Have you recently drained your car’s battery flat overnight?
Are you in the process of charging it and wondering at what voltage you should attempt to start the car?
Each car is different but in general, your car’s battery needs to be at least 12 VDC to start your car normally.
When you read this post, you will know:
- what voltages are too low to start your car
- how to measure your car battery voltage accurately with a multimeter, and
- what you can do should your car battery have sufficient voltage yet the car fails to start over.
The Volts a Car Battery needs to Start
The voltage of a car battery should read between 12.6-12.7 VDC for the engine to start normally without any hesitation.
That said, the car may be able to start with a battery voltage as low as 12 VDC, albeit with an initially slow crank and possibly with hesitation.
There is a danger of shortening the lifespan of your car’s battery when you start your car with a battery whose voltage is low.
This is because when you start the car, the engine draws high currents, tens or hundreds of amps from the battery forcing the battery voltage to drop momentarily.
The high power draw on the battery at the start puts extra stress on the already drained battery and is bad for its lifespan.
Car batteries are in general not meant to be deeply discharged.
What Battery Voltage is too Low to Start a Car?
A voltage of below 12vDC which corresponds to less than 65% capacity of the battery is too low to start a car.
Continuous attempts to start the car at such a low voltage are not good for the life of the battery.
Estimated State of Charge of a Car Battery – Voltage at different Temperatures
|No.||Battery Voltage||State of Charge (%) 0°C (32°F)||State of Charge (%) 25°C (75°F)|
What else may Stop your car from Starting
Using a car battery with the lower cold-cranking amps (CCAs)
Besides having the recommended battery voltage, if your car’s battery has is being replaced (not the original factory-installed battery), make sure it is capable of supplying the manufacturer’s recommended cranking amps (CCA).
If the CCAs are lower, your car may struggle to start, the battery will drain quickly or fail to start altogether.
Extreme weather, both hot and cold can affect your battery’s ability to supply enough cranking power to the engine.
In fact, most batteries work best when kept within 32 °F and 70 °F.
Your battery may fail to turn over your car during freezing temperatures.
To protect your car battery from extreme cold, you can wrap your battery in a thermal blanket and use a battery heater to keep it warm.
If there is enough voltage at the starter terminals but the car fails to crank then possible you have a bad starter.
You may also be interested in Common Reasons Why your Car Battery may be Dying Quickly
Tips to Measure Car Battery Volts Accurately
What you need:
A good quality multimeter
The car battery voltage is only a measure of the battery’s state of charge.
You can follow the tips below to get more accurate battery voltage readings that are a reflection of the battery voltage.
- Switch off any electrical accessories in the car, make sure that there is no load drawing any power
- if the battery has been on charge, do not measure the battery voltage right away – wait for about 10-15 min before you measure the battery voltage
- if the battery was being discharged for example, there was an attempt to start the car, wait for about 10 min for the battery voltage stabilise.
This way you will get more accurate battery voltage readings
- Charge your Car Battery Fully
You need to charge your car battery fully for the voltage readings to be a more accurate measure of the state of charge of the battery.
Avoid the temptation to start your car prematurely simply because the battery voltage is more than 12V.
This way, you are sure that your battery holds sufficient charge to deliver enough cold-cranking amps to start your engine.
You may also be interested in: What should the Car Battery Voltage be When Ignition is OFF?
Battery Volts High Enough | Car not Starting – What to Check
Your car’s battery may have a high enough voltage yet your car fails to start!
There are a couple of things you can look at that may be affecting your car’s ability to start.
Scenario # 1
- when you turn the ignition to the START position, the dashboard lights come ON, you hear a single click (relay activation), no cranking, and starting the car.
The alternator cables are probably connected to the battery but are not firm or do not make clean contact with the battery terminals
Fix: Confirm that the cables from the alternator are firm and make clean contact with the battery terminals
Scenario # 2
- when you turn the ignition to the START position, the dashboard lights remain OFF, no cranking and starting the car.
If the battery voltage is sufficiently high, then you might have a wiring problem, disconnected battery, or a problem with the ECM (list is not exhaustive)
Fix. Confirm that the wires from the alternator make firm contact with the battery terminals.
Note: This assumes that the car battery voltage is high enough (12.6-12.7 VDC)
How to Maintain your Car Battery Voltage – Start Normally Everytime
A simple but effective way to guarantee that your car’s engine always starts normally is to keep your car battery connected to a good quality maintenance charger when it is parked for an extended period.
There are good quality chargers available, more convenient to use.
You can charge the car battery simply by connecting a plug into the car’s cigarette lighter socket.
A car battery voltage should read about 12.6V DC for the car engine to start normally.
If the battery voltage is 12.4 or less, then the car battery voltage is probably too low to start the car and there is a danger that you can damage the car battery by repeatedly attempting to crank the engine at this low voltage.