Battery gone, how to restart

Get a lithium jump starter and put in bypass mode if it won't start from the fuse box. Sometimes your 12v battery is so discharged that it will drag down the voltage from the jump battery. At that point leave it or any jump start on for maybe 5 minutes before you try. Its best to monitor the voltage with any voltmeter in this case.

As far as your 12v battery, change it if it has reached this state.

If you want a battery maintainer, consider Battery Tender Jr.

 

You can open the "boot," hatch, from inside the car. It takes a bit of gymnastics.

 

A good battery will easily last two weeks. I have left mine at the airport for three weeks with no issues. Often a deep discharge will damage the 12v battery to the point it won't hold a charge for long. Have it tested after you get it charged up. I don't think charging from the boot matters vs the front. The cable from the front jump point to the back is good sized anyway. This battery does not have a large current requirement to achieve Ready or when opening the hatch. The high voltage battery spins the gas engine. But everything is computerized so the 12v voltage level is important. Lets say it was discharged to 8vdc or lower. Low voltage means computers and networks that are not running.

I do like the Battery Tender Jr for $25 US or Plus for $49. I use a Jr on a spare Prius battery and it does fine. Its a trickle charger which has multiple protection algorithms to prevent your battery from getting damaged further by fast charging, over charging, constant voltage charging, etc while still providing you the ability to leave it on the car for weeks or months at a time. The battery stays healthy and ready to go. A lot of older or cheaper chargers can't do these things for your 12v battery.

 

how old is the battery?