Why does my battery drain so fast?
Why does My 2010 Chevy Malibu battery drains too fast?
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Hi @dianesmith9580,
There could be several reasons for this to occur.
The battery is failing, it is not being charged correctly or there may be an excessive parasitic current draw on the battery due to a component fault somewhere.
Check the simple things first e.g. are all the lights etc turned off when the car is stopped, parked and locked, especially check that the trunk light is off. I think that the trunk light on/off switch is in the latch which means the trunk lid needs to be shut, so you may have to place a phone set up to take videos in the trunk to see if it is off or not
Use a DMM (digital multimeter) to check if the battery is being charged correctly in case of a faulty voltage regulator or alternator. To do this, safely park the car and with the transmission in Park (AT) or Neutral (MT) and the parking brake firmly applied start the engine and use the DMM to measure the voltage across the car battery terminals. It should measure 13.8V DC - 14.5V DC. Be safety aware as the engine is running!
If the charging voltage is OK, turn off the engine and then disconnect the -ve battery lead from the battery and connect the DMM between the -ve battery terminal and the -ve battery lead and change the DMM function to DC Amps to measure the quiescent current being drawn from the battery
Normally there's 50mA-80mA of current being drawn from the battery with everything switched off. If there's more than this, you will have to remove all the fuses, one by one and check if the current drops back to normal when a fuse is removed. Remember to replace the fuse before removing the next one. If the current does drop back to the normal value when a fuse is removed, check what the fuse supplies (fuse layout diagram in the fuse box lid) to see what it is used for.
If the quiescent current draw is within the range of normal .i.e. 50mA-80mA then perhaps the battery is failing. Get a car battery replacement service to check the condition of the battery by performing a battery test.
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You may be right about the fuse. This will be the 3rd new battery, a new starter and a rebuilt alternator. Recently hooked up the new battery, the car alarm went off but the car didn’t start.
I think it’s a fuse or loose wiring and husband thinks it’s the alternator.
The alternator really only affects the charging and not the starting (unless it is not charging the battery when the motor is running) so check the fuses in the fuse block on the battery itself. One supplies power to the starter motor and the other to the starter relay.
Regarding the battery discharging too quickly checking the charging voltage across the battery terminals with the engine running will initially indicate whether the alternator or the voltage regulator are OK or not i.e. voltage <13.8V DC or >14.5V DC then there's a problem and further testing of either the alternator or the voltage regulator will be needed
Finding the exact fuse that reduces quiescent current to within normal range (50-80mA) if it is more than this thereby draining the battery quicker will only indicate what component may be the problem as it won't be the fuse itself e.g. if the fuse designation indicates that it is used for the car alarm for instance, there may be a problem with it etc.
