Erratic charging

[JohnnyT]

I have a Triumph Tigress 250 scooter 6v electrics.When I put a multimeter on the battery when the engine is running the readings are all over the place.When I put the sidelights on they calm down a bit,but range from 0.9 to 8v.Any other way to check the battery is charging,or ideas as to why this is happening ?

[Rex]

Is it a DVM you're using?
The quick and dirty way to check charging is to see if the headlights brighten when you rev it.

[iansoady]

If it's the original style dynamo  and electro voltage mechanical regulator, they can do this as they switch the field coils between full and half current. But no idea what you have installed.

[antoni]

If you see widely varying voltage on a battery's terminals it's either discharged, or more likely, no longer serviceable.