Basic Led Questions (Car Install)

[Sol Garrett-Hanna]

Hey guys, decided to join a forum where there is lots of people who know a lot about electrics. 

I've done basic physics, circuits etc through school currently at uni doing engineering and do a fair bit of DIY at home. Mostly on cars for fun. 

But have a few questions which hopefully you guys could answer. LEDs producde heat, would running LEDs (say 16, along a strip) in a foot well cause a considerable amount of heat? They didn't come with ratings, wattage or anything. Just said 12v LED strip. 

I have noticed a few people run drivers, can I ask why thats necessary? It seems a lot of people just run a power with a switch and fuse and an earth. But would this not shorten the lift of the LEDs since car voltages can spike?

 

[Blue Duck]

Ive got LED strip in the van, doesn't really get hot as its never really on for that long but will get warm if left on for ages.

The wattages depend on the type of led strip you use 5050 / 3528 and the number of LED's per metre, It will range from about 4w/ 15w a meter.

Dunno about drivers for 12v DC? Some of the LED's die ( not that you will notice)  I guess due to voltage spikes perhaps or just the fact they are cheaply made? Maybe there is some kind of filter available? I have taken out a whole string when I changed a lamp on the van and accidentally shorted the holder on the bodywork but they are cheap and easy to replace.

Hope this helps

 

[Richard-the-Ninth]

People use "drivers" to drop the voltage from mains to.............normally 12v DC. (Leds do not "like" A.C.)  Never heard of a 12v to 12v driver. With most LED strips each LED has its own resistor so you can run it at 12v (some are 24v) with no problem

 

[SLIPSHOD & SLAPDASH]

I would have thought most modern vehicles have far more delicate electronics in them than an led strip & i wouldn't worry about it. All the strips i have seen & installed run slightly warm so that also shouldn't be a problem unless you have sheepskin footwells.

 

[Sol Garrett-Hanna]

Ah perfect thanks very  much guys! 

 

[Bruspark]

The '12v' led strips tend to be multiple repeated sets of 3 LEDs and a resistor in series. White LEDs are typically a reasonably fixed 3v each so then a resistor drops the last 3v at the desired led current.

A vehicle 12v system is only 12v when it's off! Running fast and charging the battery it's not uncommon to see 14v or even 15v. This doubles the current through each led and resistor chain (much more light output). Vehicle led lighting is specified for this (fat resistor over rated led), kitchen cabinet lighting is not. You can fit additional series resistors to reduce the problem or just accept a limited life for the strips if used when the engine is on.

Much of the led energy is emitted as light, but all of the resistor energy is emitted as heat

 

[SLIPSHOD & SLAPDASH]

Good points bruspark, hopefully the voltage should never go above 13.5v.

 

[Sidewinder]

14.2 - 14.4 used to be the setting for alternator voltage regulators going back qbout 10 years, not sure if they have been dropped, but, from recent conversations with a Senior Tech @ one of the local main dealers, I don't believe thay have.

However, you should never see 15V unless there is a fault.