Electrical Problems

[Peter04]

Hi Guys

Can anyone shed some light on a couple of problems. I have a R1200gs 2007 on a 57 plate.

I have noticed a problem with the lights as I open the throttle the head light, full beam and Aux lights Left and right (touratech) get brighter. Is this likely to be a alternator problem or a voltage control problem (if i could find it).

I have checked the earths and the alternator is charging the battery (odyssey).

Also I am about to fit a touratech xenon aux light but dont have all the wiring harness has anyone fitted one?
I have the light and ballast resistor do i need to fit a relay if so what one.

any info much appreciated.


Peter

 

[Bendy toy]

The lights will always brighten a little from tickover to normal running speed. But to be safe pit a voltmeter on the battery and run the engine to 2000 revs. It should settle at about 13.8 volts. Significantly more would suggest an alternator voltage regulator fault. Its a rare event but over volts will quickly wreck the battery.

 

[Peter04]

Hi I have now had time to do a bit of work on it its 14v when held at approx 2000revs

 

[Myke Rocks]

For your information

Light output of a filament lamp goes up as the square of the voltage.
Look at your tickover voltage and then then the voltage at say 2000 revs
with the lights on.
The rise of probably 1 volt will near enough double the light output.
Myke

 

[Bendy toy]

I fitted relays and a direct battery feed to the headlights on one of my bikes. It gave an additional 1.2 volts at the bulb and made huge difference in light output.
I've lot measured the GS headlight voltage at the bulb under load but it's unlikely to be full battery output.
HIDs use an electronic transformer so are less sensitive to a small bolts drop at the input.

 

[Peter04]

After charging the battery last night fully 12.6 volt (Odssey less than a year old). Disconnected the charger the volts this mor 12.59 as you would except for this time of year. Started the bike the volts on tick over 14.01 volts turned on the full beam still approx the Same volts.

 

[Popell]

Sounds as though you have nowt to worry about there.

 

[Peter04]

yer i think your right Popell the charging system is working and not overcharging the problem lies else where i think at the key and ignition.

 

[AberdeenAngus]

The rise of probably 1 volt will near enough double the light output.
Myke

Nope. A 55w lamp at 12v will give about 65w at 13v, and about 75w at 14v.

Peter
Sounds like your battery was a bit low. If charging it has sorted the issue, then fine.
If not then I suspect the battery might be on its way out.

 

[Popell]

True Aberdeen but pure wattage is no indication wattage, we need to look at Lumens/candels for that and the relationship IIRC is not a linear one.

Also true that a battery can appear decent on a volt meter but perform poorly under serious load - even a one year old battery can be fubar'd if allowed to discharge too far/regularly/for too long.

 

[Myke Rocks]

Nope. A 55w lamp at 12v will give about 65w at 13v, and about 75w at 14v.

Peter
Sounds like your battery was a bit low. If charging it has sorted the issue, then fine.
If not then I suspect the battery might be on its way out.

You misunderstand. It is not about the watts drawn. It is about the light output. As the voltage rises, as you say, the watts increase. But what is important is the filament colour, and hence light output.
If you take a standard incandescant lamp, and put a dimmer on it, reducing the applied voltage by half reduces the watts used by half, but the light output by circa 90%.
Myke

 

[Bendy toy]

I have a digital voltmeter on the bike. It runs at 13.8 to 14V. The battery alone (Odyssey) shows about 13V when ignition is turned off. But that full saturation charge soon drops the 12.5V. During engine start it drops to about 11V. The volts quickly recover, so it looks like only a small charge percentage is used during engine start.

 

[AberdeenAngus]

You misunderstand. It is not about the watts drawn. It is about the light output. As the voltage rises, as you say, the watts increase. But what is important is the filament colour, and hence light output.
If you take a standard incandescant lamp, and put a dimmer on it, reducing the applied voltage by half reduces the watts used by half, but the light output by circa 90%.
Myke

Reducing the voltage by half on any purely resistive load will give about one quarter of the power (V^2/R).

But - I see what you mean. Yes I agree the impact is more complex than a simple power calc however......we are not using standard incandescant lamps.
For Halogen lamps, the power to light output relationship is much closer than with a standard incandescent lamp (ie its a lot more efficient).
Changing the voltage to a Halogen lamp by 1v will give about a 30% change in light output.
I appreciate the point about light colour and human eye response.

Perhaps its enough to say that lamps are designed to run at a very specific voltage and that minor changes to lamp voltage can have dramatic impact on overall useable light output.
The opposite is also true, when you see the light output from your headlamp changing, it might actually be due to really quite small fluctuations in voltage.