Persistent 12V battery problems

If your 12v battery fails a load test, then it'll be the reason for your troubles. Have the battery tested and possibly buy a new one. With so many episodes of failed battery, there must be something wrong with it.

 

Can you please elaborate on what you did to conclude the battery is "strong".

I'm thinking the same as JC. My gut feel is that your 12 V battery is not strong and needs to be replaced.

 

The AGM batteries on these cars are severely undersized and of poor technology. I recommend installing an optima battery available at battery Mart (.com)
It is a cylindrical AGM instead of prismatic and has the correct terminals for the Prius although some modification to the hold down may be necessary. I run a Lithium battery for my Auxiliary battery ( correct name), 7 years, no problem.
The stock battery cannot sustain deep discharge more than a couple of times without plate damage. After that, you'll lunch the Dc-Dc converter (mounted to the underside of the heat sink of the Inverter, NOT separately sold) ,stressing it out by continuously charging a weak battery with high resistance (open cell) or a shorted cell (low resistance). Don't wait. Just change it. Otherwise the expense will be much higher.

 

The low mileage is good, but the present 12v is at least 5 years old, time for a new one, also get ready for the traction battery, get a new from Toyota dealer one, it's not mileage as much as age, with a new traction and quit killing the 12v you'll be good to great for another 5 years.

 

I'd put in a new 12v...and try not to run it down. The Prius is very reliable but sometimes a used Prius has been put thru difficult circumstances by a prior owner.

 

if you're gonna run it down, get an optima, they hold up better to draining. also, get a rechargeable jump pack and trickle charger. all the best!

btw, if the engine is running rough, you really should take it in for service. do you have it serviced regularly?

 

EVERY time a 12V is fully drained, it is damaged. Period. The older the battery, the greater the damage.

Get a new one and see if the problem continues.

 

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Did the Toyota dealer give you a warranty on that main battery ?
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A Toyota main, aka traction, battery should be good for 3 years or more.
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Why not go back to the dealer. Have them check the main battery and rep[lace t he 12 volt while they are at it.

 

You should never jump a prius as you can kill the inverter that costs about $4,000. You can however get a battery minder 1500 charger and an OBD port connector for it to charge your 12v battery while parked, gently with a desulphating feature. You can also check the 12v battery voltage by (starting with car off) pressing power, then holding display and turning the headlights on and off three times. Then press menu, then vehicle signal check. This displays the voltage, though it tends to be 0.3 volts lower because you are running the display. If this shows less than 12v then the 12volt battery could be your problem. Hit power one more time and stuff comes on, voltage should drop but not below 11v. Now hit power while pressing the brakes, this brings on the inverter, engine, and charging system. The voltage should go up to the normal charging voltage between 13.7 and 14.4. If it does not it means your inverter isn't working, very expensive. If it does work then you've dodged that bullet. You can now either turn the car off by hitting power or hold the display button for five seconds to reboot into ready mode.

A battery minder charger plus OBD adapter (the battery tender brand adapter is compatable but battery minder makes them too) is cheaper than replacing the 12v and easier too. If the battery has a shorted cell you will still have to replace it, but regular maintenance charges with the battery minder should save you more in batteries than it costs for the charger. Any resting voltage less than 12.4 is bad for the batteries long term health, keeping it above that can more than double your 12v battery life.

 

maybe you have a bad coil, dirty throttle body or pcv.

 

Low voltage at the battery causes low voltage on the primary side of the ignition coils, and signal degradation for control. In turn, a short firing line and ripple cause insufficient propagation of the flame front making for hot and cold spots in the combustion chamber, leading to poor idle quality and misfire and higher rpm spark blowout or misfire.

 

the battery remains 'strong'.

 

you need to test the battery voltage after everything has been off at least a few hours.

 

that's unfortunate. most people have good luck with them, as long as they keep them charged up.

 

That is a nonsense term. The force remains strong. There isn't one of those OEM batteries that were ever "strong" it is the biggest thing Toyota instructors complained about. They were always changing them at the training center. MERGED There is no way to test the battery to know for sure it's state of health without a midtronix tool or a simple load test as per the repair manual. Usually loaded to half it's capacity for 10-15 seconds, voltage shouldn't drop below 10-10.5 volts during the load. midtronix tester or a GR8 is the best way to test the battery. Both tools also measure internal resistance of the battery.