Author Topic: Map reading light bulb blown/gone-will it still draw power from battery!? (Read 1921 times)

Jocko · « **Reply #15 on:** March 03, 2020, 08:09:40 PM »

Quote from: culzean on March 03, 2020, 07:32:19 PM

Took even less on the old car and motorbike 6V systems....

My first bike had 6-volt electrics. On a wet night, I had to stick my hand in front of the headlight to check it was on!

Spencer69 · « **Reply #16 on:** March 05, 2020, 10:40:17 AM »

Final update! (promise)!

Managed to buy last festoon bulb from local car spares shop around corner & now have 3 fully functional interior lighting...2 map reading lights for passenger and driver and middle dome light that illuminates for 15 secs upon entering/exiting car.

When buying bulb, did ask about LED replacements, but they don't deal in LED's! However, more than happy at moment that this is 1 less task on current list of life's 'trials'!

On separate post by zzaj, as I admit, not a electrician, what difference would a 24v system in car make as oppose to current (no pun intended) 12v system? Is it just less chance of battery drain & more powerful electricity system!

Jocko · « **Reply #17 on:** March 05, 2020, 11:48:32 AM »

It effectively halves the current. Most trucks and buses use 24v electrics.

culzean · « **Reply #18 on:** March 05, 2020, 02:05:26 PM »

Quote from: Spencer69 on March 05, 2020, 10:40:17 AM

On separate post by zzaj, as I admit, not a electrician, what difference would a 24v system in car make as oppose to current (no pun intended) 12v system? Is it just less chance of battery drain & more powerful electricity system!

24 volts means that they can use thinner wire to carry the same power ( power ( watts )= volts x amps, so 12 watts at 12volts = 1 amp, but 12 watts at 24volts is only 0.5 amps ) and any bad contact makes less difference to the resistance of the circuit, basically the voltage drop is reduced between battery and the things that use the power and more usable power is available where it is needed..

The battery gets more complicated as instead of 6 x 2.1 volt cells you would need to squeeze 12 x 2.1 volt cells in, which means larger battery size for same A/H rating and twice as many joints between cells to go wrong. Lorries use 2 x 12volt batteries connected in series to get their 24volts. When 12 volts has been the standard for so long and everything is made for 12 volts it means it is a big problem to change. 12 volt systems are a compromise ( and a good one ) between size of battery and wiring, as as said previously were a big improvement on 6 volt systems.