... -43C!!! wow.
I don't think ANY diesel fuel will flow that cold even with serious antigel mixed in... most are only good down to -40F/C ...
in those temps, you'd need a fuel tank heater, block heater, and insulated fuel lines to run...

as far as the batteries, I'm sure they are toast.
a charger can only tell you how much the batteries are drawing. then cannot measure the capacity or cel condition...
you also could have a bad starter, but if it's cranking over, it's likely ok.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!