This time the 99 cent store cell phone car charger had an op amp -- I think -- instead of 3 transistors. I didn't care. I got a 1800 ohm R1 resistor from another cell charger and poked it in parallel with R1 on the new one. No change in output voltage. OK maybe I didn't/don't have a clue as to how the voltage is cut in half.
I tried the resistor at R2 and the voltage went up the desired amount. Pure luck. I soldered it in and spliced in an auto bulb for resistance. Anyway it is better than spending $50 for a Dewalt charger.
One last question: why does it show 30 v on the ac mode of my multimeter?
Bret Cahill