dead batteries in 2023 rav 4 hybrid

[ERD50]

OK. I believe you.

One cannot get [-]squeeze blood from a turnip[/-] jumpstart off a dead battery. A merely weak one, maybe.

Well, yes you can (to a degree)!

I think it was DD's jump-starter/charger, or maybe another I was reading about. They actually included a boost switching supply to charge that cap/battery from a near-dead battery.

For a cap especially, that would make sense, you really want to get those caps charged up to 14.1V (IIRC, that's a typical max charge voltage a car supplies) for max energy storage. Getting to 14.1V could provide just enough ooomph to get that engine turned over, vs a direct charge from a lowly 12 V or less from a shorted cell.That voltage is going to drop real fast, once that load is applied.

-ERD50

 

[Chuckanut]

Hybrid 12 volt batteries are dinky things since theyu don't have to turn over a big engine to start the vehicle. They basically provide enough juice so that when the car is started the computer and other electronics can be activated. I assume the Big Boy Traction Battery under the rear seat provides the power to turn over the engine when it is needed.



I've had the car parked for as long as 3 weeks and it has started up just fine.

 

[NW-Bound]

Hybrid 12 volt batteries are dinky things since theyu don't have to turn over a big engine to start the vehicle. They basically provide enough juice so that when the car is started the computer and other electronics can be activated. I assume the Big Boy Traction Battery under the rear seat provides the power to turn over the engine when it is needed.

Then, perhaps get rid of the dinky 12V, replace it with a capacitor charged with a DC converter off the traction battery.

If they don't do it, there must be a reason. Anybody knows why?

 

[ERD50]

Somewhat related to all this: I was curious about replacing my car battery when it needs it, whether I could use a Lithium instead of lead-acid. I thought I saw some automotive looking LFP (LiFePO4) 12V for sale. I know they'd be more expensive, but since they can be charged from near 0 to 100% so much faster than a lead-acid, I thought it might be good in a power outage. It would take a lot less driving around or idling to recharge the LFP, if I depleted it using my inverter to run some 'emergency' stuff.

But I quickly learned that's a no-go. A Lead-Acid will supply >600 Amps cranking, but even a large LFP is limited by the FETs in its battery management system (they open to keep it from discharging too low, or being charged too high), to 100 or 200 A.

Also, when approaching full charge, it will open those FETs, and now the car no longer has a battery connected, which is needed to provide a load to the alternator, and to provide burst currents.

-ERD50

 

[NW-Bound]

There are 2 more reasons you cannot use an LFP battery in a car without redesigning.

1) LFP cell makers tell you not to subject the cells to 140F and hotter. The cells die quickly.

2) LFP batteries have such a low resistance that they may cause the alternator to burn out. Alternators have a built-in voltage regulator which in the presence of a low resistance battery will force the alternators to put out large currents and burn out.

LFP chargers, in fact all lithium cell chargers, are of the constant-current/constant-voltage type. Initially, the chargers put out a fixed current that is matched to the battery specifications. The battery voltage slowly rises, and when it reaches the maximum voltage, the charger will maintain the voltage there while the battery continues to absorb more charge. The current will slowly decay as the battery gets fuller and fuller, until a terminal current value is reached, and the charging is declared complete.

At charge termination, the charger removes the charging voltage. As the battery is at rest, its voltage will slowly decay to a lower value. This is similar to the behavior of a lead-acid battery. The at-rest voltage depends on the lithium cell chemistry.

You don't want to maintain the cell terminal charging voltage when the cell is full. Doing so causes the cell to lose capacity with time.

 

[zinger1457]

I have a Toyota Avalon hybrid, when I travel for an extended period (more than a week or two) I just disconnect the cable from the negative terminal on the battery. For the Avalon hybrid the battery is located in a compartment in the trunk, takes a minute to disconnect once you become familiar with it. Was gone for 1.5 months earlier this year and it started up like a champ once I reconnected the cable to the battery terminal. Car is 4.5 years old and still on the original battery.

 

[Koolau]

I have a Toyota Avalon hybrid, when I travel for an extended period (more than a week or two) I just disconnect the cable from the negative terminal on the battery. For the Avalon hybrid the battery is located in a compartment in the trunk, takes a minute to disconnect once you become familiar with it. Was gone for 1.5 months earlier this year and it started up like a champ once I reconnected the cable to the battery terminal. Car is 4.5 years old and still on the original battery.

Any problems with electronics ( as simple as the clock needing reset when you do this??)

 

[frank]

when I disconnect the battery in my prius I usually need to reset the calendar and the clock. the calendar goes all the way back to the date of manufacture, but it is an easy thing to reset.

 

[JoeWras]

It also resets engine and emissions parameters. This is under the covers. Not a huge deal, although you may fail emissions and for a "not ready" if you do this too soon before inspection.

Having to routinely disconnect the battery is a broken design or sign you need a new battery.

 

[ERD50]

It also resets engine and emissions parameters. This is under the covers. Not a huge deal, although you may fail emissions and for a "not ready" if you do this too soon before inspection.

Having to routinely disconnect the battery is a broken design or sign you need a new battery.

+! - that "not ready" is needed, but poorly implemented. For those not aware, if you do anything that erases the Check Engine Light faults (surprising that a battery removal would do this, isn't non-volatile memory cheap these days?), many of the patrameters will read "not ready" until the car goes through enough drive cycles for the unit to determine that parameter is "good", not just "not bad right now".

The problem in the implementation, is the needed "drive cycle" isn't clearly documented, and would not be easy to know if you met it or not. They ought to give some sort of indication of "not ready" to the driver (like Flash X times at start up, or flash occasionally?). But no, the light just goes off, and the driver thinks all is good.

I have one of those cheap plug in Bluetooth units that couples with an app on my tablet/phone, and that will tell me. But the average owner isn't going to do that, and the solution is so simple, it's nuts they don't do this. You can easily waste a trip to the testing place, and then you still won't know when to try again - no feedback at all. Very poor design.

Mine is 10 YO and no longer available, but something like this:

https://www.amazon.com/dp/B078RMMMXL


-ERD50

 

[youbet]

Don't know about a hybrid, but seems to me that modern ICE cars start so easily (computer control, good spark, fuel injection) that they barely turn over at all before they start. I'm not sure you get much warning anymore, no whirrr-whirrr-whirr, putt, whirr, putt,putt, VROOOMM!!!. Just click, whirr-hummmmmmmm.

I'll make a point to listen next time, but IIRC, even in cold weather, they barely turn over before they start. So good one day, then the next, they just can't get it to turn hardly at all.

-ERD50

Yeah, that makes sense. I've never owned a "modern" ICE vehicle. I currently have a 1999 F150 V8 and a 2018 Prius. (Guess which one we tow the camper with......... ). Before the Prius, we had a 2000 Accord. So, my experience with my older ICE cars is having them crank for 2 - 3 seconds before firing. When the battery is low or near EOL, the cranking becomes strained and slower warning me to think about just how long I've had that particular battery parked under the hood.

With the Prius, I can't say I've ever actually heard the engine crank. The 12V battery is still the original so perhaps time to change it before before one day I get in and push the button and nothing happens.

 

[youbet]

when I disconnect the battery in my prius I usually need to reset the calendar and the clock. the calendar goes all the way back to the date of manufacture, but it is an easy thing to reset.

Good info. So far, I've used one of those little battery maintainers on the Prius while we're away to someplace warm in the winter.

 

[youbet]

I can only tell you what happened to me. When the RAV4 wouldn't start, I tried both my capacitor jumpers and they didn't w*rk. It just wasn't enough to over come a (likely) dead cell. YMMV

Thanks to DW not fully shutting her door, the dome light on our old F150 stayed on for several days draining the battery too far to start the engine. I grabbed the capacitor jumper I keep under the seat and it just wouldn't do the job. Wound up grabbing my trolling motor battery from the garage which took care of the problem.

 

[Koolau]

Thanks to DW not fully shutting her door, the dome light on our old F150 stayed on for several days draining the battery too far to start the engine. I grabbed the capacitor jumper I keep under the seat and it just wouldn't do the job. Wound up grabbing my trolling motor battery from the garage which took care of the problem.

Back in the day, there was always a way to get a car going. Now, my RAV4 sits in a parking structure. We are not really allowed to "w*rk" on our cars in the garage though I eventually had a guy buy me a battery and bring it to me and install it.



In the old days, I could have tried to charge it (and find out that it had a dead short.) Whereupon, I would have borrowed a car from the family business and go get a battery. We no longer have access to an extra car, so I was stuck with some guy (with his girlfriend) bringing me a battery and trying to over charge me for it. YMMV

 

[NW-Bound]

A majority of car jumpers I see on the market now use lithium cells. I don't have one, but think that they would be much better than the old ones using sealed lead-acid cells.

Lithium cells have extremely low self-discharge, ensuring that when you need them they still have some charge.

 

[Koolau]

A majority of car jumpers I see on the market now use lithium cells. I don't have one, but think that they would be much better than the old ones using sealed lead-acid cells.

Lithium cells have extremely low self-discharge, ensuring that when you need them they still have some charge.

I have used the small lithium jumpers and they do w*rk (until you have a dead cell.) It's truly hard to believe when they w*rk because they weigh maybe a pound and are the size of a paper-back novel. Unreal!

 

[JoeWras]

+! - that "not ready" is needed, but poorly implemented. For those not aware, if you do anything that erases the Check Engine Light faults (surprising that a battery removal would do this, isn't non-volatile memory cheap these days?), many of the patrameters will read "not ready" until the car goes through enough drive cycles for the unit to determine that parameter is "good", not just "not bad right now".

The problem in the implementation, is the needed "drive cycle" isn't clearly documented, and would not be easy to know if you met it or not. They ought to give some sort of indication of "not ready" to the driver (like Flash X times at start up, or flash occasionally?). But no, the light just goes off, and the driver thinks all is good.

I have one of those cheap plug in Bluetooth units that couples with an app on my tablet/phone, and that will tell me. But the average owner isn't going to do that, and the solution is so simple, it's nuts they don't do this. You can easily waste a trip to the testing place, and then you still won't know when to try again - no feedback at all. Very poor design.

Guess what? SOME manufacturers do exactly as you suggest! I kid you not. When I bought my Honda with 201k miles and emissions issues, I used this. I don't think it is a standard. On Honda, it blinks a bunch of times if emissions are not set. Here's one source: https://justsmogs.com/2016/08/check-obd-ii-monitor-readiness-without-a-scan-tool/

That said, I believe just about everyone who has a car over 7 years old or 100k miles should have a scan tool. It is probably the most useful tool I bought in the last year. It is also a cheap bluetooth unit for about $30 (and you found one for $14!). Very, very useful when you have older cars.

Emissions testing with OBDII is a mystery and somewhat proprietary for each manufacturer. Honda is known to be a PITA to get EVAP to pass. I tried all the tricks like cruising at 55mph, then coasting to 5mph multiple times. Nothing worked. I had 500 miles and this one wouldn't set. I probably would still pass state tests because they know this is tough. But I wanted it set!

Then I forgot about it. One day I looked using my scanner (only about 100 miles later), and it passed. No idea why.

So it took 600 miles after clearing codes to set an emissions parameter. That's why I think disconnecting your battery on a routine basis is not a good idea.

 

[ERD50]

Guess what? SOME manufacturers do exactly as you suggest! I kid you not. When I bought my Honda with 201k miles and emissions issues, I used this. I don't think it is a standard. On Honda, it blinks a bunch of times if emissions are not set. ....

Good to know some mfg are doing this. It really should have been a standard part of the OBD specifications, as well as a 'morse code' for the error (these could get long though), or displayed on the info screen that most cars have these days.

-ERD50

 

[Koolau]

Good to know some mfg are doing this. It really should have been a standard part of the OBD specifications, as well as a 'morse code' for the error (these could get long though), or displayed on the info screen that most cars have these days.

-ERD50

Or maybe just a big, permanent sign on the dash: Don't be disconnecting the battery cable, dummy!

 

[swabby01]

Confession Time - Not a RAV4 but a Lexus Hybrid. First week I owned it I was doing international travel and did not want to leave it at the airport. Parked it in my garage and did NOT shut the motor down correctly - first hybrid, no noise of the engine - shut the door and left. Returned to a dead battery ALL MY FAULT. Charged battery back up and have never had an issue since and the battery is now five years old. Special note: another lesson I learned is that the battery was in the back of the SUV and the rear lift gate was only electric. Figured it out but that falls into the category of "needs better design" in my opinion

 

[ken830]

I'm wondering if OP is referring to software bugs that cause the car to drain the 12V while the vehicle is sitting and fail to re-charge it from the traction battery. This is a similar problem Toyota has with the bZ4X:

 

[freedomatlast]

the 12v in my prius lasted 11 years with no problems that is why I was surprised at the problem with the new rav.

The issue with the newer Rav's wasn't an issue with the battery itself, it was an issue with a parasitic electrical drain on the system causing the batteries to fail prematurely.

 

[JoeWras]

The issue with the newer Rav's wasn't an issue with the battery itself, it was an issue with a parasitic electrical drain on the system causing the batteries to fail prematurely.

Proposed class action: https://www.classaction.org/news/20...asitic-battery-drain-defect-class-action-says

I still think Toyota is the best. However, I am getting surprised by the number issues popping up with them. Honda is even worse. These were two companies that made bullet proof vehicles, and it seems like the complexity is getting the best of them and things are slipping through.

 

[Koolau]

Proposed class action: https://www.classaction.org/news/20...asitic-battery-drain-defect-class-action-says

I still think Toyota is the best. However, I am getting surprised by the number issues popping up with them. Honda is even worse. These were two companies that made bullet proof vehicles, and it seems like the complexity is getting the best of them and things are slipping through.

I suspect that car companies are being "pushed" to start turning out more EVs and hybrids. In the process, stuff slips through the cracks. Additionally, it used to be, you bought a car, got in and drove it. You didn't really need the "book" because one car was pretty much like another. Now, they're not only all different, they're different from anything you ever drove before. You should absolutely sit down and read the manual before you drive the car. BUT, I'm sure Toyota doesn't want to insist you sit down and take an hour test on your car before they hand you the keys.

 

[meierlde]

when I disconnect the battery in my prius I usually need to reset the calendar and the clock. the calendar goes all the way back to the date of manufacture, but it is an easy thing to reset.

If the car is new enough, it may listen in on the fm band for signals that will reset the time. My 2016 malibu did this for example when crossing time zones.