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RedDevil · 01-07-2018, 02:05 PM

A bridge rectifier may take 1.2 Volt max, probably less. A proper dc-dc regulator will take a bit too, but generally more than compensates for it by lowering the current draw.

Most of my cheap China LEDs are sensitive to polarity. As a rule of thumb they work fine in the interior but fail within months in any lamp housing on the outside. But the reign of my thumb ain't perfect.

What kills most LEDs is heat changes; apparently the repeated expansion and subtraction cracks the contacts or the heat sink. The resistor on one stalk of the cheap LEDs transfers its heat into either the cathode or anode side of the LED while the other side stays cool, so they self destruct over time.

Another feature of some LEDs is that they will block the current if overpowered; some semi-conductive layer in the LED will invert or so. The current drops to a few micro-ampere and you can just see them glow weakly when it is dark.
So, a short spike in the voltage may send a resistor paired LED in that mode and from there on, as the current is restricted by the LED more than the resistor, it gets the full 12V and that too kills it.

01-07-2018, 02:05 PM	#8 (permalink)
RedDevil Master EcoWalker Join Date: Dec 2012 Location: Nieuwegein, the Netherlands Posts: 3,998 Red Devil - '11 Honda Insight Elegance Team Honda 90 day: 49.01 mpg (US) Thanks: 1,711 Thanked 2,245 Times in 1,454 Posts	A bridge rectifier may take 1.2 Volt max, probably less. A proper dc-dc regulator will take a bit too, but generally more than compensates for it by lowering the current draw. Most of my cheap China LEDs are sensitive to polarity. As a rule of thumb they work fine in the interior but fail within months in any lamp housing on the outside. But the reign of my thumb ain't perfect. What kills most LEDs is heat changes; apparently the repeated expansion and subtraction cracks the contacts or the heat sink. The resistor on one stalk of the cheap LEDs transfers its heat into either the cathode or anode side of the LED while the other side stays cool, so they self destruct over time. Another feature of some LEDs is that they will block the current if overpowered; some semi-conductive layer in the LED will invert or so. The current drops to a few micro-ampere and you can just see them glow weakly when it is dark. So, a short spike in the voltage may send a resistor paired LED in that mode and from there on, as the current is restricted by the LED more than the resistor, it gets the full 12V and that too kills it. __________________ 2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut. lifetime FE over 0.2 Gmeter or 0.13 Mmile. For confirmation go to people just like you. For education go to people unlike yourself.