I bought my scangaugeII and i notice after a while of driving, my voltage reads from 14-14.5 to about 12.1-12.5 when im idling. Sometimes while i start driving, the voltage starts to go back up but on some occasions, it still reads about 12-13 range. My car is still new, only about 15k miles. Any ideas on what this problem could be?

Doesn't sound like a problem to me..... sounds like normal fluctuation that pretty much any car on the road has. Especially a newer one with everything computer controlled.

i didnt know, thought the volt was suppose to be at constant 14 unless something was wrong with alternator. Isnt it bad if the car is running only at 12v? or at least bad for the battery?

ELD= electric load detector.... doing it's job. Honda's kicks in as needed.

thanks for addressing this Hayter. i feel less paranoid now because my '99 does it too. I had my SCII in the tacoma and it only varied .4V the whole time the engine was on but the accord is +-1V.

i didnt know, thought the volt was suppose to be at constant 14 unless something was wrong with alternator. Isnt it bad if the car is running only at 12v? or at least bad for the battery?

No, it used to be like that and running 14v always is not good as it can cook battery as its always charging it.
Newer voltage regulators don't go so much above static battery voltage.
after a start-up say you keep motor at fast 2k speed, you would see 14v for a little while then go down to like 13v. this happens fairly fast to if charging system is in good shape.
Remember its really current that alternator puts out in charging.
your idle voltage does seem a tiny bit low but i bet its scan tester being off than anything wrong (you always make tests off alternator and battery itself).you might want to see what happens with no accessories on. note idle voltage then turn on lights, defroster(front/rear) and see if you see spike go up after turning them on.
As full charged battery is like 12.6v or so, but every car manufacture can deal with charge rate slightly different, 14v always is thing of the past (unless something is wrong).

Ed

14.0 - 14.4 is normal for a 12v battery.. each cell is 2.2 volts x 6 13.2 volts
Charging voltage is usually always higher.



No, it used to be like that and running 14v always is not good as it can cook battery as its always charging it.
Newer voltage regulators don't go so much above static battery voltage.
after a start-up say you keep motor at fast 2k speed, you would see 14v for a little while then go down to like 13v. this happens fairly fast to if charging system is in good shape.
Remember its really current that alternator puts out in charging.
your idle voltage does seem a tiny bit low but i bet its scan tester being off than anything wrong (you always make tests off alternator and battery itself).you might want to see what happens with no accessories on. note idle voltage then turn on lights, defroster(front/rear) and see if you see spike go up after turning them on.
As full charged battery is like 12.6v or so, but every car manufacture can deal with charge rate slightly different, 14v always is thing of the past (unless something is wrong).

Ed

14.0 - 14.4 is normal for a 12v battery.. each cell is 2.2 volts x 6 13.2 volts
Charging voltage is usually always higher.

well I can only say my experience working on cars , I can never remeber seeing static battery at 13.2(installed/connected in car, engine off) ,most always around 12.6- 12.8(yeh it may stay higher than 12.6-12.8 right after a change but come's back down).
As I said 14v is ok after at heavy load or after starting but once running with no heavy loads (lights , defroster etc) the newer regulators run lower around 13v or so.

I'll check my 08, I doubt it's going to be different.

well I can only say my experience working on cars , I can never remeber seeing static battery at 13.2(installed/connected in car, engine off) ,most always around 12.6- 12.8(yeh it may stay higher than 12.6-12.8 right after a change but come's back down).
As I said 14v is ok after at heavy load or after starting but once running with no heavy loads (lights , defroster etc) the newer regulators run lower around 13v or so.

I'll check my 08, I doubt it's going to be different.

thanks for the input, didnt know that.

well I can only say my experience working on cars , I can never remeber seeing static battery at 13.2(installed/connected in car, engine off) ,most always around 12.6- 12.8(yeh it may stay higher than 12.6-12.8 right after a change but come's back down).
As I said 14v is ok after at heavy load or after starting but once running with no heavy loads (lights , defroster etc) the newer regulators run lower around 13v or so.

I'll check my 08, I doubt it's going to be different.

With the battery charged, open circuit voltage should be 12.6 to 12.8 volts with the engine off and all loads off. With the car running and all loads off, the voltage should be between 13.6 and 14.5 volts.
each cell is 2.2 volts... but losses thru the plates/connectors show about 12.8 on a good battery static..

With the battery charged, open circuit voltage should be 12.6 to 12.8 volts with the engine off and all loads off. With the car running and all loads off, the voltage should be between 13.6 and 14.5 volts.
each cell is 2.2 volts... but losses thru the plates/connectors show about 12.8 on a good battery static..
Seems you are correct on charging voltage of these Honda's , as I used to remember other manufactures varying voltage from like low 13v to low 14v depending on load and rpm.

Tested my 08 this morning, 12,55v static@40F.
cold was 14.5v and after warmed only lowered to 14.0 at idle. changing load hardly changed voltage much (few0.10)

The car's battery (assuming it is a lead-acid battery, and not a dry cell, gel cell, or the like) is made up of six 2.11 volt cells (not 2.2 like previously stated) in series giving you 12.66 volts. Your car's battery will never sustain a charge much above that. Never 13.2, unless it is an AGM battery like an Optima yellow top, which will actually read 13.1 with the car off. You may have a surface charge left after running the car, but that will go away after a few minutes.

On another note, unless your battery is drained, your alternator does not charge your battery. Many people are under the misconception that it is constantly charging your battery, and your battery is what powers the electronics in the car. The only time your battery is supplying power to the components in your vehicle is when the engine is off. The battery's primary function is to start the car. Once the car is running, the alternator is what powers the electronic components, and normally operates between 13.8 and 14.4 volts. All alternators will have a relatively low current output, as well as a lower voltage output during idle, but will run at full capacity at highway speeds. They are designed to do this. When the engine is running, the alternator is what is supplying power and the battery helps 'smooth out' the voltage ripples in the system, acting as basically a large capacitor.


If you are unhappy with the performance of your stock alternator, you can buy an upgraded one from daves electric (http://www.davesdcelectric.com). I just emailed them about my 07 V6 because I am planning on adding 3 amplifiers to my car this spring with a total draw of around 150-175 amps (assuming the amplifiers are about 60-75% efficienct, may be a little more of a current draw) amps with a combined suggested fuse rating of 220 amps (all 3 added up). This is a copy of the email (minus the pic they sent, which is just a picture of an alternator, not installed)

We can do the alternator on your Accord, and we are currently the only (not to mention first) company that is doing them. If you were told that it couldnt be done becuase of the internal voltage regulator, you were mis-informed. I cant speculate on the reasons for not being able to do it, but I assure you it is no problem for us to do them. (see attached pic of the one I did last week) We have been doing this particular alternator for quite some time and have had very, very good results! The alternator we have for your car is a 250 Amp unit, and will make about 125 amps at idle, and is a direct bolt on unit and it also comes with a custom 7075T6 Billet aluminum pulley. The alternator is $625, 100% new, and built from a new OEM unit to our high standards of workmanship to assure you a long lasting unit that performs to our highest standards. We can do your original unit off your car, and your price on that would be $425 including freight.

I hope this is a help to someone!:thmsup: