Short background:
We are looking to move on from my wife's Chevy Volt due to an EGR issue that has happened twice in 78k miles. She really wants another compact PHEV, no SUV, or bigger sedans. We found a '24 Prius Prime with only 4k miles that we intend to buy. Due to minor dealership clown show issues, we couldn't do the deal today, and it will be a day or two yet. While I'm waiting, I decide to google "2024 Prius Prime common issues" expecting to see minimal issues and nothing of great concern (it's a Toyota fer cryin' out loud and a Prius at that - reliable as gravity, right?...right?).
Longer rant:
Well, only one thing of real concern pops up, but it seems like a biggie. Many instances on Priuschat and reddit saying they are having no start conditions due to a dead 12V battery on nearly new cars. The signal to noise ratio is pretty poor on those forums, but there's a few theories about the causes, some of which may need to conspire with one another to achieve their goal of leaving you stranded:
1. The battery management system is really stingy about charging up the 12V battery when you drive it and feels no need to charge the battery anywhere near 100% SOC, no matter how long you drive it.
2. In some cases, the car will keep parts of the system awake after charging is complete and get into a 12V battery drain situation IF you leave the charge cord plugged in. The owner's manual even states that you should not leave the car plugged in when it's not charging. Apparently, the issue sometimes happens after just leaving the cord plugged in overnight.
3. If you use the Toyota app on your phone, or possibly leave the fob too close to the vehicle, it won't fully shut down, thus draining the battery.
If it's not too badly discharged, a jump box gets it going. Many folks have their car towed to the dealer and usually get either no problem found, or 12V battery defective. People have had the battery replaced multiple times, and the issue recurs. Sometimes the dealer diagnoses a bad ECU or other components and keeps the car for days or weeks waiting for parts. There was a TSB issued in July 2024 - seems like a firmware update - for the "battery drain after charging complete but cord still attached" issue, but I haven't found anyone who said yep, I got the TSB done and now it's all good (or seen anyone say they had the issue again after the TSB was done). Because the TSB is not a recall, seems common to need to do some arm twisting to get the dealer to perform it.
Some folks are trying to mitigate it by making sure to unplug when charging is complete and/or connecting a trickle charger, and connecting a blue tooth connected battery monitor to keep tabs on SOC. Some say switching to an AGM battery gives additional margin and alleviates the issue, but I mean... screw all that.
The Conundrum:
The whole reason for making this purchase would be to get back to a car that would just work with no hassle, and remove the cloud of doubt that the car will get you where you're going. Am I making too much of this, being gun shy after the Volt issues?
Post Script:
The car was delivered to this dealer in Nov 2024, and a personal lease transferred ownership on 12/31/24. On 12/31, Carfax shows some inspection activities and interestingly a "Battery/Charging System check" at the end of December.
The sales guy told me that this car belonged to the service manager at the dealer, he bought it a few months ago and traded it on a Raptor a couple of weeks ago. Did he nope out of it because he had a battery issue or saw too many customers with issues? It's also priced at the low end of the range for similar cars.
