Santa Fe BJ 2003, Diesel, starts with trouble

Hello all, At minus temperatures my Santa Fe, BJ 2003, Diesel, Mucken. It doesn’t start. The engine goes crazy, battery seems full, but nothing happens. What I find very strange, the battery is full, but if we bridge the car, it starts up and drives without problems. If I have driven for a while, then I have no problems at the start. Only in the morning when it is really cold. The battery is installed in a workshop only in August where can anyone tell me what power the battery must have? I can’t find anything in the manual. LG Ulko