What keeps killing my battery ?

So this is an older post but I had similar problem with wife's 2011 Prius, replaced her original battery about 3 yrs ago with an optima battery, that one only lasted about two yrs, then replaced with Toyota OEM battery and started having issues just about a month later and had to jump start her Prius on several different occasions. Finally decided chances of a new factory battery being bad was unlikely, read these posts here and watching the video's on chasing down gremlins it dawned upon me the wife had put a Verizon HUM in the Prius about 4 years ago. (Hum is a cellular device that hooks up to the OBD and is kinda a OnStar substitute ) Anyway she retired last Dec and some times a few days go by with out her using the car. I think the HUM is creating a draw on the Prius that will drain down the 12v in a couple of days so I've pulled it from the OBD, will give it a few days and see.......I will have to go back and update my Optima review is this is the case!!

 

Not surprising. Federal law says that OBD port must have a wire hot to the battery- the car can’t cut the power. So it’s up to the device to be smart enough to turn itself off when you aren’t driving the car. Not all of them are smart enough to figure out when a Prius is in use.

 

That's my guy! Eric!

 

Holy cow I think you just solved my problem. I leave my key fob in mine all the time and come out to a dead battery. I never thought of this.

 

And you never considered that you might come out to a MISSING CAR some day either ???

 

With all the crap going wrong with this car over the past couple years, I wish somebody would steal it.

 

You're last two statements could come back to haunt you, if it ever does happen and it goes to court.