Can I charge a dead 12V Prius battery through the accessory port? The wiring would basically connect a charged 12V starting battery to a cig lighter plug which would then go into the accessory (cigarette lighter) socket in the car. Obviously, the accessories are off when the key is turned off completely, so I would turn the key to accessory mode while the charging goes on. After a few minutes, I'd disconnect it and start the car. Will this work? Is it safe to do? How would the wiring go? The cig lighter socket gives out power at the tip and the ground pin is on the side(s) of the cig lighter plug. So the external 12V battery terminals, how should they be connected? Would a charged 12V battery (about 13 volts I assume) be enough to charge a "dead" 12v in the car (about 11.8 volts I guess)? ----------------------------------------- Maybe this is better: AutoCraft Marine / RV 12-Volt Starting Battery, Group Size 24M, 800 CCA M24-3: Advance Auto Parts Car 12V Battery Terminal Clip on Cigarette Lighter Power Socket Adapter Hot | eBay I assume I'd still need to flip the key to accessory mode. Is this safe on a Gen 1 Prius?
In my opinion, it would be safe, just be very careful about polarity. Why don't you just hook up jumper cables to the battery in the trunk?
If this is a regular occurrence (i.e., your 12v battery won't hold a charge for more than a day) it's STRONGLY recommended that you (a) charge the battery directly; that means, wires to the battery right in the trunk, so you don't run through the smaller fuse that protects the accessory socket and (2) start considering replacing the 12v battery. Many posts on this topic elsewhere; a type 51R is very close in mechanical size (and the battery posts line up the right way), and unless you pay Toyota for an exact fit, you will need to replace the battery connectors, which is all of $10 in parts at AutoZone or Advance or O'Reilley.
