Electrical Question for the more KNOWLEDABLE

[NickP]

Aircraft interior lighting runs on 14 or 28 volts DC. Mostvehicles of today run on 12 Volts DC with the exception of a few. I know astandard 12 Volt DC Automotive battery produces 13.9 VDC (please correct me ifwrong). So, the question is simply this; were I to use some of these interior14 VDC lights (some are just too cool to pass up) will the work or do I need tofeed them with a 14 VDC battery? Then comes the question of other electronics,i.e. ECM, light, Start Systems and so on - would they need a device to lowerthe voltage to operate properly?

I look forward to your thoughts and many thanks in advance,

Nick

[MP&C]

I would think the 14 volt variety would work and give you longer bulb life than the regular 12 volt stuff.

[chevynut]

An automotive battery actually is 12.6V at full charge, 2.1V per cell. The alternator puts out around 14V to keep the battery charged.

If the lights are incandescent, they should work at 12.6 volts, but they will be dimmer. For example, if they're 40 watts at 14 volts, they will be about 36 watts at 12.6 volts. If they're LED, I would think they wouldn't be affected that much.

I don't understand your question about ECMs and the other stuff. Why would you need to lower the voltage for them?

[NickP]

If the battery was a 14 VDC rather than a 12 VDC, would Ineed a device to lower output to the ECM, Starter or other 12 VDC normallyoperated items. I knew what I said, LOLdidn't you????? :D

[chevynut]

Ok, I understand now. But where are you going to get a 14V battery?

Whether it affects other components at 14V would have to be figured out by looking at the specs...but my gut says no. Most electronics today are CMOS, and the voltage range is pretty wide. Any linear components can usually handle higher voltages too. Most cars run around 14-14.5 volts while charging the battery.
What are you trying to do? Got any pics of the lights, or specs?

[NickP]

Here is a smathering of the LED stuff I have been loking at: http://www.skygeek.com/interior-lighting.html

[sleeper55]

A standard car battery maintains about 12.4v.
the alernator produces the voltage of 13.9 - 14.3vdepending on the setting of the voltage regulator.
the battery is just a storage compartment with a reserveto start the vehicle and run components until the alternator is up and running.
the current the alternator puts out(amperage) isdependent on the demands it sees and will maintain the battery as required.
if its in a vehicle I cant see why they wouldnt light updepending on how they are wired and how many and the efficiency of your batteryand charging system.
age of battery. clean connections. size of cables. etc...

[chevynut]

Here is a smathering of the LED stuff I have been loking at: http://www.skygeek.com/interior-lighting.html

Nick, LEDs are current devices so a resistor is needed to control the current to them, regardless of the voltage, if it's above the forward voltage of the diode (1.8-3 volts). If you don't have a resistor in series with the LED, they basically burn up. So depending on how bright you want the LED, you choose your resistor accordingly. Usually the small LEDs run about 30 mA but the ones used for lighting are more like 300mA per LED. If you notice, most of these lights have several LEDs in them. LED lights usually have the resistors already in them, or the LEDs are connected in series to drop the voltage, and are designed for the light output specified on the device. Dropping a 14V light to 12-12.5volts would have little effect on the brightness.

As I mentioned before, I don't know where you're going to get a 14V battery. Virtually all light aircraft use 12V batteries for a "14V" system. I replaced lots of batteries in airplanes, and as I recall they were all 12V lead-acid or NiCad. I think the aircraft industry only calls it a "14V system" because it charges at that voltage...and to be different. :)

So stick with the electrical system you have, and the "14V" parts should work fine.

[Rick_L]

You can get a 16V battery, they sell them for drag racing. For the most part, everything works ok on 16V. I think the ones available are kind of light weight, that's the point for those guys.

I think Chevynut's point on 14V vs. 12V for aircraft is correct.

Lots of trucks and industrial equipment now use 24V, some have split systems so that 12V devices can work and be used.

I've been hearing for about 10-15 years that cars were going to go with 36 volt systems in the near future. But the near future is here (or almost) and I haven't seen that talk increase.

The thought on higher voltage is that current decreases, so the conductor sizes can decrease. I don't know what the weight of copper conductors is in a modern car, it's bound to be significant but still not huge.

[chevynut]

Rick, I think the advances in LED lighting has kind of snuffed out the need higher voltage systems. They take so much less current that conductor size can be really small in comparison to other types of lighting. Window and seat motors still take a lot of current, but only for a short time. Heated seats and blower motors put a load on the system too. My guess is that the desire to cut conductor size had to do with the cost of copper as much as decreasing weight. What I see coming is more "smart" wiring systems with more controllers (processors) spread around the car, and with data being sent to those controllers serially so only one wire is needed to "talk" to things. You still need to get power to the loads though.

[Rick_L]

I don't think lighting drives this. And while you see more LED lights on new cars, it's not like they all have them everywhere. Not even close. Maybe the "buss" technology has more traction than the high voltage for now. But even that isn't all that prevalent.

No doubt the carmakers are using engineering economics vs. regulatory requirements vs. some kind of value to themselves and the customer. If you think about it, it would be a major change that would be fairly complex, as everything electrical would change in some way, plus the battery technology and production capability would have to be there too.

[Maddog]

A large auto manufactuer spends millions if not billions on wire, gauge reduction for lighting is a huge savings for them.

[NickP]

Thanks guys!