Latest situation. The battery was left on the CTEK for the week whilst I toured S E Asia.
Disconnecting the CTEK the power was 13.07 V. It is a sealed battery.
With the engine running the voltage was 13.7, but the voltmeter shows just under 12V.
After stopping the battery was 12.98 V.
I think I'll wait a while & maybe look at the earth under the dash & clean it up.