I'm currently prototyping with an Arduino Uno as that has a USB port and can be easily plugged in to my laptop and programmed. For the actual system I put into the van I'm going to build it on a more 'barebones' board that is cheaper and uses less power.
The additional items needed to be added to a base Arduino to provide the functionality I need:
- A Real Time Clock (RTC) -- needed to be able to record the current time and date for each voltage and current reading
- A SD Card reader -- needed to have somewhere to write the readings we are taking from the batteries
- A way to measure the current being drawn
- A way to measure the voltage of the batteries
- A way to measure the temperature of the batteries
I am looking at using a Xino Basic as it is very cheap (£7.68 including the voltage regulator, processor and VAT) and has a small prototyping area directly on the board onto which I should be able to attach the RTC, SD card reader, and sensors.
I've ordered a RTC (£1.73) and a SD card reader (£1.24) from eBay. Both are coming from China and so will take a month to get here, but at that price I couldn't resist. To measure temperature I'm using a Dallas Semiconductor DS18B20 sensor. This is a digital temperature sensor that uses a '1-wire' bus. This means multiple sensor can be daisy chained together on the same pair of wires.
As for measuring voltage and current... that is worthy of a whole separate post....