12V battery low or?

It was reported in older articles. Maybe just the S and X.

 

I love my BT100 but be aware that the alternator/starting test doesn't really test anything in our Hybrids, we don't have alternators. It does let me know when the 12-volt is low so I'll pop a battery charger on there for a few hours. (Never had to do this in our old ICE cars unless the battery was at the end-of-life but these Hybrids are a different animal.)

 

I had a troubing issue a few days ago with my 2017 Prius Prime which I cannot figure out.
With a fully charged traction battery (22 mile range), my wife "started" the car, turned on the climate control to heat up the car, left the dongle in the car and went back into the house to get our 3 year old grandaughter to bring her home (car was used earlier in the day to pick her up). When she came back, the car was off with the low 12v battery warning (and panel lights flashing). I went out and found the battery was down to 7 volts! I jumped the battery and turned the car back on. when I disconnected the jumping battery, the car again froze with low 12v battery warning. My wife transferred our grandaughter to our Kia Niro EV and brought her back.
I needed to get to an appointment so I jumped the car again, and then switched the car to use the gasoline engine. I found the battery charging at over 14v. I left it to run to charge and warm up, then drove the car 20 minutes to my appointment in gasoline mode (put a backup battery and jumper cables in the passenger's seat).
After my appointment the car started and ran fine in EV mode.
I checked the battery voltage when off and it was over 12v. I put it on a 6 amp chager and the charger indicated it was fully charged after about 30 minutes. I left it on 2 amp charging for a couple hours to make sure and disconnected the charger.
The next day the battery was over 12v and started the car fine.
We have been using the car regularly (3-4 days per week) before this happened, frequently with 20-30 minute trips so the battery should have been properly charged.
I replaced the battery, and put the "old" battery on the 2 amp charger for about 24 hours. After a couple days of sitting on the floor, the old battery still has 12.75 volts.
After not using the car for 2 days, I went out and the car started fine in EV, charging the battery at over 14 volts while "warming up" the car (its about 30 degrees F).
Has anyone else had their DC-DC charging system burp?

 

The 12V only re-charges when the car is in READY mode. That's when you'll see 14V+ on the circuit. So, it is likely your wife did not put the car in READY when she put on the heat, which quickly drained the 12V. Perhaps the 12V was already drained to the point that the car never went READY and she didn't notice the dash lights. It's easy to miss because you still get some beeps that sound normal. Plus she was preoccupied with getting the child. Also, if the "old" battery was original from 2017, then it was time to change out anyway.

 

It may have just been a loose, wet, or dirty battery connection. When you clamp-on a charger or jump box, your creating another connection - that's why removing the jump box caused the error to come back. Car powered-up on your charger or jump box, kicked the battery error as soon as you removed it.

Load test your old battery, see if it passes. that'll give you a definitive answer.

Good Luck...

 

Automotive retailers often have an electronic load tester, and will test for free. Or DIY, there are lots of these testers. Solar BA9 would be my choice if buying now; I’m familiar with its interface, works well.

 

I saw some comments on the Walmart everstart battery. Anybody else have experience with it and did you guys just recycle your old battery there? Thanks.

EverStart Maxx Lead Acid Automotive Battery, Group Size H4 12 Volt, 480 CCA - Walmart.com

 

I've replaced a battery, not a Prius battery, with Walmart - they'll take any automotive battery as a core. I bought a 78 series battery and gave them a 24 series battery as a core. If they charge you a core charge, they have to take an old battery in exchange, for you to get your core charge back.

Hope this helps...

 

Thanks Biomed01!

 

Thanks Biomed01!

 

Yes and yes. In Colorado, my Walmart had them labeled H4. Then I went to Poway, CA and got one for my sister's 2017 and it was labeled 140R. Same battery, just a different label. On both, the other designations are listed in smaller print below the main one. Pricing was the same at both locations.