Thank you. Your explanation is very clear. So, can I say that, if I use your calculation on my circuit, regardless which 12V batteries (with different potential Amp amount), it doesn't really matter, right...?
Actually, I am a telecommunication person and doing electronic stuff as a hobby too like the first person who posted this thread. My intention is change the light bulbs in my car to pure white LEDs. Similar to the website I have attached. Is there any advise that you can provide if I want to do this?
http://s40concepts.net/forum/index.php?t=msg&th=6736&start=0&rid=&S=8886a75ac3024342c68db556196a3cc4
I have one more question. When you say 150ohm is to low, does it mean that it will spoil the resistor or the LED? When will the resistor heats up..? Thank you again...
Regards,
Sim