As mentioned above cold weather needs to be considered as this will decrease the voltage and increase the amount of power to turn over a cold engine. The voltage, when the engine is running, should be in the range of When your car is running the cars alternator is charging the battery, this is why you should see a higher voltage.
Wet cell car batteries lose water during use and charging, these batteries require regular maintenance. The water level will need periodically checking. For further advice see our guide on filling a car battery with water. Your car battery is made up of 6 2. However what voltage your battery should be at any given time is dependent on:. This is why a weak battery is often discovered in winter when you are about to set off to work on a cold frosty morning!
Age: As your battery ages and is used, its ability to hold charge will diminish, with a resulting decrease in the voltage. State of charge: The voltage of your battery will change as it is charged and discharged.
Understanding at what point it is in a charge cycle is important when determining what the voltage should be.
If the cars engine is running or not: The batteries voltage will be higher when the engine is running. You can check a car battery voltage with a multimeter or buy a car battery monitor.
Both are relatively cheap and easy to use. Check out our guide on checking a car battery with a multimeter. Knowing your car batteries voltage is important in understanding the condition of the battery and the likelihood that it could fail.
When you start your car the battery provides the high energy current needed to the starter motor, which in turn turns over the engine. Once the engine is running the power for your cars electrical systems is provided by the alternator.
The car battery also stabilizes the circuit voltage of the car when the engine is running, protecting the electrical systems from voltage spikes. Without a fully functioning battery you run the risk of being stranded and unable to start your car. We advise that you check your car battery a couple of times each year, and in particular towards the end of autumn before winter sets in.
It is worth keeping a noted of the voltage readings so you can compare them overtime. Read our full guide on car batteries. Hi, thanks for the informative article. What would the car battery voltage be of different battery technologies? Hi Mark, thanks for the message. Most modern car batteries are AGM absorbed glass mat , if you want us to specifically check the tech details for a battery you have then email us on advice tontio. Hi John. You can use the same car battery voltage readings as a guide.
Stop-start car batteries are different to standard car batteries as they are designed for higher number of cycles and for increased energy demands. Thanks for the great question. Fully charged automotive batteries should measure at When the engine is running, this measurement should be If they are dim, that indicates the lights are running off the battery and that little or no charge is being produced by the alternator. If the lights get brighter as you rev the engine, it means the alternator is producing some current, but may not be producing enough at idle to keep the battery properly charged.
Should the voltage read anything below 9. If you want, you can take this test a little further by disabling the ignition or injection to prevent your engine from starting.
This will allow you to crank engine a little longer, but we suggest cranking no longer than 15 seconds. If you discover that the lights are a little dim, then that could be an indication the lights are being powered primarily by the battery. In such a case, this means there is little or no charge being created by the alternator.
With your headlights on, try revving the engine. If your lights shine brighter during the rev, it could mean that your alternator is producing some current, but not enough at idle to maintain a sufficiently charged battery.
If your interior lights are gradually dimming as the car is running, your alternator is likely to blame. If you remember hearing a slight growling sound coming from your vehicle before your things took a turn for the worse, that may be a clue that alternator is deteriorating.
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