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do highbeams kill the battery even if the bike is running?

7651 Views 85 Replies 26 Participants Last post by  s295647
Does riding with the highbeams on kill the battery? I always ride in the daytime with my highbeams on and after a long ride its like my battery is at 50 percent when I go to start the bike up. Or is my battery going bad?
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Marshall said:
Get a battery tender, keep your bike plugged in while it's parked at home. Keep your battery in tip top condition.
Bingo! Atleast charge it every 2-3 months. These bikes will not stay at full capacity like a car or truck. The battery voltage wears down after repeated cranking and needs to be charged.

I have a 2004 and the high beam switch nevers go off.
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FACTION95Si said:
I think this pretty much sums it up. I have an 03. Back in 2003 there were threads about this issue all the time.
I think this problem has been totally misunderstood and falsely blamed on the high beams. As Knight points out, it's the R/R being too close to the headers that's causing the problem. The high beams are just a symptom of the cause.
~BLACK ICE~ said:
my '03 has had that problem from the get-go. when i first purchased it the dealer told me that i was only able to use the high beams on the freeway.. hahahahaha

i have purchased a new rectifier but am too lazy to install it.

i would run the highbeams 24/7 if i didnt have that problem. i did although purchase a new battery. ;)

..... oh and yes this is like the 3459834029833498 post about high beams.
Come on man! In less than 30 minutes you can fix your problem. That R/R is easy as hell to swap out and if it's good it'll most likely solve the problem. If you continue to run the bad R/R on the new battery it will damage that one also. Get to it!
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FACTION95Si said:
Knightslugger I havn't had it tested.

Is this something the Honda dealer will do under warranty?
If you have a multimeter I can show you how to test it yourself. Pretty simple actually.

FACTION95Si said:
BTW this thread is on its 4th page. Anyone feel like this is beating a dead horse?
It almost always ends up like this...

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FACTION95Si said:
Yes I do have a multimeter here at work and I rode to work today! Tell me how please.
Run this one first...

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Alex_RR said:
after searching the problem out, it looks like the culprit is not the high beams or the battery. Can someone please confirm that the parts listed in the pic are indeed what I need to solve the problem?

Thanks for the info guys
I can't find a picture or description of the Stay and the Collar. Who said you needed those and why? All you should need is the R/R. Make sure your battery is good before you install the R/R. If the battery is bad then get a new one.
Ok. All of this talk of High beams and batteries has got me to thinking. So I went out and tested the bike. The results were interesting to say the least. Now keep in mind this bike is a 2004 w/ 24k miles on it. Original battery and R/R. No mods other than a PC, a pipe, rear turn signals and a tag LED light. My alarm should be in the mail.


Bike Off - 12.93v

  • High beams - 12.15
  • Low beams - 12.27
Cold Cranking volts w/ High Beams on - 11.09 (Lowest voltage drop while cranking)

Bike Running w/ Low Beams:

  • Idle (1,400) - 13.97
  • 2,000 - 13.88
  • 2,500 - 14.36
  • 3,000 - 14.25
  • 3,500 - 14.25
  • 4,500 - 14.20
  • 5,500 - 14.20
Bike Running w/ High Beams:

  • Idle (1,400) - 13.22
  • 2,000 - 13.82
  • 2,500 - 13.80
  • 3,000 - 13.82
  • 3,500 - 13.85
  • 4,500 - 13.90
  • 5,500 - 13.91
Battery voltage after shutdown - 13.32 (2-minute cool down)

Alright you electrical wiz kids! Tell me what this means!
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Here's the point I want everyone to listen to.

When I'm charging the battery on the table with the battery charger, the voltage going to the battery is a little more than 16v. When the bikes charging system is charging the battery I can only get 14.36 at the maximum and under the best conditions. This is why the bike charging system cannot maintain the battery. Not because of the high beams but because the R/R cannot reach it's full potential. It should be ready about 15.5v with the high beams ON but it can't even with them off.


The test above was ran like this:

Low beams were tested first on a cold bike. This shows the best case scenario for the charging system.

High beams were tested last at 210°F. You don't need the fan running to test the system per the SM but I know what you're getting at. The fan would draw even more voltage away from the battery. But there in lies the point. The system is clearly not able to maintain the battery under normal riding conditions because of the location of the R/R. We all know that if the regulator overheats it looses it's ability to control the voltage going to the battery. The voltage spikes will eventually kill the battery over time.

If the R/R would put out 15.5v as specified we wouldn't be having these problems with battery. Not using your high beams is simply putting a bandaid on a broken leg. You're only treating the symptoms of the problem and not the true cause.
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Alex_RR said:
I almost have the exact same measurments with my battery, except when I have the highbeams on at idle the battery voltage slowly starts dropping and keeps dropping. If I have the highbeams on and run the engine at 5000rpm than my battery volts climb up to 13.92

this is on an 03 with 3700 miles
Is this with the Battery Plus battery? Have you had the battery load tested?
Get on it!!!! Sounds like a bad battery.
Do you have an Autozone or Advanced Auto near by?
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Everyone needs to put a volt meter on there batteries and verify the voltage FIRST! Don't start buying parts until you know what the problem is. 99% of the time all you need to do to correct this problem is charge the battery every few months to full capacity. Keep the voltage above 12.8v MINIMUM and you won't have a hot starting problem.
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