Dim headlight=bad battery?

[SweetT]

hello everybody, I took a weekend and installed a new set of hella F550 driving lights, and running lights to my K75 and now the headlight is dimmer than normal. I findmyself needing to use the hi-beam under circumstances where the low had previously been adequate. I disconnected the lights I added and it made no differenece to the brightness of the headlight. It's possible that the headlight has been like this for a week or two but I hand't ridden after dark or I only just noticed the headlight was dim since I added all these extra lights.

I put the voltmeter on the battery and it reads 12.6v at idle, but if I turn on the hellas then the voltage drops to 11.8. Regardless of the RPM I cant get the voltage at the battery higher than 13.

Is this an indication that I need to replace the battery?

Please advise

[riderR1150GSAdv]

Sorry :cry about your troubles but perhaps it may be as simple as a bad ground to you headlight assembly.
The battery may be on the way out depending on age, or there may be a bad connection to/from the alternator.
I'd check all connections first before spending $$ on a new battery.
Good luck! :wave

[Bruce_C]

A good way to start would be to put EVERY connection you made to back the way it was before you started this project. And I mean every switch, ground point, fuse, anything you might have added. While doing this have the battery on a charger and check the battery condition using a hydrometer, which is available at Auto Zone for under $2.00.
You might have a bad battery, or you might have some lights wired in series, bad grounds or poor connections. Going back to the beginning is the best way to straighten out an electrical problem.
Bruce C :)

[Burnszilla]

I'd think about doing the 50amp alternator upgrade.

[SweetT]

Well, I'll check the splices and connections I added, but I was very careful to make sure they were all good quality. And like I mentioned earlier, when I disconnected the lights I added, it had no effect on headlight brightness. Thanks guys! :)

[Bobmws]

Check and clean the cluster of ground connections under the tank. Pull and clean the starter, it provides a ground path in BMW's convoluted wiring scheme. You may just need to service the alternator, new brushes.
Once you get the voltage up to par, add a relay set to your stock headlight wiring, the switches are known to fail, even with stock bulbs, and a relay will allow more volts to your headlight. Be sure to use #12 wire.

[antman]

Once you get that problem solved you might want to add a
"Charge Guard" by Kisan, as seen in Motorcycle Consumer news.
Usually I find that if I add equipment not made by BMW,
two years later I have to remove it because it doesn't work any more.
I also have used a headlight modulator from them for years now
with good results.
(I am a retired E.T. with no connections to Kisan.)