Dead battery. Again.

welcome!
if it's really only 2 months old, then maybe you just need to put a smart charger on it.
driving for thirty minutes on the highway in't enough to recharge it.

another possibility is the connections at the battery and chassis, perhaps some thing is loose or corroded.

keep in mind, you have two batteries. the battery indicator on the dash is for the hybrid battery, which collects regenerated energy for future use and starting the engine. it rarely will show full.

you also have a 12 volt battery, which powers up the computers so the hybrid battery can start the engine.
it's the 12v which is going dead, and it's a possibility that your short trips are causing it, and you may need to keep a battery maintainer on it. or it might just be from leaving the headlights on, but there's no need to shut them off before powering the car down.
the first question is, which battery is new?

 

probably 8 hours. please re read my post, i tried to edit it for clarity. it can be a bit too much info to take in all at once.

 

Your car sat on a car lot for a while before you bought it. While it sat the battery died. When u came along they jumped it but it was already cooked as it sat dead for a while and sulphated. It went dead again and you jumped it and then then it went dead again.
Replace the 12 volt battery its done. And for god's sake stop jumping it. There's hundreds of posts about jump start damage to a Prius on this site only surpassed by the thousands of posts about why is my 12 volt battery dead?

Driving it on the highway will not recharge the battery very well. And if its sulphated like yours, its just a waste of gas. It needs to sit on a charger for quite a while. But that won't fix your battery.
Read the owners manual.

 

To confirm Ed's post for yourself, you should take your car to AutoZone or the like and have them test the 12v battery. It is located in the well right behind the right rear tire. The battery will be north of $150, since you indicated that your car knowledge is limited, the dealership OEM battery would be a good choice.

Oh, and to reiterate Ed's statement about jump starts in the Prius, if done wrong your problems will likely be much worse. A blown inverter is very expensive and a headache to even the most knowledgeable. Spend some time on this forum researching your Prius and it will help you become more comfortable with it's inner workings. Good luck.

 

Yes you need to jumpstart it to get somewhere to get the 12V battery tested. Unless you want to remove the 12V battery and only take it there. Yes they did jump start it correctly as it did get going. But each time you jump start it there’s a change of something going wrong.

 

If you end up needing a hybrid battery, call Matt from Texas Hybrid Batteries

SM-N910P using PriusChat mobile app

 

1. If the 12V battery is sufficiently depleted so that you need a jumpstart, 20 minutes of driving is not adequate. The Prius is very slow to charge the battery, and 8-12 hours is more like what is required.
2. You do not actually have to drive the car anywhere. You can just leave the car sitting on your driveway, in READY mode, and that will charge the battery at the same rate as if you were driving 70 mph on the freeway. You have to consider the issues associated with leaving your car sitting in the driveway while turned on and whether that is safe/legal in your locale or not.
3. It would be unwise to assume that all roadside service personnel know how to correctly jump start the Prius. Some have made that assumption and found it was faulty, which resulted in a blown inverter and a four-digit repair bill. In your case you were lucky.
4. Leaving the headlights on is generally not a problem if you exited the car via the driver's side door, as the lights should turn off automatically. However if you managed to leave the lights on regardless, that will certainly deplete the 12V battery.
5. Hopefully by now you understand that the battery state of charge gauge in the MFD is for the high voltage traction battery, which is not the same as the 12V battery that you are having a problem with. Hence the SOC gauge on the MFD will tell you nothing about the condition of the 12V battery.

 

You need to expunge this idea from your memory, and go with your instincts, It is not only strange, but ridiculous. Once the lights are off, they are off.

Someone probably made an observation, added 2+2 to get 7 and published their findings on the "interwebs".

If there is, in fact, a parasitic draw, there will be other reasons for it, which will come to light upon further diagnostics. But the more likely scenario is the obvious one, your 12 V battery is at end of life and cannot hold a charge (even though it was 'new' 2 months ago, if you can believe the person who told you this). If this proves to be the case, replacing it, hopefully under warranty, will fix the problem.

 

No truth. However you should set the parking brake when the car is parked, just as a safety measure. Then you are not relying just on the transaxle's parking pawl to hold the car in position.

I suggest you make sure the 12V battery is fully-charged, notwithstanding any tests that may have been performed.

 

Hook up a battery charger.

 

Charge, with something like this, a 4~amp smart charger:



Then check the voltage one of these, a digital multi meter:



Or better, this'll give you the voltage, and assess the Cranking Amps, basically the health of the battery, and give you a rudimentary report and a verdict: "good", good but charge", or "replace":



Most importantly: read up. Lot's of battery maintenance resources on the 'net.

 

The 300 amps was probably the load they placed on the battery. Do you know the battery voltage when you arrived at Advanced Auto Parts? The loose connector to the battery certainly could give you difficulty starting and if it was very loose I could intermittently disconnect the battery from the vehicle.

 

The 300 amps is likely the as-tested cold cranking amps, which is not bad for the OEM battery. The loose connection could indeed be the problem.

 

Checking 12v Battery Health
You can easily check out your battery status/charging system using the MFD in maintenance mode. No tools required.
1. Get your Prius into "Accessory Mode" - Press the power button without touching the brake pedal.
2. Put the MFD into "Maintenance Mode" - Press and hold the "Info" button on the MFD while turning the headlights on and off 4 times.
3. Press the "Menu" field on the screen.
4. Press the "Display Check" field.
5. Press the "Vehicle Signal Check" field.
6. The 12v battery voltage will be one of the items listed, it should be above 12 volts. The reading should be about 12.4 to 12.8 Volts (normal for an unloaded battery). If it is lower, either the battery needs replacement or the charging system is not functioning correctly - see step 7.
7. Put a small load on the battery by pressing the power button again without touching the brake pedal. The voltage should stay above 12v. If less than 12.0V the battery is not well, or there is a fault or unusual load somewhere. If it drops significantly, you need a new battery.
8. Now get your Prius into "Ready Mode" - step on the brake and press the power button. The battery voltage should immediately rise to 13.8 volts (Your Prius uses constant voltage charging). If it is lower, the battery will never charge; if it is much above 14 volts, your 12v battery will get cooked. The battery is now charging at about 14V. If less than 13.6V or more than 14.4 there may be a problem with the charging circuit.
9. Shutting the car down will reset the system back to normal operation.