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12V battery charging / depletion

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#41 ·
NoelinColorado said:
I guess the practical application is if you've left the car in the garage for a couple of months okay to open the garage door, 'start' it (put it in Ready mode), and leave for 30min and call it good.
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That should work. From what I've read the ICE will only start if the TB is below some threshold. Otherwise, the car should just charge the 12V battery from the TB when put into ready mode.
 
#42 ·
JetStream said:
From what I've read the ICE will only start if the TB is below some threshold.
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The Owner's Manual states otherwise:

2021 Toyota RAV4 Prime Owner's Manual said:
EV driving may be canceled automatically in the following circumstances:
  • When vehicle speed is more than approximately 84 mph (135 km/h).
  • When power is needed temporarily, for example when the accelerator pedal is depressed firmly or when accelerating suddenly.
  • When the temperature of the hybrid system is high. The vehicle has been left in the sun, driven on a hill, driven at high speeds, etc.
  • When the temperature of the hybrid system is low.
  • When the heater is switched on when the outside temperature is below about 14°F (-10°C).
  • When the windshield defogger switch is pressed.
  • When the system determines that the gasoline engine needs to be started.
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Those cover basically every scenario possible, especially that last condition. The engine (when in READY mode) could start at any point.
 
#43 · (Edited)
That is true but I was referring specifically to when the car is sitting idle, not in READY mode, but just sitting (as in a garage for 6 months).
I thought I read somewhere that the ICE can come on without any user intervention (ie not in READY mode) if the HV battery voltage gets too low. I'll try to find where I saw that.

Edit to add: I couldn't find anything in the manual but when I read this it seemed legit. Now that I think about it though.....it seems like this couldn't possibly be accurate since there would be nothing to stop the car from starting the ICE inside a garage and that can't be something Toyota would ever do. I'd guess the low TB voltage causing the ICE to start falls under the category of
  • When the system determines that the gasoline engine needs to be started.
and it must only be possible when the car is in READY mode. Sorry for any confusion caused.
 
#44 ·
JetStream said:
That is true but I was referring specifically to when the car is sitting idle, not in READY mode, but just sitting (as in a garage for 6 months).
I thought I read somewhere that the ICE can come on without any user intervention (ie not in READY mode) if the HV battery voltage gets too low. I'll try to find where I saw that.

Edit to add: I couldn't find anything in the manual but when I read this it seemed legit. Now that I think about it though.....it seems like this couldn't possibly be accurate since there would be nothing to stop the car from starting the ICE inside a garage and that can't be something Toyota would ever do. I'd guess the low TB voltage causing the ICE to start falls under the category of
  • When the system determines that the gasoline engine needs to be started.
and it must only be possible when the car is in READY mode. Sorry for any confusion caused.
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Right. If the engine started when the car was parked and not in Ready mode, people could die.
 
#46 ·
TJPacific said:
Looking at a 2021 RAV4 Prime XSE, and about to buy. One thing bothers me: hybrid 12V batteries are pretty notorious for depleting quickly if you use accessories (radio, 120V outlet in cargo area, etc.) if the car is not being driven, or is not on in Ready mode when parked.

The dealership is telling me: "With the RAV4 Prime, you don't have to worry about that -- you can just park the car, use accessories all you want, and the ICE engine will automatically kick in to recharge the 12V as needed to avoid depletion. (And without having to turn the vehicle on to Ready mode.)"

Anyone know if that is true or false?
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Well Toyota is not so high technology company and designing R4P they tried to mimic any other ICE car. Then you car is off, 12 volt battery feeds some electronics in your car. Without using your car for more than 30 days, your 12 volt battery will be depleted. When you start you car, it uses traction battery to charge 12 volts. The traction battery can never be depleted, because when its remaining actual charge is 13%, your ICE kicks in and you drive in HV mode. The only way to deplete the traction battery to not use your car for a very long time. Lithium Ion batteries keep charge for a long time but not forever. If it happens you may permanently damage it.
For 120 volt outlet it uses 12 volt battery. However to activate 120v outlet you must turn on your car. So your 12 volt battery feeds DC/AC inverter and the traction battery charges your 12 volt battery at the same time.
Personally I think Toyota could do a better job. Tesla's 12 volts battery is always maintained by high voltage battery. Because of that Tesla recommends to leave their cars plugged in if they not used for extended period of time. In other hand because R4P uses computer to manage charging, it takes too much juice from 12 volt battery. Leaving a car like this may deplete the 12 volt battery in few days.
 
#47 ·
brainfreeze said:
For 120 volt outlet it uses 12 volt battery. However to activate 120v outlet you must turn on your car. So your 12 volt battery feeds DC/AC inverter and the traction battery charges your 12 volt battery at the same time.
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Are you sure about that? Using the 12V to supply 1500W would require 125A, which is a whole lot of current. Using the high-voltage battery accomplishes the same task with only around 5A. There's a reason that ICE vehicles without a high-voltage battery limit their 120V outlet to around 100W.
 
#48 ·
generaltso said:
Are you sure about that? Using the 12V to supply 1500W would require 125A, which is a whole lot of current. Using the high-voltage battery accomplishes the same task with only around 5A. There's a reason that ICE vehicles without a high-voltage battery limit their 120V outlet to around 100W.
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Unlikely, I believe it uses DC-DC converter line that charges 12 volt battery. I know Toyota makes 12 to 120 volts 400W inverter DC-AC Inverters | Toyota Industries Corporation . Though the dont specify voltage for 1500 watts only stating "using the electrified vehicle's high-capacity battery". Since, mostly all inverters are designed for 12/24 volts, I assume 1500watt inverter is designed for 12 volts but maybe you are right and Toyota uses high voltage DC current for that.
 
#49 ·
brainfreeze said:
Unlikely, I believe it uses DC-DC converter line that charges 12 volt battery. I know Toyota makes 12 to 120 volts 400W inverter DC-AC Inverters | Toyota Industries Corporation . Though the dont specify voltage for 1500 watts only stating "using the electrified vehicle's high-capacity battery". Since, mostly all inverters are designed for 12/24 volts, I assume 1500watt inverter is designed for 12 volts but maybe you are right and Toyota uses high voltage DC current for that.
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The owner's manual suggested that it uses the traction battery.
Toyota RAV4 Owner's Manual page 423 said:
When the 120 VAC power outlet cannot be used
If the AC 120 V switch is pressed but the switch indicator does not illuminate, the protection circuit may have operated.
In this case, perform the appropriate procedures as follows.
  • […]
  • Check the charge of the hybrid battery (traction battery) (P.165). If the charge is low, shift the shift lever to P, allow the engine to run to charge the hybrid battery (traction battery), and then press the AC 120 V switch again.
  • […]
  • If the vehicle has been stopped in a cold area, to protect the hybrid battery (traction battery), the power outlet may not be able to be used. In this case, drive the vehicle for a while to warm up the hybrid battery (traction battery), and then press the AC 120 V switch again.
Click to expand...
 
#51 ·
generaltso said:
As does logic.
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And math.

There's also p. 188 where the energy-flow monitor will indicate when the 120V AC outlet is on and that power is flowing from the traction battery.

The owner's manual is helpful. It eliminates a lot of guessing that happens on this forum.

Image
 
#52 ·
I'd say another way to run down the traction battery would be to leave it parked in cold weather at low charge for a long time. There must be battery heaters running off the HV battery to keep the HV battery from freezing. That will draw down the charge level quicker than normal self-discharge. I don't know the exact numbers for 'cold' and 'long time' but if my R4P was going to be outside in sub-zero F weather for more than a few days I'd want to make sure it was parked with a good charge on the HV battery.

I think the Nissan Leaf owner's manual actually has some numbers in it for this situation but I don't know them off the top of my head.

For the 12V computer drain I assume a R4P is about the same as any other car with comparable electronics.. The 12V battery doesn't need the CCA rating that a normal ICE car needs but it probably needs the same Ahr reserve capacity. I just left my RP4 parked for 3 weeks and it started up without issue.

Have Prius owners seen low 12V battery issues when their cars were parked for a month? That seems like a fairly short time for a 12V battery to be drained by a car that should be 'off'.
 
#53 ·
With the concerns of the 12V battery being depleted and the car not being able to start, what about replacing the relatively small 12V in the Prime with another, larger battery that is less likely to run down? Physical size constraints aside, what risk is there of replacing the battery with another similar voltage battery?
 
#54 ·
PCK said:
With the concerns of the 12V battery being depleted and the car not being able to start, what about replacing the relatively small 12V in the Prime with another, larger battery that is less likely to run down? Physical size constraints aside, what risk is there of replacing the battery with another similar voltage battery?
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I’ve been doing some Google-Fu this morning trying to determine the 12-volt battery type for the RAV4 Primes, and if anyone has upgraded or replaced theirs with a higher reserve capacity.
 
#55 ·
generaltso said:
It’s when the green Ready light illuminates on the dash. It means the car is ready to drive. It’s the EV equivalent of the ignition being started.
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My 2021 Rav4 prime when sitting in the ignition on, or ready mode, not driving, a message on the dash comes on and says the vehicle will turn off if left on for 10 minutes. How would charging continue if it turns off.
 
#56 ·
JetStream said:
I agree this is a minor issue and I wouldn't be worry it. But an alternator in an ICE does adjust its output current based on the voltage of the 12V battery. The voltage regulator adjusts the field current of the alternator to do this.

On a R4P, I'm sure the DC-DC converter performs similarly and adjusts its output based on what is needed. I don't know exactly how this is done but I imagine there is a PWM adjustment in the DC-DC converter that controls this.

But... 1) there isn't really anything you can do to change it and 2) it seems to work well since I haven't heard of any complaints about 12V batteries being under charged. Some early Leaf models had issues with this but Nissan seems to have improved their algorithms around the 2015 model year and later models don't seem as susceptible to the issue. A few Leaf owners use a 12V battery maintainer but I'd guess it's less than 1% of all owners. I've had my Leaf 4+ years without any trouble with the 12V battery. I'll probably check the battery voltage sometime in the next year or so to see how it's doing but in general I don't worry about it.
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2021 R4P in Accessory mode, turned off the vehicle to preserve battery power after about 5 minutes. I run often in EV Mode, and only use HV Mode on the freeways or interstates. About 30 percent of my mileage is local in EV Mode and it can be a week or two between freeway driving in HV mode. Had the system checked at the dealer today, and I believe they just checked the battery and said battery tested Green, and they could not duplicate at this time. I did run yesterday in HV mode for about 2 hours, which may have recharged the 12v battery. I tested the battery, car off last night and the voltage reading was 12.5, which is okay, but I feel it should be closer to 12.7. In looking into battery replacement to see what I would face, the owner's manual says to replace with a ventilated calcium type battery. The Dealer did not know anything off hand about a calcium battery. Further checking, they said only 11 on route from Japan and all are spoken for by California Dealerships. The Dealer here in Ohio, did not know when one could be shipped in. Two questions, does the 12v battery only charge as needed in HV Mode, and what should be the car off sitting voltage, as the dealer would not or could not answer that?
 
#57 ·
jack8202 said:
2021 R4P in Accessory mode, turned off the vehicle to preserve battery power after about 5 minutes. I run often in EV Mode, and only use HV Mode on the freeways or interstates. About 30 percent of my mileage is local in EV Mode and it can be a week or two between freeway driving in HV mode. Had the system checked at the dealer today, and I believe they just checked the battery and said battery tested Green, and they could not duplicate at this time. I did run yesterday in HV mode for about 2 hours, which may have recharged the 12v battery. I tested the battery, car off last night and the voltage reading was 12.5, which is okay, but I feel it should be closer to 12.7. In looking into battery replacement to see what I would face, the owner's manual says to replace with a ventilated calcium type battery. The Dealer did not know anything off hand about a calcium battery. Further checking, they said only 11 on route from Japan and all are spoken for by California Dealerships. The Dealer here in Ohio, did not know when one could be shipped in. Two questions, does the 12v battery only charge as needed in HV Mode, and what should be the car off sitting voltage, as the dealer would not or could not answer that?
Click to expand...
Also the Calcium battery is priced at $1439, therefore can an AGM Battery safely replace the 12v Calcium battery?
 
#58 ·
jack8202 said:
2021 R4P in Accessory mode, turned off the vehicle to preserve battery power after about 5 minutes. I run often in EV Mode, and only use HV Mode on the freeways or interstates. About 30 percent of my mileage is local in EV Mode and it can be a week or two between freeway driving in HV mode. Had the system checked at the dealer today, and I believe they just checked the battery and said battery tested Green, and they could not duplicate at this time. I did run yesterday in HV mode for about 2 hours, which may have recharged the 12v battery. I tested the battery, car off last night and the voltage reading was 12.5, which is okay, but I feel it should be closer to 12.7. In looking into battery replacement to see what I would face, the owner's manual says to replace with a ventilated calcium type battery. The Dealer did not know anything off hand about a calcium battery. Further checking, they said only 11 on route from Japan and all are spoken for by California Dealerships. The Dealer here in Ohio, did not know when one could be shipped in. Two questions, does the 12v battery only charge as needed in HV Mode, and what should be the car off sitting voltage, as the dealer would not or could not answer that?
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Also, I do drive my vehicle at least three to six times a week, but often that is in EV mode.
 
#59 ·
jack8202 said:
My 2021 Rav4 prime when sitting in the ignition on, or ready mode, not driving, a message on the dash comes on and says the vehicle will turn off if left on for 10 minutes. How would charging continue if it turns off.
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This message is probably the message that happens if you have not been driving for almost an hour. You get a similar message if you park and open the driver door without turning the car off. This is to ensure that you do not unintentionally leave the car on where the engine might come on and cause carbon monoxide to accumulate.

The 12 volt battery is always being maintained when the car is in READY mode. This means that no matter whether the engine is on or off, EV mode or HV mode, the battery is being maintained. 12.5 volts when off is perfectly normal. The textbook voltage of a fully charged 12 volt lead acid battery is 12.6 volts. However, there is some battery drain that happens after the car is shut off. This will lower the battery voltage lower than the textbook value. In addition, the battery voltage will go down with age.

Calcium battery - have no idea what this means. The battery is a standard flooded lead-acid battery. No need to buy the imported Toyota battery.
 
#60 ·
wscan said:
This message is probably the message that happens if you have not been driving for almost an hour. You get a similar message if you park and open the driver door without turning the car off. This is to ensure that you do not unintentionally leave the car on where the engine might come on and cause carbon monoxide to accumulate.

The 12 volt battery is always being maintained when the car is in READY mode. This means that no matter whether the engine is on or off, EV mode or HV mode, the battery is being maintained. 12.5 volts when off is perfectly normal. The textbook voltage of a fully charged 12 volt lead acid battery is 12.6 volts. However, there is some battery drain that happens after the car is shut off. This will lower the battery voltage lower than the textbook value. In addition, the battery voltage will go down with age.

Calcium battery - have no idea what this means. The battery is a standard flooded lead-acid battery. No need to buy the imported Toyota battery.
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The Manual definitely says Calcium battery. If you google, they are now being used in many Electric vehicles as the accessory battery. Suppose to last longer and more maintenance free as they loose almost no electrolyte over a long period. Toyota started using them in the Primes built in Japan, which mine was.
I had been driving the car for over an hour, which should have charged the battery, yet without getting out, I shut it off and then decided to listen to music as I waited. Put it on Accessory mode, and about 5 minutes later I got the message shut off the vehicle to safe battery power. Tried again to run it and it shut off again in 1 minute. I ran the car coming home for another hour before checking the battery with a tester, that is when I got the 12.5 volt reading. The Dealer did a check, but all they told me was the battery had a green light and they could not get it to do the shut down in Accessory mode.
 
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