I get into my 2012 Prius and hit the start button. Everything goes on as usual for a half-second then black. Power completely gone. No warning, no nothing! I had just been driving it 30 miles during the day and all was fine. Now at night in a parking lot this happens. The battery in my fob has been low for months (I keep getting the message on my display when I turn off the car). But I don't think this has anything to do with it. My friend who knows cars and has an older Prius is sure it's the 12v battery. He has changed his twice. How can I know for sure, how much does it cost and is it easy to replace? Lastly, why no warning and...why??? So obnoxious.
I would have thought it is the HV battery that turns MG1 and starts the engine, not the 12V in a Hybrid? Anyway I'm not sure though.
The 12 volt battery is used when you start the car. It performs several important functions, such as pumping up the pressure for the brakes, applying power to the controller that runs the inverter, emergency lighting, etc. Some of this demands high power for a short time. When a battery gets marginal, it may work OK under light loads and then fail under high demand. The 12 volt battery can be tested at the local auto parts place. There is nothing magic about it.
Yes,by HV I meant the main battery. But I defer to other more knowledgeables here on your specific cause of unable to start, if it isn't HV battery.
How would I know? What are the symptoms of a dead main battery? The car was jumped and ran. Once I turned it off at home it was dead again.
The 12 volt battery is more likely to have died than the HV battery. The 12 volt batteries often fail in 3 to 8 years under normal circumstances.
The 12v powers up all the computers and checks that everything is functioning normally. Then it trips the relays to activate the hybrid system and the hybrid battery takes over. Then it takes over powering the computers, and charging the 12v battery. Eventually it will start the engine to charge the hybrid battery and drive the car. If you get a 12v battery from Toyota, it will most likely last more than 5 years.
Ok, got it. The HV hybrid battery would come into play only After 12V battery-powered computer chips and related components gave the go ahead. Thanks.
many cars of 2012 are manufactured in 2011, meaning that battery may have been 10 years old. Crack open that maintenance manual & this would have been a non issue. Folks leave an aux 12v battery in a car that long, it's at their own peril. Mystery solved. Move along here. Any other maintenance not being done? maybe check your cabin filter? egr? tire pressure? Oil that looks more like black tar? The Prius is pretty forgiving but at some point, you have to pay the price. Report back once 12v is replaced .
This was a warning. But you have to recognize it is talking to you. Most 12v batteries in regular cars last three or four years and usually strand people when they fail. A Prius 12v battery is a better AGM chemistry used less aggressively than a conventional car. So it lasts 7-8 years normally. You actually had exceptional life. Any auto supply or dealer would have warned you if you asked. Such as "I had to jump my battery and the next time I stopped and started the battery did not work again." They would have said 'Lets check that battery.' $200-$250 later you would be good again, at least on that issue. Warning! A 2012 Prius can and will have bigger and more expensive problems. Consider upgrading to a newer car.
That by itself is all you need to know that the problem was the 12 volt battery. That's what was jumped, and as soon as there was sufficient 12 volt power, the traction battery (which is what really turns over the engine) turned out to have plenty of juice.
THAT is how you know that the problem is with the 12 V battery. Some things just FAIL with no warning. Get used to it. Now you need a new fully charged 12 V battery AND need to get the charging voltage tested.
You are going to find that there aren't that many choices for an "exact fit" and none of them are exactly "cheap". But yes, if you plan to keep it for a while, don't "cheap out".
They are agm batteries with a vent connection. Most auto supplies will have a match and may swap it free if you remove the back panels first. Around $200. The best is a Toyota but I have heard they are in short supply so no free installation or discount. Page 382
