I have been making little circuits for my TD. They will all end up in one box soon but for now they are easier to describe. This is a real easy build, cheep too. The IC costs £1.52 ($3) and the other bits cost very little. I found the circuit and details at:-
http://www.uoguelph.ca/~antoon/circ/batmon12.htm
I altered it a little I made the 10th led red and tuned the 9th LED to 12.65 instead of the 10th so I would get an indication that the battery is being successfully charged.
The LED's left to right.
1. (red) set at 11.89V
9. (green) set at 12.65V
10. (red) something above that
Clive
PS As a newby I am shy about posting to a sticky. Should I re post this to "Battery State of Charge Chart"?