15 volts at idle and higher rpms?

[resq302]

Ok, it could probably be because of this darn heatwave here or my brain has just melted to the point where I cant remember anything anymore.  I just installed a new / reman'd alternator on our 69 GTX (as someone had painted the old entire alternator aluminum silver!) and after starting it up and checking the battery voltage with the car running, it showed the battery being charged at 15.03 volts.  I turned the headlights on and same reading, maybe jumped up to 15.08.   I want to say that is just at tad bit on the high side as I seem to remember that it should be somewhere in the 13.8 - 14.8 volt range.  Some assurance would be helpful.   

[Dino]

That is indeed a tad high.  Not high enough to get nervous though.   

Did you install the same type alt as the stock one or more amps?  If more amps it may be overcharging the battery.

[resq302]

I would imagine it was the same as the armature width between the two casings was about the same thickness.  The ammeter inside the dash is just a hair to the right of the 0 (no charge) so I know it is not really over charging it.  Everything else is exactly the same though.  We did install a solid state electronic voltage regulator (original appearing case) prior to installing the new alternator however, we did not take a battery reading at that time.  I guess as long as it does not go over the 15 volts, I won't worry about it.

[Pete in NH]

Hi,

That 15.08 volts is a tad high. I don't know if I would get too concerned over it as unless you measured it with a know accurate and calibrated meter. Yes, the normal range is 13.8 to 14.5 volts or so. I don't know about those reproduction electronic regulators that look like the original mechanical ones but the Mopar electronic regulators are temperature compensated. In the summer when temperatures are high or when the engine compartment is really warmed up you want to reduce the charging voltage so you don't overcharge the battery. In cold temperatures you want to boost the charging voltage as the chemical action in the battery is less efficient.

These are the specs. for the Chrysler electronic regulator: -20 F = 14.3 to 15.3 volts, 80 F = 13.8 to 14.4 volts, 140 F = 13.3 to 14.0 volts, and over 140 F = less than 13.8 volts. Chrysler specs. these temperatures 1/4 inch from the regulator.

[resq302]

Hi Pete,

The device I used to test it at the terminals for the battery was the Actron digital multi meter.  Tests dwell, ohms, volts, etc.  One very similar to this only this one seems to be the newer updated model.  Mine is more flat on the bottom.

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_auto-analyzer-digital-multimeter-actron_9020008-p?searchTerm=actron

[Pete in NH]

Hi Brian,

We all get fooled by these new digital type meters into believing since they give you an actual number that is what the voltage is. I have a digital meter that should be within 2% of the true voltage as It occasionally does get checked against a reference standard and calibrated. I would think most general purpose meters are within 2 to 5 %. At 2% of 15 volts the reading could be + or - .3 volts, at 5% it would be + or - .75 volts. Like I said I wouldn't be too concerned about the reading you got unless I knew the accuracy of the meter.

[resq302]

Thats why I was double checking.  If it was an upper limit of 14.8 and it is reading 15.0, I'm happy.  If it was reading 15.8 then I would be a little more concerned.  The battery is also going on 8 years old and is an over the counter replacement I got from Mopar back in 2005.  Within that time, most of it has been spent on a battery tender while some of it being off of the tender (I used the tender some other place and forgot to hook it back up to the battery when I was done)   and sitting on a piece of 2/4 off of the concrete floor in my garage.  So it could even be the beginning of the battery starting to go on its way out.  Although, it starts up the car nice and strong every time!

[71 SE3834V]

I'll just throw this out there for the heck of it but it's not necessary to do the 2x4 thing. I read an article a long time ago that explained where this thinking came from. If I remember right back in the early days of batteries the casings were made out of a material that could "leak" current to ground (the earth). Modern materials of the last 50-75 years have made it unnecessary. Batteries will drain down if left sitting unused for long periods which is what I believe leads people to think they need to do it.

[flyinlow]

What voltage did the meter show before you started the engine? (battery voltage)  Check your other vehicles and see what they read.  The alternator normally raises the system voltage about 1.5-2.0 volts.

As the battery loses capacity with use it is easier for an energetic regulator to have the alternator raise the system voltage. Probably OK. Start saving for a new battery. Eight years is a good run. 

[resq302]

Yeh, we are not expecting too much more out of this battery but I think it is how you take care of them in how they last.  We have pretty much always had this one on a battery tender its whole life.