To make your own PCB LED light bulb, you will need a soldering iron and some solder, some LEDs and a pre-drilled circuit board. You will also need an old, burnt out incandescent light bulb. To make a LED light bulb for about three dollars, look online for bulk LEDs. You can find them out of China now for about a dollar with free shipping PCB for a hundred LEDs. The circuit board can be found for about $2. These are pre-drilled with the copper rings on the soldering side. You will also need two pieces of scrap wire about three inches long.
White LEDs require about 3.2 to 3.4 volts PCB each. Your RV or car battery runs between 12 volts to 14 volts. Normally it runs around 12.5 volts to 13 volts on average. To save money, we will not be using a voltage regulator or current limiter for the LED light bulb. Instead, we will use enough LEDs in series to allow them PCB to limit their own current.
If you string 4 LEDs together, plus to minus and plus to minus, then you will have a total voltage of between 12.8 volts and 13.6 volts across the LEDs. By calculating 3.2 volts x 4 LEDs, we get 12.8 volts total. On the high range, 3.4 volts x 4 LEDs gives us 13.6 volts total. Using these PCB calculations, the vehicle or RV average 12.5 volts to 13 volts is perfectly in the range of our LEDs, so no limiting PCB resistor will be needed. Even if the battery does go over 14 volts for a short time, it should not harm the LEDs. They may get a bit warm, but should be fine. 
