Ducati Monster Forum

Moto Board => Tech => Topic started by: GLantern on October 14, 2008, 08:53:43 AM

Title: Calculating Surplus Wattage
Post by: GLantern on October 14, 2008, 08:53:43 AM
I am trying to figure out how much extra wattage i have available on my 1098 for accessories this is the piece straight from the manual detailing how much each electrical piece is using.  The 1098 forums has been little help and i know you guys are really knowledgeable.

The main components of the electrical system are:
headlight:
bulb type: 2 x H11 (12 V-55 W).
side light:
bulb type: 2 x H16W (12 V-6 W).
Electrical controls on handlebars:
turn indicators:
Front: LED.
Rear: bulb type: R10W (12 V-10 W)-orange.
Horn.
Stop light switches.
Battery, 12 V-10 Ah.
Alternator 12 V-480 W.
Electronic voltage regulator (rectifier), protected by a 30 A
fuse near the battery.
Starter motor, 12 V-0.7 kW
Tail light and brake light:
LED.
Number plate light:
bulb type: W5W (12 V-5 W).

I had done the math from the manual guessing on my own and it states the alternator puts out 450watts. And between the lights etc its using around 140watts so that would leave 310 watts available?  Am i correct in my assumptions?
Title: Re: Calculating Surplus Wattage
Post by: Speeddog on October 14, 2008, 09:52:54 AM
Headlight + taillight + brakelight + plate light + instrument lights + ignition system +horn
140 Watts is a reasonable guess.

Keep in mind that the alternator isn't *always* making 450 watts, at idle and lower rpm it can't do it.
I don't know what it makes at idle.

Depends on what kind of load you're considering.
Electric clothing?
Title: Re: Calculating Surplus Wattage
Post by: GLantern on October 14, 2008, 09:59:13 AM
Its about 125watts of electric clothing, gloves and jacket linerm and eventually a 15watt GPS.
Title: Re: Calculating Surplus Wattage
Post by: Speeddog on October 14, 2008, 10:04:22 AM
You should be fine with that, there's folks here who run a good bit of heated gear, perhaps they'll chime in.

You could rig up a temporary voltmeter just to be sure.
Also, Aerostich sells some pretty nice permanent voltmeters.
Title: Re: Calculating Surplus Wattage
Post by: GLantern on October 14, 2008, 10:18:13 AM
Quote from: Speeddog on October 14, 2008, 10:04:22 AM
You should be fine with that, there's folks here who run a good bit of heated gear, perhaps they'll chime in.

You could rig up a temporary voltmeter just to be sure.
Also, Aerostich sells some pretty nice permanent voltmeters.

Awesome thanks for the info this question was on the 1098 forums since last week with no worthwhile reply, DMF 4 life!  [bacon] [bacon]
Title: Re: Calculating Surplus Wattage
Post by: Capo on October 14, 2008, 11:55:58 AM
This is a little closer estimate. The load column is what could be drawn, the real column is a realistic draw during normal operation.

                               Load        Real
Headlight Main Beam   60           55
Side Light                    5              5
Number Plate              5              5
Rear Lamp                  5              5
Brake Lamp               21              0
Indicators (2)             20              0
Instrument Panel        2                2
Fuel Pump                60              60
ECU                         48              48
Fans                        60                0
Horn                        60                0
Total                      346             180
Title: Re: Calculating Surplus Wattage
Post by: Raux on October 14, 2008, 10:24:05 PM
dont forget high beam and lo beam run at the same time right?
Title: Re: Calculating Surplus Wattage
Post by: Capo on October 15, 2008, 12:03:27 AM
Quote from: Raux on October 14, 2008, 10:24:05 PM
dont forget high beam and lo beam run at the same time right?

No
Title: Re: Calculating Surplus Wattage
Post by: Raux on October 15, 2008, 12:06:26 AM
Quote from: Capo on October 15, 2008, 12:03:27 AM
No

sorry idiot me. i was thinking 696. it has seperate lights for high/low
Title: Re: Calculating Surplus Wattage
Post by: NAKID on October 15, 2008, 09:27:24 AM
Quote from: Capo on October 14, 2008, 11:55:58 AM
This is a little closer estimate. The load column is what could be drawn, the real column is a realistic draw during normal operation.

                               Load        Real
Headlight Main Beam   60           55
Side Light                    5              5
Number Plate              5              5
Rear Lamp                  5              5
Brake Lamp               21              0
Indicators (2)             20              0
Instrument Panel        2                2
Fuel Pump                60              60
ECU                         48              48
Fans                        60                0
Horn                        60                0
Total                      346             180


Why would your real numbers for brake lights and fans be zero? Also, what do you think would happen if you had to use the horn with all the gear on?
Title: Re: Calculating Surplus Wattage
Post by: Capo on October 15, 2008, 09:39:29 AM
Quote from: NAKID on October 15, 2008, 09:27:24 AM
Why would your real numbers for brake lights and fans be zero? Also, what do you think would happen if you had to use the horn with all the gear on?

Well because they are not on all the time, whereas the others are.
How often do your fans come on? How often are you on the brakes (as a percentage of running time), how often and for how long do you use your indicators?
What the OP is after is what output from the alternator would be available to power other devices. What has not been considered here is the demand of the battery charge requirement on the alternator.
Title: Re: Calculating Surplus Wattage
Post by: NAKID on October 16, 2008, 08:47:37 PM
Well, I agree that they are not on all the time, or even on all that often, but they are significant. You can't discount them because they are on at times. The fans and brake light, for instance, are on at the most important time, when the rpms are lower and the bike is not making full electrical power. If he is using heated gear, that will be on at the same time as the brake lights, the fans, headlight, all of the high draw items...
Title: Re: Calculating Surplus Wattage
Post by: GLantern on October 16, 2008, 09:41:20 PM
Quote from: NAKID on October 16, 2008, 08:47:37 PM
Well, I agree that they are not on all the time, or even on all that often, but they are significant. You can't discount them because they are on at times. The fans and brake light, for instance, are on at the most important time, when the rpms are lower and the bike is not making full electrical power. If he is using heated gear, that will be on at the same time as the brake lights, the fans, headlight, all of the high draw items...

Well i figure if im just sitting there i wont have the gear on it really would only be when im moving.
Title: Re: Calculating Surplus Wattage
Post by: Langanobob on October 17, 2008, 02:57:32 AM
QuoteAlso, what do you think would happen if you had to use the horn with all the gear on?

That's what batteries are for.  If there's a brief load that's higher than the alternator output, the battery provides the needed juice for a short time and gets slightly discharged.   Soon as the horn is off or speed picks up the alternator regains the load and recharges the slightly discharged battery. It's sort of the same principle as when you start your bike; the alternator is  not charging and the battery gets slightly discharged but the alternator kicks in on it starts, catches up and recharges it.     Only time there might be a problem is if someone rode around very slowly for a long time with the horn blaring continuously, brakes, bacon warmer and turning indicator on.
Title: Re: Calculating Surplus Wattage
Post by: Capo on October 17, 2008, 03:51:54 AM
Quote from: Langanobob on October 17, 2008, 02:57:32 AM
That's what batteries are for, in addition to starting non-kickstart bikes.  If there's a brief load that's higher than the alternator output, the battery provides the needed juice for a short time and gets slightly discharged. Soon as the horn is off or speed picks up the alternator regains the load and recharges the slightly discharged battery.   Only time there might be a problem is if someone rode around very slowly for a long time with the horn blaring continuously, brakes, bacon warmer and turning indicator on.

Thank you for clarifying my point.
In real terms, the CONSTANT load should not exceed 90% of the alternator output. Cyclic and infrequent loads will be supplied from the alternator surplus and the battery.

I have NEVER seen my rad fans operate during normal operation and that includes some tests of the radiator capacity involving reducing the effective radiator width by 100mm.
I would think that giving the climatic conditions that would cause the use of grip heaters, there would be even less likelyhood of the radiator fans operating.
Title: Re: Calculating Surplus Wattage
Post by: GLantern on October 17, 2008, 04:40:21 AM
Wow thanks so much for all this info!  Talk about answering everything! [thumbsup]
Title: Re: Calculating Surplus Wattage
Post by: Keld on October 21, 2008, 09:50:06 AM
Quote from: Capo on October 14, 2008, 11:55:58 AM
This is a little closer estimate. The load column is what could be drawn, the real column is a realistic draw during normal operation.

                               Load        Real
Headlight Main Beam   60           55
Side Light                    5              5
Number Plate              5              5
Rear Lamp                  5              5
Brake Lamp               21              0
Indicators (2)             20              0
Instrument Panel        2                2
Fuel Pump                60              60
ECU                         48              48
Fans                        60                0
Horn                        60                0
Total                      346             180


And then you have to add x watt for charging the battery
Title: Re: Calculating Surplus Wattage
Post by: Capo on October 21, 2008, 10:23:43 AM
Quote from: Keld on October 21, 2008, 09:50:06 AM
And then you have to add x watt for charging the battery

And that would be what?
Read above, when the load exceeds the capacity of the alternator, the battery makes up the shortfall. When the load is less than the output of the alternator, the surplus is available for charging the battery (if the regulator requires it).
Title: Re: Calculating Surplus Wattage
Post by: Keld on October 21, 2008, 11:38:25 AM
Yes but if battery voltage is low it vill need some of the current from the alternator ,  at the same time as your other loads. 
Title: Re: Calculating Surplus Wattage
Post by: Capo on October 21, 2008, 12:15:03 PM
Loads are satisfied first, the regulator will charge at a rate according to the surplus capacity of the alternator.
Title: Re: Calculating Surplus Wattage
Post by: Howie on October 21, 2008, 12:57:17 PM
Quote from: Keld on October 21, 2008, 11:38:25 AM
Yes but if battery voltage is low it vill need some of the current from the alternator ,  at the same time as your other loads. 

An alternator with a wound rotorneeds current to make current.  Your Duc has a permanent magnet rotor.
Title: Re: Calculating Surplus Wattage
Post by: Keld on October 21, 2008, 08:34:04 PM
Quote from: Capo on October 21, 2008, 12:15:03 PM
Loads are satisfied first, the regulator will charge at a rate according to the surplus capacity of the alternator.

According to your list there will be a surplus, so the battery will will charge at the same time as your other loads draw current.

The rectifier/regulator dont "see" any difference between loads  and charging needs. It just try to keep the voltage att same level.
Title: Re: Calculating Surplus Wattage
Post by: Keld on October 21, 2008, 08:44:13 PM
Quote from: howie on October 21, 2008, 12:57:17 PM
An alternator with a wound rotorneeds current to make current.  Your Duc has a permanent magnet rotor.

I  know the difference, But I did not say that the alternator needed current , I said the Battery  8)
Title: Re: Calculating Surplus Wattage
Post by: Capo on October 21, 2008, 11:52:15 PM
Quote from: Keld on October 21, 2008, 08:34:04 PM
According to your list there will be a surplus, so the battery will will charge at the same time as your other loads draw current.

The rectifier/regulator dont "see" any difference between loads  and charging needs. It just try to keep the voltage att same level.


At last you got it.

I never said that the regulator monitors currrent, it looks at the battery voltage and charges at a rate according to the power available from the alternator.