Battery voltage required to easily crank?

[acarr6]

Hey guys, the battery in my car is original from 2011, and has been having a tough time cranking lately. I use a charger with it, but just wondering what normal voltage for a smooth crank is? After I park the car it drops from 12.6 to 12.3 over night, then continues to drain of course. Going to replace with oem as per recommendations. Would 12.2/12.2 cause a long crank? Car has a 4.4L so I assume takes a little more juice.

[nycplumber]

My car had zero issues starting with 11.9 before I replaced battery

[drwankel]

These cars throw lots of electrical gremlins related to battery voltage long before you ever notice cranking issues. Same is true for most Euro cars. Very different vs most Japanese or American cars, where a slow crank is indicative of a failing battery.

[acarr6]

Originally Posted by drwankel

These cars throw lots of electrical gremlins related to battery voltage long before you ever notice cranking issues. Same is true for most Euro cars. Very different vs most Japanese or American cars, where a slow crank is indicative of a failing battery.

Started to notice it last year. If I start it right off the trickle charger it goes no problem. If I don't trickle charge and leave it for a few days.. long crank. Only put 400 miles on in the last 12 months and wasn't always hooked to charger. Keep in mind the battery is nearly 12 years old lol

[acarr6]

Swapped the battery, started up right away. Interestingly - the old one was from a 2 series. 850CCA vs our 900.

[Redd]

Cranking is more amp dependent than voltage. As a battery ages, the CCA (cold cranking amps) reduce. So even though you may be getting the 12.x V that you need, the CCA may not be enough. Our M3s need a huge battery not because it needs the Ah but because it needs a much higher CCA to turn the big ol' 4L V8. Manufacturers also size the batt to take into account aging and CCA drop over time. This is why you get away with a much smaller Ah capacity lithium batt because Li batts offer massive CCA.

At 12 years old, you have already gotten your money's worth out of that batt by a factor of 3x.

[drwankel]

Originally Posted by acarr6

Swapped the battery, started up right away. Interestingly - the old one was from a 2 series. 850CCA vs our 900.

The current dealer replacement is a slightly smaller CCA than the original battery. If I remember correctly, factory was 900cca, current dealer replacement is 850cca. New battery is physically the same size. Original one is NLA as far as I am aware. Lines up with your stated CCA numbers.

I'm guessing your new battery isn't OEM? The previous battery might have been a dealer 850cca, which isn't wrong.

Lastly, you keeping the car on a trickle charger is likely masking the electrical gremlins that come with a failing battery. Unexpected upside.

[acarr6]

Originally Posted by drwankel

The current dealer replacement is a slightly smaller CCA than the original battery. If I remember correctly, factory was 900cca, current dealer replacement is 850cca. New battery is physically the same size. Original one is NLA as far as I am aware. Lines up with your stated CCA numbers.

I'm guessing your new battery isn't OEM? The previous battery might have been a dealer 850cca, which isn't wrong.

Lastly, you keeping the car on a trickle charger is likely masking the electrical gremlins that come with a failing battery. Unexpected upside.

The new battery is oem. He said this is the new replacement. 92ah 900CCA. Got straight from dealer