How Long Can A Car Battery Sit Unused

The answer is not as simple as perhaps you think! You can leave a brand new battery for around 3 months with no lasting damage. Older batteries could go flat in a week if they are in a weak condition.

Through this brief article, we’ll try to explain why and advise on maintaining your car battery in optimum condition.

Damage Caused When Car Is Unused For a Long Time

A battery in excellent condition will hold its charge for an extended period. As the battery charge reduces, the acid begins to attack the battery’s metal plates. This causes sulfation, reducing battery life and its ability to hold a charge.

Don’t forget that if your car has an alarm, it will slowly flatten the battery. Allowing your battery to go completely flat will shorten its working life.

What Causes Car Batteries To Fail?

The leading cause of car battery failure is that you do not keep it fully charged. When you start your car, it takes a lot of the battery charge, which must be replaced.

Many drivers only travel a few miles, which is not enough to charge the battery fully. Add in all the power-hungry accessories, such as air conditioning, and your car’s battery will never be fully charged.

An undercharged battery will suffer from stratification and sulfation. These two problems can damage the internal battery components and also prevent the battery from charging correctly.

How Long Does a Car Battery Last Without Driving?

How long a battery will hold a charge depends on its age condition. A brand new, fully charged battery will last two months or more. That said, it’s not a good idea to leave them this long.

  • An older, weak condition battery will lose its charge much more quickly.
  • If your car has an alarm system, the battery will go flat more quickly. Alarm systems are a constant drain on your battery.

Regularly charging your car battery is the best way of preserving its useful life. If you have a standard charger, then once every few weeks should be sufficient for a good battery. Alternatively, you could run your car engine for thirty minutes every week to charge the battery with the alternator.

The best option is to use a trickle charger that has a maintenance mode. This type of charger can be left attached to the battery permanently. It will automatically keep the battery at the optimum charge.

How Long Will a Car Battery Last If Disconnected?

Disconnect car battery for longer storage without draining it.
Source: tedstowingandautoservice.com

Disconnecting your car battery is a good idea if you will leave it for long periods. If the battery is new, it should hold a charge for a month or two. Older batteries will go flat much more quickly.

We recommend that you remove the battery from your car when left for long periods. Charging a battery that while connected to your vehicle can sometimes affect the car’s electronic systems.

How you store your car battery is also important. Try to find storage that maintains even room temperature. Extreme temperatures, either low or high, can damage your battery.

How Long Can a Car Battery Sit On The Shelf?

You can leave brand new batteries on the shelf for several years, but we do not recommend this. The battery will need to be charged regularly to maintain excellent condition.

How to maintain a car battery sit unused
You should invest in a smart trickle charger to keeps your battery at its optimum level of charge. We recommend using quality chargers such as Battery Tender, Noco Genius1.

If you store your battery on the shelf, there are two options for maintaining its performance:

  • The best option is to connect your battery to a smart trickle charger that keeps it at its optimum level of charge. Smart trickle chargers will switch on and off automatically to maintain the optimum level of charge. This also prevents overcharging, which can damage your battery. Chargers, like those made by Battery Tender, are designed to keep your battery in good working order. 
  • The alternative option is to charge your battery every few weeks with a standard charger. The problem here is that each time the battery loses charge, it degrades its performance. There is also the risk that you will forget to charge the battery! Even if you remember, the battery will gradually deteriorate.

Find the best purchasing options for Smart Trickle Charger here:

Noco Genius 2 Smart Trickle Charger

Noco Genius2 Charger

Battery Tender Plus charger

Battery Tender Plus Charger

How To Store A Lead-acid Battery When Not Use?

Sealed Lead Acid Battery

These types of batteries can be stored for long periods, even up to two years. How you store them is very important. Make sure the location is somewhere the battery cannot get damaged.

Most important is the storage temperature. Try to find somewhere with a steady temperature of around 10-15 degrees Celsius or less. While in storage, regularly check the voltage, and if it drops below 60-70% of full capacity, charge it.

Lead Acid Battery

These are becoming less common now, but you may find one. It is best to dry store these batteries. However, take care when handling the acid as it will burn skin and damage anything it touches.

5 tips to store a lead acid battery when not using it
Step by step guide to store your lead-acid car battery when not using it.

To store it, follow these instructions:

  • Fully charge the battery.
  • Drain the acid into a holding container.
  • Store the battery dry.
  • The storage environment should be moisture-free at a reasonable temperature. Not excessively hot or cold.
  • When you need the battery again, refill with acid, and check the level of charge.

The table below shows how high temperatures can affect your battery discharge rate.

TemperatureDischarge rate after 6 months of storage
0°C97%
25°C90%
40°C62%
60°C38%

So What Is The Best Way To Store a Car Battery?

The optimal way to store a battery depends on its type:

  • Standard lead-acid batteries can be dry stored as described above.
  • Sealed batteries should be disconnected from your car and stored in a dry location with low temperatures. Connect a smart trickle charger, and check the battery charge once a month.

Note: a smart trickle charger is expensive, which can monitor the charging status, stop charging, and recharge the battery automatically. If you don’t want to spend more money, a traditional trickle charger is good but you cannot leave it unsupervised to prevent overcharging.

FAQs

How to keep the car battery charged in lockdown?

The optimal method is to remove the battery from your car, store it in a dry, cool location, and connect a trickle charger.

Is it OK to not drive your car for a month?

A month is not too long, but it will depend on the car’s condition and battery. The best solution is to remove the battery and connect it to a trickle charger.

Can a car battery sit uncharged for two years?

A brand new battery can sit on the shelf for two years, but if the charge falls too low, it will be permanently damaged.

What happens if you don’t start your car for a week?

If your battery is in excellent condition, then nothing will happen over a week. With a weak battery, you may find the car won’t start.

Would a brand new battery go bad if unused for a year?

Not necessarily, but leaving the battery uncharged for a year is not a good idea.

RELATED: How Long Does It Take To Charge A Car Battery?

1 thought on “How Long Can A Car Battery Sit Unused”

  1. kishore reddy

    Hi
    I have an automatic car and plan to be away for an extended period over 7 months. What is the best solution ref. the battery.

    1. Disconnect the battery and charge it to a trickle charger
    2. Disconnect the battery and drain the acid and store for this period
    3. What damage could I expect regarding the rest of the systems in the car
    4. Once I get back do I just check the battery charge and connect to the car and start driving

    Look forward to hearing from the experts
    . Thanks

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