70 amp charger cooking 12v LEDs?

MEXICOWANDERER wrote:

Gdetrailer wrote:

time2roll wrote:
It is voltage not amps that will affect LED lamps.
You really need to check the LED specifications.
Quality LEDs are good from about 9 to 30 volts.

REGULATED LEDs will typically have 9 to 30V range..

UNREGULATED (AND HENCE THE ONES THE OP IS DISCUSSING) DO NOT HAVE 9-30 volt range..

Regulated LEDs use a constant current switching regulator power supply..

UNREGULATED LEDS either use a RESISTOR to "regulate" the current draw OR NO RESISTOR AT ALL (IE LEDS IN SERIES WITHOUT A RESISTOR)..


The unregulated LED modules tend to have a VERY NARROW OPERATING VOLTAGE and may or may not be happy at any voltages above 13.8-14.2V (typical auto CHARGING voltages when engine is running).

There is no way that anyone here on this forum will be able to tell the OP if his selection will be fine or not at 14.4V or higher..

OP will simply have to try them and see for themselves..

As a side note, VOLTAGE DOES AFFECT THE AMOUNT OF CURRENT LEDS DRAW..

Unregulated LEDs are especially vulnerable since they will sharply draw MORE current any time they have MORE VOLTAGE applied than what they were designed to typically operate at.

Regulated LEDs due to the switching regulator are kept at a constant current although the INPUT current can change up or down with the voltage changes.. Feed a regulated LED 9V and it will draw more current at the input than say 15V would..

:B

IMHO

Right
On
The
Money
Answer

GDEtrailer.

I spend hours each day playing with LEDs from 20 milliamp to 500 watt ratings. Trying to outguess and predict P/N junction temperatures (effective heat sinking) versus an absurdly sensitive milliamps tolerance is ummmm... unwise. Volts (in tenths) per degrees reaches a "certain" value, then above that the heating goes nuts. BOINK! Failed LED. I try to maintain a 122F (40c) chip lens temp max limit. For me, this temperature causes me to withdraw my finger rapidly and say HOT!

As I increase volts from say 12.2 to 13.0 I would have to guess many unregulated LED SMDs gain 50% in brilliance. Lumens, brightness, whatever.

yup, you want to drive LED's with a constant current. trying to do that with a voltage source is fraught with problems even if the voltage source is highly regulated, which a RV voltage source is NOT. junction voltage has a negative temp coefficient, often resulting in thermal run away. and as mex observed, brightness is a highly nonlinear function of applied current. Ideally for max brightness you drive it with a duty cycle pulsed current since brightness is not a linear function of applied current. so you pulse the current at something above 60hz but keep the rms value below the max. and the current drive should have some element of temp compensation as well to reduce current with increasing device temperature to avoid thermal runaway.

today many LED's have the regulation circuitry built into the die and don't require much additional circuitry. But beware of possible high RF generation from some devices. It can vary from almost none, to making watching tv or listening to the radio or stereo almost unbearable.