LAB-134-Harley-Davidson Alternators, Stators, Regulators, Rectifiers-Charging System | Complete Guide

Official website: http://www.lawabidingbiker.com

Podcast-A special thanks to guest Evan Grist of Fort Collins, Colorado, who is an electrical engineer and affiliated with RMSTATOR, a manufacturer of high-end power sports electrical parts. Via Skype, we were able to bounce our questions off Evan. In this episode, we'll teach you everything you need to know about your Harley-Davidson charging system. We break it down to what bikers actually need to know in an understandable way.

Your Harley-Davidson, or most motorcycles for that matter, use the same type of charging system, often referred to as a permanent magnet alternator. In a car, an alternator is belt driven. In a motorcycle, it is driven by magnets embedded around the flywheel. The flywheel is permanently affixed to the crankshaft, which is spinning with the engine RPM's.

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So, the easy way to generate power is with a stator inside that flywheel magnet system. A stator is a metal core and is made up of a bunch of stamped steel plates that are riveted together. It's insulated with some sort of powder coat or plastic to protect the wires. There are windings wrapped around it, which are a particular gauge of solid core copper wire that's insulated. So, you end up with coils of wire wrapped around the stator. Those are attached to a wiring harness, which exits the side case of the motor & heads to the regulator/rectifier. And finally, to the battery to charge it.

With the motor running, you have your crankshaft spinning with the flywheel attached to the end with the magnets spinning outside of the stator. Those magnets spinning past and around the metal core with wire wrapped around it generates electricity. And there you have it.

You may hear this referred to as an alternator at times. If you hear someone call this an alternator on a motorcycle, they are generally referring to the entire package, the flywheel and stator. You do see Harley-Davidson refer to it as an alternator in their manuals.

Regulator/Rectifier:

The alternate current (AC) current created by the stator cannot be sent directly to the battery. It needs to be prepared, limited, and changed to direct current (DC) to correctly charge your battery. The current would destroy your battery if not first sent to the regulator/rectifier.

In a motorcycle, the stator flywheel set up creates electricity and sends it to a separate regulator/rectifier. In a car, the rectifier/regulator is built into the alternator.

On a Harley-Davidson, you'll recognize the separate regulator/rectifier as a little black box with cooling fins machined into it and it often times sits up front behind the rear tire attached to the frame.

Regulator/Rectifier=2 Functions:

Rectifier:

The rectifier is responsible for converting the alternate current (AC) current created by the stator to direct current (DC). Basically, it chops off the negative polarity portion of the current that the battery can't use. Then it passes the current to the battery.

Regulator:

The regulator protects the battery voltage and when the battery voltage climbs too high it shuts off current to ground and bleeds it off as heat. That is what the heat fins on the regulator box are for, to dissipate the heat. If the regulator did not monitor the voltage to your battery it would destroy it.

Note: Often times a bad regulator can do just that, send too much voltage to the battery.

Battery:

All the current required to run your motorcycle comes from your battery. The stator system charges your battery and replenishes it. You could actually run your motorcycle just fine for some time without a working stator as the battery has reserve current. Of course, the battery would eventually die.

Aftermarket High Output Stators:

If you add too many electrical accessories then you'll come a point that your stator just can't produce enough current to keep the battery charged. There may be subtle hints over time-like your bike starter is sluggish and has trouble cranking the motor over.

There are available aftermarket high output stators. However, it is not wise to install an aftermarket high output stator just because. You should only do this if you actually need it to keep your battery charged.

If your motorcycle is not consuming all that extra current the high output stator is producing then you end up dumping that entire load on your regulator. This is a quick way to ruin your regulator by overheating it.

Can I test the load my electrical accessories are creating?

You can look in your service manual and see what your stator is rated for in amps. Then you can find your electrical accessories (lights, heated grips, heated seats, stereo amps etc) you have added and find out what wattage they are rated for.

A good rule of thumb is you can convert to power by multiplying the stator amps (current) x the battery (voltage). You can use 13 as a good all around battery voltage. That is a good healthy battery staying charged just above 12 volts.

Example only: Let's say the stator is rated for 10 amps x 13-volt battery: 10 x 13=130 watt charging system. So you have a 130-watt charging system in this example.

Now, you can take the wattage of all those electrical accessories and see if you're under or over your 130 watts and how much you have to play with.

Volt Meters:

You can check your system by putting a volt meter on your battery. Or add a volt meter gauge to your motorcycle. I have a Vance & Hines Fuelpak 3 Electronic Fuel Injection (EFI) tuner on my Harley. It syncs to my smartphone wirelessly via Bluetooth and I can monitor real-time data such as voltage. My smartphone is attached to my handlebars with my Biker Gripper Mount.

You can turn all your electrical accessories on and make sure you have your engine at a good regular riding RPM, so your stator is charging at full output.

Note: if your meter is reading anywhere at or above 13 volts you are in great shape. Remember, your Harley is a 12-volt system, so just above that means it can keep up. 13 volts is the point where the battery is not discharging with all your accessories on.

Regulation Point:

Generally speaking, 14.6 volts is a hard set regulation point on most 12 volt systems such as a Harley. Basically, this does not allow the regulator to send voltage to the battery any higher than 14.6 volts.

Harley Charging System Failures:

Stator Failure:

If the stator fails, your battery will no longer be charging when you're riding your motorcycle.

Often times, a short can happen in the windings around the stator. The insulation on the wires can wear down over time or a wire can break. If the copper inside the insulation rubs against the flywheel as an example, you could have the windings short to ground. This is a problem because it all loops back to the regulator through your battery negative connection.

The motor, the frame, and everything metal on the motorcycle are tied to battery negative. Battery negative is tied to the regulator and the regulator is tied to the stator and it loops back. If you have a short to ground then you have no output from the stator.

Multi-Meter & Testing Stator:

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