# How many volts should my car battery lose overnight?

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A car battery should not lose it’s charge overnight. It may lose a tenth of a volt or bit more, but not anything really noticable. If you are losing more than that overnight, then you have something that is draining the battery.

## How much car battery drain is normal overnight?

A normal amount of parasitic draw for newer cars is between 50-milliamp to 85-milliamp current draw. A normal amount of parasitic draw for older cars is a reading less than 50-milliamp. Anything past these amounts indicates an electrical issue and should be addressed by a mechanic.

## How quickly should car battery voltage drop?

If you measure the voltage immediately after the end of a drive, it should be more like 13.2, and drop to 12.7 within a few minutes as the chemical reactions in the battery slow down and stop when you stop charging it.

## Why is my car battery losing charge overnight?

A slow battery drain when everything is off is called a parasitic power loss. … Since the alternator isn’t generating vehicle electricity, the problem component pulls from the battery, slowly draining it overnight until your vehicle won’t start.

## What voltage is too low for car battery?

What voltage is too low for a car battery? A car battery is dead if its voltage is anything between 11.75 and 11.89 volts. Any reading between that range means that the battery is no longer functioning and a car owner should consider a replacement.

## How much voltage drop is acceptable overnight?

If the motor had just been running and just switched off it should have 14.0V. Left standing with everything off overnight, it will settle down to 12.8V. After a week’s standing it will droop to 12.6V, depending on ambient temperature. After a month it should still have about 12.4 to 12.5V.

## What drains a car battery while it is off?

Even while your car is off, your battery provides power to things like the clock, the radio, and the alarm system. … What may drain a car battery when it’s off are things such as interior lights, door lights, or even bad relays.

## What are the signs of a weak car battery?

5 Unmistakable Signs Your Car Battery is Failing

• Clicking sound when you turn the key. …
• Slow crank. …
• Needing to press on the gas pedal to start. …
• Backfiring.

## Do batteries lose voltage over time?

Very simply, batteries lose voltage as they’re used up, but no, you could not turn a 9V battery into a useful 1.5V one as it would be so steep down the “out of power curve” that it would only last a matter of seconds.

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## Is 11.9 volts enough to start a car?

When the voltage of the starting power supply is lower than 11.8V, it will be difficult to start the car. … When the battery voltage is lower than 10.8V, it is generally impossible to start the car. You need to replace the battery or use Jump Starter to start the car in an emergency.

## How long should you leave a car running to charge the battery?

Be sure to drive your car for about 30 minutes before stopping again so the battery can continue to charge. Otherwise, you might need another jump start.

## Why does my car battery died after sitting for a few days?

As mentioned above, there are many components in your car—like clocks, computers and security alarms—that continue to draw power from your vehicle when it is turned off. This is called key-off battery drain or parasitic drain, and it could cause you to wind up with a dead battery after multiple weeks with no driving.

## At what voltage is a 12v battery dead?

Resting fully charged 12-volt batteries are around 12.8-12.9 volts, and flat dead ones are at 12.0 volts, so 12.4 volts on a resting battery means it’s about 50% charged.

## Is 11.7 volts enough to start a car?

Your alternator has recharged your battery to its full capacity. Usually a new fully charged battery is 12.68 or 12.75volts. Even with a new battery 11.8 volts is normal before starting. There is always a drain on the battery from the car’s ECU.