Voltage monitoring on Scan gauge

[_jp_]

I don't normally have the voltage displayed on the Scangauge, but have been monitoring it recently.

I understand the concept of the smart alternator but wondered what "normal" behaviour is as I often see voltages as low as 11.9v at times and normally around 12.2v with normal driving. When coasting and braking it shows 14.5v, but this is not often on my typical drive to work.

I also understand turning on the lights or HVAC causes the voltage to show around 13.6v. I'm one of these people that drive with both of these turned off most of the time.

The battery is a 3.5yo Century n70zzl.

I did a search and there are a few mentions of voltages showing this low with no lights or HVAC turned, but nothing really getting to the bottom of the behaviour.

Why the discrepancy between the SG reading and the multimeter on the battery?
Is the whole time I'm driving at below 12.6v meaning it's not charging sufficiently?
Am I worrying about nothing? Had I not started monitoring the voltage, I wouldn't be trying to analyse the behaviour lol. Oh, and I'm an overthinker.

I'm interested to know what others (with a standard single-battery configuration) see on their SG when they drive with lights and HVAC turned off.

[Paul NT]

Obviously one of the readings is wrong, I'd say the SG. I've put an eBay special cigarette light voltage monitor in the 12v outlet on the dash, and monitor continuously, probably 2 or 3 dollars. My ultragauge blue incidentally reads the same as my multimeter and cigarette light voltage monitor,
Cheers, Paul

[mr gus]

I also reckon the scangauge is not quite right... For reference my ultragauge usually sits at 14.1 with the engine on. Lowest is 13.9 ish. Lights +- aircon doesn't seem to make a huge differe ce.

[nj swb]

Voltage drop.

The scan gauge is reporting the voltage that it can see, which is taken from the diagnostic port, which is supplied from a fuse that is shared by multiple circuits in the car.

So the voltage seen by the scan gauge is NOT battery voltage, but some indeterminate voltage affected by the voltage distribution in the individual vehicle, the wiring used in that distribution system, and other loads shared on the same branch.

Get used to what's "normal" rather than outright values, and look for changes in those values.

[_jp_]

Thanks for the replies guys.

My other concern is why would the SG have it's own "volt meter"? I would have thought it pulled the info for the voltage from the ECU via a PID like all the other parameters?

[NJV6]

My ultragauge shows consistently 0.1-0.2 volts lower than measuring straight on the battery.

[erad]

I have found over the years that the Scangauge voltage reading seems to vary according to the ambient temperature. When it is cold, it runs typically around 14.3 volts, but in really hot weather, it can go down to 13.9 volts. Also, it varies according to load, but I would expect that to happen. I am not worried about this, and now know it seems to be normal.

Yesterday, I started the Pajero for the first time in 3 weeks, and it has been COLD here. The voltage prior to starting was 11.9 volts, but it came up to 14.4 volts for about 6 km, and then gradually dropped to 14.3. This would have been charging the battery up a bit.

[Dug1]

You will find that you have a smart charging system which cuts the alternator out when under power/load (eg put ya foot down) and cuts back in when coasting etc.

There is a current sensor on the -ve lead near the battery. My ASX does this but my NX does not. I suspect I have a problem with the NX which I will need to suss out when I have the time.

Your system is doing what it is meant to do. My Ultragauge reads the voltage at the ECU which is consistent with battery voltage.