If you're forced to jump start a Prius from another vehicle make sure you hook up the cables to the front jump points in correct polarity. Incorrect polarity will do alot of damage. Its worth it to buy a new set of jumper cables that have polarity safety feature built in to it. Make sure the donor car's engine is not running. Limit the inrush. Personally I would not jump start a Prius if the dead battery was lower than 8 volts because when you're hooked to another car's battery there is no current limiting and the dead Prius will see a real big initial inrush of current . That's not good. The Inverter & every ECU in the car is hanging off that 12 volt line and will not enjoy that. Lower than 8 volts I would have the car towed home and replace the battery or put it on a charger in 2 amp mode. Alot cheaper in the long run.
I would really own and use a small jump start pack, rather than risk several thousand dollars in inverter damage if you mix up the plus and minus connecting to another car. BTW, never attempt to jump start anything using your Prius, another use for your jump start pack! Clore JNC300XL 'Jump-N-Carry' 900 Peak Amp Ultraportable 12-Volt Jump Starter with Light : Amazon.com : Automotive
To jump start just connect jumper cables to the 12v battery in the back. I only use the jump points under the hood to help open the back hatch when it is totally dead. The best way, if you have time is to open the back hatch and charge the 12v to full with a modern battery charger.
The best way is to use the front jump points. That's why Toyota put them there and I thank them for that. There's no difference between the front and the back. Stay out of the trunk. Easy to short sh*t out back there especially if it's your first time in the trunk.
The front points are connected to the rear battery with two very long wires. One wire and the body is the second wire I guess. anyways I think the front is more confusing with all the fuses and relays. The rear battery has two posts and they say + and -. There is nothing to short in the rear or front unless you connect backwards, then you are screwed. I would like to see a comparison test of the results of backwards jump between front and rear connection points. I have a feeling a backwards connection at the rear would damage less but I would need to try it. Backwards at the front fries a few relays under the fuse box. I have repaired the aftermath of a backwards jump.
It's at page 544 of the 3rd gen Owner's Manual. Do be careful with polarity, a mix-up could be costly. Also, the positive contact, in the engine bay fuse box, has copper on one side, plastic on the other. With some jumper cables the contact has to be on one side of the clamp, so look them over.
This is not the first time I disagree with the manual. If for no other reason than the simple fact that the front point + is too thin for many jumper cables to attach securely. The back is a nice thick post that works well with jumper cable clamps. When charging the battery I usually see the back hatch open, this includes dealership shops and independent shops. If you are going to charge a battery fast ( jump start) or slow ( regular charge) why use a 20 foot piece of wire on top of your extension cables? Just connect directly to the battery.
We will never know unless people start jump starting from the back. One truth remains constant - people who jump start backwards will claim they hooked everything up correctly, 100% sure of it. But seriously if the short is at the battery end of the long 12v input wire that goes to the front would the relay damage and possible fried inverter still occur?
" one test is worth a thousand opinions" Not that I'm going to try it I just have been waiting for someone who has done it to chime in with some real world experience.
