Monday, March 9, 2015

How To: Check my motorcycle's charging system. Is my motorcycle charging system functioning properly?


We all know that batteries in motorcycles can be troublesome. Whenever we have an issue with a battery, we always check that bike's charging system to be sure there is no deeper issue causing damage to a battery. If you are having battery issues with your bike, we advise you to refer to our Motorcycle Battery article to help to troubleshoot your battery issue.

If you have replaced a battery or otherwise know that the battery is good, you should check your motorcycle's charging system. Batteries must be fully charged and functional to test your charging system properly. If you have a Repair Manual for your bike this should be described in detail for your bike. If not, we're here to help.

Your late model motorcycle charging system includes the battery, a regulator/rectifier unit, and a stator/rotor component. The battery is the voltage storage unit. The regulator/rectifier has 2 jobs. It rectifies the AC current coming from the stator to DC current. It also regulates the maximum amount of voltage returning back to the battery at a set value. The stator is the AC generating unit. Its windings generate electricity along with the magnets in the rotor physically passing by them.

Check that these components are functioning: 


1. Remove any covers from your battery so that you have access to the positive and negative terminals. Check your surface voltage of the battery with a voltmeter. Most conventional and sealed motorcycle batteries should be in the ~12.7-13.3 volt range at rest. If your battery is low you must properly charge the battery before going any further. 


2. 
Start your motorcycle. Increase your RPM's to mid-range while viewing the voltage returning to the battery terminals. You should see the voltage increase from idle to mid-range RPM. The voltage will generally go from ~12.7 to a max of ~14.2 or so. Different bikes will reveal different voltages, but generally you will see an increase and then a plateau of voltage. This is your regulator/rectifier at work. It is converting the AC voltage from your stator to DC, and keeping the voltage to a maximum value that will not overcharge the battery. If you are seeing numbers higher than ~14.2, an ever-increasing amount of voltage returning to the battery, or a low voltage of just ~13 volts or so returning to the battery, chances are that your regulator/rectifier is faulty. This is the second most common component in a charging system to fail, next to the battery itself. Overcharging can quickly burn up a battery or charging wire, and low voltage will not charge a battery enough to continue to run all electrical components on your bike. 


3. 
If you are seeing that there is no increase in voltage back to the battery with increased RPM's, as stated, it may be your regulator/rectifier unit. However, it may be your stator in this case not functioning. You will need to check that you are getting the proper AC voltage out of the stator plug itself (where the wire leading to the regulator/rectifier plugs into the stator as pictured above). If you are getting no AC voltage there is a stator or rotor issue. Generally you should get 18-26 AC volts per 1000 rpms directly out of your stator. 

4. 
Replace any faulty parts. Examine any connectors, fittings, and wires in the charging circuit as pinched wires or faulty connectors will also pose a problem. We suggest that you follow a Repair Manual for your bike.

-Steve Rullo


Check out the Knowledge Section of www.rullocustomcycles.com for other informative articles.

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