FOB is dead -- how do I roll up the windows?

Yes, if the charging station is plugged in but not charging, the 12V battery in the car is being drained by the charger in the car continuously checking the status of the charging station . On the Tesla, there is no separate 12V battery; the traction battery handles everything. I don't know about other EVs.

 

I've always assumed (yeah, I know) that safety was the main reason that the traction battery isn't used for startup. Basically, the computers boot up, do their pre-flight checks and, if everything looks okay, the traction battery is brought on-line by activating big clunking relays that are hidden away inside the battery unit. That way, there's almost no chance of having high voltage outside the battery box unless the computers are active and happy. Even Tesla uses an auxiliary battery. It used to be lead-acid but now is lithium.

A second reason for the 12V battery is that you can boost a 12V battery that's gone dead. I don't even want to think about the unwashed masses trying to boost a 350V traction battery!

I agree that the 12V charging in the PP is substandard for a few reasons. Toyota basically considers the 12V battery to be a consumable item that doesn't deserve much consideration. First, they don't use temperature compensation (which I've ranted about before). Second, they don't properly charge the 12V battery when the traction battery charging cable is plugged in. Then they shrug it off with "Hey, it's not our fault is you killed your battery. We warned you in the manual!" Third, they use a relatively small, inexpensive wet cell battery rather than an AGM battery because they know the battery will die in a few years so why use an expensive one.

Ed

 

Really... That's interesting. I didn't know the wall charger also charged the 12-V battery. I am guessing the owners who are seeing 12-V battery problems are the ones who only do short trips or operate the accessories with the car not in the ready mode.

 

It only trickle charges the 12v while actively charging the traction battery. Once the traction battery is charged it no longer charges the 12v, but it still uses the 12v to check and maintain the EVSE connection... So if you leave the car plugged in for 2 weeks after it's fully charged the EVSE connection could drain your 12v.

 

I just checked my 12-V battery with the system off—it read 12.6 V, indicating 100% SOC.

I started charging the traction battery from ~ 0% SOC, and the reading on the 12-V battery didn't change. Perhaps that's because it's already fully charged and the system doesn't want to overcharge it.

I noticed that the base of the European (EN-standard, LN1) battery is very peculiar. Therefore, I wouldn't mess with the American (BCI-standard, 140R) or German (DIN-standard, H4) batteries. Get an OEM LN1 EN-standard battery from the Toyota dealer when you need a replacement. The non-European batteries probably won't fit as well and as safely and securely.

 

Again, the main problem here is that people don't drive their cars frequently and/or do only short trips. It's OK to leave the car in storage for a month as long as you do long trips regularly for most of the year. I wouldn't leave the charger connected for extended periods with the car in storage. This is no brainer for safety reasons at least.

 

To be precise, there are two different levels of charging that occur while the traction battery is being charged. One is as shown in my comment #20 above, and at ~13.5v. This actually charges the 12v battery SOC to almost full. The battery stays at 12.65v after resting.

Another level of charging occurs at ~12.7v. This is more of a maintainer mode. It does not bring the 12v battery SOC any higher than before the start. What I don't know is how the car decides which way it charges the 12v battery. Certainly, if the 12v battery voltage is well above 12.4v at the time the charging session starts, then maintainer mode is used. I think there is a threshold level of the 12v battery voltage that starts the Active charging mode at a higher 13.5v, but at ~12.3v, either mode can be used.

Again excerpt from my comment on this thread: Hopefully, ultimate 12v battery charging system discussion on PP | PriusChat
EVSE Maintaining: The second is ~12.7v maintainer mode charging that just keeps the 12v battery at near a full level without actively bringing the SoC any higher. This too only happens during the time the traction battery is actively being charged. I explained this observation in this thread.

 

I found the minimum drive needed to maintain the 12v battery at least above 12.2v is once a week for a 1-hour drive. I have never let the car sit longer than 2 weeks without driving. But it does drop below 12.0v if let it sit for 2 weeks. So, I don't know if it is safe to let a car sit for a month after doing a long trip. And also, a long 4-5 hours continuous drive on the highway is not as effective as parking the car for ~3 hours in PARK.

In a few experiments, it was shown that parking PP in READY mode for 3hrs continuously charged the 12v battery to full while 4.5 hours of highway drive did not fully charge the 12v battery.
See: 12v Battery Is Discharging, Re-Charge Now ! | Page 17 | PriusChat

 

That's the other problem. People don't charge the traction battery, which makes the charging of the 12-V battery less efficient with the ICE being on too often. The traction battery should be charged at least once a week.

 

Yeah, but you can't charge the traction battery once every week if the car sits for a month not moving. The 12v battery charging occurs only while the traction battery is actively being charged. Unless the car is put on READY once a week and depletes the charge. But of course, the mere act of putting the car in READY without driving is the most effective way to charge the 12v battery at 14.5v. So, if the car is up on READY for 1 hr every week, there should not be a problem of drained 12v battery even if the car sits for a month.

But, for all practical purposes, if the car has to sit for a month, I would connect a maintainer and let it sit with it for the entire duration.

 

I left the car in the garage for a full month last summer—no 12-V battery issues whatsoever. In dealer lots, they are left undriven for even longer. Again, the real problem here is not how long they are left undriven—it's how they are driven when they are driven. A fully charged battery will probably last for more than three months without being charged. However, if the car is not being driven properly, the battery charge will diminish every day and will eventually become zero. If you do EV driving every week and your trips are greater than fifteen minutes, it's unlikely that the 12-V battery will ever go much below 100% SOC between your drives.

 

I am not saying after 1 mo all 12v batteries in every PP are going to die. The point is longer the car sits undriven, the lower the 12v battery SOC is going to be left in the battery. Sitting for one month or even longer in a garage after the 12v battery was fully charged may be fine if done once in a great while when the battery is still fairly new. But if you continue to repeat that practice over and over, after several years of use, the 12v battery is more likely to die sooner than later. Then there is the quality of the battery itself and user-induced draining, such as leaving lights on or keeping too many accessories.

I have not had my PP battery problem yet (fingers crossed), but my son's hybrid CRZ which was driven every day for ~40 miles had a dead 12v battery. It was less than 2 years old battery. And it was a second after-market 12v battery replacing the OEM battery in a then 3-year-old car. The battery was totally shot and not holding the charge even after fully charging it with a charger, so I had to replace it with a new 12v battery, which made it the 3rd battery in 5 years. Then, we have a Nissay hybrid Pathfinder that was purchased 5 years old with an original 12v battery. This car is driven only once every 2-3 weeks for less than 20 miles most of the time and occasional very long haul of over 500 miles. This battery lasted another 3 more years after our purchase until one cold morning temperature at -26F when the car would not start. Checked the battery, and it had a 12.6v resting voltage, but upon load test, CCA was too low to start the car in that cold temp when the hybrid traction battery could not be used to start the engine.

The point is, every car, every battery behaves somewhat differently. Not all PP batteries behave exactly the same way, but we all know it has a finite life span. If I want to prolong my 12v battery life, then I would not let the car sit for a month without the battery maintainer connected.

I don't know what you consider 100% SOC on PP's 12v battery. But using the chart below, my PP's 12v battery definitely goes down below 100% SOC even if I drive every week for greater than fifteen minutes.


The graph below is the 15-day span of the 12v battery voltage (SOC) plotted. Each upward spike represents my daily drive of duration longer than 15 min for each trip. Some downward spikes are the quick current draw that dips the battery voltage temporarily either when the car is first started or during parking, such as opening the door. After the drive on 2/17, the car sat for 5 consecutive days. The battery voltage (SOC) was down to 12.25v (65%). After a trip, the traction battery was fully charged for ~6 hours, and this brought the battery voltage (SOC) back to 12.66v later on 2/22. But within a sing day, by 2/23, the battery voltage (SOC) was down to 12.33v (70%). Yes, the 12v battery in my PP drops from 12.7v to 12.3v in less than 24 hours. I try not to let my 12v battery go below 12.2v(60%), but if that happens, then I connect my external 12v battery charger to bring it back up to 12.7v (100%) promptly.

 

I doubt it was 12.7 V on 02-23. You need to wait for a while for the charge to stabilize after charging.

Could it be that all these gadgets that you are connecting to your car are the reason why your battery is draining so fast?

I wonder the other possibility is the ambient temperatures where you live. For example, the last time I drove my car was three days ago, and my 12-V battery still showed 12.6 V (100% SOC) today.

Moreover, this also happens with nonhybrid cars. I had a brand-new Corolla once, which I was driving very unfrequently, and the battery completely died when the car was less than a year old and only had a few thousand miles on it.

 

Even if the battery did not fully charge to 12.7v, the fact still remains that the battery is not maintaining the same level of SOC for long. I have a graph from the day I actually used the external charger to fully charge the battery, The red dot on 1/10 indicates when the battery was charged at 14.5v to full charge 12.7V (100%). I have driven the car for two days in a row after that on 1/11 and 1/12 but did not drive 1/13-1/14. The battery SOC steadily decreased from 12.7v to 12.41v in 4 days (1/15). Then the battery recharges after the drive each day but continues to go down more and more each day. If I drive every day, I would not notice much change, but if I let it sit for a few days (1/22-1/24) the gradual change shift to more drop and eventually went down to 12.14v by the end of 15 days period. A full charge of 12.7vwill drains down to 12.2v within ~2 weeks with some driving.

Again this is all with fairly constant driving (not every day, but certainly more than once a week) for about 30min to 1 hour for each trip. If the car is driven every day, then the 12v battery gets replenished every day and does not have enough time to drain down too far, and it tends to stay around 12.4v most of the time. But if the car is left undriven for a few days, then it will keep dropping down to ~12.2v. In most cases, if I maintain at least a 1-hour drive one day a week, then I can maintain this minimum level of 12.2v (60%). If I let go longer than a week, it will likely to continue dropping below 12.2v.

No, I don't think so. Certainly, the battery monitor I used has a little current draw but it is rated 1mA. I only check once every few days or so to connect to my phone to log the data. I have nothing else that stays connected and drawing on the battery that is not an OEM. And I have checked the daily changes of the 12v battery SOC with a multimeter only and a very similar rate of SOC drop has been reported. Furthermore, the same battery drain has been reported by many other PP owners. For example, this 12v Battery Is Discharging, Re-Charge Now ! | Page 14 | PriusChat reports 12.7v to 12.1v (0.6v) drops in 16 days.

Temperature does affect the SOC of the 12v battery. I have seen the voltage drop overnight to the lowest point in the morning corresponding to the temperature change, and then during the day, as the temperature warms up the voltage will go up spontaneously. However, those fluctuations are small, in the range of less than 0.1v.

One thing to add to all of those observations is that even though I and many others witnessed the persistent low-level parasitic draw on the PP's 12v battery, I have not had any battery problem on my PP to date. Having more than 12.0v SOC on the system almost guarantees that the car will start. What I don't know is when the battery eventually gets to the point when it starts causing the problem. It is unlikely that happens within 1 to 2 years after purchasing a car new with presumably a new battery. But I have seen enough reports by others in this foram having such trouble very early on their ownership of new Gen4/PP. So, I am taking a great measures to avoid such trouble.

 

Another facet of the safety angle is that emergency responders generally already know how to de-energize a vehicle's 12V system to make it electrically safe, before starting to slice and dice the vehicle to extract trapped or injured occupants. Keeping the same sort of electrical architecture, carefully built such that de-energizing the 12V system inherently shuts down and isolates the high voltage battery, improves safety for both the occupants and the first responders coming to their aid. The emergency response industry doesn't have to learn very different methods for handling hybrids and BEVs.

 

This is still a mystery to me. The battery capacity is 45,000 mAh, and each 0.1-V drop in the open-circuit voltage corresponds to about 10% SOC or 4,500 mAh, which is 190 mA over a 24-hr period. In terms of power, it is about 2.3 W. I wonder what is drawing that power. If your data is correct, the battery wouldn't last for more than about five days, which we know not to be the case in general. Again, could it be that there is something in your car, like the car constantly trying to communicate with the cellular network, which is causing the drain? Could it be because you canceled the Toyota Connected Services, it's causing problems with the car's network search?

 

Not likely. As I stated, the same phenomenon, a fully charged 12v battery dropping SOC, 0.2-0.3v in 7 days or 0.5-0.6v in 2 weeks has been reported by many PP and Gen4 owners. It is not specific to my PP. I don't believe all of them have gone through the trouble of Opting Out of Connected Service as I did.

Besides, some reported cases are from earlier models without telemetry. My base observation was mostly on my previous PP (2020 PP LE) which sat ~1 week at a time and was driven only once per week for a duration of about 1 hr. The data I presented above for this year is on my current PP (2021 PP Ltd) with more frequent trips than the previous 2020 PP LE. On average I currently drive 1 trip per week about 1hr duration + additional 2-3 shorter trips of ~30min duration. Both cars were less than 1 year old. Unfortunately, the battery concern did not hit me until I started working from home due to the pandemic in early 2020. So, I never even bothered to check the 12v battery on my first PP (2017 PP Premium). So, I have no data to compare for that model year.

Based on mostly my observations and some reports by others:

1. When the battery is less than 1 year old, it is less likely that the 12v battery falls below 12.0v.
2. With a more than 3 years old battery, the chance of deep discharge with light use (not everyday use) increases.
3. With everyday driving, the battery SOC tends to stay at around 12.4v-12.5v.
4. With once a week ~1 hr driving, 12.4v can be maintained when the battery is still new (less than 1 year old)
5. With less than once a week ~1 hr driving, the battery tend to dip to 12.0v-12.2v
6. The SOC drop is not perfectly linear. It tends to equilibrate at ~12.4v with daily drives, and at ~12.2v with less frequent drives.
7. I have not let my car sit longer than 2 weeks undriven. Thus I don't know the effect of long-term storage.
8. If my 12v battery SOC drops to below 12.2v, I promptly charge it with an external charger.
9. As I said, I have not had any battery problems on any of my PPs, 2017 PP (unmonitored, driven daily), 2020 PP (monitored, driven only once a week), 2021 PP (monitored, driven 2-3 times/week)
10. I don't know if any of my battery care regimens will increase the life of the battery in a long run (years)

AND the bottom line is that if the 12v battery has at least 12.0v SOC, it can start the car. It starts showing problem behavior such as car not starting, battery low warning indicator lit, charge port lid not opening, SKS not responding, etc if the battery SOC drops well below 12.0v, needing a jump to correct the problem. I do not know if the battery experiencing this type of discharge below 12.0v can be charged back up and stay healthy for a long time. My feeling is that more often than not, once the battery is let deeply discharged once or twice, it is less likely to be rejuvenated, thus it is time to think about replacement.

 

Somewhere in another thread, the parasitic drain was listed as about 85 ma. Do the math with a 45 AH battery and you get about 22 days to drain the battery. Note that there's a lot of assumptions in that calculation. But that will only happen:
1. IF the battery actually has 100% of its rated capacity
2. IF it's fully charged
3. IF the PP will allow that kind of drain and still start, and
4. IF the temperature is nice.

Each of those conditions will reduce the actual time that the PP can sit and still start. So basically, since Toyota views the battery as disposable, it would take a miracle to reach 22 days. For most users, #3 will be the big factor. My weather is viciously cold in the winter so #4 looms large because the cold temperature reduces the battery's capacity by as much as 50% and the simplistic charging system doesn't charge it properly. That triggers items #1 and #2. As a result, I have to watch my battery closely and use a maintainer frequently since I don't have a garage or other shelter.

Ed

 

As I said, I left the car exactly for 30 days last summer, and there were no issues.

 

Congratulations. Based on my experience and the messages I've seen on this forum, your accomplishment is extremely unusual. I hope you bought lottery tickets!

Ed