My Prius has sat for too long and the 12v is reading 9v and the car will not start. I'm curious about my options here and what would work best. If I jump start the car, will the 12v get charged by the hybrid battery? Should I get a battery charger or just replace it, as the car is almost 12 years old with the original 12v?
Jump it and then go for a good drive, say half hour. That should recharge the battery. Let it sit overnight and then check the charge. Other option if you have a battery charger use it. My 2010 Prius had its original 12v battery and after sitting overnight its charge is 12.3 volts.
Will do, thanks! If I do this and tomorrow the charge is down again, does that mean the battery needs to be replaced?
12v battery is kind of weak spot in these and it is good to have one of those compact jump packs onboard. Even the low end ones provide enough juice to get car started. I have one and it has saved the day couple times already. Jumping from those terminals under bonnet take just one minute. if battery is old it is good idea to buy new. 12years is definitely old. But even new battery go dead surprisingly quickly if car not driven. When buying new i recommend buying AGM. Original is AGM
Probably. I'm looking at a table showing voltage vs % of charge. My 2010 battery shows 12.3 volts overnight which equates to 65% charge. At 12 volts you have only 25% charge which would probably start your Prius but which you should probably replace.
12 year old 12 volt battery showing 9 volts, it's time for replacement. If you've got 120 volt AC outlet near the car, definitely look into chargers, something around 4~5 amps max, and "smart". They can be left on indefinitely when the car's just sitting.
The BEST thing to do is replace the battery with a Toyota battery. You will need a 4amp or less charger and charge the battery for 8-10 hours. Then it will be fully charge and under normal use won't have to worry about for 6 or more years. They have a 7 year warranty. And yours is 12 years. I think it has served its perpose. Anything you do to that battery is wasting your time and will probably strand you somewhere at the worst time.
Counterpoint: I have had one cheap Amazon jump pack, and one name-brand jump pack, and both failed to start cars with bad batteries for me, when I needed them in a pinch. Many of them are just cheap Amazon junk. But even the Halo brand one didn't work right when I needed it. It was fully charged but several years old and just didn't work the way it was supposed to. Just flaky stuff. I would, however, fully agree with the suggestion that it's past time to replace the 12 volt battery, 12 years is too long! A new AGM battery is expensive but will probably go another 9-10 years safely.
A regular car. The Halo unit had some kind of failure that it would never turn on the relay that powered the jumper terminals. The flashlight worked and the USB power worked, but it wouldn't turn on the jumpers. The Amazon one, the battery was just cheap and didn't have enough juice to do anything after a year or so. My point is just that it's never a good idea to have Cheap Chinese Crap as your backup plan.
