[jhandy]

so the way I understand the problem is that the car is stuck in "limp home mode".

there is a electric throttle valve switch on the side of the throttle body. It may be loose or a poor connection, or maybe failed altogether.

unless you charged the battery while it was still connected to the car, I cant see how the charging of the battery could have damaged the switch. May be coincidence.
looks like a square with two nuts on each wing, and a plug in the bottom.
If you know how to use a multimeter, you may be able to test it.


2000 Porsche Boxster F6-2.7L
Vehicle Level Powertrain Management Computers and Control Systems Testing and Inspection Diagnostic
Trouble Code Tests and Associated Procedures P Code Charts P1502
P1502 Notes P1502
412 Throttle Jacking Unit, Spring Test - Above Limit

Function
The position of the throttle is controlled by a digital position controller which emits a pulse-width-modulated (PWM) duty cycle and a direction bit.
After the output stage has been deactivated, the throttle is brought into emergency air position by means of two springs. This return of the throttle must take place within a certain time. If this time is exceeded, a fault is stored in the memory.

Diagnosis conditions
Ignition on (approx.30 sec. )
Stationary vehicle
Engine not running
Engine temperature> 5 °C
Intake air temperature> 5 °C




In any case, part number 99660611600. 4$ from china, 97$ generic replacement, 161$ from porsche.