So far, I learned KiCAD. Prototyped the analog on breadboard, came up with this design and created this schematic in the KiCAD. It took 16 ~ 18 hours of work till now. I had to create schematic library packages for the PIC16F883 microcontroller, BTW.
I used to draw schematics and create PCBs in CirCAD. Since it is commercial package, costly and really costly ($$$$), I needed an alternate package for the moment. I explored a few options and found KiCAD doing the job, at least for now.
I wanted to come up with a battery monitoring system to collect a battery’s charge discharge data for measuring and plotting it’s performance. The system should charge the battery at a defined current – normally fixed by the charger. Then goes over a discharge cycle with a predetermined load (e.g 0.1C), collecting the performance characteristics such as rate of voltage drop, actual current delivered, discharge cycle time and total cycle time. Then the cycle is repeated with different loads (e.g. 0.2C load, 0.3C,…,2C). The number of steps (load cycles and load values) should be selectable in software. The results should be logged to a permanent storage for import. The imported data can be used to measure, plot and graph the battery characteristics, thus giving the performance and life expectancy under different load conditions.
About the Circuit:
It consists of four modules: the analog frontend, the charge/discharge controller, the microcontroller and the display. The long term storage (using EN25F80) is still pending.
The analog frontend takes three lines from battery – the battery’s +ve & -ve terminals directly and a third lead that connects the battery to load or charger. The charge/discharge controller is built around IC ULN2003 with a total of five relays – one for charger and four for load. Each realy on the load will carry a specific load attached to it – I chose 16Amps, 8Amps, 4Amps & 2Amps. This allows me to discharge the battery under test (BUT or DUT) at a rate anywhere from 2A to 30A in 2A steps.
More to come soon…
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