Typically, your car can sit about four weeks to two months without driving before the battery dies. The reason your car can sit only for so long before it dies is the fact that your car battery is in use even when you're not behind the wheel.
To keep your battery fit and healthy, it's helpful to start the car up once a week and let it run for 15 minutes, in a well-ventilated place. Never leave your car's engine running in an enclosed space like a garage, as this can cause a deadly build-up of carbon monoxide gas.
A lot can depend on what condition your car battery is in. If you know your car battery is relatively new and has been kept in good condition, it can probably sit unused for about two weeks before it goes flat. If you've left your car unused for over two weeks, it's quite likely you'll need professional assistance.
If your car, particularly the battery, is new and in good condition, the charge will last about two weeks without needing to start the vehicle.
A healthy 12 volt battery should maintain a voltage range from 9.6 - 10.5 volts under the load for a good 30 seconds straight.
No, you can't charge a car battery while idling. At best, it'll charge the battery a few amps, but not nearly the hundreds of amps it took to start the engine. After a few days of starting and then idling the engine, you'll steadily deplete the battery instead of charge it.
Batteries and Oil
If you leave your batteries without starting your car for even two weeks, it can lose charge and even stop working altogether. The same goes for your car's oil. Old, unused oil can be harmful to your car, so if it hasn't been used for some time, you should make sure to have the oil replaced.
The suggestion is to charge once a month in warm weather and once every three months in cold weather. Another thing to avoid is deeply discharging your battery. Something like running the headlights and stereo with the engine turned off. That'll take months off the battery life every time you do it.
Your car battery could die.
Unfortunately, when your car sits idle for weeks or months, the battery has nothing to charge it and it could eventually die as a result. Need help jumpstarting your dead car battery? We've got you covered.
This can be a result of various factors including the number one cause which is leaving headlights, glove box lights, or cabin lights on overnight. Parasitic drain can also be caused by defective fuses, bad wiring, and poor installation of a new car battery.
Factors that can shorten its life include an extended period of partial or full discharge, vibration from not being properly secured, under- or overcharging, extreme temperatures, water loss, electrolyte contamination and corrosion on terminals.
A fully charged 12 volt battery should read at 12.6 volts on the multimeter. If the reading is lower than this, you'll want to charge your battery with either a battery charger or by taking your car for a drive.
A trickle charger can take up to 48 hours to charge a battery to full capacity as most only use one to two amps of power. You can even leave some smarter trickle chargers for days or weeks at a time, but it's best to check with the manufacturer if this is suitable.
Don't let your vehicle sit idle for more than two weeks - at least get your vehicle started and get it running for a while. You'll end up saving yourself time and money on repairs, and you'll ensure that your vehicle is ready to go once you need it again.
Generally speaking, you don't want to leave your car untouched for more than two weeks. Store it for less time than that if you're especially concerned about your battery draining.
Generally speaking, you should turn your engine on every week for at least 15 minutes. However, there is no hard or fast rule. Some cars may only be a few months or years old versus those that could be 20+ years.
You'd likely have to leave your car running for hours to even come close to a full charge. This is due to the amount of charge that is initially lost when cranking the engine. Some studies have shown that it can take between 15-30 minutes to recoup this initial charge.
Most car batteries will last between 500 and 1,000 charging cycles, which works out to a lifespan of between three and five years, depending on driving and weather conditions.
The battery will charge faster if you rev the engine faster. Why? Because the faster the crankshaft turns, the faster it turns the belt that runs the alternator. And the faster the alternator turns, the more electricity it produces to run all the electrical stuff in the car — and recharge the battery.
Some cars will get up to five or six years out of their battery, while others will need a new one after only two years. In general, your car will usually need a new battery after three to four years. Replacing your car battery is another part of routine maintenance.
Is it better to charge a battery at 2 amps or 10 amps? If you want a faster battery charge rate, go with the 10 amps. Low charging current at 2 amps can be unreliable, but it won't hurt if you have two chargers.
“Electrical devices or lights left running, a defective charging system or alternator, and extreme weather are some common reasons but maybe it's just time to get a new battery.”