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Discussion Starter · #1 ·
Last week I noticed that my xenon headlamp flickers wildly when I crank a cold engine on my '98 TBS. Previously, the xenon light output would remain steady during cranking - even when it was cold soaked into the low 20 deg F range.

A little background:

I swapped the stock Triumph alternator for a like alternator from a Kawasaki ZRX1100 because of a broken alternator shaft bolt.

The battery is about 2 years old, never on a tender, but I commute regularly, year round.

The engine turns over strong, and starts up every time.

I checked the open-circuit battery voltage: 12.3V JUST AFTER shutdown (still has residual surface charge). Cranking voltage unknown.

Q1: What is a healthy open circuit voltage for the battery after sitting overnight? What is an acceptable drop during cranking?

(My comment: 12.3V seems low based on my experience with automobile batteries. I expect 12.6 nominal, and closer to 13V immediately after shutdown.)

Q2: Could the Kawasaki-spec alternator be charging at a lower voltage resulting in a lower charge state on the battery?

I've heard the stories about optimal battery condition requirements for the T3 bikes. And, I'm concerned about damaging the xenon bulb with the voltage fluctuations. I just need to isolate the battery as the problem, and not the alternator.

I put the battery on a 0.35A trickle charge and will check the state tomorrow morning. Any other suggestions?


Q2:
 

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Mine is always 12.7 or thereabouts, even after a long run. Cranking drops down to about 10.9, it is charging at 13.2 whilst running at 3.5 thousand rpm
Edit forgot to add: all bikes will vary somewhat, even the same make and model. No lightswitch?
 

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Mine is always 12.7 or thereabouts, even after a long run. Cranking drops down to about 10.9, it is charging at 13.2 whilst running at 3.5 thousand rpm
Edit forgot to add: all bikes will vary somewhat, even the same make and model. No lightswitch?
Pretty sure putting a switch on the headlamp's illegal in the states. Doesn't mean it's not a bad idea...
 

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Most headlights on bikes have an interrupter circuit when starting the bike, the TB has.

Charging from the alternator is generally around 14.3-14.7v

That's pretty normal even for cars.


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Mine has an on/off switch on the right hand bar. I always switch the lights off when starting. My multimeter could be reading low too.
 

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Most headlights on bikes have an interrupter circuit when starting the bike, the TB has.

Charging from the alternator is generally around 14.3-14.7v

That's pretty normal even for cars.


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Ride on ! :)
Perhaps NZ had TB's shipped with this feature? My '02 TB does not have this feature; the headlight is on while the ignition is on, no matter what; during starter operation, etc.

That's why I installed a switch (which is illegal in the states; it is legal, and not an uncommon feature (although not on my bike) to have a starter interrupt, but it's not legal to add the ability to arbitrarily disable the headlight on a motorcycle. At least not in Washington, DC; other states may vary, but AFAIK, it's universal in the US.
 

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Discussion Starter · #7 ·
Thanks for the feedback, all.

After a night on a .35A charge, the battery read 12.7, and got no flicker from the xenon upon starting this morning. This probably isn't conclusive evidence since battery voltage right off the charger can be misleading.

I suspect that the low battery voltage and the swapped alternator are not a coincidence. I'll run a few more tests to be sure. Eventually, I'll extract the bolt-half from the alternator shaft and reinstall the original alternator just to rule out this part before buying a new battery.
 

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What voltage did the meter read on the battery with the engine running ?


My '98 TB is a UK model, it does have a headlight switch but if the headlight is switched on when you start the engine the headlight is interrupted momentarily whilst the engine starts.

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Headlight Circut

What voltage did the meter read on the battery with the engine running ?


My '98 TB is a UK model, it does have a headlight switch but if the headlight is switched on when you start the engine the headlight is interrupted momentarily whilst the engine starts.

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Ride on ! :)
All the lights are 'interrupted' on my bike when the start button is pressed. This is caused by the virtual 'dead short' across the battery when current is fed to the starter motor brushes. In other words, the starter is sucking out all available current the battery can produce and there is none left for the lighting circuts.
 

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Discussion Starter · #11 ·
Followup

I put the battery on a 350mA trickle charge overnight. Battery showed 12.8V. Let the battery sit for 24 hours without a charger and still held 12.8V.

Put about 350 miles on the bike over the last few days, and still showing 12.8V, and no light flicker. I'm confused as to why I was getting a low reading before, but I don't seem to have a problem now. I'll just wait and see if the gremlin reappears.
 
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