The idea is to build something akin to the NASA BM-1 battery monitor. This is a unit that retails in the UK for around £95 incl VAT. So I'm wanting to build something that is cheaper than that.
Three specific things I want to be able to do with this unit, which you can't with the BM-1:
- Output the voltage, current and temperature readings real time via a serial port (so it can interface with another general motorhome control project I'm working on)
- Record the voltage, current, and temperature to some kind of storage (an SD card most likely) every few seconds so that the data can be subsequently graphed on a computer to get a better idea of battery performance.
- Be able to set the meaning of 'empty' for the battery. The BM-1 tells you what the state of charge is as a percentage, but with lead acid batteries you don't want to take them down below 50% state of charge regularly. So when the BM-1 says 50% left, does that mean 50% until the battery is half empty, or 50% until the battery is at 0% and damaged.
I'm going to be building this on top of an Arduino-based system. No doubt there will be mistakes along the way and this might end up costing me more than a BM-1 in the process of learning, but hopefully the end result will be something that can easily be replicated by anyone else.