help,another charging question

[daves86vmax]

my bikes charging sys would drop as motor got hot especially in stop n go traffic..i checked everything and narrowed it down to the r/r..bought a new one from python for the 85 max and all was good again.ran fantastic with no issues.now after putting about 900 miles its doing it again.is it common for new r/r's for that year to not hold up?soon as it heats up battery voltage drops to 12.2 to 12.4 or so,i let it cool overnight and start it and check it and its 13.5 or so.should i get the r/r for the later models thats supposedly better with the cooling fins..im pretty sure its not the stator since it was fine for those 900+ miles,i thought i fixed it..help!!!

 

[jfeagins]

my bikes charging sys would drop as motor got hot especially in stop n go traffic..i checked everything and narrowed it down to the r/r..bought a new one from python for the 85 max and all was good again.ran fantastic with no issues.now after putting about 900 miles its doing it again.is it common for new r/r's for that year to not hold up?soon as it heats up battery voltage drops to 12.2 to 12.4 or so,i let it cool overnight and start it and check it and its 13.5 or so.should i get the r/r for the later models thats supposedly better with the cooling fins..im pretty sure its not the stator since it was fine for those 900+ miles,i thought i fixed it..help!!!

Does the voltage drop further if you put on high beams, turn signals & brake lights ALL at the same time?

I mean, if you've ridden around and the battery is fully recharged after the startup, wouldn't the regulator automatically stop charging as much?

 

[Buster Hymen]

Those voltages that you give, are they with the motor running or with it off at the battery? Also check the plastic connector that joins the stator up to the R/R.

 

[RaWarrior]

Nope....the stator is by definition a "generator"(it's usually referred to as that in service manuals and parts fiches), it produces current whenever it is in motion. An alternator(like in a car) can vary output (amps) to match demand. The R/R converts the AC to DC, and limits that output to about 14-15 volts....nothing more.

However in either case, voltage should never be that low. Voltage (volts) and charge (amps) are two different things. An amp meter placed between the bike and battery would show + amps right after startup, assuming everything is working. That would slowly taper off to zero as the battery charges and the system reaches equilibrium. If you shut the motor off but left lights on, it would read -amps. The charging system is still producing it's rated output, but in effect it's being wasted since there's nothing to accept the charge.

Sometimes it helps to define voltage by it's technical term: potential difference. Think of voltage as a difference between two points in a circuit. Not of power, but of potential. 14.5 volts has the potential to charge the battery, but not if the battery is already fully charged. The difference between the charge at the two posts of a battery is unitized in volts. That's why even a totally dead battery can still read 11.5 volts or so. It has potential(volts), but extremely little amps. Think of voltage as the size of the valve, and amperage as the pressure behind it. The valve gives it potential to have a high power flow, but not if there isn't any pressure.

Anyway, a reading of 12.2 volts means your bike is running negative, and if you ran long enough like that the motor would start to run poorly from weak/missing spark, and eventually die on the side of the road. It wouldn't crank, and wouldn't bump-start either. A good fully charged battery should read 12.6, so the bike is consuming more power than it's making. 13.5 is what the Max tends to run at...kind of low, but acceptable. I'd suspect the R/R is no good. Like you said the stator was fine for a while, and those rarely ever go bad....there's really nothing to break.

If you replace it again, get a stator from an R1....better design.

 

[daves86vmax]

the voltage i was getting was while running,did you mean get a r/r from an R1

 

[Miles Long]

Nope....the stator is by definition a "generator"(it's usually referred to as that in service manuals and parts fiches), it produces current whenever it is in motion. An alternator(like in a car) can vary output (amps) to match demand. The R/R converts the AC to DC, and limits that output to about 14-15 volts....nothing more.

However in either case, voltage should never be that low. Voltage (volts) and charge (amps) are two different things. An amp meter placed between the bike and battery would show + amps right after startup, assuming everything is working. That would slowly taper off to zero as the battery charges and the system reaches equilibrium. If you shut the motor off but left lights on, it would read -amps. The charging system is still producing it's rated output, but in effect it's being wasted since there's nothing to accept the charge.

Sometimes it helps to define voltage by it's technical term: potential difference. Think of voltage as a difference between two points in a circuit. Not of power, but of potential. 14.5 volts has the potential to charge the battery, but not if the battery is already fully charged. The difference between the charge at the two posts of a battery is unitized in volts. That's why even a totally dead battery can still read 11.5 volts or so. It has potential(volts), but extremely little amps. Think of voltage as the size of the valve, and amperage as the pressure behind it. The valve gives it potential to have a high power flow, but not if there isn't any pressure.

Anyway, a reading of 12.2 volts means your bike is running negative, and if you ran long enough like that the motor would start to run poorly from weak/missing spark, and eventually die on the side of the road. It wouldn't crank, and wouldn't bump-start either. A good fully charged battery should read 12.6, so the bike is consuming more power than it's making. 13.5 is what the Max tends to run at...kind of low, but acceptable. I'd suspect the R/R is no good. Like you said the stator was fine for a while, and those rarely ever go bad....there's really nothing to break.

If you replace it again, get a stator from an R1....better design.

Well done, Mr. Warrior (may I call you Ra?) Electrical theory and application can be a mystery to many people(I include myself) .Troubleshooting electrical problems can be frustrating, time consuming, and expensive(as in replacing perfectly good parts), even among those with an electrical background. Troubleshooting requires patience and analytical thinking .
Your analogys to plumbing (valves, pressure, etc) serve well to help understand the basics. Thank you! Miles

 

[davidon]

I'm sort of noticing a similar problem as Dave when motor is hot and remains hot in slow/stop traffic. I recently put a volt gauge in so just after start up battery at idle gets 14V and stays there while running. When I parked at idle after hot I now get a 13V reading. I had the same problem at Thunder last year in the parade (stop and go) and konked out in the middle of it and had to bail.
I have all the upgrades,fixes, R1 R/R etc so i'm baffled. Don't know if the harness itself needs replacement since it is original off an 88. Thats the only thing I have'nt replaced.