Derek
07-17-2005, 06:28 PM
Here's what i want to do:
I have a pair of motorola 2-way radio's that i want to power off a motorcycle battery [for use on the bike] instead of using the NiCd battery that came with it.
Here's the details: Motocycle battery is 12V and the radio's max input is 4.5V 500mA
If i run couple of wires off the 12V battery to the radio and have a resistor in the positive wire i can achieve the voltage drop required - using the following:
12 - 4.5 = 7.5 / 0.5 = 15ohm
with following power rating:
7.5 / 0.5 = 3.75W
So, i'm looking to use a 15ohm resistor with a 5W rating?
Can some kind person please confirm this is correct :)
I have a pair of motorola 2-way radio's that i want to power off a motorcycle battery [for use on the bike] instead of using the NiCd battery that came with it.
Here's the details: Motocycle battery is 12V and the radio's max input is 4.5V 500mA
If i run couple of wires off the 12V battery to the radio and have a resistor in the positive wire i can achieve the voltage drop required - using the following:
12 - 4.5 = 7.5 / 0.5 = 15ohm
with following power rating:
7.5 / 0.5 = 3.75W
So, i'm looking to use a 15ohm resistor with a 5W rating?
Can some kind person please confirm this is correct :)