12V battery voltage range

[vladm2018]

I was running LeafSpy last night in the car and noticed that it was showing 11.92V and 17.42A consumption. It is about 40% charge.
Today in the morning after overnight charge it went up to 12.11V. I just wonder what others see on their 12V battery and how prevent from draining it too much?

[LeftieBiker]

Your 12 volt battery is very low. The normal range for a rest voltage without LeafSpy is 12.5 to 13.0, with most older Leafs in the 12.6 range. Below 12.5 and you have a problem. Voltage with LeafSpy tends to be higher, around 13.0 volts, so your 12 volt battery is likely at death's door.

[vladm2018]

I put a voltage meter in my 12V plug and monitored it through the day. When the car is ON and moving, the voltage is 13-14V as normal for most of the cars. Just switched OFF it is about 12.7V. What is interesting is when the car is ON without starting battery (no brake pedal pushed) it drains battery very fast. I thing the whole battery could be drained in about 30 minutes.

[Leaf15]

My battery is about 12.25V, 12.3V in the morning without any charging. So based on voltage it is > 50% charge. When I put maintenance charger that produces 1A charging current, after 8 hours it switches to float - means battery is fully charged. Leaf has at least 40Ah battery, So how 8Ah could fully charge this battery is a bit of a mystery to me, considering there is a parasitic drain by the car electronics. It should be at least > 14 hours to reach this point. I have CCA tester and it shows 424 CCA out of 410 CCA battery is rated for (usually new battery exceeds CCA ratings). Anyway, I recently got a good deal on 46Ah LiFePO4 battery with 10Ah emergency backup (in case of main 46Ah is discharged) and after installing it and making a few miles trip - it holds 13.35V next morning. I am keeping original battery on desulfating maintenance charger for now to see if any changes in CCA, although it looks like it is in good shape, but real time performance says otherwise. I am using voltmeter at the battery terminals to measure voltage.

[GerryAZ]

I was running LeafSpy last night in the car and noticed that it was showing 11.92V and 17.42A consumption. It is about 40% charge.
Today in the morning after overnight charge it went up to 12.11V. I just wonder what others see on their 12V battery and how prevent from draining it too much?

A few minutes with that much load will draw the small 12-volt battery down. What did you have turned on to have that much load? High beam headlights, HVAC fan, etc? It is best to have the car in READY mode (ready to drive) when parked with accessories running because the 12-volt battery is charged by the traction battery through the DC-DC converter. The DC-DC converter is not active in ACCESSORY mode so the 12-volt battery will discharge.

Edited to add: DC-DC converter output is about 13.0 volts for float charging the 12-volt battery while the car is in READY mode (normal driving) and while the traction battery is charging. The DC-DC converter output is about 14.0 to 14.5 volts when the 12-volt battery is low enough to draw significant charging current. The exact float and bulk charging voltage output from the DC-DC converter is temperature compensated so it is higher at low ambient temperatures (lower when under hood temperatures are higher).

[flydiver]

I put a voltage meter in my 12V plug and monitored it through the day. When the car is ON and moving, the voltage is 13-14V as normal for most of the cars. Just switched OFF it is about 12.7V. What is interesting is when the car is ON without starting battery (no brake pedal pushed) it drains battery very fast. I thing the whole battery could be drained in about 30 minutes.

You might simply monitor it with nothing on after a fresh charge. Even a decent battery will rapidly drop some voltage immediately after JUST being charged. It slows down and levels off after awhile. That state is more revealing than right off the charger, and maybe a bit warm.
For example, noting that this is a 4 year old battery but with only 11K miles on the Leaf.

Immediately after a fresh full night charge on a battery tender - 13.06v
A few minutes after disconnecting - 12.88v
After sitting all day in a cool garage with nothing on - 12.32
From my limited experience it'll sit at that level or close for days.