SG2 battery voltage
 

i was wondering how accurate the battery voltage number by scangauge is? when my car has been out overnight in near freezing tempratures the voltage is 11.8v off and 14.7v idle. does this mean my battery is done? the car does turn over slightly lazily when weather is cold, but when its warm it starts like a champ.

Double check the voltage with a voltmeter of some sort. That will tell you. From my experience, I think my SG was .1V off (if it was even that much). Its fairly accurate IMO.

Yes that battery is toast
 

Be ready to replace it at any minute, you are on borrowed time at 11.8 volts.

...something else to remember, each "bolted-junction" in an electrical path can (worse-case) have a "voltage-drop" of 0.1VDC! So also check ANY connections that are "bolted" together (ie: clamps onto battery, terminal-to-teminal junction, etc.) for tightness.

ok i checked all connections and they all seemed to be tight. there is a bit of black grease on the clamps though. i also drove thr car on the highway at about 2500 rpm for an hour without any accessories on. i have lots of accessories including an aftermarket 600w amplifier. then when i got home i took readings and it read 12.7v car off and 14.3v on. so i think my battery was just low on charge. now my only concern is discharge rate. i will be checking the voltage again tuesday to see if it can hold up in ~30'f temprature.

Have you checked the fluid levels in the battery? Every battery I've owned has needed fluid at some time. One item I like to add is VX-6 battery additive. Seems to keep them working longer. Amazon.com: Charge-It Concentrated Battery Additive: Automotive

nope i havent used battery additives for a decade since car batteries are sealed now. plus i was told that all they do is clean the lead surface of sulfates and they do Not return the active material for charging.

My ScanGauge typically reads 0.1 - 0.2 volts low compared to a voltmeter reading at the battery itself.

You say you checked the voltage via the ScanGauge with the car "off". But was the ignition turned to "on" or "accessory"? If so, that will drop battery voltage some (compared to not having the ignition key in).

You can check voltage via the SG without the ignition key by waking it up -- pressing a button -- and calling up voltage gauge.

my first check with 11.8v was with key in acc. my second check after driving the car with no acc on was 12.7v while car was off with no key in ignition. i just chwck the voltage after it being off for 24hrs in freezing temps and voltage is 12.4-12.5v car off.

In these temps, 12.4-12.5 via the SG with no ignition key is fine.