Author Topic: Electrical Loads for a '91 ST ( ST1100 ) *  (Read 4922 times)

Offline KoTAOW

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Electrical Loads for a '91 ST ( ST1100 ) *
« on: April 05, 2009, 02:15:17 PM »
Original article can be viewed here:

Submitted by Mike Martin.


Electrical Loads for a '91 ST

I wanted to know what the normal electrical loads for my bike are, and how much reserve there is in the charging system for my heated gear, higher power headlamps, cruise control, radio, etc. So I pulled all the fuses out, fired up my regulated voltage supply (1998 Explorer - 13.8 volts), and measured the current draw for each circuit, starting at the top (key "On"):


Fuse #    Rating        Description                        Measured Current        Comment    
  110 amp Meter, tail, position 3 amps
  210 amp Indicator, horn 1 amp While sidestand, neutral, and oil pressure indicator lights
were illuminated, not tested for horn
  310 amp Turn, stopSee comment 0 amps normally, 2 amps for turn signal, 4 amps for brake lights
  410 amp Ignition, alternator, start 5 amps Not checked with the starter button depressed
  510 amp Fan 0 amps With the fan not operating, not checked for fan load
  610 amp Clock 2 milliamps
  720 amp Headlight 7 amps With the standard 45 watt bulbs


All these tests were performed with the engine not running. Checking #4 with the engine running showed the same load.

Totaling the figures for #1, #4, #6 and #7, the loads which are constant, while ignoring the loads for #2, #3, and #5, which are intermittent loads, gives a 15 ampere draw. With my 28 amp alternator, that only leaves 13 amps available to re-charge the battery, handle the intermittent loads, plus the added draw from accessories. By the way, my Kimpex grip heaters draw 7 amps on high, 4 amps on low, and my Gerbing jacket liner, 6.5 amps. My H4 headlamps (60/55 watts each) put me over the limit. So I put an interrupt switch on one of my low beams for when I need full heat.

I have since installed a 40-amp alternator. :^)

2001 M. E. Martin, All rights reserved
« Last Edit: January 04, 2013, 02:52:30 PM by Tom Melnik »