[Shaun2019]

Charging problem on my car , brand new interstate battery and rebuilt alternator from a reputable shop that I showed me on the machine it was charging. I got into it and started checking it found that the yellow wire has 4.74 volts on it will charge around 14.05-14.15 volts will charge fine but turning on wipers,high beams it holds steady then all the sudden after 20 mins will drop to 13.15 volts with 2. 34 volts on the yellow wire. I found that the wire ends up in the fuse box in a quick plug checked it there had the same 2.34 volts . Does anyone have schematics on this car 2012 Nissan Altima 2.5 coupe

 

[d0ugmac1]

that might actually be normal...14.2V is only for active charging..when the battery is fully charged, the alternator stops charging and the battery assumes it's normal 13.2V (just off the charger state). After 20min, it's not unreasonable to see the voltage change as described above. You can get the FSM (shop manual) over at nicoclub.

 

[Throckmorton]

It is normal. Stop worrying and enjoy your car.

 

[Throckmorton]

https://www.nissanclub.com/threads/alternator.518533/post-5639110


Your 2012 has a battery current sensor.

The battery current sensor is installed to the battery cable at the negative terminal. It detects the charging/discharging current of the battery and sends a voltage signal to the ECM.
Some vehicles have a battery current sensor that is a separate part from the negative battery cable, while others have a battery current sensor that is integral with the negative battery cable.

• The ECM uses signals from the battery current sensor to judge whether or not to perform power generation using variable voltage control.
• If the ECM determines that variable voltage control is needed, the ECM calculates the power needed, based on the signal from the current sensor, and sends that power generation command signal to the IPDM E/R.
• The IPDM E/R converts the ECM power generation command signal into a PWM signal and sends it to the IC voltage regulator.
• Now you know why the voltage is constantly changing.
• Drive you car, enjoy your car, put your volt meter and OBD2 away.
• Do not over think this.

 

[Shaun2019]

Yes, donated and downloaded the manual. After reading the manual, #4 wire is controlled 2.2 volts to 4.8 volts on the altanator. I'm a diesel mechanic don't normally see this shit lol . I sit down with some schematics figured it out . Fancy real fancy ?. My wife's car just always making sure it's right before I turn it loose.

 

[McGyv303]

Alternator


Your 2012 has a battery current sensor.

The battery current sensor is installed to the battery cable at the negative terminal. It detects the charging/discharging current of the battery and sends a voltage signal to the ECM.
Some vehicles have a battery current sensor that is a separate part from the negative battery cable, while others have a battery current sensor that is integral with the negative battery cable.

• The ECM uses signals from the battery current sensor to judge whether or not to perform power generation using variable voltage control.
• If the ECM determines that variable voltage control is needed, the ECM calculates the power needed, based on the signal from the current sensor, and sends that power generation command signal to the IPDM E/R.
• The IPDM E/R converts the ECM power generation command signal into a PWM signal and sends it to the IC voltage regulator.
• Now you know why the voltage is constantly changing.
• Drive you car, enjoy your car, put your volt meter and OBD2 away.
• Do not over think this.

2012 S2.5 Altima
Does the Battery Current Sensor need to be recalibrated when you switch to an AGM battery from the stock flooded? The Optima isn't being recharged to full.

Charging voltage starts out at 14V, then drops to 13.5V within a couple minutes. AGM battery is only charging to about 30%.