Ford Focus Diesel battery condition with dashboard diags

Ford Focus Diesel battery condition with dashboard diags, A follow on to my previous video, this shows despite the car sounding fine on cranking the battery is in fact very weak.
When I checked battery voltage with a data logging DVM the voltage dropped to 11.1 Volts with the glow plugs on after the car had been run and the under bonnet temperature had risen to around 10ºC. On Cranking the engine warm, the voltage dropped back to below 8.2 Volts, showing the battery has gone high resistance due to age.
What amazed me was how low the voltage was, the starter makes a good effort cranking despite such low output.
I would imagine a test at below freezing on a cold engine will show voltages in the region of 6 volts..