Charging battery with a digital charger - odd?

Does the battery go flat when the bike is left unused for a week or so? If so, and it doesn't lose chargewhen disconnected, then the current is going somewhere.

A faulty rectifier can certainly give these symptoms.

If it goes flat when disconnected, the battery is faulty.

When the Optimate is connected to the battery when mounted on the bike it shouldn't continue to charge at maximum if you leave it to complete its cycle. It should diagnose a loss if one is occurring and indicate accordingly. Does it?

Is there a Zener diode in the system?Lucas used a 13v zener for voltage regulation at one time.Regards John.

I hope I am not being over simplistic, but remember that your Norton is wired the opposite way round from your "Modern Honda". Hondas have negative earth electrics, Nortons (And most other older British bikes) have positive earth electrics, with the positive terminal of the battery connected to the frame and the negative one connected to all the ignition, lighting, charging etc. Warning: Connecting a battery the wrong way round will fry your rectifier...

Hi,

John's suggestion is the most likely, you will probably find that the Optimate is trying to put a fairly high voltage into the battery and the zener diode (or diodes depending on the age of the bike) is dumping anything over 13 - 14V.

Do you have a late commando with one Zener diode mounted on each footrest mounting plate, or an earlier one with only the one zener mounted on a heat sink ?

If the latter you can remove the wire from the zener to prove if it is this causing the issue. It may be that the zener is triggering at the low end of the range. There is not much you can easily do if it is other than find another zener with a slightly higher voltage.

I can explain in more detail if required.

Regards

Tony