Isolated current and isolated voltage sensor for up to 850V & 200A based on ADS1115 and attiny1614 with isolated RS485 / MODBUS. (based on https://github.com/stuartpittaway/diyBMS-CurrentShunt)
The current measurement uses an ACS758ECB-200B hall-effect based current sensor IC.
The voltage measurement is isolated using an ACPL-C870 Precision Optically Isolated Voltage Sensor.
The analog signal from both measurements are converted using a ADS1115 16 bit ADC.
Coulomb calculation takes place in using an attiny1614 and communication uses isolated RS485 / MODBUS.
The project is based on https://github.com/stuartpittaway/diyBMS-CurrentShunt and was created to allow using high voltage batteries for diyBMSv4.
The schematics and board are in the directory KiCad.
The firmware in the directory code is losely based on Stuard Pittaway's diyBMS CurrentShunt. It uses the same MODBUS RTU registers.
The charge that goes in and out is calculated by sampling the current 128 times per second using the ADS1115 and measuring the time beween each sample. These are then integrated first to mA*ms (uAs) and then every second to mAh (milliamphours).
The voltage is measured every 1 second as it's irrelevant for charge calculation but interesting for power calculation and over/undervoltage checks.
Maximum compatibililty to diyBMS-CurrentShunt should be maintained to allow using the diyBMS4 ESP32 code unmodified.
Please note that due to compatibility the double registers are in mixed endian (floats compromised of 2 16bit registers in little endian, but individual 16 bit registers are big endian) BUT the 32bit integers are big endian.
Use read-modbus.sh # code/read-modbus.sh to read the modbus registers.
This is a DIY product/solution so don’t use this for safety critical systems or in any situation where there could be a risk to life.
This board was designed to work with high DC voltages which are notoriously dangerous to work with and are a risk to life. Please make sure you have the appropriate knowledge and always use fuses specified for DC.
There is no warranty, it may not work as expected or at all.
The use of this project is done so entirely at your own risk. It may involve electrical voltages which could kill - if in doubt, seek help.
The use of this project may not be compliant with local laws or regulations - if in doubt, seek help.
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