I picked up several 3V adapters from Radio Shack to try out. They are candidates to replace my seemingly inadequate 3V 200mA adapter.
I first used my digital multimeter to measure the voltage and amperage of a fresh pair of AAA batteries in the controller. When the controller is turned on but not charging, the batteries produce 3.00V and just 7.5mA. When the controller is charging the car, they produce 2.48V and possibly over 200mA. My multimeter cannot measure amperage over 200mA, but it would occasionally display measurements in the range of 190mA to 199mA, which may or may not be significant.
The table below shows the voltage measurements for the various AC-to-DC adapters. The fields are as follows: voltage when not charging, voltage when charging, Radio Shack part number, price, voltage and amperage rating.
3.66V 1.92V 273-1661 $XX.XX 3V 200mA
3.19V 2.44V
273-1667 $15.99 3-12V 800mA
3.20V 2.82V
273-1756 $16.59 3V 700mA
3.18V 3.02V
273-1754 $19.99 3V 1000mA
3.14V 3.00V
273-1695 $19.99 3-6.5V 2500mA
3.83V 2.58V
273-1755 $13.99 3V 500mA
4.04V 2.20V
273-1662 $14.99 1.5-12V 300mA
I noticed that the red LED looked different depending on which adapter was being used for charging. With the 200mA adapter it appeared dimmer than usual. With the 700mA, 1000mA, and 2500mA adapters it appeared orange instead of red because the green LED was slightly lit at the same time. With the 800mA adapter it appeared the same as with the AAA batteries. Therefore, it seems that the appearance of the red LED is related to the voltage when charging. However, I am not sure if it is better or worse to have a charging voltage that is lower, higher, or the same as that of the batteries. I assume that having nearly the same charging voltage would be ideal, as is the case with the 800mA adapter. One advantage of the 800mA adapter is its variety of voltages for other devices, but one disadvantage is that it is the largest and heaviest of the adapters.
If someone is able to measure the actual amperage when charging, I would be interested in that measurement.
I plan to post pics and detailed instructions of the mod later.
Edit: I measured two more adapters and added their voltage measurements to the table above.