Low Voltage in Rear Power Outlet

When I told them what Toyota said, he mumbled something like "typical." He said he'd ask the service manager what they could do since Toyota corporate refuses to fulfill their battery order. He even said, "you'd think they'd just divert some batteries from the production line." I guess I'll see what the manager says Wednesday. This is too much drama for a battery.

In the meantime, I did some testing. I tested the battery yesterday cold at 12.1V at the posts. I left the car in ready mode for a few hours and tested the battery at 12.65V. I let it sit for a few hours, then ran the headlights for 60 seconds and tested again - 12.5V and slowly climbed back to 12.6V. Good sign. Then I drove the car about 5 miles to run an errand and plugged it back in. This morning the charge was back down to 12.2V. I'll have to test whether the drive is draining the battery, the charging, or just sitting.

 

14.5V

 

Maybe. Right now it seems that the possibilities are:

1. The battery's self-discharging rapidly.
2. Driving the car is not charging the 12V battery as fast as it's being drained.
3. Charging the car is discharging the 12V battery.

These will be easy to test.

I'm just trying to figure an easy way to keep 12V power to the car while I break the connection to get the Fluke in there to measure the current while the car is off. Maybe I'll rig a 10-AA battery holder I have to the negative cable before I disconnect. It will have plenty of power (2Ah) to feed the electronics while I get some alligator clips in there.

 

It's fine after being parked for 2 hours in ready mode. I don't know if it's fine after a drive. I'll check it. I have to run an errand tonight that will be about an hour of drive time. I'll take measurements before and after the drive.

 

Welp, I think we have our answer. After driving just a tad under 50 miles over 90 minutes, my 12V battery lost charge. It started the trip at 12.37V and ended the trip at 12.25V. Sure enough, when the car is in park the voltage reads about 14.5V, but in drive the voltage dropped all the way to 12.6V. Just turning on the headlights drops the voltage to 11.8V.

Something is happening to the charging system that is triggered by shifting the car into drive. I just can't figure out what.

Can anyone else with an 18 Prime confirm the voltage drop? It doesn't seem to happen if you just start in your driveway and throw it into drive with the brake on. You have to actually drive around a bit sometimes, and then when you get home you can toggle the voltage drop back and forth between drive and park. It even works shifting between reverse and drive. No voltage drop in reverse. You don't have to go out to the battery to test it. You can see the same thing in the 12V outlets.

 

OK guys, I'm about to pull the trigger on an aftermarket battery. If I'm able to get one and install it, I'll let you know how it goes.

Is it possible to keep the 12V system energized by connecting a small battery to the jump start terminal? I don't want to lose all the settings, etc.

 

Thanks. The Prime doesn't have a lug like other Prii. I'm trying to think of a good way that doesn't involve trying to keep something connected to the actual battery cables I'm trying to work with.

 

I'm trying to determine if the 12V battery is causing the issue, or if the issue is causing the 12V battery problem. Getting really tired of not being able to use any 12V accessories in the car and having to pop the hood every day to check whether my battery is dead. Plus, Toyota is clearly unwilling to work on the issue without first replacing the battery. Perhaps I should just let the battery go dead and have it towed to the dealer.

 

The thought had crossed my mind, but I'm willing to bet that the car has sufficient sensors to "know" the battery was drained intentionally.