Skip the auto shop - Our mechanics make house calls

Q: Why won’t my battery hold a charge if it’s new?

asked by on

My 2009 Honda Pilot with 45,000 miles has a problem keeping the battery charged. The battery will just be dead some mornings. Other times, it is so weak that the motor barely starts. The alarm is sometimes involved. I have replaced the battery twice now and this problem is getting exhausting! What should I do?

The problem you are describing is what we call a parasitic draw on the battery, which is an excessive draw that prematurely kills the battery either over a certain amount of time or overnight. In order to test the system draw, an amp probe on a positive battery cable is used to see if more than 50 milliamps are being drawn.

There are two potential issues which may be killing your battery. The first, the A/C relay may stick closed after shutting off the engine, which would draw excessive amps and cause your battery to die in 8 or more hours. Replace the A/C relay to fix this. The second problem is that the sunroof module is causing excessive draw, killing the battery with in a week or two. Reprogram the roof module at the dealer to correct this. Another problem could be that the body control module is not going to sleep after shut down, which may be due to the door ajar switch or other issues. A thorough diagnostic would be needed to uncover what exactly is keeping the module awake. A trained mechanic, such as one from YourMechanic, can perform a battery inspection to determine why your battery is will not hold its charge at your home or office.

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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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: Will not start. Acts as if it's not getting gas.

As you may know, the motor requires a very precise mixture of fuel and air in order for it to run properly. When the fuel injectors are not spraying an even, uniform pattern of fuel, this causes an imbalance in...

Q: I believe my oil gasket is out, would that cause my transmission fluid to drain also

From what you've described, some of the sand may have gotten into the external oil seals of the transmission and engine. This can cause the seal to get damaged and fluid to leak out. I would recommend having the fluids...

Q: Truck dies if gas pedal not pressed

Hello. It is likely that the battery has a dead cell and is unable to receive a charge. This is more likely to happen as a battery ages. Usually, you can jumpstart the battery and the vehicle will run until...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.