What is the ANSI number of the headlamps? Usually this will be a
three-digit or four-digit number, maybe with an "H" on the front. This
will enable you to find the rated voltage, rated lifetime, etc. It also
allows you to see if a "long life" version of the lamp is available.
If this isn't already happening, buy lamps from a reputable manufacturer
like General Electric, Philips, Wagner, or Sylvania. If it is a 12 V
lamp, try the local auto parts stores for a good selection.
Michael's idea is the #1 thing. The actual voltage on the bulbs
compared to their rated voltage. Higher than rated voltage greatly
reduces the life.
Agreed. It might be interesting to hook up a voltmeter at the lamp
terminals and check the voltage both standing still and while driving.
The golf cart may regenerate into the batteries when coasting, which
tends to raise the system voltage; depending on how the lamps are
powered, this may also raise the lamp voltage.
Also, try not to have the headlights on when the golf cart is plugged in
to the charger; this may also raise the lamp voltage.
Sometimes people use a voltage reducer module so they can use cheap
12V bulbs on a 36V or 48V system.
Or, the manufacturer just wires the lamps across the "first" 12 V
battery in the string. This is OK when the battery is being
discharged, but might lose when the battery is being charged - it
depends on the charging voltage.
Vibration doesn't help either..
It may be worth checking to see if someone has replaced a rubber or
spring mounting with a solid mount. You will probably need a parts
diagram for the golf cart or assistance from a dealer to figure this
out for sure.
Matt Roberds