IRoomba Charging Adapter Question

I received a Power Adapter to be used with the wall-wart power supply
that came with my original IRobot Roomba. The power adapter is 3/4
inch swuare by 2inches long and marked "part no 9787, made in China".

Supposedly it allows the Roomba wall-wart to be permanently connected
to the Roomba when not in use, to somehow do something to the battery
pack in the Roomba so it is always charged. Apparently when the
Rppmba is left connected to the wallwart indefinitely, the battery goes
into some sort of discharge.

Today the Roomba was acting like its battery was low and I shut it off.
Then when I let it sit unplugged for a couple of minutes, and started
it up, it ran for 30 minutes with nary a low power indication.

When I called Roomba/Irobot, they said the power adapter was not for my
machine, and I should just manually plug the wallwart in for 12 hours
before I was ready to use the Roomba.

Long story, but does anyone know what is inside the power adapter?
There appear to be a few caps, one transistor, an LED, a 8-lead surface
mount DIP, and a few resistors. I am curious what it was supposed to
do for whatever Rooma it did work with.

H. R.(Bob) Hofmann