Hardware Needed

To build this I'm going to be using the Arduino platform. This is a microprocessor platform with a very big community online and lots of tools and accessories. There are a number of 'official' Arduino boards (e.g. the Arduino Uno or Arduino Leonardo) that are developed, plus a whole load of 3rd party compatible boards. they all share a standard shape so that additional boards called 'shields' can be stacked on top. Shields include things like relay boards, wireless boards, motor driver boards, etc.

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....