seconds (hot) to 2 minutes (cold) after being turned on, so if you think more power is required, is it because the ones turned on haven't come online fully yet, or do you need to turn another one on? No easy way to find out, apart from only do updates once every 2 minutes. (which is what I'm trying now)
* Everything is breadboarded at the moment, so once happy with it, design and build a single PCB.
Anyway, some pics of the system running at the moment.
The breadboards + relay boards + Arduinos:-
Status display, cell voltages, grid and solar power, battery voltage, and three inverter and charger status (DC and AC power and temperatures):-
Waveform showing the grid and solar power - solar is in blue, grid is in yellow. A horizontal line 1/4 of the way up the screen is 0W. The timebase (time to sweep one cell horizontally) is set to 20 seconds, so this represents about 6 minutes:-
The rest of it, inverters, charger, main control relays, battery in the background:-
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