12 volt battery life

When I had my Prius, the first winter I had problems with the 12 vdc battery. A relatively short commute in winter temps of -40, headlights on, max defrost, electric defrost always on, really sapped the life out of the battery.

I had a condo at the time, and it had heated underground parking. Received permission from the building maintenance person to hook up a VDC Battery Minder. There was a handy plug in at the wall for maintenance use they just didn't want me plugging in the block heater

With the Battery Minder hooked up, the battery recovered and remained perfect even when I sold the Prius

The DC-to-DC section is perhaps the limiting factor. If the Prius is always in Ready, like the Duffy Taxi ones around here, the battery will be fine. Short trips, and a lot of sititng around, forget about it

But other vehicles that have to sit a lot will also have problems with the battery. Only difference is that when that battery has to crank a motor over, you notice sooner

My FJ is rarely driven and the factory Panasonic battery went dead a couple of times until I also hooked up the Battery Minder to it. Had a defect in that battery last fall, top of the case developed a crack and started leaking

I replaced the FJ battery with a Duracell Extra Heat Protection from NAPA. This design looks like the older AC Delco and is truly sealed. Cranks a lot faster, the Battery Minder easily keeps it charged

 

Jut replaced my 2007 12v battery after 4.5 years (48,000 miles). Shopping for my new 2012 Prius Four, left 2007 on after removing a CD to test the new one which apparently depleted the 12v battery. I expect my 2012 battery to last 3 or 4 or more years.

(Need to change my signature to reflect out new 2012)

 

Replaced the 12v battery at 157,000 miles in 2006 Prius. The car's diagnostic computer (

) showed the battery voltage at 9.7v (normal 13.6-14.4) with the start button in accessory mode. Three local dealers were charging $191-$200 for the battery (car has smart key). With a 20% coupon from a dealer website for buying parts on weekend, the cost would have been $160 + tax +refundable $18 core fee. A mechanic got the battery for me for $150 + tax. It took about 1 hours to change the battery. I used a portable jumperstarter to supply power to the GPS and radio to hold the settings while the 12v battery was disconnected. A dealer quoted me $345 to replace the battery so I saved about $200 and learned how to jump my car.

 

Billissimo, very helpful thanks.

 

As a precaution, having only had the car for a couple of weeks and with winter here, I have got rid of the old 12volt battery. It's been replaced with a new Bosch that has a 4 yr guarantee. I have also attached the CTEK eylets direct to the terminals and left the connector (which is capped off) poking up from the compartment ready for the charger just in case it's needed. Another precaution, I am getting more paranoid in my old age!!

 

If you google, you will find many complaints about Prius having starting problem. My car did exactly the same to me when it was 2 months old with 2K miles on it. In my case, I got out of my car for about 15-20 seconds and then reenter it and supprisingly, the car started normally. I expect that my car starting problem will repeat after reading through those complaints.

I strongly believe that the starting problem in my Prius causes either by a glitch in the onboard computer system or in the key detection sensor/antenna. It's more likely the later one. Last week, my car refused to let me lock the doors. I had to reenter the car and then get out and then I could lock the doors normally. This incident make me think there is something wrong with the key detection sensor/antenna.

I can say for sure that your car battery is fine. Next time, instead of jump start your car, please try to unplug the negative terminal of your battery to reset whatever error in the computer system or its sensors. I'd like to hear back from you if that experiment would allow you start your car again...

 

A number of people have complained of glitchy computer issues when the 12V battery was low. Even if your car is new, it's still possible that it sat on a lot for a while (or a light was left on) and the battery drained enough to cause a permanent degradation in its performance. A multimeter can tell you for sure; with the doors closed and everything off, it should measure a little over 12V (12.5V or more is good, or at least close to that; 12.0V is bad).

 

Every computer has a built-in voltage-regulator circuit and should be able to run at a wide range of voltages. I doubt that a couple volts difference at the 12V battery would cause any computer glitch unless it is really crappy computer. In hybrid cars like Prius, the 12V batteries are not used to crank its starters like regular cars. Jumping start your Prius just doesn't make any sense unless its battery is totally or partially dead. If you turn on your headlights or parking lights and see all of them light up at their normal brightness, the battery should be good to go.

The more I think about this, the more I believe the key-detection sensor or its transmitter/antenna is the culprit. The complicated, sofisticated key system in Prius just doesn't behave normally once in a while. Your car can not start because it doesn't detect your key inside the car. Of course that some other things could contribute to this problem also, like your brake-pedal switch is incorrectly set; your key battery is dead; your key is shielded by metallic objects; radio signal communicating between your key and its sensor is interfered by nearby stronger signal...

It's funny that I used to tell people that no one can break into my Prius without breaking the car's windows because of the new key technology. Turn out I can open any Toyota doors using the same technology within a few seconds wthout using its key, at least in theory. (Sorry, I can not tell you how because of the security reason.) Anyway, please do not leave any valuable items inside your newer Toyotas. Shopping season is about to start. Please do not let it ruin your holidays.

 

The voltage reading at the battery is more an indication of the battery state of charge (SOC) than whether the battery is good or bad. A battery can have a low SOC and still be good. If you have a low SOC, charge the battery and have it tested at a repair shop or auto parts store. If the battery tests bad, replace it. If the battery tests good, figure out why you have a low SOC. Typical causes for low SOC are leaving lights and accessories on, short trips and/or infrequent use of the car. Lots of good batteries get replaced prematurely because they are assumed bad due a low SOC when all that is necessary is a charge. If the low SOC is due to short trips and/or infrequent use, a battery maintainer is a good choice to keep your battery healthy. You can also just periodically charge it with a regular charger. If you don't correct the cause of low SOC, your second battery won't last any longer than the OEM.

The OEM battery on my 2010 is now 4 1/4 years old. The first three years, the car was driven to work 28 miles one-way and often on the weekends so the battery was sufficiently charged from driving. Beginning year 4, the car is now driven only about twice per week on short trips so I charge it about once per month to keep the battery at a high SOC. I expect to get another two or three years out of the OEM battery.

 

In regular cars, the batteries' state of charge (SOC) is very important, especially during the cold weather. The batteries need to have enough power reserve to provide strong currents to the starters at the start up. In Prius, probably the car would needs only a few hundred milliamperes to run the computers, sensors, door locks and also to activate the HV battery's relay; assuming all others electrical devices are off.

If someone's Prius doesn't start next time, please try this one:

 

i use a Ctek smart battery charger

that works great and keeps my battery in good condition

instead like with other storage chargers this one stops charging when the battery is full .and restarts when the battery voltage drops below a preset point

 

Are you sure it's not the traction battery that had a low charge? I know the Prius starts off of the traction battery, not the 12v battery. The 12v battery powers the computer(s). So what battery is getting "jumped" when you connect the jumper cables?

 

The 12v battery is the one that takes the charge from jumper cables. Either the engine charges the traction battery or regenerative braking does.

 

So what besides the computer runs off the 12v battery?

The key fob has a battery in it too. If it goes bad, you have to hold the fob up against the start button to start the car.

 

That's because the key fob has a security feature built in to prevent another key fob from starting your car.

From Vincent1449p: When the car is in Ready, the DC-DC Converter handles all the electrical loads on the 12V bus It drops the HV Battery nominal voltage of DC 144 V to approximately DC 14 V. Since 14 V is higher than the Aux. Battery, it is charging the Aux. Battery.

When the HV Battery SOC gets below 40%, the Power Management ECU will command ECM to start the engine so that MG1 can charge the HV Battery. Once the SOC reaches above 45%, the Power Management ECU will command ECM to stop the engine. The cycle repeats once the SOC drops below 40% again.

 

Why would you need to supply power to the accessories while changing the 12V battery? Is it the required procedure for the Prius for changing 12v battery?

 

My original battery is on its 48th month and only failed once because I left the interior light on for 24 hours. I don't want the dealer to gouge me when I need a new one so I ordered a Optima battery as a spare. I'd charge it up once very few months and make sure it is ready when needed. The battery from Optima USA is close to $100 but my Canadian Toyota service dealer quoted me almost $300 plus labour to install. The worst part was it would take a day to order it in.
I expect the current one to last another 12 months, or longer. Now I have a spare and also a peace of mind.

 

I concur with this reply. My original 12v in a Prius 2nd gen lasted nearly 6 yrs. The orig Toyota replacement is now 4+ and going strong.

 

BTW...It's easy to install oneself..and the Toyota dealer charged me around $130 dollars...back in 2010.

 

Best price I could find today on a Prius Optima Yellow Top was on Amazon with free shippng. Just ordered it. My '04 has 115K miles on it but is still running with the factory original 12v. We bought the '04 new and have driven it almost every day since. I guess with Ohio winters we have been lucky to go that far. Once I install the new battery, I'll take the car on a nice long run.

Bill the Engineer