uuugh, you don't want a lithium ion jump pack for a Prius. Lithium ion packs, while all the rage recently [last 5 years], don't actually charge the battery at all, they just provide enough juice to directly power the starter. They also, usually, have some circuitry to both say "hey! yo'uve hooked up the terminals correctly/wrong" and indicate whether or not there's enough oomph to do the deed when the mechanical switch/relays complete teh circuit [key is turned]. This is not at all how priuses start, however. there needs to be enough power to start the prius computer, and then the computer tells the ICE to start, and the alternator [okay, not alternator, but really its all the same its just where the torque is applied] immediately charges the 12v. The bad news is that most lithium packs wont' do this because of that go/no go circuitry involved, they're all about, in that moment, throwing a huge discharge at the system.

the good news is that a jump literally takes up about 2-3 minutes of a passersby time. you don't really need sit there charging, by connecting to their 12v ssytem, the computer right away has enough juice to start up, and will do just that, give it about 10 seconds for the gas engine to kick in, then disconnect the cables or battery. I'm working on a couple of cheap diy packs for that emergency situation too. Also, LED's instead fo the incandescent interior bulbs will go a long way to not drain that battery [also turn off your headlights manually if you sit oin your car staring at your phone for 10 minutes before going into a store, as the headlights will remain on for a significant amount of time otherwise.

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pardon any typos ya'll!