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Discussion Starter · #1 ·
Hi,
We left our 2020 RAV4 hybrid at the airport for 10 days.
On trying to start it, initially it would make a bit of a whirring noise and dash lights would come on, but it would not start.
After letting it sit a while, tried it again with same results.
Got my jumper battery out and was getting ready to see if that would get it going, but tried one more time without it, and it did start and ran normally. It has been fine since.
It appeared that the traction battery was about half charged when the hard start problem occurred.

Questions:
  • Is this problem due to the 12 volt battery getting too low?
  • Why did it eventually start?
  • What is fundamentally causing the no start problem?
  • Any way to avoid this problem?
  • Was there some way to put it in electric mode and get it to drive that way? (I did not think of trying this at the time)

Thanks - Gary
 

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Many people have had this issue unfortunately. For many the TSB fixed it - but think some still had issues after. Nevertheless, go to your dealer and ask for the related TSB.
 

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Did you keep the brake pedal depressed as you pressed START button?

12V battery will always be the Achilles issue w/ Hybrids/PHEV/EV.

For Toyotas, a strong enough 12V is absolutely required. The 12V powers the ECUs, which then tell the computers to have the HV (High Voltage) battery "crank" ICE, as needed. As you can see, the 12V battery NEVER cranks the engine like traditional cars.

The problem w/ today's cars and all the dang electronics, esp the "smart" key or keyless start button, is the drain on the 12V battery. When you power OFF the car, the keyless system is always in standby looking for the key fob signal to get ready to unlock and start the car. Some cars have a security or power saver feature to deactivate the smart key, thereby decrrasing 12V battery drain.

The best way to avoid your experience is:
1) get a smart 12V battery charger that has an AGM setting, and regularly recharge the 12V batt. A regular 12V battery charger will never fully recharge an AGM battery, and AGM batteries are becoming the norm for many vehicles. You'll want to regularly recharge your 12V batrery to ensure it is always fully recharged. A batt that stays fully charged will always lice a longer life than a batt that is in a constant state of discharge.
2) The next time the car will sit for a prolonged period (airport, home, etc). Deactivate the smart key to decrease 12V drain and attach theb12V batter charger.
3) Noco and CTEK make quality 12V AGM compatible battery chargers. The CTEKS come w/ the terminal ring eyelets that stay attached to the factory battery terminals, in addition to battery clamps. The Noco sells the terminal ring eyelets as an accessory.
 

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Discussion Starter · #4 ·
Thanks.

That makes sense that (I guess) they use the motor/generator to the starting with the traction battery, and the 12 volt battery is not involved starting the engine, only in running the electronics required to manage the start.

I will look into the TSB.

My understanding is that the traction battery charges the 12 volt battery. I'm wondering why it can't keep the 12 volt battery charged enough to start the car? It seemed like there was plenty of juice left in the traction battery.

I guess that if the car had not eventually started on its own, then hooking my Lithium jump pack onto the 12 volt battery would have done the job and enabled it to start?

Can anyone comment on the effectiveness of the TSB?

Gary
 

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2020 RAV4 HYBRID LIMITED
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Thanks.

That makes sense that (I guess) they use the motor/generator to the starting with the traction battery, and the 12 volt battery is not involved starting the engine, only in running the electronics required to manage the start.

I will look into the TSB.

My understanding is that the traction battery charges the 12 volt battery. I'm wondering why it can't keep the 12 volt battery charged enough to start the car? It seemed like there was plenty of juice left in the traction battery.

I guess that if the car had not eventually started on its own, then hooking my Lithium jump pack onto the 12 volt battery would have done the job and enabled it to start?

Can anyone comment on the effectiveness of the TSB?

Gary
This would be the correct way to jumpstart your hybrid.
 

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Just curious, can you clarify “didn’t start”? Did the Ready light come on? In summer weather, mine often doesn’t start the ICE until I’ve driven it down the block a bit, especially if the HVAC is not demanding heat.
 

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Correct. The HV Battery recharges the 12Vbattery when the car is in READY mode (the equivalent of conventional gas engine only car is on and running). When READY is displayed, the car is "running," even if the gas engine is NOT.

There is a DC to DC bus that steps down the 200+V from the HV battery to say 13.7V for the 12V battery, and maybe it's 10Amp max recharge rate.

You want the two elec systems isolated: HV and 12V batt. If the HV battery was always recharging the 12V batt, even w/ car off, you run the danger of having two problems instead of one. Also you will have WORSE MPG. People leaving an interior light that normally causes the 12V to become discharged and possibly to weak to make the car READY, now will cause the HV batt to become weaker.

It is in your interest to regularly recharge the 12V batt on your own, esp if you do NOT drive a lot. Let's say at least 30min/day or at least 2hrs/wk. The more you drive AND for LONGER DURATION, the greater the 12V batt will always be fully recharged and live a longer life, than a 12V batt that stays in a state of discharge.

Lastly, if you listen to the radio for prolonged periods of time, best to listen in READY mode. The HV batt will maintain the 12V batt, and the engine will kick in as the car determines it needs to. If you are in an enclosed garage, probably best not to do READY mode due to CO (even though today's cars have much lower levels of CO output). Listening to the radio in ACC(essory) mode for prolonged periods will just drain the 12V batt, and could force the need to jump the car.

Toyota can come out w/ a million TSBs and programming changes to the 12V DC-DC charging bus, but the problem will always remain:
1) all the dang original electronics (ie Smart Keys) and owner aftermarket installed accessories (ie dash cams always running when car is OFF) presenting a constant drain on 12V battery.
2) owners not aware/instructed to turn off smart key when vehicle not being used for a period of time (ie vacation).
3) owners not aware of how the Toyota Hybrid/PHEV charging system works. Short trips BAD. Not driving enough (duration wise) BAD.
4) owners listening to radio in ACC(essory) mode for prolonged periods, BAD.
5) owners not aware of importance of keeping 12V batt fully charged as much as possible is to their benefit. Longer 12V batt life, less likely hood of requiring a jump.
 

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Our 2020 Rav4 and our other previous and current vehicles are routinely left unattended for two to three weeks at a time in both cold and warm weather, operated for short trips, left in acc mode until it times out and put back in acc again. None of them ever required boosting or charging. Generally get eight or ten years out of batteries. Just lucky, I guess!
 

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Discussion Starter · #10 ·
Just curious, can you clarify “didn’t start”? Did the Ready light come on? In summer weather, mine often doesn’t start the ICE until I’ve driven it down the block a bit, especially if the HVAC is not demanding heat.
Hi,
Wish I could say for sure, but I was not looking that closely. A few lights in the instrument cluster definitely came on each time I attempted a start, but can't say if the Ready light came on.

Gary
 

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If the 12 volt is dead, but the HV has a charge, why can't you just drive off in EV mode? No, I don't own one, so I'm obviously missing something.

Just seems like you should be able to totally remove the ICE and still drive. Works for Tesla and the new Mustang and a few other cars.
 

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You are incorrect about the 12V battery on Tesla and Ford.

Toyota, Tesla, and Ford, use a 12V to power the computers to get the car "started". A discharged/dead 12V, the car won't function b/c the computers do not have sufficient power levels (12V). If the computers are not properly powered, the HV battery and electric motors will not allow the car to move. Also, the 12V has a safety function. Read this link to see that the Ford Mustang EV got "bricked" due to discharged/dead 12V battery.

For Toyota, the 12V also acts as a redundant fail safe for the pressurized brake accumulator. Toyota Hybrids and PHEV lack constant vaccum, as the engine is NOT running continusouly. To compensate for that there, is a pressurized brake fluid device, that stores pressurized brake fluid, so you have "power brakes" available at all times. The accumulator also has capacitors as the primary power supply. The 12V battery acts as a secondary redundant back-up supply should the capacitors fail. The car will let you know if the there is anything wrong w/ the brake accumulator; you'll see warning lights/messages, and hear a safety tone (if the capacitors fail) to further reinforce the need to pull over immediately and stop driving the car. I imagine all auto makers with Hybrids/PHEV/EV employ a similar braking design: high pressure accumulator for "power brakes," capacitors as a primary power supply, and the 12V battery acting as a redundant back-up power supply for the brake accumulator.

Lets not forget, the 12V powers the hazzard lights at ALL times. This is important in an accident. When Tesla's are involved in a severe accident, their massive battery pack is switched off. If Tesla's did NOT have the 12V battery, the driver would not be able to activate the hazzards.
 

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Thanks, NameofUser. I learned a lot from your post. Like I said, I don't have have a hybrid, and am less likely now to get one. I'll bet the manual takes page of page to try to say what you did in a couple of paragraph. You should ask them for a job.
I know that electric is the future, with hybrids being a sort of bridge to that future.
I'm going to look very hard at the Corolla Cross (non hybrid) when they come out this fall. I've had the RAV for 4 years. Great car, no problems, but at my age I want to try something different. I don't need to keep a car for many years. Always looking at the "greener grass" before I end up pushing it. :D
 

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I have a Rav4Prime (SE). Is the 12V battery an AGM type?
Second question: how can the smart key system be turned on/off?

TIA.
 

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I have a Rav4Prime (SE). Is the 12V battery an AGM type?
Second question: how can the smart key system be turned on/off?

TIA.
I echo your second question. From what I can gather, there is a sequence you can press on your FOB to disable smart key on that end. Then in your infotainment settings, apparently there is another way to turn off smart entry. What I do not know is if they do the same thing or not. maybe the first just disables it on the FOB side whereas the second is the one you have to do to save the vehicle battery?
 

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3) Noco and CTEK make quality 12V AGM compatible battery chargers. The CTEKS come w/ the terminal ring eyelets that stay attached to the factory battery terminals, in addition to battery clamps. The Noco sells the terminal ring eyelets as an accessory.
Hate to hijack the thread, but I couldn’t find a definitive answer searching the forum about trickle charger/maintainer; is it ok to put the ring terminals on the 12V in the back of the hybrid and run the connector out into the cargo area to maintain the battery? My parking situation (backed into my garage) makes this ideal. Picking up my new-to-me 2019 Hybrid LE next week, wondering if this is alright. Dealer wouldn’t give me a straight answer, but I feel like that’s more to do with trying to sell me a $500 Toyota aftermarket unit than it has to do with them not being sure it’s ok.
 

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I think the Battery Tender Jr is good for AGMs. I use those exclusively on three of my vehicles. If they aren't moving, they're plugged in.
 

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Turning off your smart key (holding lock and pressing unlock twice) won’t do anything to preserve your 12 V battery while you’re away… However there is a setting in Carista (or Techstream) which is “Stop monitoring for car key signal after…” and then you can choose 0-5 days. If you choose, say, 2 instead of 5, that’s 3 fewer days your car is burning a small amount of power looking for a key signal. So I guess that can help. I don’t recall if that’s an option that can be set from the infotainment screen.
 

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Many people have had this issue unfortunately. For many the TSB fixed it - but think some still had issues after. Nevertheless, go to your dealer and ask for the related TSB.
T-SB-0095-20 is the T-SB he is referring to. It speaks specifically about a premature 12v battery drain.
 

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Thanks.

That makes sense that (I guess) they use the motor/generator to the starting with the traction battery, and the 12 volt battery is not involved starting the engine, only in running the electronics required to manage the start.

I will look into the TSB.

My understanding is that the traction battery charges the 12 volt battery. I'm wondering why it can't keep the 12 volt battery charged enough to start the car? It seemed like there was plenty of juice left in the traction battery.

I guess that if the car had not eventually started on its own, then hooking my Lithium jump pack onto the 12 volt battery would have done the job and enabled it to start?

Can anyone comment on the effectiveness of the TSB?

Gary
I have experience with the 'battery drain' TSB. I bought my RAV4 Ltd hybrid on a Tuesday, (demo model with >7k miles on it) sat in my garage Wednesday, and was deadern' a doornail on Thursday. Found the TSB on this forum, had the car towed to my local dealer (not the dealer I bought the car from), and they checked everything out for me. Nothing else amiss, did the TSB service and it's been fine since. Never going back to where I bought it...obviously.
 
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