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Discussion Starter #1
Problem: the lights were probably left ON because we've shut the engine off through the right door (so driver's door was not opened after turning off engine). A few hours later when got to the car we could hear a soft click-click-click sound. Everything was dead.

I've tried to jump start the car but it didn't work. This is what I did & noticed:
* I've left the cables on with the other's car engine running for more than 30 minutes (in 2 separate attempts). Followed the procedure for jump start from the manual
* The green light on the power button will come ON, but nothing else happens at all (the alarm doesn't start, the clock doesn't start, the screen doesn't start, nothing at all). The interior light will turn on (but it's dimmer than normal).
* I did check all the fuses from the fuses block. None of them is blown.
* I measured the battery (between the red pole on the fuse block and the ground). It shows 5V.

The car does have the pre-installed alarm system (Karr). Could this get in the way of the jump start?
 

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I don't know if the "Karr" alarm will prevent jumping the car, but that is a useless alarm for a Prius and will drag down the 12v system when the car is off. Disconnect the alarm, disconnect the 12v battery, and put it on a charger for a few hours (refer to the owner's manual for the proper size charger.

How old is the 12v battery? If it's more than 4 years old, replace it. Personally, since it has had a deep discharge, I would replace it even if it's 3 years old.
 

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Discussion Starter #3
Battery is 5 years old. I've read recommendations about replacing it after 3 years old, so this is my next step. Just wondering if there was something else I might have missed.
 

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Just replace the battery. There's no sense wasting any time on a 5 year old battery that has been through a deep discharge.
 

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I've replaced my 12v battery about every 3 years. It seems to only last that long. A deep discharge seems to require a new battery. I guess these small batteries don't like to be discharged. I've learned to tell when 12v battery is on it's last leg and only missed it once (and had to jumper the car).

The charge rate on the 12v battery is pretty low so it takes time to recharge it when the car is running again (or hooked up to an external charger). Look for posts on "Prius Online" going back several years for more info on the charge rate.

At a voltage of 5v you might have to hook it up to a charger for several hours to see if the battery will hold enough charge to even get the car to a dealer. I say that because the battery is a bit odd and has special tubing to get the gasses from charging out of the trunk area you may want to go directly to a dealer.
 

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Hi, guys,

I guess I should consider myself really lucky. I'm still on the original 12V battery in my 2005 Prius (8 years of use as of July 14th this year). In its lifetime it has only seen 2 events of a dome light left on for about a 3 to 4 hour duration followed immediately after discovery by a half hour stationary "Power On" charge cycle before shutting back down.

I will probably consider replacing it as a precautionary measure before this next winter sets in. I will start monitoring it on a more regular basis with the MFD screen in "Maintenance Mode".
 

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Ct. Ken V;194666 I'm still on the original 12V battery in my 2005 Prius (8 years of use as of July 14th this year).[/QUOTE said:
A man who fell from a 40 story building was heard to say as he passed the 20th floor, "So far so good."

Being stranded has different values for different folks. I for one do not like to risk my wife being stranded. That said, I had to drive 30 miles to rescue her because the 7 year old battery in her prius acted up. I jump started the car and sent her off to the dealer for a new battery.

I'm not sure I am so risk adverse as to change the battery every 3 years but I sure won't try to get past 5. Different climates and usage patterns and various "OOPS events" like dome lights etc. will give different lives to batteries in addition to the random battery life factors inherent in batteries.

Optima batteries are "insurance" and longer life at a price and have recently become available for the Prius. Other choices may have recently become available or may soon. When I changed our Prius battery there was exactly precisely one source, Toyota.

patrick_g
 

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Same problem; exited wrong door after I turned the car on to eject a disk from the CD player. The car started later--I'd only left the lights on for a few hours--but the charge looked weak. When you go to the panel showing power usage on the display, is the battery graphic showing the power level of the little battery in back or the big battery pack that runs the electric motor? The display shows only two bars; I've been recharging the little charger now using a 6 amp charger for about 4 hours. If this isn't charging the big batteries, will they just recover from driving around? Confused in Palo Alto
 

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Same problem; exited wrong door after I turned the car on to eject a disk from the CD player. The car started later--I'd only left the lights on for a few hours--but the charge looked weak. When you go to the panel showing power usage on the display, is the battery graphic showing the power level of the little battery in back or the big battery pack that runs the electric motor? The display shows only two bars; I've been recharging the little charger now using a 6 amp charger for about 4 hours. If this isn't charging the big batteries, will they just recover from driving around? Confused in Palo Alto
The display shows the traction battery (HV battery) not the 12v battery. The traction battery will charge back to normal by driving or leaving the car in READY and in Park. When the engine cycles off, the HV battery should be at a normal charge. Don't leave the car in Neutral as the HV battery won't charge and you'll run down the 12v battery.
 
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