Parking for 4-5 weeks; Do I need a trickle charger?

There is a chance the car will have enough 12v left to start the car. Probably a better chance it won't especially if the 12v battery is pretty old already.

A "Battery Tender Jr" is a good $30 maintainer available at Walmart or Amazon. Great if you are leaving it at home but unlikely to be useable at a public garage since you have to plug it in to 120vac.

The best option might be to purchase a lithium jump starter, be sure it is fully charged and store it in the cabin under the passenger seat.

Then, understand how to open the driver's door with the mechanical key in the keyfob. Know how to jump start it under the hood in the fuse box since a dead battery will prevent hatch access. The Prius owners manual has instructions. I would photocopy the instructions for easy access and try the procedures.

The lithium jump start box will prevent a reverse polarity jump from a "helpful" bystander using conventional jumper cables and could come in handy down the road.

 

Either hook up a smart charger or disconnect the neg lead. Either will work for that time period. These days we're driving as little as once a week:

 

If you disconnect the negative lead you end up crawling over the backseat and pulling up multiple floor layers to access since the hatch won't open. Plus the garage attendant won't do it when they park the car in NYC.

 

Yeah it is awkward. One work-around would be to have a small jump pack. When you return, pick up the car: open drivers door with metal key, pop hood, connect jump pack at fuse box, and bob's your uncle.Maybe lock the jump pack in the car, say under driver's seat.

 

Now that is a good idea. But Bob's my brother.

 

it depends on the health of the 12v. i used to leave my 2012 for a couple months every winter, then it died in 2019

 

If you don't have a battery tender plugged in, you can reduce battery drain by turning off the SKS. Though this will force any valets to use the dead-fob-battery method of starting the car.

If one must crawl in that way, don't work on the battery from that condition. Instead, manually open the hatch from inside, then step out to get in better and safer position to work on the battery connections:




But I like Mendel's idea of using a portable jump pack in front to provide power to electrically unlock the hatch. Be sure to close the driver door before connecting the jump pack in front, so that the brake booster pump triggered by opening the door doesn't overload the jump pack.

 

Good point.