Battery runs down after 3days. Can this be an electrical problem.

Vehicle information needed

not necessarily
it could be a flat battery in the fob key for the immobilizer
could be problem cam/crank position sensors
could be bad connections in the harness
best have the fault codes read before you waste money chasing the fault

diesels need a fast turning starter to compress the air to a hot enough temperature to ignite the atomised fuel at the injectors. There in lies the problem I would suggest. 1 the battery is not good enough .2 the injectors are dirty /blocked and are squirting and not atomising. IF this is the case you will be getting "diesel knock". If you have removed the turbo then you will need to get the fuel pump reset as there will be excess fuel being used ( knocking and black smoke on acceleration). AS for quietening down the engine and compartment it has taken much engineering by manufacturers to get the engine as quite as they are now and this engine was noticeably noise when new.

When the car is not running, something is consuming more electrical power than normal to run the battery down. Another problem could be that the battery is more than 5 or 6 years old and it is at the end of its useful life.

This symptom is usually caused by a bad connection at one of the main battery cables. Will the car start with a jump?

The battery is run down too low. When the light came on, alternator stopped working- the vehicle ran off the battery, until the lights and other electricals ran the battery down too low.
Recharge the battery, and have the alternator tested. It will probably need replacing. If you bring it into a parts store, they will test it for free.

test for voltage draw; if none, (or less than 700ma) replace battery.

try some proper jump leads and not then cheap chinese things ,you need cables with a copper inside the diameter of your ring finger and double connectd to each side of the clip before you can even think of trying to jump a engine ,these cheap cables are only for charging one vehicle to another not passing 200 amps through

Main cable from battery has a joint in front footwell check this

have fusable links that run to solenoid on top of starter checked. have start switch on steering colum under dash checked