Hi,

I Agree with what B.B is telling you all the way around.
There are No flat out rules here but a willingness to flex. (:-)

You have to remember that the coldness effects rest voltages of batteries.
Amperage and capacity will vary as so will the charging voltage rate.
Governing it is built into the regulator’s circuitry to protect the alternator or the whole electrical system as one piece as far as that goes.. It is a stand alone, take care of itself system.
A few tenths of a volt means a lot to the regulator.
That’s why “good connections and conductions are required.”

12.65 is a full battery and 12.0 is nearly dead and may not crank but blows a horn.
Alkaline cell batteries are measured from good to dead in a few tenths of a volt.

Basically, you need the minimum of one volt over resting voltage to maintain a battery or more to apply a charge to make current move into the cells plates.
Temperatures and charge status varies with loads but like B.B. says low is better than over 14 volts.
The best range, in my experiences, have me look for the car to be 13.2 to 14.2. Very very seldom I see the high end. In the thirteens is good.
A High charged condition to a low charge condition has to be put into this “equation” as entries are allowed to vary like the weather or demands.

If you are having problems it goes back to “good cells and connections are required.“


Phil