Just Bought the Parts to Make the AC-Charger - Litle more than I wanted to Spend
 

I just bought all the parts at Radio Shack, heres a price breakdown.

2701801 Project Box 3x2x1 $1.99
2750645 ToggleSwitch $2.99
2760026 Red Led $0.99
2781221 SolderingWire $4.49
2741576 5.5 DC Jack $0.99
2731717 Adapter Plug $0.00
2731756 3VDC 700MA Adapter $16.59
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Total with tax was $30.78

It might be worth it seeing as how if you do the 3V mod to the car youll go through batteries quicker but who knows.

I just built mine last night. It works great. I charged my unmodified car with a stock battery for about 90 seconds and it ran 11 minutes on my track and another 6 miniutes on its' roof (to run the battery down). I think the charger helps with giving a full charge to your car's battery.