Total Electrical output for 1983 GS650GLD

[Anonymous]

I'm hoping someone can help me with this.

I am currently modding my bike to make it more suitable for long distance riding/touring. I currently have auxiliary driving lights installed, as well as a plug in for my electric vest.

What I would like to know is what the total output of the charging system is, and also how much excess power is available (in Watts)

My driving lights (55W halogen) draw 35W per bulb, for a total of 70W (these lights have been tested on several occasions, running in the wee hours of the morning or late at night for several hours with no ill effects on battery charge or startability)

Not sure what the draw on my electric vest is, but I have used it with the driving lights on and was still able to start the bike after an hour or so of riding with both accessories going.


Does anybody know just how much you can add to this bike in the way of electrical accessories without killing the battery?

I would like to add heated grips and a couple of auxiliary brake lights to my top case and hard sidebags.

[focus frenzy]

280 watts total at rated rpm (should be 5000rpm but can't find that for sure)
I had done load test on my bike early this summer but can not remeber the numbers I came up with. (using a MAC inductive amp probe)

[Anonymous]

Thanks for the info. Any idea what the standard load is? spark, charge, headlight.

Also, is there any way of boosting the power output? higher output alternator?

Owen

[earlfor]

Leon is correct in that the max output is 280 watts at 5k rpm. However, the situation is a bit more complicated than that. You bike does not have an alternator in the sense that a car has one. On a car, charging current/output adjusts to load and can remain constant with engine rpm changing. This is not true of the GS charging system. Output is fixed and increases directly proportional to engine rpm. Load is not considered.
Your output will be the same at 5k rpm regardless of whether any electrical devices are on or off. Any excess current/output goes to ground and is converted to heat and absorbed by the cooling fins on the regulator/rectifier. If load is not balanced to output the system does not work. Too much output and not enough load leaves too much excess current to heat up the R/R, and you burn out R/R's and boil batteries.
With too much load, not enough current is left to keep the battery charged and you end up with a dead battery.

Your stator outputs 280 watts @ 5K rpm. Output is linear. At 2500 rpm, the output is 140 watts. At idle of 1200 rpm, the output is 70 watts.

Headlights, ignition, turn signals and tail lights consume the same amount all the time, so the amount of "free" wattage depends on what rpm you are runing the engine.

You should be able to use the rpm you normally cruise at on the highway to get an idea of how many accessories you can run on a trip. This will not apply though for stop and go, in town driving, You would run the battery down in that circumstance, due to lower rpm and reduced output.

A stock headlight is 55 watts
turn signals (two at a time activated) 46 watts
tail light (single bulb) 8 watts
tail light stop element 23 watts
ignition 20 watts
Add 20 watts draw for aging wiring and connectors, switches, etc.

Then add up all electrical draws in watts and multiply x 1.3. That will be the wattage output needed to maintain the battery at the level it started at due to charging inefficiencies of a lead acid battery. Or, to put it another way, if you put 130 watts of power into a battery for one hour, it will absorb 100 watts of engergy. The rest is lost to heat.

When you know the draw of everything you will be using and the rpm you will use it at, you can make an educated guess of how much additional load the system will handle. But, that guess will only be valid for one set of conditions/rpm.

Earl

Thanks for the info. Any idea what the standard load is? spark, charge, headlight.

Also, is there any way of boosting the power output? higher output alternator?

Owen

[Anonymous]

Thank you Earl. That is exactly the kind of info I was looking for.

Going by those numbers, cruising at highway speed (~5500rpm), I should have somewhere around 150W excess power for accessories, given a standard load of the following items:

Headlight: 55W
Taillight: 8W
Ignition: 20W
'Lost Power': 20W

At least now I know that I can run my electric vest and my driving lights for extended cool night riding without killing my battery.

Owen

[earlfor]

If you are running your headlight (55 watt) plus two aux lights (70 watt), tail (8 wattt), ign (20 watt), lost power (20 watt), that totals 173 watts. That times 1.3 for minimum to maintain battery voltage is 224 watts already required without accounting for nominal turn signal and brake light usage. That leaves 50 watts excess and that is excess only if you maintain 5K rpm. Since you have 50 watts excess from a max output of 280 watts, that is an 18% surplus. Therefore, in excess of an 18% reduction in rpm will mean you are operating at a loss. 82% of 5000 rpm is 4100. Below that rpm, your battery will be being depleted.
This is for the system before adding anything to the stock accessories and lights you are already running..
Unless everything additional you intend to run consumes a total of less than 50 watts, the system will not be self sustaining. I suspect if you have been running an additional load in excess of that, the only reason you have not had electrical system failure is that you have not run for a long enough length of time to deplete your battery below a voltage level that will run the bike.

As I said, it is not a regulated system. It is a load balanced system and is designed to provide slightly more than is required by standard accessories, but not so much more that the R/R will not be able to absorb the heat. Voltage/electrical pressure is regulated, but flow/watts/amps is not and what is produced must be used to keep the system in balance.

You only have about 50 watts excess.

Earl

Thank you Earl. That is exactly the kind of info I was looking for.

Going by those numbers, cruising at highway speed (~5500rpm), I should have somewhere around 150W excess power for accessories, given a standard load of the following items:

Headlight: 55W
Taillight: 8W
Ignition: 20W
'Lost Power': 20W

At least now I know that I can run my electric vest and my driving lights for extended cool night riding without killing my battery.

Owen

[Anonymous]

I agree with you Earl. I consider my driving lights to be auxiliary items because I only run them at night, never during the day, and the vest only when it's cold out (below ~5C)

I don't really factor in the extra power drawn by turn signals and brake light as they are only intermittant usage, and therefore not too big a drain on the system (at least not so much that they will flatline my battery right off)

I've only really been concerned about the drain imposed by my auxiliary driving lights and the electric vest, as they are the high draw items that will see the most use, at least in the spring and fall. During the summer, I'll only have to worry about the lights.

I tend not to run with my driving lights on while tooling around in the city at night, as I don't really need them. I put them on mainly for highway use so that I have a better chance of spotting wayward wildlife before it jumps out in front of me.

Owen

[earlfor]

Owen

The secret (if it is such) :-), to a long life from a battery and R/R is to balance the system. Its best to use all the output with just enough left over to keep the battery charged. Clean connectors are a big plus too.

Earl

I tend not to run with my driving lights on while tooling around in the city at night, as I don't really need them. I put them on mainly for highway use so that I have a better chance of spotting wayward wildlife before it jumps out in front of me.

Owen

[Anonymous]

Great bike gallery Owen!!