Stingray Corvette Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
246 Posts
Discussion Starter #1
This past weekend the wife and I did a 600 mile road trip through Southern California and for a change I put the info system on Perf.

And the voltage indicator drew my attention almost immediately because it would be all over the place, the highest I saw it was 14.2V which AFAIK is too high, but then I also saw it read 12.8V which is too low for charging.

The car has no problems starting not even this morning after a night outside in 25F degrees.

I am going to guess that it’s just a cheap/bad voltmeter on the car and no really worth the hassle of having the dealer look into it.

PS. At home the car is always plugged into a battery tender.


Sent from my iPad using Tapatalk
 

·
Registered
Joined
·
10,212 Posts
You said you have a tender. Disconnect your plug from the tender and connect it to a voltmeter instead. That way you can see what your hand-held voltmeter says that the car is doing. That will tell you if your car's internal gauge is reporting accurately or not.

By the way, 14.2 V is not too high when charging. That is normal.
 

·
Registered
Joined
·
246 Posts
Discussion Starter #4 (Edited)
You said you have a tender. Disconnect your plug from the tender and connect it to a voltmeter instead. That way you can see what your hand-held voltmeter says that the car is doing. That will tell you if your car's internal gauge is reporting accurately or not.

By the way, 14.2 V is not too high when charging. That is normal.
Isn’t 13.8V the ‘normal’ charging voltage for a 12V battery?

I’ll get my Fluke hooked up next time if I remember... although I am already thinking of what the wife is going to ask me.. when she see my multi-meter hooked to the car while drive... :D

Sent from my iPad using Tapatalk
 

·
Registered
Joined
·
10,212 Posts
Isn’t 13.8V the ‘normal’ charging voltage for a 12V battery?

I’ll get my Fluke hooked up next time if I remember... although I am already thinking of what the wife is going to ask me.. when she see my multi-meter hooked to the car while drive... :D

Sent from my iPad using Tapatalk
Well, "normal" depends on various factors. For example, the CTEK MUS 4.3 charges at 14.4 V normally. However, if the "cold weather" charging mode is chosen, then it increases the charging voltage to 14.7 V. Furthermore, if you choose the "recondition" option for a battery that is in bad shape, it charges at 15.8 V.

The CTEK MUS 4.3 "Test and Charge" tender reports a battery is okay if the voltage is at least 12.6 V; it reports that the alternator is okay if it outputs at least 14.0 V.

Oh, I don't know about the other part... Maybe your wife will think you are the cool beans if you drive around with a multi-meter plugged into your car. :D
 

·
Registered
Joined
·
5,019 Posts
This is completely normal with modern charging systems from GM and other manufacturers. Output voltage is computer controlled to provide only what is necessary at the time, lowering parasitic drag from the alternator and (marginally) improving fuel economy. But add in enough marginal improvements, and it starts to make a difference. So after a cold start, voltage will be higher for a while to recharge the battery. When you're running lots of accessories that draw power, at low rpm, voltage will go up. But cruising on the highway, with lights and A/C and heated seats, etc. off, voltage will drop.
 

·
Registered
Joined
·
246 Posts
Discussion Starter #8
When you're running lots of accessories that draw power, at low rpm, voltage will go up. But cruising on the highway, with lights and A/C and heated seats, etc. off, voltage will drop.
That’s what I suspected as well but after starting the car in 35F weather and heading out on to a highway and cruising at 55mph, I saw 12.8V with seat heating on and switching off the heated seats did not change that.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
5,019 Posts
As long as the computer says the battery is adequately charged, it'll keep the voltage as low as possible. It might crank up voltage after a while if you leave the heaters on. But the heaters probably don't really draw much power compared to things like the headlights.

Mine varies from a low of 12.8 to a high of 15.1 (but that high is rare).
 

·
Registered
Joined
·
15 Posts
Completely agree that this is perfectly normal behavior. The indicated voltage is a function of the battery's state of charge and loading at the time, and what the car's electronics are doing to charge the battery. As others have posted, it can go up to 15V or even a bit more. In fact I would worry if the reading did NOT fluctuate over this sort of range!
 

·
Registered
Joined
·
2,933 Posts
Modern charge systems display voltages that alarm we old timers. And they jump around a lot. Start worrying when it displays 11.9 or less.
 

·
Registered
Joined
·
218 Posts
I think the voltage varies not just with electrical load, but also just to vary the charging rate on the battery to keep it from building up internal deposits.
I have had mine be charging at normal rates driving on the highway, and then drop to 12.8 volts with no apparent change in the electrical loads.
 

·
Registered
Joined
·
2,933 Posts
Modern charging systems will also respond to ambient temperatures, and will cut back the voltage as ambient temperatures rise into what is considered "hot" weather.
 

·
Registered
Joined
·
868 Posts
Normal in my experience with several of my vehicles. Lots of variables at play but that range is perfectly normal in my experience..
 
1 - 15 of 15 Posts
Top