Skip the auto shop - Our mechanics make house calls

Q: What Are the Top 5 Things That Will Change Your Car Battery?

asked by on

What are the top 5 things that will drain your car battery?

There are many reasons why a car battery will drain, but it depends on the year of your vehicle. If you are driving an older vehicle, it could be something like an aftermarket alarm system, a poorly installed aftermarket stereo system or a clock in the car staying on. It could also be as simple as a light staying on in the glove box or the trunk. There are many ways to check for a battery drain.

To check if the trunk light is staying on, put your hand on the trunk lid in the area where the bulb is. If you feel the heat from the bulb being on, unplug it or remove the bulb. Sometimes it could also be that the alternator may not be charging the battery enough and it acts as if something is draining the battery.

If you have a vehicle manufactured since 2000, then you could be having computer issues. Vehicles today are getting more and more sophisticated with technology and have more onboard computers. In the late 1990s and early 2000s, vehicles had only one computer; now a vehicle could have over 30 different modules that stay on even after you shut off your vehicle. These modules often draw a few mA (milliamps) because of something called KAM (Keep Alive Memory). Whether it’s the clock in the radio or the last known position of the memory mirrors, these tiny amounts of KAM-induced current typically will only add up to 20 or 30 mA at most. That means the vehicle can sit parked for days, or even a few weeks, without any problems of excessive battery drain that might prevent starting. As long as the vehicle is driven periodically for the alternator to recharge the battery, there is no problem.

All of these computers are supposed to go to sleep or shut down completely after a certain amount of time. Sometimes they don’t and they need to be reprogrammed to do so. If you leave accessories plugged into your cigarette lighter such as a phone charger or a GPS, these could also drain down your battery. I recommend that you unplug them when you are not in the vehicle for many reasons other than battery issues; I have seen cell phones melt down in a vehicle and cause fires inside the interior.

The easiest way to check on what is draining your battery is to use an automotive meter, connect it in series with the positive side of the battery, and have the settings on amps. There should be a reading of less than 1 amp, depending on the year of the vehicle and what make it is. Now start removing fuses one by one till the amps drop to nothing. Once they drop to nothing, then you have found the circuit that is the issue. However, you should only be doing this if you have extensive knowledge about cars and trucks. Otherwise, you should have a certified technician look at the vehicle to remedy the situation for you and replace the battery if needed.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. What Are the Top 5 Things That Will Change Your Car Battery?

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: What's wrong with my car

If the passenger side floor was saturated, then you should pull up the carpeting and check all the wiring and possible computers, control modules, etc, that are located on the passenger side. Some may be on the floor under carpeting/insulation...

Q: Negative battery terminal sparks/smokes no power to car

Hi there. Check the condition of the starter wires when they were installed. See if the small remote wire on the starter solenoid is touching the main battery cable wire on the starter solenoid. If these two wires were to...

Q: I can not locate the starter on my 2007 Chevy Impala. I did go to you tube but the two vídeos were not helpful. 2007 Chevy Impala

Hello - the starter on this engine is located on the driver-side, front (of the engine/vehicle). It is best accessed from below the engine - and unfortunately, there are a lot of hoses and heat shields in that area. For...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.