Everything mentioned so far is good, but let's not loose sight of the
fact that a motorcycle is _far_ from an ideal 12 volt system.
I'd actually be quite concerned about the health of the charging
system and battery if it actually measured 12 volts while running.

The picture on ebay is a bit fuzzy, but I believe I see what looks to
be a SM resistor visible in the string. Assuming it is, and assuming
"they" have correctly valued it for 12 volts - both big assumptions -
you could be putting nearly twice the rated current through it.

Based on more assumptions, previous experience, and your "groups of
three" comment.... I'll assume that it's three LEDs in a string with a
current limiting resistor. That resistor should be sized by Ohms Law;
R=3DE/I, where "E" is actually (supply voltage - sum of LEDs Vf).

Making up some numbers for this, let's assume 12v, 50mA current and an
individual Vf of 3.4v. this becomes

(12 - 3.4 - 3.4 - 3.4) / 0.05 =3D 36 ohms

But putting that in an automotive system with a 13.8v nominal supply gives =
you
(13.8 - 3.4 - 3.4 - 3.4) / 36 =3D 0.1A or 100mA.

There's lots of reasons for LEDs to fail, too much current is pretty
high on everybody's list.

And don't forget that any automotive application has very dirty power
with lots of spikes and surges and other nasties, all of which have
negative effects on your LED life.

-Denny
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.