Leaderboard

FYI, the cargo area hatch can not be opened if the 12v battery is dead; best to stow the jumper battery/cables under the passenger seat.

Another option is to pick up a portable jump start box with USB & 12V power outlets $50-$100. Price is basically dependent on features & battery type, lead [cheapest] NiCad, lithium [highest] & total output. Beware NiCad batteries can show signs of loss of capacity due to "battery memory". If you use one regularly until battery is down to 10% or so before recharging to 100% you will not have any problems but if if only used to about 80%, NiCad batteries will sometimes lose capacity. In other words it's "use it or lose it". I've had one for several years now & it has come in handy many times [except when it's there & I'm here]. Thanks for the read.

They are all connected to the same power feeds. In your situation, the best bet here is to turn the car on, but (of course) leave it in park. The motor will come on if the big battery runs low.