Modifying the 7XX/9XX Electrical System Load

[Shazaam]

The question of whether you can run both headlights together, add auxiliary lighting, or use heated clothing on a Ducati comes up regularly. When you add additional electrical loads to a motorcycle several factors are involved.

First is the electrical output capacity of the alternator. The 1995–1998 superbike models were designed with a 350 watt 2-phase electrical system. The 1998 ST2 is unique, it was Ducati's one and only 450 watt 2-phase system. For the 1999 model year 1999, Ducati partially redesigned the charging system going from the 350 watt 2-phase design to a 520 watt 3-phase alternator.

Here's how the alternator power output is intended to be used: low beam (55W), high beam (55W), sidelight (5W), tail lights plus brake lights (21W), turn signal lights (10W), number plate light (5W), instrument cluster bulb (2W), warning light bulb (1.2W), fuel pump (clean filter)) (60W), horn (60W). cooling fan (60W), electronic ignition (48W), computer (24W.)

If only the high beam or the low beam headlight is on at one time, the total of the above loads is 350W. This is called the system design basis used to size the alternator. However, this is different from the normal operating conditions.

For example, a common operating condition for an early model would be low beam on (55W), high beam off (0W), sidelight off (0W), tail lights plus brake lights on (21W), turn signal lights off (0W), number plate light on (5W), instrument cluster bulb on (2W), warning light bulb off (0W), fuel pump on (60W), horn off (0W). cooling fan on (60W), electronic ignition on (48W), computer on (24W.)

The total of the above loads for this operating condition is 275W. This leaves 75W (350-275) or 245W (520-275) for (say) a 999 available to run auxiliary equipment and to charge the battery. However, if you add electrical loads you can see how under different circumstances you can (sometimes only briefly) have an electrical load demand that exceeds the alternator design capacity. Under these circumstances your electrical current through the wires from the alternator to the voltage regulator is maxed out at 29 amps (for a 350W system) or 43 amps for a 520W, the regulator is operating at maximum capacity, and your battery is discharging.

[Chest2Tank]

Excellente! You have the best info. Thanks a ton!

Now, how should I plug these fog lamps in.....

[TheFrog]

This is great info.

Would someone know if we can assume the same about the 1x98, Streetfighter and Multistrada?

Cheers,
Olivier

[Stick]

Originally Posted by Waldorf

This is great info.

Would someone know if we can assume the same about the 1x98, Streetfighter and Multistrada?

Cheers,
Olivier

Best place to look is your owner's manual, towards the back of the book. I know the older Multi's are 520W. The 1098 might be unique. I think they backed off a few watts again to save weight...

Slight correction to Shazaam's post: 1997( EU) and 1998 ST2 had a 420W. And the 2-"WIRE" stators are called single-phase.
Also note that he summed up all the loads. How often do you "run" your 60W horn? That one is definitely an intermittent load...
About 6 years ago, I MEASURED the real running power flowing out of the battery on my ST2, and it was right around 200W to run the FI engine, ECU, low beam, and other "normal" loads.
I did it by unplugging the stator plug, so that the bike had to run off just the battery. And since I had access to a "DC clamp-on ammeter", that made the job very easy.

[ecca]

Originally Posted by Shazaam

For example, a common operating condition for an early model would be low beam on (55W), high beam off (0W), sidelight off (0W), tail lights plus brake lights on (21W), turn signal lights off (0W), number plate light on (5W), instrument cluster bulb on (2W), warning light bulb off (0W), fuel pump on (60W), horn off (0W). cooling fan on (60W), electronic ignition on (48W), computer on (24W.)

The total of the above loads for this operating condition is 275W. This leaves 75W (350-275) or 245W (520-275) for (say) a 999 available to run auxiliary equipment and to charge the battery.

Hi Shazaam, I have fitted two 55W spotlights, DP heated grips and GPS to my MTS1100 and plan on using a EXO2 heated vest which draws 2A. I estimate that the total power of those items, when turned on, will be 200W thereby leaving 45W free.

My query is, will the remaining unused 45W be sufficient to charge the battery?

[st2lemans]

Originally Posted by ecca

Hi Shazaam, I have fitted two 55W spotlights, DP heated grips and GPS to my MTS1100 and plan on using a EXO2 heated vest which draws 2A. I estimate that the total power of those items, when turned on, will be 200W thereby leaving 45W free.

My query is, will the remaining unused 45W be sufficient to charge the battery?

It depends what RPM you are turning.

The alternator only starts putting out full power at 5000RPM or so.

My ST2, for example, hits break-even at 2000 (no lights), 3000 (low-beam), or 4000 (low+high beam). (below break-even the battery is discharging)

Get a volt meter and measure at the battery. If you see 13.8V (or more), you are charging. Do this with different loads/RPM. Then you will know for sure.

Tom

[ecca]

Thanks for the advice Tom.

[99duc996s]

good important info, thank you

[DirtyDucRider]

This is an awesome thread! Thanks for the info!


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