Deleted and reposted - it's amazing how a wet slidy drive clears the brain!
That's good research and it makes sense.
I figure that they monitor current to determine when the battery is fully charged and drop the charging voltage from the normal max of 14.4V (probably 14.2V) down to a float voltage of about 13.4V. The fully-charged acceptance current - aka float current - is up to 2A for a large 12V battery.
[ Before my
sideways clarity I was curious if it was another "ECU controlled" alternator which AFAIK is only for improved acceleration but at the expense of fuel economy (in most circumstances). ]
Normal vehicle charging systems use mere voltage regulation and have no need top monitor current - ie, alternators sense the voltage and adjust rotor current to maintain it at (say) 14.2V.
It'll be interesting to see if Nissan (and others) continue with this system. It is probably to improve battery life. In theory a 12V lead-acid battery should normally be charged at 13.8V and then drop to its float voltage of ~13.4V once fully charged. In practice, in vehicles charging voltages are now typically 14.2V or a max of 14.4V (steady-state) as the older 13.8V was too low to reverse sulfation that occurs in discharged batteries - hence leading to premature failure - and few bother with float voltages. Temperature compensation is usually the only sophistication that vehicular charging systems have.
The current sensor appears to be a loop sensor as opposed to a shunt (series resistor). Hence it should not be bothered by higher currents to & from the battery (even if the cable size could be and is increased), not that changing the alternator makes much difference to what current the battery accepts, or supplies.
If the battery -ve goes direct to the engine and is left as is, cranking won't improve unless the +ve cable from the battery to the starter is improved. However improving the engine to chassis cable if the battery- goes to chassis will improve cranking.
But a heavier cable can probably be run thru the current sensor even if stripping and re-sheathing one end to thread thru, through the inner diameter of the sensor is probably plastic that can be partially removed, though I'd ensure it is still insulated from the cable, and weatherproofed.
Note too that if the higher output voltage is preferred (ie, to its 14.2V - 14.4V instead of its ~13.4V
float voltage), running a load of 2A or more direct from the battery should do the trick. The current sensor will sense that "extra" load and think it's the battery's recharge current and - by never dropping to less than a few Amps - deduce that the battery is not yet fully charged and will maintain the higher voltage.
That of course assumes that the current sensing is to adjust the voltage (for/to float) as I described. If the sensing is for other reasons, let me know and I will reinvestigate.
And there are other possibilities to maintain higher voltages. One of them is to fit a normal alternator (I suggest at least a 2-wire, ie, one that has an S or Sense input).