# Question: How Do I Know When My 12v Battery Is Charged?

## How do you know when a battery is fully charged?

So you can determine charge by simply measuring the terminal voltage.

As the battery becomes fully charged, the terminal voltage reaches a maximum value provided by the battery manufacturer.

For eg.

Li-ion cells used in laptops are said to be fully charged when their terminal voltage reaches 4.2 volts..

## Is 11.9 volts enough to start a car?

The Minimum Voltage Range To Start a Car In general, while both the engine and the generator are in the working state, the voltage of the battery should be within 13.7 – 14.2V. … In the standard state, a fully charged battery should show a 12.6-12.7V.

## What happens if a deep cycle battery goes flat?

If your battery shows a good voltage when it’s fully charged, but quickly drops voltage to 11V or less when using power, this usually means the battery has a faulty cell and needs replacement. … When a deep cycle battery is fully discharged (dead flat), it should reveal a reading of approximately 10.5V.

## Can a completely dead battery be recharged?

A car battery is considered discharged when the voltage drops below 12 volts. While your vehicle’s alternator can keep a healthy battery charged, it was never designed to completely recharge a dead car battery. … Most of the time, you don’t even have to remove the battery from your vehicle.

## How long should a 12 volt battery hold its charge?

The actual resting voltage, or the voltage a battery will settle at 12-24 hours after being removed from the charger, is closer to 2.1 volts per cell, or about 6.4 volts for a 6v battery, and 12.7 volts for a 12v battery. These numbers assume 100% healthy cells, and may vary a bit lower for older batteries.

## Is it safe to leave a trickle charger on all the time?

Otherwise, keep the battery charging until it is full. Some trickle chargers can safely be left connected for months without doing harm to your battery, providing an easy long term battery maintenance strategy. Others may only be left connected for a few days at most.

## Can you overcharge a deep cycle battery?

Both overcharging and undercharging will have serious adverse effects on the lifespan of a deep cycle battery. In particular, you can seriously shorten the lifespan of a battery if it is used in a deep cycle application that it was not designed for.

## What voltage is too low for a 12 volt battery?

No 12-volt battery will remain at over 14 volts for more than seconds unless it’s being charged. The lowest limit is 10.5 volts (used in testing) and obviously unsatisfactory in practical use. Experienced RVers try to use no more than 20% to 50% of the energy available in a battery before recharging.

## Does putting aspirin in a battery work?

Put two tablets of aspirin in each battery cell and wait no more than 1 hour (the acetylsalicylic acid combines with the sulfuric acid to get off one more charge.) … Be warned that adding aspirin will shorten the battery life, as the aspirin will react with the sulfuric acid to form acetic acid.

## What should a 12 volt battery read when fully charged?

about 12.9 voltsSo a 12volt battery will measure at about 12.9 volts when it’s fully charged and about 11.4 volts when it is fully discharged. That’s a total of 1.5 volts that represents the full range of charge on a 12volt battery.

## How do I know if my 12 volt battery is bad?

If your battery is reading 0 volts, chances are the battery experienced a short circuit. If the battery cannot reach higher than 10.5 volts when being charged, then the battery has a dead cell. If the battery is fully charged (according to the battery charger) but the voltage is 12.5 or less, the battery is sulfated.

## Can you overcharge a 12 volt battery?

A 12V lead-acid battery will not be damaged by overcharge if the voltage is kept low enough to avoid electrolysis, and the charging current is kept below 0.2C (5 times less than the Ah capacity). … If it can put out more current than the battery can take then the battery may overheat.

## Is it OK to leave a car battery charger on overnight?

Even though there is no risk of overcharging with the use of a high quality charger, the battery should not remain connected to the charger for more than 24 hours. A full charge is usually achieved by charging overnight. … Even after a deep discharge, some chargers enable at least partial reconditioning of the battery.

## Can you overcharge a battery?

It’s complicated, as leaving your battery plugged in all night certainly isn’t dangerous but it might make your battery age slightly faster. “Overcharging” is the term that gets thrown around a lot with this one. … This did, in fact, cause damage to the battery and reduce performance. Hell, it even led some to explode.

## What happens when battery is fully charged?

Once the battery is fully charged, it will draw a small amount of energy. This is to maintain the state of charge. The charger will supply this energy and this mode is the Trickle Charging Mode. Continual charging of the battery will gradually reduce its capacity over time, but this process will take several years.

## Can you start a car while the battery is charging?

Yes, if the battery is charged, it won’t make a difference if charger is connected or not. But No, if the battery is discharged, it won’t start anyway since a charger cannot source enough current. … It won’t hurt the charger, the battery or the car.

## How do you make a dead battery work again?

Bring Dead Lead Acid Battery to Live AgainStep 1: Preparing the Battery. 3 More Images. … Step 2: Fill the Water Inside the Battery. we need in this step to fill the battery with Distilled water to activate the acid again. … Step 3: Mix Water With Acid and Charging. … now pull the wasted water from the top of 3 holes by the syringe and let the battery charging.

## What happens if you leave a battery charger on too long?

A: If you leave the charger connected continuously, even at a mere 2 amps, the battery eventually will die. Overcharging a battery causes excessive gassing — the electrolyte gets hot and both hydrogen and oxygen gas are generated. … On sealed batteries, the buildup of gases could cause the battery to burst.

## What does a blinking green light mean on a battery charger?

When the green light is blinking the unit is fast charging the battery. … When the green light is blinking the unit is fast charging the battery. When the green light is on but not blinking it is maintaining the charge on the battery.