Third day with new car, dead 12V battery, second day in a row :(

Toyota definitely needs to address something... but plenty of user error here I think.

 

Doing that with any car that is infrequently driven is probably a good idea. The gen2 Prius had an off switch for the SKS, because the early versions could kill the 12V within a week of being parked.

 

I drive my car 5 days a week, even if only for short grocery trips, or to back the car out of the garage for recycling and garbage day - so I almost never leave it plugged in for more than 24 hours. But I have done it on a couple weekends before. Never had an issue either.

As for the headlights, they stay on but if your key moves far enough away, it turns off the lights. The same way the key will turn on the cabin lights as you approach the car when you get close enough. Those also seem to be on a timer though since I've noticed they turn off after a few minutes.

I wouldn't be surprised if its related to some glitch that doesnt turn off the lights properly. Maybe the keyfob is close enough, but also far enough away for some people based on where they store their keys that its constantly catching/losing signal and cycling the "on approach" cabin lighting on and off overnight. That kind of thing can definitely drain a small battery over a long enough time period on its own, and combine that with other 12v drains, like the battery checking system for exmaple... maybe its a set of combined factors coupled with a software glitch or lack of failsafe check in the software to manage the 12v.

Why the car doesn't self-check the 12v health and then shut down certain functions with an associated alert to protect the batter from itself I don't know. From what I understand the car can tell you when the 12v is getting low, when the systems are on anyway. So I wonder if it couldn't do the same when plugged in - check in on itself - then go into "keep minimum charge mode" at some point.

 

There is quite a bit of speculation concerning the cause(s). The two main things we know for certain are leaving the AC charger connected for extended periods of time and excessive use of ACC mode will drain the 12V battery. Other potential prospects include any after-market devices that would continue to draw current from the 12V battery after shutdown. I'm skeptical of the key fob theory until we see some evidence otherwise. My cabin lights do not turn on when I approach my car unless I use the fob to unlock it. I suspect that over time, a common denominator will be revealed among those having this issue.

 

I adjusted the settings so that the exterior lights turn off immediately when I open the door.

 

Some dealerships add tracking devices to cars. Has those suffering from dying batteries checked for that?

 

So any time it's in the Ready state, the 12V battery is being charged by the traction battery?

 

Yes.

If your wiring up a battery maintainer; IMHO the closer the charging leads are to the battery, the better it will work. The current from the battery maintainer doesn't have to navigate through the wire-bundle in your car to get a charge to your battery.

 

Not sure how much better though. With the gen 4 12 volt battery in the front it's trivial to connect at the battery. With our 3rd gen, battery in the hatch, I connected the positive wire of my charger's quick-connect cable where 12 volt positive cable connects to the under-hood fusebox, and the negative wire under the head of a bolt going into car body. Works fine.

 

I might add an SAE pigtail to the battery itself in the future. I'll definitely add a Bluetooth voltage monitor to see if there's a parasitic drain.

 

Ha ha, good luck asking Toyota to fix issues regarding the use of third-party accessories/modifications.

 

I forgot to mention that I also had a CARISTA OBD Scan Tool plugged in when my battery died the first time which I don't use regularly any more. Haven't read about this being a significant source of 12V drain but probably didn't help.

 

Contact Linear Logic for what they have to say. There might be updates that reduce the energy draw. Unplugging the Scangauge at the device might be enough to avoid problems.

There still could be an issue of a poor battery or too much drain from the car, that lead to the gauge pushing the battery into the dead zone.

 

Scangauge II does shut off when the car’s off. There’s also a setting for hybrid cars with auto-stop. Never had a phantom drain issue with mine.

It did causes problems though: check hybrid system warnings started popping up, together with brake lights and work-to-rule brake behaviour. Disconnecting it, no further problems. Toyota tech speculated it could have been its constant weight on OBD port.

 

I have found no it isn’t. It always does on start and on return so far as I have seen, but not always when driving. I watch what it’s doing but charge is holding higher with lojack disconnected. Otherwise there is nothing to do except if battery gets low, charge it. I usually will charge if monitor shows below 75% or so when I return. Or sit in ready mode twiddling fingers watching it charge % by % from the traction battery.

 

Mine lit up the engine and traction control when plugged into the Sonic. Linear Logic did a free firmware update, and no more problems. They have great customer service, which is why I suggested contacting them.

Cars with alternators vary the current. It should stay high while the 12 V is below 100%, but not always.

 

Yes, but only if certain conditions are met. There is a battery multisensor, and the system will not charge a full battery or a very hot battery etc.

 

This is different. People make comments here that don’t have the data from a battery monitor. They are just guessing things. The Gen 4 I have turns off charging when the volts go below 13 in ready mode. It can stay above 13 a whole outing, then the next outing it is different. Charging may start and stop several times. I would need to get the service manual and do whatever it says to diagnose, probably requires a dealer type scanner.
So far when I put the car to ready in the driveway, the battery is charging at that moment. When I go into my driveway coming home, usually backing in reverse, then selecting Park, the system is charging.
The problem is so far only one other person has a battery monitor and he says his stays charging. Mine does too, sometimes.

 

It's built in, the DCM is the tracking device. Nothing needs to be added to this car for the dealership to track it (and control it if they want). And it's always live and pulling from 12v. There has been some cases of the DCM draining batteries but it was widespread on a different auto maker.

It's an easy enough test though, a single fuse will stop it from pulling from 12v.