As a result of several tea break discussions at work (one of the advantages of working with a couple hundred design engineers) the final controller design is now coming together.
It will be based on a LinkSys WRT54GL wireless router that has been specifically designed by the manufacturers to use Open Source software - OpenWRT in this case (something to do with being the first company to be sued for not complying with the terms of the GNU Public License perhaps!)
Opening up the box allows the addition of a serial port which will drive a Dallas DS2480B chip which is a uart to 1-wire master controller chip. This will allow me to then 'talk' to the DS2348 battery charger chips I have ready to install. These chips measure temperature, voltage and current, which can also be accumulated within the chip to keep a record of total charge - in other words the chips track what goes in and out.
The router provides ample 'local' intelligence to monitor the system and make battery charge/discharge decisions but it also provides a link back to the house for more persistent data storage and manipulation. There are GPIO lines that can be used to switch the dump load - there is even a hack to fit an SD card for backup storage.
