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Discussion Starter · #1 ·
On 18 Feb 2021 we took delivery of a 2021 Toyota RAV4 Prime Plug-in-hybrid from Westcoast Toyota in Pitt Meadows BC . The vehicle has performed flawlessly, with one major exception.

One of the reasons for selecting the RAV4 was Toyota’s reputation for reliability and relevant experience with hybrids. Reliability is very important to us as the vehicle travels on forest access roads well beyond cell phone service which means a long walk to help. Even within cell coverage or via Toyota Roadside Assist, help for a dead vehicle is hours away, probably not until the next day.

On two occasions the 12 volt battery of the RAV 4 PHEV has died overnight. After prompting, the dealer checked that “the system has the latest software in accordance with Service Bulletin. “T-TCI-5389 DCM Reset and Firmware Update (LG)”. The dealer staff, on both occasions of failure, accused us of “not driving enough” yet did not even ask if the vehicle had been driven the day prior or if it was plugged in overnight (yes to both). Attempts at further discussion made it clear that the dealer staff have no interest whatever in finding a solution.

A request to Toyota Service produced another legalistic evasion and a request that we deal through the dealer. So, we have asked the dealer:

1. To remain operational, must the RAV4 be driven a minimum distance per trip/day?
2. Must it be driven in HV mode?
3. How many days can the RAV 4 remain inactive then reliably start?
4. If/when the 12 volt battery discharges again, what would you like us to do:

No answer yet to these questions. So, the present situation is that we have a Toyota RAV 4 PHEV which has its reliability compromised by an unknown defect which is aggravated by a Toyota dealer with no interest in finding a fix.

In the hope of helping find a fix, I am maintaining a log of voltage of the 12 volt battery at the start and end of each driving day. When the RAV4 PHEV is in the garage a 1.5 amp battery maintainer is connected to the 12 volt battery and the key fob is disabled.

Has any RAV 4 owner found a fix for overnight discharge 12 volt battery.


Ron
 

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1. To remain operational, must the RAV4 be driven a minimum distance per trip/day?
2. Must it be driven in HV mode?
3. How many days can the RAV 4 remain inactive then reliably start?
4. If/when the 12 volt battery discharges again, what would you like us to do:
I'm not a dealer, but my take:

1. NO
2. NO
3. See here (short answer, way more than a day).

That said, the 12v battery shouldn't discharge overnight unless something is left on to cause it to drain, or there is indeed a problem.
 

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Discussion Starter · #3 ·
I'm not a dealer, but my take:

1. NO
2. NO
3. See here (short answer, way more than a day).

That said, the 12v battery shouldn't discharge overnight unless something is left on to cause it to drain, or there is indeed a problem.
I agree, the 12 volt battery should not go flat overnight, but it has, on two occasions.
 

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2021 RAV4 Prime XSE in Magnetic Gray
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I agree, the 12 volt battery should not go flat overnight, but it has, on two occasions.
Do you have any added accessories installed on the car? Dash cams, aftermarket electronics, anything of that nature?

The next time this happens, take a multimeter to the battery terminals located in the rear of the car. If it reads 10.5V, you have a bad cell. Bad cells can sporadically come back to life, so one moment the battery is outputting 10.5V and the next 12.6V.
 

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There was an issue with the inverter bolts needing replaced. There was a TSB about this causing an issue with the 12v system. I will try and search and post if I find it. I seem to remember people complaining about their battery going dead with this one and with have a scan gauged attached. There was also one about the connected services causing an issue with the battery draining that there was a tsb.

T-SB-0007-21 Poor DC-DC Ground Connection.pdf
 

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There was an issue with the inverter bolts needing replaced. There was a TSB about this causing an issue with the 12v system. I will try and search and post if I find it.
Seems to be a problem with the link. The TSB can be found here. And thanks for that, I forgot about that one! :)
 

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2021 Rav4 Prime XSE Pro Audio/Dynamic Nav/Weather Packages Build date: June 2021
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Perhaps the battery itself is hosed? Easy enough to test and would be low hanging fruit to r/o first.
 

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Discussion Starter · #9 ·
Do you have any added accessories installed on the car? Dash cams, aftermarket electronics, anything of that nature?

The next time this happens, take a multimeter to the battery terminals located in the rear of the car. If it reads 10.5V, you have a bad cell. Bad cells can sporadically come back to life, so one moment the battery is outputting 10.5V and the next 12.6V.
Thanks for the suggestion. Yes, I have a GPS and a dashcam plugged into the "cigarette lighter". Both devices have an accelerometer which shuts them off if no motion - and I check when the vehicle is out in the garage.

To discharge a 100 amp-hr battery in, say 12 hours would require an average current of 100 amp-hr/12 hr = 8 amps, far beyond the draw from these devices.
 

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Discussion Starter · #11 ·
Looks like the pdf didn't attach only the image of the pdf. Thank you
Thanks for the reference.
The scanguage has reported no trouble codes and the VIN is higher than the bottom one on the "Production Change" box, so looks as though TSB-007-21 does not apply.
However, will ask the dealer to confirm.
 

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Hi, keep in mind that on a 12V system 1A = 12 watts. It ain't much. Even if you have a small-ish parasitic load that is low wattage you're cycling the battery over and over when it's not in ready state. It's impossible to tell without seeing your setup and the load, but if these devices aren't very very asleep when not in use the cycles could very well toast your battery, where it will charge to full voltage but it's capacity is compromised. A load test may or may not reveal this.

I'm placing my bet on the accessories and a compromised battery. In your use case it would be worth having a boost jump kit or spare battery as reserve. Hope this helps-

Oh and if you have a Scanguage, that'll suck it down too (pretty quick) if you leave it plugged in and don't have the secret firmware update.
 

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Our experience with PHEVs is that the 12 volt batteries are the weakest part of the overall design. Our 2018 Audi etron is on its 3rd 12 volt in 4 years. I just swapped my 2019 Kia Niro PHEV with only 12,000 miles, on its 2nd battery. Any minuscule drain will toast the battery. Even if it’s warranted your still inconvenienced with downtime and dealer visits. We’ll see if the R4P 12 volt is more durable.
 

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Thanks for the suggestion. Yes, I have a GPS and a dashcam plugged into the "cigarette lighter". Both devices have an accelerometer which shuts them off if no motion - and I check when the vehicle is out in the garage.
I had a battery in my 2014 Honda Civic that was a dud, but would pass a load test. It had a cell that would sometimes behave. These batteries have six cells at 2.1V each. 6x2.1 = 12.6. On a given day, it may test at 10.5V indicated a bad cell, and other days 12.6V.

I suggest you keep a multimeter in your glovebox. If your RAV4 Prime does this again, immediately check the battery. You want something along the lines of 12.6V. 12.5 or 12.4 is a discharged battery. 10.5 is a bad battery.
 

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We’ll see if the R4P 12 volt is more durable.
I can attest to the R4Prime’s 12v battery durability when I experimented (four times) draining the 12v to the point of nothing happening when you press Power button (w brake on). OK, it was less of an experiment and more of ‘having too much fun’ looking at ScanGuageII values to send it in for firmware upgrade. “I can remember to unplug it before I leave my R4P,” I told myself. Four brick-w-alligator-clips jump starts later and I was ready to send it in. Whenever I email LinearLogic for upgrades and mention my current favorite Forum (Rav4World) they often offer free firmware upgrades. Make sure to specify that you have a Rav4 Prime when you communicate with LinearLogic regarding firmware upgrades.

Anyway, after draining overnight, not starting, using jump positive post in fuse box in engine compartment to restart four times in two months, I finally got the firmware upgraded and I have not had any 12v problems since the upgrade. I always have a BlueTooth OBD dongle plugged in, but I make sure to buy ones (BlueDriver, OBDLink MX+, ScanGauge II) that advertise minimal power use when in sleep mode, and they have not drained my 12v close to a year later. I think the R4Prime has effective 12v power level triggers for shut down mode. It shut my (low) 12v system down 4 times and the 12v battery still holds a charge and powers an extra (sleeping) OBD dongle. We’ll have to wait to see how long the R4P 12v lasts after early draw-downs. I have come to expect 5-7 years before replacing 12v on a Toyota Hybrid or Plug-in
 

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Wasn't this an issue with the regular Rav4 Hybrids?? I recall a lot of threads about drained 12v batteries on the hybrid forum, and I recall it being a possible concern with the Prime.
 

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One lesson learned is to NOT listen to the radio without READY showing on the dashboard. This kills the 12V battery and then throws a bunch of codes.
 

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