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Raspberry pi 12v battery monitor12/27/2023 The TS1100 amplifies the input value by a factor of 100 so the 0.005R resistors will give us a voltage at the ADC of 2V for a current across the shunt of 40A. For the current measurement of the solar input and battery output, we decided to use 5mR shunt resistors connected to TS1100-100 current sense amplifiers. To measure the voltage, we used a simple resistor voltage divider to drop the battery voltage down to a level that the ADC could manage which was ☒.048V. We decided to base most of the circuit on parts we already use on our expansion boards mainly because we know they work well with the Raspberry Pi and we have a large stock of the chips and components so the build cost will be reduced. This is the same ADC that we use in the ADC Pi expansion boards that we make for the Raspberry Pi. To measure the voltages and current we used a Microchip MCP3424 18-bit ADC. The main purpose of the system is to measure the battery voltage on the 12V batteries, the current coming from the solar panels and the current being used by the 12V circuit around the house. We can also upgrade to the Raspberry Pi 2 if we need more power by simply unplugging the old Raspberry Pi and plugging in the new one. The B+ has Ethernet and four USB sockets so we can connect the Raspberry Pi to our network and if we need to expand it in the future we can do so using USB adapters. The system will be designed around a Raspberry Pi model B+. The first stage of designing the new system was figuring out what we wanted it to do. The new system will use mains power to run the Raspberry Pi and all of the associated electronics and the 12V battery system will be used for the USB chargers and lighting which have low-voltage cut-out circuits built into each device. Several times throughout the winter we have to use a car battery charger to top up the batteries and stop the voltage from getting too low. For most of the year when it is sunny the panel keeps the batteries charged but in the winter when you get several weeks of dark overcast weather and short days the panel cannot keep up with the power being used by the Raspberry Pi and the two 160Ah batteries run out of energy. One issue we found with the current system is the 100W solar panel that we have to keep the 12V batteries topped up is not big enough to run a Raspberry Pi 24 hours a day 365 days a year. We also wanted to add extra communication systems for talking to wireless temperature sensors around the house and other systems that we are planning on adding in the near future. What we wanted was a single unified system that would take the bulk of the wiring and sensors and place them on a single circuit board. The old installationĪs the photo above shows the current system is a maze of cables joining the various parts together with separate current sensor boxes for the solar panels and batteries and distribution fuse boxes for the 12V power system that runs around the house. This system has served us well but over time we have found a few small problems with the setup and a few extra things that we would like to add. Three years ago we designed a solar data logger based on a Raspberry Pi which monitored the solar heating and PV system in the house as well as measured the amount of energy we were using.
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