Light bulb voltage and current

I am building a radio controlled model boat and wish to run 2 sets of minature lights from a 12v supply. I have two 6v 4Ah batteries to be wired in series to give me the 12 v. This supply will run 2 speed controllers for 2 motors. I also want to run separately in parallel, two switchable (on \ off) lighting circuits from this supply.

The minature bulbs run on 12v and each bulb has a current rating of around 80mA. To ensure the brightness of the bulbs the lighting circuits will be in parallel. One lighting circuit will have 2 bulbs in parallel and the other will have about 10 bulbs, also in parallel. However, I don't know if the bulbs will blow due to the current in the circuit ie 2 x 4Ah = 8Ah(?) and them being rated at 85mA each.

Am I able to wire the bulbs as described (hope I made this clear) to operate properly or, does each bulb (or circuit) need a resistor in series to stop them blowing? Can you advise?

I guess what Im trying to discover is, if the supply voltage and the operating voltage of the bulbs is the same ie 12v, does it matter about the current in the circuit (8A) and each bulb (approx 80mA) being different?

Posted by David Neve on 11/04/2003, at 10:51 GMT

Light bulbs

What you are trying to do is fine. The important thing with bulbs is to supply them with the right voltage, so suppling 12V bulbs with 12V will work ok. If they were 6V bulbs on a 12V supply, then they would blow after a short time.

Each bulb will consume as much current as it needs from your batteries, so the lower the current they consume, the longer you batteries will last.

Posted by Tim Surtell on 11/04/2003, at 10:54 GMT