[Skibane]

11.8 volts while driving isn't normal.

You might occasionally see 12.8 volts for a few seconds (when the VVCS kicks in), but not 11.8.

After sitting overnight, a fully-charged battery will typically drop down to around 12.4 or 12.3 volts - So your overnight voltage is a little low, too.

Incidentally, On 2.5L and 4.0L Frontiers, cutting this wire prevents the VVCS signal from reaching the alternator's built-in voltage regulator, allowing the regulator to function just like any "normal" regulator that lacks VVCS:

After cutting the wire, typical battery voltage is 13.3-13.8 volts whenever the engine is running.

 

[Skibane]

My wife’s Buick fluctuates between 11.2 and 14.6 according to the factory gauge when driving, asked the dealer about it, he said normal, talked to a couple automotive electric specialists and they said it’s normal too, although 11.2 is a bit low.

With no charging source present, a fully-charged battery produces around 12.5 volts - just sitting there idle.

In order to momentarily drag the voltage all the way down to 11.2, you'd need a huge electrical load on it - and still no charging source present.

Thanks for the info. I was thinking about cutting the wire but it seems there might be something wrong with the battery so I'm going to take it into the dealer for warranty repair

Since your voltages are normal part of the time - and your battery apparently is still capable of starting the engine - I'd be more inclined to suspect an intermittent problem with the charging system.

 

[Skibane]

I would bet that it's this connector (shown in the green box):

 

[Skibane]

There are 6 wires going into that connector, all about 22 gauge. Feeling adventurous, I unplugged the connector and tried to start the engine. Starter did not engage, dashboard read Alternator Check (amongst the other usual things), and the electric fan rev'ed up like it was trying for liftoff; plugged the connector back in and it stopped. Not a promising avenue of investigation.

On the 2nd Generation Frontiers, that same connector also has the control signal for the fuel pump relay - So, yeh, don't expect to be able to start the engine with it unplugged.

 

[Skibane]

Yeah so near the negative battery terminal there's a black thing attached to the wiring, I disconnected that from its wire harness.

That's the battery current sensor.

On 2nd Generation Frontiers, it's located on the negative battery cable itself, just a few inches away from the negative battery post clamp.

 

[Skibane]

With the battery current sensor disconnected, the voltage regulator inside the alternator is still measuring battery voltage, and is operating the same way as every charging system built before the advent of VVCS operated.

The only thing the current sensor does is to tell the engine computer how much current is flowing into or out of the battery. The engine computer then uses this info to occasionally instruct the alternator voltage regulator to reduce the alternator's output for a few seconds, in the interest of improving fuel economy.

With the current sensor disconnected, the engine computer never sends this instruction to the voltage regulator, so the voltage regulator operates on its own.

 

[Skibane]

No, it doesn't affect the battery gauge at all.

With the VVCS disconnected, the gauge will still be just as useless as ever.