My Wife complained that the Car would not Start.

When I checked I got that dreaded Solenoid Click and no Cranking. Another, one of those it worked the day before but not the next Morning.
I checked the Battery Voltage with My Harbor Freight Digital Volt/Ohm Meter and it 12.5 Volts; appearing to be fully charged.

Test Time:
I had My Wife try to start while I kept the Volt Meter applied to the Battery and found that when the Key was turned to start the Battery Voltage dropped to 2 Volts!
That is an indication that the Battery itself is shot and not carrying the load or there was a short in the Electrical System.

A Short Circuit is less likely because shorts often burn something and becomes an Open Circuit.

I have some extra Batteries from the Electric Wheel Chair I had from when My Hip was Broken. They are 1 year old.
In order to connect the Wheel Chair Battery I had to changed the Ground Cable to a longer one because Battery Terminals are opposite of the big Bosch Battery that was in the Car.

Well the Wheel Chair Battery worked and the Car has been starting and charging normally for over 1 Week now; so the Bosch Batter must had died.

But, strangely My max charging Voltage for 5+ years has never been over 13.7 Volts.
Now My charging Voltage is 14.4 Volts!

My best guess on this is that the old Ground Cable must have had some resistance issues.
I say that is because about 3 months ago I had cleaned the Cable to Chassis Contact area and Battery Terminals and I did not get more than the 13.7 Volts max I always had; so I don’t think the Voltage went up due to me cleaning the contact again when I installed the New Cable.
　
　
　

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84 300D, 82 Volvo 244Gl Diesel