I looked in the thread index, and could not find any specific charging system specific test.... But as I am sure I have seen several reply's regarding this.... I decided that with the many wondering electrons lately, I'd write a quite simple system up. Pardon me if this is buried somewhere where I could not sniff it out.:d. The following procedures are simple and not derived from any manual, but rather a few years testing the systems on different bikes. So bear with me, as I might mention something that the manual differ's with. Starting with a simple explanation of the charging system on the 800GS, which is quite similar as on many other bikes. You have a flywheel that holds a permanent magnet that when spun over a coil (in this case 3 coils) created inductive energy. Each of the three coils have two connections one side of each coil are connected together as a common ( NOT ground) and each of the other connection goes to the R/R ( regulator/Rectifier) The inductive voltage being released from the Stator ( 3 coils) are AC. Those 3 phases (legs) goes to the R/R, where they are turned into DC via a fev diodes,,,capacitors for noise and ripple control.... and in the case of my Mosfet r/r....a Chip ( intergrated circuit) The now rectified and regulated to about 13.8-14.5 volt is then fed to the battery, where it supplies " juice" to charge the battery, and to run the system. It does this to the tune of 400 watts. Simple enough...great... then lets move on. How on earth do you know if it is working or not?????? Well.... you have to buy a multimeter to find out, as many don't have an idea.... until stranded somewhere. It really is a simple test that in a few short minutes can reveal if your charging system is up to the snuff. First ( and this of course can vary from person to person.... But I prefer a quick and dirty check at the battery to determine a base line. So with the key off the battery should be above 12.5 volts. I realice this is low..... and indicate a severely discharged battery....but never the less That's what I go by..... A fully charger battery will yield above 12.85 volts.... Then with the meter connected start the engine..... It should jump to a minimum of 13.80 volt......wait a few seconds for the battery to stabilize..... If it does not jump to 13.80 volts... Time to dive in further. Shut off the bike and locate the three wires coming from the stator. Easiest way to do this is locate the r/r ( little box on the right side of the engine mounted to the frame with cooling fins on it) follow the three wires going back from the r/r to the stator..... if you can disconnect then great. Then disconnected measure each wire's resistance to ground (chassis) It should be infinite....ie no reading. If it is not infinite... The wire that is not infinite...indicates a shorted coil, and the stator needs to be replaced. If those test are good...then proceed to test the resistance between each wire.... It should be between 0.5-2 ohms. If it is more... There is an open circuit in the coil that measured more..... and the stator needs to be replaced. If those tests are good... then start the bike..... Then you need to measure the ac voltage coming from the stator........ by inserting the probes into the terminals on the stator plug..... The measured voltage between each wire should be above 50 volt ac.... if not.... the coil which wires does not produce 50 volts ac, is bad, and the stator needs to be replaced. If they all do....then reconnect the R&R after stopping the engine. Start the engine. If you do not see a rise from idle battery voltage as in the beginning......to the 13.80 volt dc.... the the r/r is bad, and needs to be replaced. That's it....your done.... This should be the only tests that needs to be done...... That said... the above test is generic....but will yield the results you need in determining whether your charging system is up to the test.... Good luck.