I'm trying to power two servos and three ESCs with my Mega2560. Some post I've read suggested using a LiPo battery to provide power instead of using the 5V from the Mega. I want to test to make sure my setup is correct, so I decided to test it with a spare servo. ... And I let the magic smoke out, so that servo is gone. Apparently the max voltage is 6V. The battery provides 7.4V. I'm thinking of using a resistor to reduce voltage. I'm trying to use the equation V=I*R, but I don't know what the current on a 180 mAh, 2S, 1.33Wh, 7.4V LiPo battery is. I tried testing for it with my multimeter, and I got nothing. ... Am I just asking a stupid questions here? It's been a while since my circuits class and I might be missing something here.
'm thinking of using a resistor to reduce voltage
Then stop, resistors do not reduce voltage they restrict current. Two will allow you to make a potential divider but that will not work to power anything with a heavy current.
You need a voltage regulator to cut down voltage in order to power something.
You can use this UBEC “Universal Battery Elimination Circuit” to power your servo from 5V to 6V.
I would suggest to use a phone chaging plug for usage in cars. They normally have an input range starting from 6 point something volts up to 30V. They have an output of 5V and in the bay you catch them for very few $.
The advantage is good regulation of the output and very low power dissipation.