Battery keeps going dead

There should be a warranty on your battery, return it and get a new one.

As for the hatch, you can get that part replaced

 

Your first priority should be repairing/replacing the latch. A new battery will be drained by the car until that is fixed.

Be very careful jumping the 12 volt battery, doing it badly can cost $4000 for a new inverter.

 

As Jimbo alluded to: it's likely the ajar hatch that's draining your battery. When it's not closed there's courtesy lights (and other stuff?) drawing current.

 

you should have the rear door catch repaired with an original part by a qualified mechanic.

 

It's kind of a big deal to get the back door latched and sealed properly. If you don't do that, get one of those cheap carbon monoxide detectors and pay attention to it. Don't wake up dead.

And what do you mean by "front" battery? The large, high voltage hybrid battery is in front of the smaller 12V battery, which is near the back bumper. The open hatch should not be draining the hybrid battery overnight--that's out of the circuit (isolated from 12V loads) when the car's off, AFAIK. If the hybrid battery is draining overnight, it's probably not due to the open door.

 

It might be more than just the courtesy light. For sure shut that off asap though. On our 3rd gen if hatch is open some dang footwell lights also go on.

 

I believe Lori means the 12V battery, just isn't aware in the Prius, it's actually in the back. I've noticed the behavior on my Prius that the 12V battery seems to get drained much more quickly than it should when a door is ajar (example, if I'm working on my car for a day and have the door open). My best guess is that the Prius turns on an ECU or two that draw power when a door is open, which in turn kills the battery. I don't think just turning off the lights is sufficient. I think you have three options:

1. Fix the door latch yourself. It shouldn't be too hard to get one from a junkyard or perhaps ebay.
2. Go to a mechanic to have it fixed.
3. Either short or open the sensor circuit so that the car always thinks the rear hatch is shut. If there's an air gap in the trunk from it not sealing properly, I'd due as Andrew suggested and get carbon monoxide detector in the cabin. Breathing exhaust fumes is a no-no.

If the trunk still securely latches, I'd probably go with option 3 on such a high mileage car, as I have the electrical expertise to do it. However to do this you'll need to look up the sensor in the Prius' wiring diagram. There might also be a way to mechanically cause the sensor to always think the door is shut. If your trunk doesn't latch, it's a safety issue, and you need to fix it.

You most likely need a new 12V battery as well. Being completely drained a few times kills most lead acid batteries.

 

Check and make sure there's no debris in the latch

 

welcome to priuschat lori!

 

(1) As someone else mentioned, it is more than just the courtesy light. Some other electrical stuff, possibly an entire computer or controller, is also staying powered up waiting for that door to be properly and completely closed.

(2) If it keeps draining the 12V overnight, it is functionally dead NOW!

 

Easy mistake to make, just needed to clarify. Welcome to the forum, and good luck fixing your car.

 

I'm not clear on what's not working with the hatch latch. I do know, if you're (for example) transporting something that won't allow the hatch to close, you can spoof closing by putting something like a large chain link, padlock or caribiener (sic?) in where the hatch would go.

Not sure if this is applicable here.

 

Not sure what the official Toyota name for it is, but the Body Control Module (Generic Electric Module / Lighting Control Module / Electric system Controller) is staying AWAKE because one of the door switches is sending a signal that the door/hatch is not closed.

Given the SMALL - low Cold Cranking Amps and more importantly small Reserve Capacity battery that a Prius uses, it does not take much of a current drain to KILL IT DEAD. The 12V batteries in a Prius are about 1/3 the capacity of a battery in a typical car.

Any decent body shop can fix this quick and cheap, way lower cost than a mechanic shop