So a few years ago I used regular jumper cables with another car to jump start my Pruis 12 V battery using the connector in the breaker box and the spot recommended for the negative lead. Worked great. Now I have purchased a portable jumper and notice how short all of the cables are. Where would be the best location for the negative lead since it cannot reach the spot Toyota recommends? Can the negative lead go on any metal nut sticking up close to the breaker box?
Yes, as long as it's well grounded. FYI, some "jumper" clamps only have one side of the clamp connected to the wire. Only one side of the jump terminal in the fuse box has a metal/copper plate, so attach the clamp accordingly. Posted via the PriusChat mobile app.
Is this for a Prius v (forum you've posted in) or Prius Prime (per your avatar)? One thing: if you're regularly needing to jump-start your Prius, maybe look into remedying that, instead of relying on a jump starter. Is your use of the car sporadic, lots of short trips? What's your parking situation: street, carport, garage, apartment parking lot? Do you have access to 120 volt AC outlet? Is it secure? (The last two in consideration of getting a maintainer charger.)
I made a pigtail with an EC5 pigtail used by the jump starter with ring terminals in it and fastened it to those on the battery. The connector sticks out of the battery compartment out a crack out the edge of the carpet. I already used it once when the 8 years old battery died on me.
And the sneakier clamps still have a toothy copper jaw on both sides, so you have to look kind of carefully to see which one isn't connected to the wire at all, and make sure the one that is connected goes to the side of the fuse box jump terminal where the metal plate is. The fuse box is right next to the inverter/converter housing, and I've never had trouble getting the negative lead on mine to reach over to one of the cover bolts on that. The converter is the source of the car's 12 volt power system anyway, so that's not a bad choice of grounding location.
I recently added this EC5 extension so that I do nit have to lower the rear seat after opening the passenger seat's rear door and craw under the hatch area. Placing the cable under the carpet, the end connector can be reached inside right behind the rear seat at the "dog leg" of the rear door jamb. In a hurry or at night, there is no way to get the jump box connected incorrectly, which might damage the car's electrical fuses and electronics. Here is a jump pack that still uses the universal EC5 connector.
I once got a Check Hybrid System warning on the dashboard after using my PowerProbe to check ground between one of the inverter cover bolts. There was a code for Unexpected Ground, or something to that effect. Posted via the PriusChat mobile app.
Wasn't there to see what did happen, and it's too bad not to have the actual code, but the inverter assembly is very solidly grounded by design, serving as it does as the source of the car's 12 volt system, and makes a fine ground location for jump connections, as I've done many a time.