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You might want to do some simple addition and subtraction before you hang too much on the charging system of your S-10. I don't have a copy of the service manual in front of me, but if memory serves the alternator on the Super Tenere puts out about 600 watts (about 40 to 42 amps depending on voltage and RPM). First you gotta' remember it takes a pretty fair amount of that current just to run the electronic ignition, fuel injection system, fuel pump, etc., etc., etc., so that reduces what farkles you hang on there... Then you still have the following:
2 stock headlamp bulbs - 55 watts each (about 4.6 amps) x 2
4 turn signal bulbs - 10 watts each (about 0.8 amps) x 4
Etc., etc., etc., etc. all the way through all the instrument lighting, taillight, license plate light, etc.
Granted, Yamaha was nice enough to put a pretty fair amount of excess capacity in the S-10's alternator, but anytime you start hanging lots of lights and heated gear (basically anything that produces waste heat, like vest, heated grips, halogen bulbs, etc.) you can go into "deficit spending" pretty quick. And don't forget the battery is not a bottomless pit of current... You don't want to operate the charging system "on the edge" as you want it have enough excess capacity to be charging the battery fully between starts. It takes a lot of current to initiate that fuel pump, bring the fuel injection system to pressure, have the electronics go through their self-test, and spin that starter motor.
On my bikes I like to sit down and figure out about how much current it takes *just* to run the bike... Then, and only then do I start figuring out how much my radar detector, GPS, tank bag charging goodies, etc. - i.e. what I feel are *must haves* on any trip I take. Now *after* adding those in the mix I can start thinking about big, bright lights, heated gear and grips, etc. No matter what I'd like to add to the bike I always stop short by about 75 to 100 watts... Why? Because the rating of charging systems is usually done at about 4,000 to 6,000 RPM, and you may not always have the revs that high, and because charging systems don't always put out rated current anyway, not to mention regulator/rectifiers can often degrade over time and not allow full charging, etc.
Better to have a bit of current *in the bank* than run the electrical system the way Washington runs our country's budget...
Just my two centavos... YMMV.
Dallara
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