I have a 2011 Prius that won’t start without a jump. I work on a remote island at the moment and my car is parked on a more populated island. Every two weeks I’ve gone over, started it up, and driven it around a bit just to keep it from sitting too long. Been doing this for 3 months. But this time it wouldn’t start. Got a jump, drove okay, but when I turned it off everything died immediately. All lights, dash etc. Got another jump, drove again, this time for an hour. Same problem when I stopped. The battery is new, replaced in December 2024. There’s a ton of mouse and rat droppings everywhere. Is it possible they chewed through something important? Is it more likely the battery? Where do I start looking?
You should put some rat poison in the car. They may die in the car, so it may stink. But dead rats can't eat wires. It is possible they ate through wires. But the 12v battery is not a high amperage one because it doesn't start the car. Could you remove the battery and bring it back with you? If so, put an AMG 5 amp or less charger/maintainer on it so it will have a full charge when you go back. You could also open the fuse box under the hood and disconnect the large white wire. Than wrap a piece of rubber hose, like from a bicycle, around the cable, just to be safe. That disconnects the 12v battery from the rest of the car. Then it won't discharge so quickly If you can't revive the battery, it should still be under warranty, and could be replaced. Just make sure you charge it up before installing it. Is it possible someone could drive it for 30 minutes or so once a week for you?
most likely the battery, they don't like to sit. charge it up and see if it holds. if not, replace it. when not using it, put a maintainer on it, or disconnect the negative
Quick disconnect for the negative, add a solar panel trickle charger in the window for when the car sits.
I would also check for good continuity at the negative battery cable junction with the vehicle frame. The battery as you know is way back in the right rear corner of the vehicle. The negative battery lead connection to the vehicle is below the hatch sill rubber seal on the right side and may at times be subject to condensation resulting in corrosion. Look closely at the metal and paint surfaces around the connection for corrosion or paint bubbling. If all appears well then just loosen the connection and give it a couple of twists back and forth to make sure and tighten back up. May as well inspect the clamp connections on the battery while you're there.
Driving it around a bit isn't going to recharge your aux. (12V) battery. These cars aren't like the old gas cars that shoves 14VDC into the battery as long as the engine is running. The battery needs to be recharged on a battery charger or maintainer when it gets that low. Get a cheap DVM to check voltage. Take that battery back for a warranty replacement. If you see mice droppings there's likely wire damage and parasitic draw on the battery; due to chewed electrical wire insulation. You'll need to rip the interior apart to inspect for damage. You'll also need to do the same for the exterior wiring of the car.
You could indeed have a perfectly healthy 12v battery but the problem is at some point it got discharged and the amount of electricity Prius designers send to the 12v is so miserable that you'd have to drive the car for 12 hours to fully recharge it. You need a smart charger of 10amp or greater that can recharge and repair your 12v battery.
Including the cars interior? You better mesh the egress points, using anti-rodent mesh secured with sheet metal screws. 1/4” spacing galvanized steel mesh is best, a hardware store item. Specifically: the cabin air intake behind glove box, and the two cabin air exhausts at back corners. The first requires removal of wipers/cowl (@NutzAboutBolts video for spark plug change explains) and the latter it’s best to remove bumper. That’s killing your battery. Scenario like that you need more, a battery disconnect or get it on a smart charger.
Thanks for all the tips guys. I was able to charge the 12v with a smart charger. However, the damage from the mice is much worse than I thought. ABS not working, two windows that won’t roll down, lights that flicker etc. and the more I look the more problems I notice. The mouse smell is overpowering; I think I have to rip the whole interior apart. Might just call my insurance and see if this is covered, this feels way beyond my experience level.
Condolences on this... Once you've cleaned, inspected and repaired wiring and all is well again it won't seem as bad as it seems right now!
