upgrade charging system?

[xHeart]

After checking the connectors, the alternator output under load hovers at 13.56v. The voltage drop test with B+ is 0.28, while voltage drop at battery negative (-) terminal is 0.06, both at 1500-2000 rpm.

Alternator charging never goes above 13.60v.

[misha]

Did you measure directly on alternator or on battery terminals?

[xHeart]

The set up for voltage drop test using multimeter, and then increasing rpm to 1500-2000:
Black probe at negative (-) battery terminal while red probe at the alternator casing, it reads 0.06v.
Red probe at positive (+) battery terminal while black probe at the B+ post at alternator, it reads 0.28v.

[misha]

Check output directly on the alternator while engine is idling.
Red probe on b+ on alternator and black on it's housing.
You should get 14-14.2v at idle.
If not...voltage regulator or alternator are faulty.
If you do....b+cable needs to be replaced because the voltage doesn't get to the battery.

Voltage drop needs to be checked after driving the car for at least 30min and without turning the engine off prior to voltage drop testing.

[jimmy57]

The 120 amp alternator from 960 is also a choice for more charging power.

[abscate]

That’s a big drop on the B+

Do you have an IR gauge you can check the temperature of the cable after 15 minutes running with all the lights on ?

[xHeart]

Check output directly on the alternator while engine is idling.
Red probe on b+ on alternator and black on it's housing.
You should get 14-14.2v at idle.
If not...voltage regulator or alternator are faulty.
If you do....b+cable needs to be replaced because the voltage doesn't get to the battery.

Voltage drop needs to be checked after driving the car for at least 30min and without turning the engine off prior to voltage drop testing.

Cold start and idle reads/hovers 14.08-14.12v with your set up misha. So cable?

[misha]

Yep!

[xHeart]

Yep!

Just positive (red cable) or negative cable too?

[misha]

Usually the part from positive battery terminal to starter is the one which fails.
In your case you should replace the negative too.
Replacement MUST be the same thickness as original or slightly thicker...but DO NOT replace it with thinner cable.
25mm2 is EU spec....i guess that this is equal with 2awg(U.S)but check the conversion table.