Great day here in the northeast. 60* out with the sun shining and it rained last night further reducing the left over salt on the roads. So took the car out for a ride. This is the first out since bringing it back from a new alternator replacement. Unplugged the Ctek which was sitting on step 7. Took a quick voltage reading and it was at 13 but it was right after removing the charger. I got in and plugged the volt gauge into the lighter port. Started it up and it went to 12.9V then 13.4V . Backed her out and went for a drive. Gauge was a moving target. 12.9 , 13.4 , 13.8 , 14 , 14.4 , 13.7 , 13.4 and on and on. It's still got me wondering so I'll just keep the dealer informed. Now if I leave the charger off over night and check the battery it is at 12.4-12.6V but I'm starting to think maybe the battery might be an issue. It was dealer replaced in 2014. Also what was interesting was on deceleration on a long hill the voltage went up to 14.4V and when I leveled out at normal speed it went to 13.4. Maybe someone else with a 2010 and newer can just track your voltage . Just as an FYI in 2010 Jaguar when with a different alternator then the 2006-2009 models. It is 2-3x the cost plus they went with a control module with feedback from the ECM on voltage demand. It still smells a little fishy to me but I'll drive it and keep the involvement of the dealer as it it under warranty for a few more years. OH the drive was GREAT and even cleared out the pipes.

 

A lead acid battery makes about 2.2v per cell, or 13.2v at full charge when in top condition. 12.6 on a full charge is a touch low.

To charge a battery, the alternator output must exceed the battery voltage (emf) by a small margin. In the older days you would generally regulate to around 14.1v to do this.

As we've all seen, modern charging systems regulate more to need than sending a constant output.

After starting your car, There is a need to replenish so a higher output would be expected for a short while. This is reflected in the charging voltage and current if you are able to monitor that.

At steady state conditions the alternator supplies all of the system needs, with the battery only there to aid in period of peak load if required, so your voltage readings should reflect what your 12v system is needing.

Based on your observations, I'd say it it's working properly.

 

I guess we have different data as most of the info I've read has 2.1V per cell X 6 cells . From the sources I have seen a normal fully charged battery depending on temperature is 12.4 - 12.6 Volts. I agree all of the newer systems have more sophisticated electronics and charging rates are based on determined needs of the ECU . I had also purchase a few extra digital volt gauges and used on on my Lexus tonight. Interesting enough (6 year old battery) it fired up with 14.2V and settled down to 13.9 as we took a 1/2 hour drive to get to the restaurant . Coming home it danced from 13.9 , 13.8 , 14 , 13.7 and so on . So I'm starting to think I may be overthinking this and will just follow it and see what happens. At this point any voltage over 12.6 is acceptable even though I'm not seeing under 13.0 V. Live and learn as the involvement of microprocessors in the charging system has changed the game for this old motorhead.

 

Waaaayyyy back when I was in high school auto shop, we dove kind of heavy into batteries and alternators (relatively) and nearly every test and procedure had the lead acid batteries at 13.2 volts (2.2 per cell). I don't know how chemistry would or could have changed over the years, but it was definitely 13.2 volts back then, over and over ad nauseam.

 

This gets pretty funny as when you search the web I have found resting voltage vs temperature in various ranges but the highest I have seen is 12.67V at 70*. Here is just another example so it's where you find the data and who wrote it. I think I'm tired of searching and will let it sort itself out. https://en.wikipedia.org/wiki/Automotive_battery

 

Same here in the aviation industry. Just grabbed my 1985 reference books, 2.2 per cell at no load on a lead acid battery.


Vince