I now have enough data to conclude trickle charging at 25mA using high voltage is completely safe and can be conducted unattended on the basis of plug in and forget. High voltage does give higher peak capacity - this will need to be re-confirmed through contrasting with longer term charging using standard alternator voltage of 14.2V. The battery capacity gyrates probably because of environmental factors such as temperature, and atmospheric pressure.
The battery will go into rest while I get on with other stuff that blocks my access to the garage.
These are the consecutive daily readings:
330cca, 78% life, 7.84mOhm, 13.65v, 13.87v connected, mains 1.5-1.8w
330cca, 78% life, 7.84mOhm, 13.64v, 13.84v connected, mains 1.5-1.8w
331cca, 78% life, 7.82mOhm, 13.59v, 13.78v connected, mains 1.5-1.8w
330cca, 78% life, 7.85mOhm, 13.65v, 13.87v connected, mains 1.5-1.8w
331cca, 78% life, 7.82mOhm, 13.6v, 13.79v connected, mains 1.5-1.8w
332cca, 79% life, 7.8mOhm, 13.58v, 13.77v connected, mains 1.5-1.8w
333cca, 79% life, 7.78mOhm, 13.59v, 13.8v connected, mains 1.5-1.8w
331cca, 78% life, 7.83mOhm, 13.59v, 13.81v connected, mains 1.5-1.8w
334cca, 80% life, 7.76mOhm, 13.56v, 13.75v connected, mains 1.5-1.8w
334cca, 80% life, 7.76mOhm, 13.54v, 13.71v connected, mains 1.5-1.8w
333cca, 79% life, 7.78mOhm, 13.53v, 13.69v connected, mains 1.5-1.8w
333cca, 79% life, 7.78mOhm, 13.57v, 13.78v connected, mains 1.5-1.8w
331cca, 78% life, 7.82mOhm, 13.59v, 13.81v connected, mains 1.5-1.8w
328cca, 77% life, 7.89mOhm, 13.6v, 13.85v connected, mains 1.5-1.8w
330cca, 78% life, 7.85mOhm, 13.57v, 13.78v connected, mains 1.5-1.8w
331cca, 78% life, 7.82mOhm, 13.54v, 13.74v connected, mains 1.5-1.8w
334cca, 80% life, 7.76mOhm, 13.49v, 13.65v connected, mains 1.5-1.8w
333cca, 79% life, 7.77mOhm, 13.49v, 13.66v connected, mains 1.5-1.8w
331cca, 78% life, 7.83mOhm, 13.58v, 13.78v connected, mains 1.5-1.8w
328cca, 77% life, 7.9mOhm, 13.57v, 13.83v connected, mains 1.5-1.8w
325cca, 75% life, 7.97mOhm, 13.61v, 13.85v connected, mains 1.5-1.8w
325cca, 75% life, 7.97mOhm, 13.64v, 13.9v connected, mains 1.5-1.8w
327cca, 76% life, 7.93mOhm, 13.59v, 13.83v connected, mains 1.5-1.8w
326cca, 76% life, 7.96mOhm, 13.62v, 13.88v connected, mains 1.5-1.8w
326cca, 76% life, 7.95mOhm, 13.62v, 13.89v connected, mains 1.5-1.8w
324cca, 75% life, 8.01mOhm, 13.65v, 13.92v connected, mains 1.5-1.8w
323cca, 74% life, 8.03mOhm, 13.64v, 13.84v connected, mains 1.5-1.8w
323cca, 74% life, 8.03mOhm, 13.66v, 13.94v connected, mains 1.5-1.8w
321cca, 74% life, 8.07mOhm, 13.66v, 13.94v connected, mains 1.5-1.8w
325cca, 75% life, 7.98mOhm, 13.61v, 13.85v connected, mains 1.5-1.8w
321cca, 74% life, 8.07mOhm, 13.65v, 13.96v connected, mains 1.5-1.8w
324cca, 75% life, 8mOhm, 13.6v, 13.86v connected, mains 1.5-1.8w
327cca, 76% life, 7.93mOhm, 13.58v, 13.78v connected, mains 1.5-1.8w
327cca, 76% life, 7.93mOhm, 13.57v, 13.8v connected, mains 1.5-1.8w
327cca, 76% life, 7.91mOhm, 13.56v, 13.8v connected, mains 1.5-1.8w
325cca, 75% life, 7.98mOhm, 13.6v, 13.87v connected, mains 1.5-1.8w
326cca, 76% life, 7.95mOhm, 13.57v, 13.78v connected, mains 1.5-1.8w
329cca, 77% life, 7.88mOhm, 13.54v, 13.75v connected, mains 1.5-1.8w
326cca, 76% life, 7.96mOhm, 13.58v, 13.83v connected, mains 1.5-1.8w
329cca, 77% life, 7.88mOhm, 13.5v, 13.71v connected, mains 1.5-1.8w
329cca, 77% life, 7.88mOhm, 13.51v, 13.71v connected, mains 1.5-1.8w
332cca, 79% life, 7.81mOhm, 13.47v, 13.63v connected, mains 1.5-1.8w
333cca, 79% life, 7.78mOhm, 13.43v, 13.58v connected, mains 1.5-1.8w
330cca, 78% life, 7.84mOhm, 13.47v, 13.63v connected, mains 1.5-1.8w
330cca, 78% life, 7.84mOhm, 13.47v, 13.63v connected, mains 1.5-1.8w
329cca, 77% life, 7.86mOhm, 13.49v, 13.68v connected, mains 1.5-1.8w
327cca, 76% life, 7.93mOhm, 13.5v, 13.72v connected, mains 1.5-1.8w
327cca, 76% life, 7.94mOhm, 13.54v, 13.75v connected, mains 1.5-1.8w
327cca, 76% life, 7.94mOhm, 13.52v, 13.76v connected, mains 1.5-1.8w
327cca, 76% life, 7.92mOhm, 13.53v, 13.74v connected, mains 1.5-1.8w
327cca, 76% life, 7.91mOhm, 13.54v, 13.75v connected, mains 1.5-1.8w
326cca, 76% life, 7.95mOhm, 13.56v, 13.78v connected, mains 1.5-1.8w
327cca, 76% life, 7.92mOhm, 13.54v, 13.72v connected, mains 1.5-1.8w
326cca, 76% life, 7.95mOhm, 13.53v, 13.75v connected, mains 1.5-1.8w
325cca, 75% life, 7.97mOhm, 13.56v, 13.79v connected, mains 1.5-1.8w
326cca, 76% life, 7.95mOhm, 13.57v, 13.8v connected, mains 1.5-1.8w
324cca, 75% life, 8mOhm, 13.56v, 13.81v connected, mains 1.5-1.8w
327cca, 76% life, 7.94mOhm, 13.52v, 13.74v connected, mains 1.5-1.8w
327cca, 76% life, 7.94mOhm, 13.52v, 13.73v connected, mains 1.5-1.8w
325cca, 75% life, 7.99mOhm, 13.52v, 13.77v connected, mains 1.5-1.8w
323cca, 74% life, 8.03mOhm, 13.57v, 13.81v connected, mains 1.5-1.8w
326cca, 76% life, 7.96mOhm, 13.53v, 13.75v connected, mains 1.5-1.8w
324cca, 75% life, 8mOhm, 13.56v, 13.77v connected, mains 1.5-1.8w
323cca, 74% life, 8.03mOhm, 13.57v, 13.84v connected, mains 1.5-1.8w
323cca, 74% life, 8.03mOhm, 13.61v, 13.87v connected, mains 1.5-1.8w
322cca, 74% life, 8.05mOhm, 13.57v, 13.82v connected, mains 1.5-1.8w
326cca, 76% life, 7.95mOhm, 13.52v, 13.74v connected, mains 1.5-1.8w
327cca, 76% life, 7.93mOhm, 13.51v, 13.71v connected, mains 1.5-1.8w
324cca, 75% life, 8mOhm, 13.52v, 13.76v connected, mains 1.5-1.8w
325cca, 75% life, 7.97mOhm, 13.52v, 13.76v connected, mains 1.5-1.8w