Draining battery once in a while - 05 LC

[Asanka]

My buddy's 05LC has a battery-draining issue that happens once in a while. No lights, or no clear way to figure out what caused this drain. This has happened at least 5-6 times over 5 years. New battery or used doesn't matter; a new alternator was installed sometime in 2023. There are plenty of modifications, but this happened with all those are disconnected too. Any thoughts or hints on issues like a relay getting stuck?

 

[TLCPNW]

Is there a DVD screen unit installed? That's a known culprit.

I believe there's a few threads on the subject that a quick Google search would find. I always search the keyword/phrase and then "ih8mud" which works way better than the search here.

 

[Zuberg]

Not sure if your friend does this, but leaving headlights set to auto can also drain the battery. Just another possibility.

 

[Asanka]

Aware of the drain from auto headlights, which is tiny. Starts fine after being parked for a week or more, but completely dead overnight on a random day.

 

[Dirt J]

Aftermarket audio system?

 

[Asanka]

Aftermarket audio system?

No, attempted teyes a year ago but reverted back to stock.