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03 Odyssey - What is draining the battery?

We have an 03 Odyssey that we have to jump start if it sits for more than 1 day. We aren’t leaving lights or radio on. Our mechanic can’t figure out what is wrong. He has replaced the battery 3 times and says that is not the problem. What we are doing now is disconnecting the cables to the battery at night, so it will always start in the morning, even after two days of not driving it. It works, but it’s a pain! Any suggestions about what is causing this problem?

You could start pulling fuses each night until you find the circuit with the problem.

The battery drain might be from a computer/module that’s failing to go to sleep.

Normally when a vehicle is turned off, the computers/modules can remain awake for up to 45 minutes and then shut off or go to sleep. If a computer/module fails to go to sleep it can draw the battery down in a short period of time.

To check for a current draw on todays vehicles with these computer/modules requires a different approach than when vehicles didn’t have them. So unless your mechanic is familiar with these new techniques for testing for a current draw, it’ll never be found.


It is strange that the tech is having a problem finding the extra current draw. Usually it is a pretty straight forward proceedure. The alternator can be at fault sometimes. Here is a link that goes over the things to look for on this sort of problem.

Thank you for your quick responses! Very helpful.