Tip #20: A battery that dies every few days usually has something draining it
If a battery that tests healthy keeps going dead while the car is parked, something is drawing power with the ignition off. Common culprits are lights left on, plug-in accessories, aftermarket electronics and modules that never go to sleep.
Tip #20 in one line
If a battery that tests healthy keeps going dead while the car is parked, something is drawing power with the ignition off. Common culprits are lights left on, plug-in accessories, aftermarket electronics and modules that never go to sleep.
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Call nowWhat a parasitic drain is
Every modern car draws a small amount of power when parked, to keep the clock, alarm, keyless entry and computer memory alive. That is normal. A parasitic drain is anything drawing more than that, enough to flatten the battery over a night, a weekend or a week at the airport.
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Call nowUsual suspects
Lights you cannot see from the driver's seat: a glovebox light, a trunk or cargo light, a vanity mirror light, or a dome light switched to stay on.
Anything plugged into a power outlet or USB port that stays live with the key off, such as phone chargers, coolers and tire inflators.
Aftermarket electronics: hardwired dash cameras with a parking mode, remote starters, alarms, trackers and amplifiers, especially if they were installed without the right connections.
A door, hood or trunk that is not fully latched, keeping the car awake. A smart key left very close to the car can also keep some systems active.
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Call nowHow to narrow it down
Walk around the car after locking it at night and look for any light that stays on. Unplug every accessory. If the car has a hardwired camera, check its low-voltage cutoff setting.
If the problem continues, a mechanic can measure the current the car draws while parked and pull fuses one at a time to find the circuit responsible. That is a diagnostic job for a shop; we do not do repairs.
Make a note of when the dead battery happens. If it only fails after the car has sat over a long weekend, the drain may be small. If it fails overnight, it is larger and easier for a mechanic to find. Telling the shop which accessories were recently installed, and whether the problem started after a repair, can shorten the search considerably.
Keep in mind that a weak battery and a drain can both be true. Have the battery tested too.
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Call nowIn the meantime
Each deep discharge shortens a battery's life, so do not let it keep happening. If you are stuck, a jump start with a battery and charging test is one flat price quoted on the call to (908) 444-0129, and the dispatcher can quote a tow to your mechanic on the same call.
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Call nowMore on batteries
Keep reading, or go back to every post on the blog.
- Dead car battery in a New Jersey winter: why it happens and what to do
- Tip #11: Jump-start in the right order, and finish on bare metal, not the battery
- Tip #12: Never jump a battery that is swollen, cracked, leaking or frozen
- Tip #18: Test an aging battery in the fall and replace it on your schedule, not the weather's
- Tip #19: If the car dies while driving, suspect the alternator before the battery
- Tip #85: Test your battery every fall once it is a few years old
- Tip #87: If your battery keeps dying, have the alternator load-tested at a shop
- Tip #93: Modern cars and EVs drain their 12-volt battery while parked
- All posts
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