Wondering if you should be concerned about the likelihood of the car battery being drained if you plan to park the car for an extended period or how to prevent the battery from being drained?
If this is you then read on.
Battery Drain by a Car Alarm – the Facts
Yes, a car alarm system that’s armed whether in standby mode or activated drains some of the battery power less so in standby mode.
The current drawn by a car alarm is a result of the combination of the car alarm light and the alarm circuity.
Can a Car Alarm Kill the Battery?
The current draw of a car alarm when armed is in the order of a few mA. It can therefore take several days before a fully charged 50Ah AGM battery is drained to 50% of its capacity.
Over time, the combination of the power draw from the car alarm and other onboard electronics continues to draw down the battery’s power, and as you may be aware the life of the battery suffers if it is maintained in a partially discharged state (~ 12.4V and less).
So, yes, over time a car alarm system can drain the car battery flat. If the battery is on its way out – it is aging or a poor-quality battery can kill it too.
To maintain the car battery’s health, leave it connected to a car battery maintainer.
Will Anti-Theft Light Drain Battery?
The anti-theft light uses some of the battery power however, its draw is in the order of a few amps and even then on every second or so.
For context, if the LED uses 10 mA and lights up after a second delay, a 50Ah battery can last an estimated 200 days before it is discharged to 50% of its capacity! Note. This only considers the LED alone.
Based on this, I wouldn’t be overly concerned about the impact of the current draw by the anti-theft LED – it is nearly negligible.
Tips to Stop a Car Alarm from Draining the Battery
Is your car parked for an extended period without periodic recharging of the batteries (through regular driving)?
If so then there’s an increased risk of the battery being drained especially if it is parked in a noisy place and its sensitivity is set too high.
Minimize the danger of draining your battery by:
- reducing its sensitivity when the car is parked in a noisy environment
- connecting your car battery to a battery maintainer to trickle charge and regular top-up charge when your car is parked for a week or more.
How Long for Car Alarm to Drain the Battery?
There are several variables at play that determine how long can a car alarm go off before the battery dies. In standby mode, a car alarm can take several weeks to significantly drain a car’s battery.
When triggered, however, a car alarm can drain a car battery within a day or couple of days depending on:
- what warning features are installed – siren or flashing lights. These increase the battery drain and shorten how long a battery lasts
- the battery capacity. A smaller battery capacity (Ah) will last a shorter time
- whether the battery is fully or only partially charged
- the battery condition. An aging battery tends to lose its ability to hold charge and will last a shorter time.
- how sensitive the alarm has been set. If it is triggered when the slightest noise is detected the battery will last a short time.
Related Questions
Does a Car Alarm Still Sound if the Battery is Dead?
If the car alarm has a backup battery then the alarm can still go off if the car battery is dead.
The backup battery continues to power the alarm’s electronics when the car battery fails or is disconnected.
Why a Car Alarm May Sound When Disconnecting or Changing the Battery
Some car alarm systems have a sensing feature to detect changes in voltage in the car’s electrical system such as when disconnecting or replacing the car battery to deter attempts to disarm the alarm by disconnecting the car battery.
Check your car alarm manual to confirm if this is the case. This is usually a programmable feature that can be turned off if you experience false alarms.
Closing Thoughts
Yes, a car alarm can drain the car battery over time. If planning to park the car for an extended period with the alarm armed, leave the car connected to a battery maintainer.
