I personally WOULDN'T DO IT !
Electronic problems are very likely !

 

I think you are backwards. Jumping another car, except another hybrid, from a hybrid/prime will fry your expensive electronics. The boosters were designed specifically for doing this, instead of using your expensive car. I will never let a pair of jumper cables touch my hybrid to give or accept a boost. Always use the booster pack.

 

Why can you not use a NOCO booster? I thought they made it to do just this?? Are you looking at the disclaimer they put on their units to protect themselves??

No. I have been advised by the factory not to do so, and I have a friend who did it on a car like mine but the previous model who tried with the NOCO, and he fried both the engine and DCT ECU. Funny thing is that my owners manual for the car with the dead battery states that it can be done with a booster, but my car ran out of warranty last year and is going up for sale, so why take a chance.

But I hear you all and I will take your advice to heart - thank you. I've just ordered a CTek Pro 25S so if nothing else, I can try and get the battery going that way.

 

And by the way, the 12 volt system is always being charged/maintained when the car is in READY mode. The ICE is not needed to charge the 12 volt battery. In any case, as previously noted, the manual says to never use the car to jump start an ICE vehicle. Only jump starts of other hybrids is permitted.

 

Don't do it!

 

Can't use a Noco Booster as there's a high risk of frying stuff in the car with the dead battery doing this as per the manufactures recommendations and warnings.

Why can you not use a NOCO booster? I thought they made it to do just this?? Are you looking at the disclaimer they put on their units to protect themselves??

 

The problem people have had jumping a hybrid with a booster pack is the short leads on the booster pack cables. The owners manual clearly shows the proper negative connection way over on the far side of the engine. This is to protect the sensitive electronics near the fuse box under the hood. They use any old ground within reach of the cable they have and risk frying the electronics. Use the proper jump points and you will be fine. This will mosy likely require using an additional cable to extend the reach.

 

So the car in question that needs to be jumped, is not a hybrid - nor was the car that belongs to my friend who fried the ECU and TCU with a NOCO. From what I understand, if the 12 volt battery goes dead on the Prime, disconnect it and charge it.
On the car with the dead battery, one is supposed to remove the battery compartment cover which is in the passenger footwell after which you attach the positive lead to a jump connector on the top of the fuse panel which is situated on top of the battery with the battery ECU, and then ground to the bracket that holds the battery inside of the compartment. This is how the owners manual of the ICE car want you to connect for a jump start. My biggest fear here is to damage both the Prime and the ICE car as I have no experience jumping from a hybrid to an ICE car. But if the owners manual of the Prime says it's a nono to use the Prime as a power source, then that's how it is.

Speaking of jumping and charging the 12 volt battery on the Prime. Does anyone know if some kind of dealer reset is needed if one disconnects the 12 votl battery in the Prime? Just curious in case I need to change or charge the AGM in the Prime.

Thank you again all

 

So the car in question that needs to be jumped, is not a hybrid - nor was the car that belongs to my friend who fried the ECU and TCU with a NOCO.

In the olden days, cars were much simpler and it was easy to jump start. The only thing you had to remember was to make the last connection (the ground) away from the battery, so you lessened the risk of a spark igniting the fumes from the battery.

Today with the sophisticated electronics in all cars, you have to ensure the proper jump points are being used to protect the electronics. I no longer carry jumper cables, just the jumper pack. I know how to safely jump my own car and will not let anyone else do it. I will let someone borrow my jumper pack, but I will not connect it for them. They have to connect it and shield me of any risk of hooking it up wrong.

I have heard of connecting the jumper cables/jump pack and just letting it sit to allow the dead battery to accept some level of charge from the jump source. This would help reduce the demand on the jumped car's charging system by getting some level of charge on the dead battery.

If your battery is dead, it is probably too late to try to use a battery pack to preserve the settings. It might work if it is still partially charges, but then again the partial charge might be enough to not need to charge externally.

The car manual should have a list of things that might need to checked/reset after reconnecting the battery. Here is from my car's manual.

 

Thank you for the details. Yes, it used to be a lot easier. It's kind of insane to think about how many ECU's are in some cars these days, and all of them can be damaged from a wrong jump etc.

I think I did the right thing by just getting a charger that can at least get the battery to a point where the car will start. That's all I need. Fingers crossed.

 

I know about transient electrical currents when first turning on electronics. And I know about how little current it takes to fry these micro-chips. But, what gets me confused is putting a jump pack on a weak battery to give it enough boost to start an ICE. Is it not like putting another battery in parallel which is similar to having a single battery??

I do know that when hooking up the batteries together, that a single spark can cause all sorts of havoc with electronics. Some can be permanent damage. Even just installing a single battery, if there is spark then it can cause weird things to happen. Well, everyone seems to know more than I do. That is why I am here to learn.

 

Think of it this way. When you hook up a battery charger, you are really applying a voltage across the weak battery. The weak battery (lower voltage) and the battery charger (higher voltage) will attempt to equalize, but the battery charger will maintain the voltage until the battery reaches the proper charge level.

When you connect the jump pack, you are also applying a voltage across the weak battery. The same sort of equalization will happen, but the jump pack has a fixed amount of power, so it's voltage will drop as the weak battery increases its voltage. The rate each battery will change is related to the amp hour capacity of the batteries.

 

I understand that the optimal solution is to put the booster directly on the 12 Volt battery in the trunk!

 

That is very inconvenient because that battery is buried below several panels. Better to use the. Designated point in the engine compartment and use the ground point on the engine as shown in the owners manual.

 

i would steer away. use a little boost battery. if you try make sure the ICE engine is running else you are giving a jump start from a car that is effectively off

 

if you try make sure the ICE engine is running else you are giving a jump start from a car that is effectively off

The engine running has nothing to do with the available power from the 12V as there is no alternator on these cars.

OP's question has largely been answered. Toyota says not to jump another vehicle with the RAV4 Prime. Doing so puts you at risk of an expensive repair.

 

You could use the 12 volt battery in your Prime to "jump" another Toyota Hybrid, but NOTHING ELSE. The reason for this is because Toyota Hybrids only need about 1000 watts of power (83 amps) for the first couple of seconds to start up the brake booster pump, the power steering booster, and the various computers and instrument panel lights. After this start-up surge is completed, the power needed by the computers is about 42 amps (500 watts). Once the computers boot up, which takes no more than 5 seconds total, the traction battery will supply 12 volt power via the DC converter, recharging the week or dead 12 volt battery and you can disconnect the jumper cables.

But if the car needing a jump start is, say, a "regular" Toyota ICE car, meaning not the Hybrid models, or any other car that's not a Toyota Hybrid, the donor car has to have a battery with enough current capacity, called "cold cranking amps" on the battery label, to supply up to 700 amps (and maybe a lot more in very cold weather) to crank the starter motor fast enough for the gas engine to start and thus to spin the alternator. The battery in your Rav4 Hybrid or Rav4 Prime isn't designed to supply 4 or 5 kilowatts of cranking power for a conventional starter motor, or even the heat pump motor, which is a 3-phase synchronous motor which is powered from the traction battery through the a/c Inverter.

Another thing to keep in mind is that the electrical system in your Rav4 Prime is connected to about a dozen different computers, each of which is extremely sensitive to voltage surges. Jump starting another car off of the 12 volt battery in your Rav4 exposes your car to the risk of a "kick-back" voltage surge from the other car that could damage some very expensive components in your Rav. It's really not recommended by Toyota to jump start other cars off of any of their Hybrid models, and ultimately, you simply can't jump start a conventional ICE car anyway because the puny batteries in Toyota Hybrids aren't powerful enough to crank a 12 volt engine starter motor.

If it's YOUR OWN Rav4 Prime that has the dead battery, and you need to jump start your car from someone else's, you can do so if you are careful and follow this procedure:
1. First you have to get into your car. If it's locked and the battery is dead and the windows are all rolled up, you use the emergency mechanical key that's part of your fob to unlock the driver's door. You should practice this procedure so that you will know what to do in an actual dead battery situation. You will need light-duty (8 gauge or 10 gauge) jumper cables, 20 foot long ones are usually sufficient. Buy a set and store them under the driver's seat, or somewhere that you can get at them easily (NOT in the spare tire well! You can't open the rear hatch if the battery is dead!)
2. CRITICALLY IMPORTANT! The engine in the donor car MUST NOT be running! If it is, turn it off and remove the key from the ignition so that no one can start the car by mistake. The reason for having the donor car's engine not running, is that you don't want to risk a voltage surge traveling through the jumper cables between the two cars, and there's a substantial risk of this if the donor car's engine is running. A voltage surge could damage computers in your car.
3. Once you have unlocked the driver's door with the emergency mechanical key, open the hood. You won't be able to open the rear hatch yet since there's no way to unlock it short of crawling back there and popping it open with the emergency mechanical latch button.4. On the driver's side of the engine bay, there's a fuse box. Pop this open and locate the emergency jump start terminal. It has a plastic flip-up cover to insulate it. Flip the cover open, and attach the red jumper cable between it and the red (positive +) terminal of the donor battery. This photo is from a Rav4 Hybrid; the Prime has the same terminal.

5. Over toward the left side of the engine, there's a hunk of aluminum sticking out towards the front of the car that looks like a handgrip. This is where you attach the Black jumper cable to the Negative (-) terminal of the donor battery. Remember that in modern cars, the electrical system is Negative Ground, meaning that the engine block, the car's steel body panels, and the various framing and suspension pieces are all electrically connected to the Negative battery terminal.

6. Once the two jumper cables are connected, double check that the engine in the donor car isn't running, then get into your Rav, and start it the usual way (press on the brake pedal and push the power button). If the battery in your key fob is weak, the car might have trouble sensing it, in which you might need to take a moment here to replace the fob battery, too.

7. Once the READY light on your instrument panel is lit, it means that that power is flowing from your traction battery to re-charge the 12 volt battery, and you can disconnect and stow the jumper cables. NOTE: Let the car idle in READY mode for at least 30~45 minutes, or drive it somewhere for that long, to allow the 12 volt battery to recharge.

8. Clearing Trouble Codes. Here's where you might want to invest $40 in an OBD-II bluetooth scan tool, and install the Car Scanner app on your phone. When your 12 volt battery goes dead in a 2023 Rav4 Hybrid or Prime, the Check Engine Warning Light will be lit after you jump start the car, and there will be 3 or 4 trouble codes stored in the Engine Control Unit. This is ridiculous, and I can't imagine why Toyota would ever think that just because the 12 volt battery went flat, that a trouble code needed to be generated. But the fact remains that you will either have to ignore that warning light on the dash, or go to a mechanic/dealership to get it cleared, or clear it yourself with an OBD-II scan tool. Dead batteries in Toyota Hybrids happen often enough that, in my opinion, Toyota should give owners a scan tool with the car, same as they give you a key fob. BTW, I'm still waiting on my second fob, too. Grrrrrr!

NOTE: On my 2023 Rav4 Prime, I have had the 12 volt battery go dead on me 3 times in just the first 3 months of ownership, due to leaving a Dome light on, or leaving an OBD-II scanner plugged in overnight. There is supposed to be a timer that turns off the dome lights after 30 minutes, but I think there are certain circumstances wherein this timer gets bypassed and the dome light in the cargo bay won't automatically turn off. Also, the emergency flashers will never automatically turn off, and it looks like at least some models of OBD-II scanners don't have auto-off timers. Anyway, everybody who owns a Toyota Hybrid needs to carry jumper cables and know how to jump start their car. I had to do this a half-dozen times in my 2029 Prius Prime in the 4 years I owned it. The 12 volt batteries in these Hybrids are tiny, and they just have no reserve capacity. I killed the battery in my Prius once just by having the car's radio playing for a couple of hours in Accessory Mode one afternoon while I was working on the car.

 

You could use the 12 volt battery in your Prime to "jump" another Toyota Hybrid, but NOTHING ELSE. The reason for this is because Toyota Hybrids only need about 1000 watts of power (83 amps) for the first couple of seconds to start up the brake booster pump, the power steering booster, and the various computers and instrument panel lights. After this start-up surge is completed, the power needed by the computers is about 42 amps (500 watts). Once the computers boot up, which takes no more than 5 seconds total, the traction battery will supply 12 volt power via the DC converter, recharging the week or dead 12 volt battery and you can disconnect the jumper cables.

But if the car needing a jump start is, say, a "regular" Toyota ICE car, meaning not the Hybrid models, or any other car that's not a Toyota Hybrid, the donor car has to have a battery with enough current capacity, called "cold cranking amps" on the battery label, to supply up to 700 amps (and maybe a lot more in very cold weather) to crank the starter motor fast enough for the gas engine to start and thus to spin the alternator. The battery in your Rav4 Hybrid or Rav4 Prime isn't designed to supply 4 or 5 kilowatts of cranking power for a conventional starter motor, or even the heat pump motor, which is a 3-phase synchronous motor which is powered from the traction battery through the a/c Inverter.

Another thing to keep in mind is that the electrical system in your Rav4 Prime is connected to about a dozen different computers, each of which is extremely sensitive to voltage surges. Jump starting another car off of the 12 volt battery in your Rav4 exposes your car to the risk of a "kick-back" voltage surge from the other car that could damage some very expensive components in your Rav. It's really not recommended by Toyota to jump start other cars off of any of their Hybrid models, and ultimately, you simply can't jump start a conventional ICE car anyway because the puny batteries in Toyota Hybrids aren't powerful enough to crank a 12 volt engine starter motor.

If it's YOUR OWN Rav4 Prime that has the dead battery, and you need to jump start your car from someone else's, you can do so if you are careful and follow this procedure:
1. First you have to get into your car. If it's locked and the battery is dead and the windows are all rolled up, you use the emergency mechanical key that's part of your fob to unlock the driver's door. You should practice this procedure so that you will know what to do in an actual dead battery situation. You will need light-duty (8 gauge or 10 gauge) jumper cables, 20 foot long ones are usually sufficient. Buy a set and store them under the driver's seat, or somewhere that you can get at them easily (NOT in the spare tire well! You can't open the rear hatch if the battery is dead!)
2. CRITICALLY IMPORTANT! The engine in the donor car MUST NOT be running! If it is, turn it off and remove the key from the ignition so that no one can start the car by mistake. The reason for having the donor car's engine not running, is that you don't want to risk a voltage surge traveling through the jumper cables between the two cars, and there's a substantial risk of this if the donor car's engine is running. A voltage surge could damage computers in your car.
3. Once you have unlocked the driver's door with the emergency mechanical key, open the hood. You won't be able to open the rear hatch yet since there's no way to unlock it short of crawling back there and popping it open with the emergency mechanical latch button.4. On the driver's side of the engine bay, there's a fuse box. Pop this open and locate the emergency jump start terminal. It has a plastic flip-up cover to insulate it. Flip the cover open, and attach the red jumper cable between it and the red (positive +) terminal of the donor battery. This photo is from a Rav4 Hybrid; the Prime has the same terminal.

View attachment 199355

5. Over toward the left side of the engine, there's a hunk of aluminum sticking out towards the front of the car that looks like a handgrip. This is where you attach the Black jumper cable to the Negative (-) terminal of the donor battery. Remember that in modern cars, the electrical system is Negative Ground, meaning that the engine block, the car's steel body panels, and the various framing and suspension pieces are all electrically connected to the Negative battery terminal.

View attachment 199356

6. Once the two jumper cables are connected, double check that the engine in the donor car isn't running, then get into your Rav, and start it the usual way (press on the brake pedal and push the power button). If the battery in your key fob is weak, the car might have trouble sensing it, in which you might need to take a moment here to replace the fob battery, too.

7. Once the READY light on your instrument panel is lit, it means that that power is flowing from your traction battery to re-charge the 12 volt battery, and you can disconnect and stow the jumper cables. NOTE: Let the car idle in READY mode for at least 30~45 minutes, or drive it somewhere for that long, to allow the 12 volt battery to recharge.

8. Clearing Trouble Codes. Here's where you might want to invest $40 in an OBD-II bluetooth scan tool, and install the Car Scanner app on your phone. When your 12 volt battery goes dead in a 2023 Rav4 Hybrid or Prime, the Check Engine Warning Light will be lit after you jump start the car, and there will be 3 or 4 trouble codes stored in the Engine Control Unit. This is ridiculous, and I can't imagine why Toyota would ever think that just because the 12 volt battery went flat, that a trouble code needed to be generated. But the fact remains that you will either have to ignore that warning light on the dash, or go to a mechanic/dealership to get it cleared, or clear it yourself with an OBD-II scan tool. Dead batteries in Toyota Hybrids happen often enough that, in my opinion, Toyota should give owners a scan tool with the car, same as they give you a key fob. BTW, I'm still waiting on my second fob, too. Grrrrrr!

NOTE: On my 2023 Rav4 Prime, I have had the 12 volt battery go dead on me 3 times in just the first 3 months of ownership, due to leaving a Dome light on, or leaving an OBD-II scanner plugged in overnight. There is supposed to be a timer that turns off the dome lights after 30 minutes, but I think there are certain circumstances wherein this timer gets bypassed and the dome light in the cargo bay won't automatically turn off. Also, the emergency flashers will never automatically turn off, and it looks like at least some models of OBD-II scanners don't have auto-off timers. Anyway, everybody who owns a Toyota Hybrid needs to carry jumper cables and know how to jump start their car. I had to do this a half-dozen times in my 2029 Prius Prime in the 4 years I owned it. The 12 volt batteries in these Hybrids are tiny, and they just have no reserve capacity. I killed the battery in my Prius once just by having the car's radio playing for a couple of hours in Accessory Mode one afternoon while I was working on the car.

Good info. I hadn't looked into Jumping batteries, but now i can give an answer to someone with a dead battery... Sorry, "My car with all the EV and computer stuff will be damaged if I try to jump you!"
Key fob... 9 months for me to receive my #2 Fob. (I Believe this is the standard wait time) On my phone Toyota app I saw a notification under Health and Alerts (Main Screen) When i clicked on it it stated, "Your 2nd key is now available at your dealership L.H.M." You should call them once you receive the notice to set a appointment. If the parts department is smart enough... you can give them the code on your existing Fob. They can compare it to the received Fob to see if it matches. I skipped this part and the dealership had my R4P for 3 days waiting on the correct Fob to be delivered.

 

so i bought a '24 Prime a few weeks ago and have ordered a 3000 amp portable jump starter - will that work to jump the 12 volt battery in my Prime if it goes dead?

Yes.

This is the one I have, and I extended one cable so it can reach the recommended grounding point.

 

Yes.

This is the one I have, and I extended one cable so it can reach the recommended grounding point.

View attachment 202570

View attachment 202571

I'd be interested to hear how you extended the negative lead. is the wire spliced or did you open the adaptor and replace with a longer wire?

 

Save yourself and a friend unnecessary headache and expense. Call AAA for him. I carry a Jump charger that you can power from cig lighter to charge the battery. Let them use this $80 part if they are desperate. Don't fry your $50k car.

 

Just curious, even with the precautions and following that bulletin, if the ecu got fried, if toyota would honor a new ecu under warranty. I would not expect to have ecus readily available.
in all my years of owning toyota hybrids, i have replaced batteries, but jump starting, never, not even once. 🙏🏼

 

Just curious, even with the precautions and following that bulletin, if the ecu got fried, if toyota would honor a new ecu under warranty. I would not expect to have ecus readily available.
in all my years of owning toyota hybrids, i have replaced batteries, but jump starting, never, not even once. 🙏🏼

Toyota can tell if the ECU got fried as a result of improper ground connection on the jump cable. If you use the ground point as described in the manual, the ECU circuit board will not burn in the way that is shown in the tech bulletin.