Here's the link,
http://www.ifirobotics.com/docs/firs...up-charger.pdf
It looks fairly sensible to me, really. The regulator puts 7V on the Vout. The 43 Ohm and 22 Ohm resistors act as a voltage divider between the ~12V battery and this 7V. At 12V, this would keep the output around 8.7V. Then you have the 8.7V reference to clamp the voltage at 8.7V. The diode is, I think, to protect the regulator when the battery voltage is extremely low or non-existent. There's a constant load of atleast .08A on the 12V battery, but as long as this circuit is after the main switch, it shouldn't be a problem.
EDIT: Okay, thinking more, D1 seems reversed. But the circuit makes sense to me without it.