This feels like a dumb RR question...

[Steve]

It is telling ME that there might be a bad connection between the battery and the light circuit. Might be bad contacts in the fuse holder or broken strands in the wiring. Just for fun, check the voltage at the headlight fuse (with the bike running). Check the voltage at both sides to see if it is the same. If it is low at the fuse, check the wire that feeds the fuse for broken strands. Might even consider replacing it with a larger wire. Bikes are rather notorious for inadequately small wiring. A headlight will draw about 5 amps, the rest of the lights a couple more. When the brakes are on, add another 2 1/2 amps per brake bulb (some bikes have more than one). Figure there might be around 10 amps possible draw. The books say that 16 gauge will be adequate, but 14 or 12 gauge will be even better. If the supply is limited for ANY reason (corroded connections, small wire, etc.), sufficient current can not flow, and voltage will suffer. That is why the voltage rose as much as it did when you disconnected the headlight. I would expect a bit of a rise, but not that much.


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[shamer]

Well,

I just can't seem to narrow down exactly where the problem is here - at least not any further than the headlight.

Today I took apart the fuse block & cleaned everything up. Voltage from the battery to the fuse block is good and so is the ground. I measured resistance between battery (+) and each fuse circuit (ignition on for the switched ones) and all were fine EXCEPT, of course, the headlight fuse which measured about .5 Ohms higher than the others. This mesurement held true when going from the fuse block to the headlight itself so I know it is somewhere along that path. I just can't narrow it down to where - I even pulled the gas tank & went through each connector but that made no difference. Hmmm, I wonder if it could be in the hi/lo beam switch - does current actually travel through that switch? Maybe I'll go check that right now...

Thanks again to each of you! If I can get this part figured out I should be pretty good - I hope. When I pull the headlamp out & run the bike I get a perfectly within spec charge of 14.6V at the battery. I just hope that it'll stay within spec after I get this sorted out...

Shawn

[crc1214]

Turning off the headlight and it resulting in a temporary voltage increase (engine running) is normal. Sorry, but 15.7 volts is completely unacceptable. Maximum acceptable under any condition, at any rpm, is 14.8v. I have returned new R/R's that charged at 15 volts as faulty and they have been replaced by dealers at no charge.

Earl

Earl, I used to think 14.8 was the max as well, but 15.5V is completely acceptable according to Suzuki, at least in my manual for my 83 750E. I couldn't believe it when I read that, but it's true. 15.5 is the MAX, but 15.5 it is. And the battery used in that model is a 14L-A2, which from what I've gathered is used in 99% of the GS's (except of course when a combine battery stashed in a backpack must be used.....LOL!!)
Anyhow, mine charged at 15.5 too, it would never go above, but it would get up there and stay up there because I pretty much stay above 5,000 RPM's at all times. Now granted, I was using a sealed battery in it, but I never had any problems with the battery or with any bulbs blowing or anything.

[Boondocks]

Earl, I used to think 14.8 was the max as well, but 15.5V is completely acceptable according to Suzuki, at least in my manual for my 83 750E. I couldn't believe it when I read that, but it's true. 15.5 is the MAX, but 15.5 it is. And the battery used in that model is a 14L-A2, which from what I've gathered is used in 99% of the GS's (except of course when a combine battery stashed in a backpack must be used.....LOL!!)
Anyhow, mine charged at 15.5 too, it would never go above, but it would get up there and stay up there because I pretty much stay above 5,000 RPM's at all times. Now granted, I was using a sealed battery in it, but I never had any problems with the battery or with any bulbs blowing or anything.

A 100% fully charged standard flooded lead-acid battery has a resting voltage (no surface charge) of 12.65V. A 0% fully discharged battery has a voltage of 11.89V or less. Thus, only 0.71V difference between 100% charge and fully discharged.

Charging a battery is a compromise. In order for a battery to fully charge, it must have some gassing, the bubbles released when the water in the electrolyte is "boiling". Gassing begins at about 14.2V. A battery charged slowly at a rate of 13.8-14.1V may have a long life, but without a higher voltage finishing charge the battery will sulfate and the charge capacity will diminish with each charge cycle. Voltage in the 14.4-14.7V range allow a battery to charge faster, reach full capacity, and be less susceptible to sulfation. It will not charge as safely at high temperatures, and is subject to grid corrosion on the positive plate.

Smart battery chargers are much more sophisticated about charging a battery than a simple R/R, and will optimize the charging time, finishing rate, and float voltage. A R/R is a "dumb" device and suffices to keep the battery charged sufficiently under most conditions, but can't optimize battery charging. All R/R's when made are set to a maximum voltage output before they regulate the voltage. None are set as high as 15.5V, or even 15.0V for that matter. The fact that a manual deems a range of 14.0-15.5V as acceptable is more of an admission of poor quality control than anything else.

A charging rate of 15.5V will:

a. Boil the water from the electrolyte very quickly in a flooded battery (filler caps), exposing the plates. Exposed plates will quickly sulfate, thus the battery can suffer from both sulfation of the negative and corrosion of the positive plates, with a consequent loss of battery life.

b. Drastically reduce the life of bulbs, which are designed to work at nominal battery voltages but may be rated as high as 14.4V or so. Exceeding the design rating will always result in faster bulb burnout.

c. Not show the signs of overcharge abuse as quickly with a sealed AGM battery since the battery is sealed under pressure. Nevertheless, charging at 15.5V is way out of the safe range for this battery and its life will suffer accordingly.

The manuals say that the range of 14.0-15.5V is acceptable. 15.5V may be acceptable if the criterion is whether the bulbs blow immediately, but for not much else.

[shamer]

Well, the process I've been going through sure is proof that voltage drop is cumulative. Each time I've gone through connections & have a done a bit of cleaning I've incrementally improved my charging situation.

Tonight I went through & cleaned up quite a few grounds - I also added additional ground wires with 14 guage wire soldered to ring connectors and attached to bolts at the headlight and tailight areas. These met together at the negative side of the fuse panel (one of the small screws at the bottom). Does anyone see a problem with me having done this? In the past I've added redundant grounds to my other vehicles to keep all the wiring happier & avoid problems.

But, I still find myself with 15.2V at the battery! It was getting late & I didn't have a fully charged battery to start (12.5V), so I'm going to drive the bike to work tommorow (15 minute commute) and see what I get for a reading in a real world situation.

Thanks again, I'm slowly getting there\\/ ...

[Boondocks]

Tonight I went through & cleaned up quite a few grounds - I also added additional ground wires with 14 guage wire soldered to ring connectors and attached to bolts at the headlight and tailight areas. These met together at the negative side of the fuse panel (one of the small screws at the bottom). Does anyone see a problem with me having done this? In the past I've added redundant grounds to my other vehicles to keep all the wiring happier & avoid problems.

No, improving ground connections a good idea. Many wiring problems and voltage drops are caused by poor grounds.

But, I still find myself with 15.2V at the battery! It was getting late & I didn't have a fully charged battery to start (12.5V), so I'm going to drive the bike to work tommorow (15 minute commute) and see what I get for a reading in a real world situation.

Thanks again, I'm slowly getting there\\/ ...

Did you try temporarily connecting the sense wire directly to the battery positive as I suggested earlier to see if the charging voltage lowers to the correct range?

[shamer]

Did you try temporarily connecting the sense wire directly to the battery positive as I suggested earlier to see if the charging voltage lowers to the correct range?

No, I haven't - but not because I'm ignoring your good advice! In fact I wish I had done it tonight, but I forgot. But, I'm able to easily test the voltage at sensor wire and each time I've seen an improvement at the battery, it has been mirrored at that sense wire. I've been testing that wire frequently looking for improvements each time I cleaned a connection. Tonight, before I called it quits to help put the kids to bed, it showed 14.7V, so I feel confident that the RR is working poperly.

You're right, tho', I should run that test as well - thanks for the reminder!

[Boondocks]

Your work on fixing the voltage drop at the sense wire has paid off. You're right, if the battery is charging at 14.7V, that is proof that the R/R is working properly. If the sense wire is still below battery voltage, the R/R may still be putting out a little extra voltage. Temporarily connecting the sense wire to the battery will tell you what the R/R voltage should be without a voltage drop.

Congratulations on the results of your efforts.