I'm so unobservant...

My morning commute has been in complete darkness for several weeks now. One morning last week I was sitting in a left turn lane with my turn signal on. I noticed that as my flasher blinked, the green neutral indicator lamp also varied in brightness in time with the flasher.

When I got home that evening I tested my battery voltage and stator output, both in spec.

Later in the week I noticed some fluctuation in the brightness of the digital screen portion of the instrument panel in time with the flasher. So yesterday I did a load test on the battery. The tester asks for battery cold cranking amps (cca) before testing. I put in 100 cca (I could swear I read that spec. somewhere) and ran the test. The result was " battery at 165%" Sooo I put in 160 cca and retested. Wonder of wonders the result was 101%. Gawd I'm an electrical genius. :crazy:

This morning I looked in my service manual, and found the battery is actually rated at 10 amp hours (ah). I don't know the relationship between cca and ah. But I find it hard to believe the battery for a VFR would be more than 160 cca.

So after all of this painful tedium there is a question!

Is this normal, my bike always did it (and so does yours) and I just never noticed it before?

Thanks in advance for any feedback. And for sure thanks for reading this far!

 

The YTX12 is listed at 180 cca.

What was the voltage at idle?

 

Thanks for that cca spec karazy.

I rechecked battery voltage today since I hadn't written anything down last week.

12.75 v engine off after sitting half an hour, after I rode (20 miles) home from work today.
12.95 v after charging with Battery Minder until it attained "float".
12.18 v at idle, high beam on.
14.59 v at 5,000 rpm, high beam on.

 

Sounds about right. Voltage regulation in these isn't anything like on a car, especially at idle.

 

sounds spot on mate cheers :drinkers:

 

Let's agree to disagree.

IMHO your idle voltage is a tad too low. If you were stuck in traffic, on a hot day, the fan would probably drain your battery, as it has for many people before you. The fact that the blinker is causing your instruments to flash, is a sure sign of this.

The problem is a product of the properties of electrical generators. The faster they spin, the more electricity they can create, until the fields become saturated and a maximum for that specific genny is reached. On the other end of the spectrum, there is a min RPM required to provide the min voltage that is needed to do the work. In your case, at 12.18V, it clearly shows that it is not spinning fast enough to maintain your battery, that has a resting voltage of 12.75.

To fix this problem, you just have to inrease the idle RPM until the voltage is at the desired level. I suggest a min of 13V, but preferably around 13.5V.

:crazy:

 

Now that you mention it...

A week or so before I noticed the issue in post #1 above, I synched my "starter valves". This led to resetting my idle speed afterward. I set my idle rpm at the low end of spec. Possible charging problems never occurred to me. So once again I may be the source of my own problem!!

I'll adjust the idle up and recheck the voltage.

 

Here's a flowchart to check all the components.

http://www.electrosport.com/technical-resources/library/diagnosis/pdf/fault-finding-diagram.pdf

 

The reason rpm matters so much on these bikes (and doesn't so much on a car) is that we have a permanent magnet + stator system. It's output voltage is a function of rpm. It gets to over 70VAC at higher rpm. The regulator/rectifier burns off the excess as heat (stupid design, but a limit of the capabilities of the silicon of the time). Anyway, at lower rpms, it's not moving fast enough to create a full 13VDC. So it runs a bit low. From what I've been able to tell, most motorcycles are running at a loss at idle (or at least aren't producing enough voltage to charge the battery).

 

Strangly my VFR over reads on the rev counter by approximately 250rpm ! I only found this out when I fitted a PC3 & used the live connection to my laptop.
It was confirmed the first time I went to a dyno shop, so I like you had been setting my idle at the low end & now I know that was 1000 revs assuming a 1200rpm idle as per the manual. I now have it set to 1200rpm as per the PC3/Laptop readout & the rev counter reads just shy of 1500rpm !!!!!
Talking to the dyno operator, its quite normal for bikes to over read on the rev counter !

So up your idle rpm until you see a good voltage with the lights on, at least whilst riding in the dark all the time.

The newer Mosfet based rectifiers are much better at controlling battery charging voltage. I fitted an after market one when my RR went pop earlier in the year & its brilliant.

 

I set my 2000 VFR idle at 1400 rpm and I have a new LiFe battery and new Mosfet RR (these were installed as preventive maintenance). I get 14 volts at idle......yes my neutral light dims ever so slightly in time with the turn signals. The Headlight does not (or anything else). Quite frankly what you are experiencing is completely normal and many of my bikes have done it, hehe