Alter_Ego
Sorry to hear of your problem. Hopefully by now you have purchased a new battery and your riding again. Now, a few thoughts about your alternator.
If you do not own a "volt/ohm meter" you might consider purchasing one. There should be some relatively inexpensive ones available and they can be of great help when one needs to find electrical faults.
If you choose to buy one of these make sure it has the ability to check AC (alternating current). This is the type of current your alternator supplies to the rectifier diode.
At any running speed, your alternator should produce enough current to keep the bike running. This is especially true if your headlight is turned off.**
A voltage test across the battery terminals with the engine idling should produce a voltage of at least 12 volts even if the battery is dead or broken. If the engine speed is increased this voltage should increase to at least 13+ volts.
If this 13+ volt power is not present at the battery terminals with the engine running, it does not necessarily mean your alternator is bad.
A loose wiring connector, a corroded grounding (earth) connection or a defective rectifier diode can produce the same results.
While the rectifier diode may be difficult for you to check, the loose or corroded connections should be fairly easy to examine and repair.
If there is a problem with having adequate voltage from the alternator and it is not related to loose or corroded circuits hopefully it is the rectifier diode. This item should be much less expensive to replace than an alternator would be.
If you have a volt/ohm meter you might be able to check for current being supplied to the rectifier diode from the alternator by testing the AC current.
With my new EFI G5 the alternator supply wires are yellow and there are several of them. They eventually end up at the rectifier diode which converts the AC to DC (direct current). The DC wires on my bike are red (+) and black (-). If the AC supply side is receiving power from the alternator with the engine running the alternator is good and the problem is most likely with the rectifier. I mentioned my yellow alternator wires because hopefully yours will be the same however because my Enfield is a 2011 it may be different.
While your riding, the alternator should be charging the battery at all times with the excess current going to power your ignition circuit, your lights and horn. Unfortunately, if the battery is defective it may take the charge but be unable to return it to the electrical system.
Battery's have 5 internal connections which connect the cells. Over time these can break and if one of them does it may be making a small amount of contact with itself. Under these circumstances the battery will appear to be providing full power but when a heavy current is required the connection will temporarily fail. This is the reason a "load test" is made when testing a battery. It requires the battery to provide a large amount of current and failing this test prooves that there is an internal break.
**Some of the Royal Enfields have a separate AC (alternating current) circuit to power the headlight which does not use the rectifier or diode. If your bike is one of these your headlight could work while the engine is running off of the battery's power even while the alternators DC (direct current) supply is defective.
Good luck to you.
