My 2008 Prius Will Not Start After Sitting 3 weeks

The dedicated positive jumpstart terminal is located in the main relay/fuse box located next to the inverter.

Measure the voltage across the 12V battery using a digital multimeter to confirm the battery is dead. If below 12V, the battery is fully discharged.

If you can't afford a mechanic, are you able to replace the 12V battery yourself?

Obviously your jumpstart technique will influence the success or failure of the attempt. And if you managed to reverse the polarity of the battery voltage you may at minimum have damaged the fusible links within the main relay/fuse box, and at worst may have destroyed the inverter.

If you are unsure about how to deal with the problem, I suggest you seek professional assistance. The cost of recovering from a botched jumpstart is going to be much greater than the cost of dealing with the original issue of a dead 12V battery.

 

Ditto Patrick's advice. Many have found out that a mistake while jumping the Prius has a comma in the cost of the solution, not a laughing matter.

 

Read the manual, follow the directions.
If the jump is hooked up correctly, the interior light will light up.
Let it sit for 2 minutes with the jump hooked up.
Press the power button, shit into reverse and touch the gas.
If it starts, remove the jump, set the heat on high, fan on low and open the windows to force the engine to stay on for as long as possible.

 

Editorial only: you've gotta fix the above, lol.

To contribute to OP's issue: can you clarify, what are you using to jump, another vehicle or a jump pack? If the latter: maybe it's dead?

Or again, connection mix up.

 

None of the above is necessary.

If jumping with another car, make sure the donor car is NOT running. The Prius does not draw any significant current and the alternator from donor could produce undesirably high current.

Simply (¡correctly!) connect the jumper leads, press start on the Prius. Once the car has "beeped" twice and has READY on the dash, disconnect the jumpers and you're done.

If the idea behind "set the heat on high, fan on low and open the windows to force the engine to stay on" is to ensure the battery is being charged, again, it is not necessary. The Prius will charge the 12 V battery quite nicely as long the car is in READY. The ICE will come on as necessary to keep the HV battery with enough charge to keep it happy. Note also, if the 12 V battery is completely flat, that it will take 8-12 hours of sitting in READY to get anywhere near a full charge to the 12 V battery. It would be a better option to use a standalone fully automatic battery charger with an AGM setting and do the charge overnight to avoid "watched pot syndrome".

 

sometimes a bad battery will prevent a jump from working properly. you may have to take it out of the circuit. how many miles on her?

 

The owner's manual shows a bolt on top of the shock tower, for negative cable connection:



You're looking for bare metal, either bolt, or any significant piece of steel, a bracket or similar. Bare metal on the engine is good too, the more substantial the better.

You can download a pdf of the owner's manual, just google:

Toyota TechInfo

Typically first result is the right site. Click on the "Manuals" tab, then fill in your info and search for documents. One will be the owners manual. Click it, it'll open in the browser, and you should have an option to save as a pdf on your hard drive, or phone in a pinch.

 

Why would it show a connecting point all the way on the other side of the engine bay? My manual shows the similar bolt on the shock right behind the fuse box.

 

They wanted to be well, well away? I don't know, lol. Yeah, any port in a storm.