After sitting in ambient temp for >3hrs you should see >12.8v.
Key on pump off, expect a 0.6v drop.
Cranking may drop about 2.0v.
In diagnostic mode the engine won't run so key on and pump on, it doesn't seem to alarming to be under 12v.
That said it should also be charging by 2500 RPM and roughly speaking the voltage is now very dependent on the battery depth of charge.
A fully charged battery could show 14.4v.
A depleted battery (even a good new battery) could show 13.5v.
It is current that charges the battery not voltage. So anytime the voltage is say about 13.0V, more current in Amps is charging the battery. As it reaches 14v, less current is flowing and we see the voltage climb, yes? Yes!
Just like your home charger, when you see it floating at 14.5v after charging 16hrs, there it little but a trickle flow of current into the battery. Maybe 150mAmps and the voltage is high. This normal.
Neither indicate a failed battery. Load testing a fully charged battery to insure it meets its CCA rating is what we test for. But obviously an aged fully charged battery can pass this CCA test but fail to start the bike as aged batteries build internal resistance which drains them over time.
That said a battery that shows a nominal voltage of say 12.5v, is placed on a charger and immediately jumps to 14.4v AND fails load testing, these are traits that say this bsttery is Shot. Replace it!
Mine routinely sets for 3 to 4 months without charger of any kind and fires the bike in 2 to 3 seconds. It was 6 years old and never charged by anything but the bike.
They only need charged if your riding style or environment or the load imposed (excessive) has them depleted (below 12.95v when parked). Meaning, don't leave them for weeks on end not fully charged. It degrades their performance rapidly.
Test them after riding YOUR normal routine after setting roughly 2 to 3 hours. If the voltage is below 12.9v they should be topped off. Otherwise, just leave them alone.
Make sense?
