12 volt battery mysteriously losing charge & car won't start

With the inbuilt telematics, the car is constantly connected to the internet for remote functions when off so there will be increased Battery drain on later models.

When I use the remote climate control to start the car in winter there isn't usually much of a delay before it starts.

All new cars have the inbuilt telematics, but many only for SOS functions so I assume they aren't powered up when the car is off.

33 minutes ago, sportse said:

With the inbuilt telematics, the car is constantly connected to the internet for remote functions when off so there will be increased battery drain on later models.

This is one of the reasons why I have deliberately avoided the app, setting up a profile and connecting everything up.   I am hoping that this may mean that the car won't be suffering Battery drain because it isn't connected to the net (although I'm not confident about that).

I also disable the key when I'm not using the car because I believe that this is supposed to reduce the drain on the car's 12v Battery (and the key Battery as well but I don't really care about that - replacing same being a quick job).

OP's car probably best to change the Battery for a bigger capacity/better quality if possible. My car is also 2023, Yaris so has a smaller 12v Battery. Mileage has been quite low this year and no problem so far. Longest period of not using or ready mode is 5 days. 

Follow the advice of the forum and it may just cost the price of a new Battery, save the hassle and cost of changing car. If usage pattern or ready mode has been good then can request/demand a new battery from dealership. Buy a jump start battery to have some form of peace on the moors. 

The owner manual states:

• ACC - Some electrical components such as the audio system can be used.
• “ACCESSORY” will be displayed on the multi-information display.
• To prevent 12-volt Battery discharge
• Do not leave the power switch in ACC or ON for long periods of time without the hybrid system on. 

It's appropriate to park the car, and use the ACC mode to power the radio for a few minutes. The car should be able to support this usage as outlined in the manual provided by the manufacturer. If it doesn't then the car isn't fit for purpose.

Just leave the vehicle in park & ready mode while listening to the radio like any clued up Toyota / Lexus hybrid owner would do.

19 minutes ago, W1P30UT said:

The owner manual states:

• ACC - Some electrical components such as the audio system can be used.
• “ACCESSORY” will be displayed on the multi-information display.
• To prevent 12-volt battery discharge
• Do not leave the power switch in ACC or ON for long periods of time without the hybrid system on. 

It's appropriate to park the car, and use the ACC mode to power the radio for a few minutes. The car should be able to support this usage as outlined in the manual provided by the manufacturer. If it doesn't then the car isn't fit for purpose.

 

Well it's your choice - We've told you what the best practise is to enable you to use the radio without any problems resulting, but if you want to continue to do it the way that is known to cause problems then you have the right and freedom to continue doing that.

I admire your tenacity in sticking doggedly with the wording of the manual in the face of common sense.

11 minutes ago, W1P30UT said:

The owner manual states:

• ACC - Some electrical components such as the audio system can be used.
• “ACCESSORY” will be displayed on the multi-information display.
• To prevent 12-volt battery discharge
• Do not leave the power switch in ACC or ON for long periods of time without the hybrid system on. 

It's appropriate to park the car, and use the ACC mode to power the radio for a few minutes. The car should be able to support this usage as outlined in the manual provided by the manufacturer. If it doesn't then the car isn't fit for purpose.

 

 

 

 

 

 

Hi, 

This is true and actually it’s not a problem, but on healthy 12v batteries.
You and anyone who suffer low 12v Battery issues, flats, non starter etc have bad batteries and the only option is to replace the Battery with new. These bad batteries could have happened even before the car was delivered to you. Either way it is premature wear and should be covered under warranty. Push Toyota for new Battery and give your Corolla a second chance. 
You can argue and reject the car on these basis. It’s your right.
However most other modern cars including standard petrols non hybrids like vw polo or anything else that has connected services will suffice the same faith if you drive only occasionally and less than 30 min each time. 

 

2 hours ago, SDR said:

I also disable the key when I'm not using the car because I believe that this is supposed to reduce the drain on the car's 12v battery (and the key battery as well but I don't really care about that - replacing same being a quick job).

How does the car know you have disabled the key?

19 minutes ago, RabButler said:

How does the car know you have disabled the key?

From what I understand I think it stops looking if it doesn't see a key for a while. This should also happen when the key is too far away such as in the house (or in a Faraday pouch), although with lots of houses if you keep the keys in the hallway and the car on the drive it will still be able to communicate. I think this is a security risk as well as a Battery risk.

Remember newer Toyota products have motion sensing keyless fobs which stop transmitting the signal after a few minutes once they stop sensing movement. 

No real need to switch the keyless system off or place these in a Faraday pouch.

1 hour ago, RabButler said:

How does the car know you have disabled the key?

If it's a keyless entry fob, you hold down LOCK and press UNLOCK twice and it turns the fob transmitter off until you press one of the buttons again - Saves the Battery life of the fob and makes it impossible to use relay attacks on.

It won't make much difference to the car's Battery (Unless it's draining because the fob and car are too close and they keep pinging each other) - For that you need to turn of the smart entry system completely which shuts down all the power hungry keyless entry transmitters. (But not the remote unlock receivers, which use much less power)

IF you use the car regularly there's no point, but if it's going to be left for a long time, e.g. holiday, that might reduce the power draw on the 12v Battery just enough that it won't be dead when you get back.

1 hour ago, RabButler said:

How does the car know you have disabled the key?

I am not 100% sure that it does (which is why I said "believe") but based on this from the manual:

• In the following situations, the smart entry & start system may take some time to unlock the doors.

  • The electronic key has been left within approximately 3.5 m (11 ft.) of the outside of the vehicle for 2 minutes or longer.

  • The smart entry & start system has not been used for 5 days or longer.

My car lives under a car port right outside my back door and the key is within 3.5m of the car.  I figured that car and fob are probably close enough to be communicating so I would prevent that by switching off the fob.   I am hoping that is sufficient without turning off the smart entry system completely.

I would do it anyway because of the relay theft issue.   For the last few years I had been keeping my car keys in a Faraday pouch - until I read this:   https://www.honestjohn.co.uk/askhj/answer/187360/do-faraday-pouches-wear-out-

Sure enough, I tested mine, it was useless.   With the keys in the pouch in the kitchen I could easily open the car.

Ironically, just about everyone has a really good Faraday cage in their kitchen.   A microwave;   and it really does work  (it has to or microwave energy would escape the thing).   Which is fine unless you turn it on with the keys inside...

2 hours ago, forkingabout said:

Remember newer Toyota products have motion sensing keyless fobs which stop transmitting the signal after a few minutes once they stop sensing movement. 

No real need to switch the keyless system off or place these in a faraday pouch.

It seems so but all I can find in the manual is this (I was actually looking for something else!):

The electronic key function is suspended when

The electronic key function may be suspended when the electronic key is kept unmoved in a same location for a certain period, such as it is left on a same place. This is to reduce Battery consumption. The function will be restored automatically when the electronic key is moved, such as it is picked up.

Problem is that it says "may be" and "certain period".   As with quite a lot of the manual, it's open to interpretation.   Without certainty that this applies to my car and, if it does, what the "certain period" actually is, I am not minded to rely on it.

Just to clarify, it's only the keyfobs that supposedly go to sleep when sitting still. The car system continues to make transmissions to try and detect a fob that's both awake and in close proximity - this does turn off eventually, but it takes a couple of weeks, unless it's been disabled altogether via the menu system. I did a crude study of the Battery draw a couple of years ago and you can quite clearly see the current spikes, just over a second apart, that disappear with keyless entry turned off. The net effect on energy consumption is significant, but not huge. Link below for anyone interested.

https://www.toyotaownersclub.com/forums/topic/203030-constant-battery-drain-problem/?do=findComment&comment=1602456

The proximity sensors and the keyless entry are the smallest thing to worry about 12v Battery draining. Also this is one of the best extras these cars has and why would you like to disable it.
You will be better off to disable connected services, turn off all automatic functions like auto fold side mirrors, auto parking brake, home lights functionality if you have any of these. 

All these extras  can be done manually when necessary and while the car is still in ready mode to preserve 12v Battery. All electronic actuators are high energy consumers and the one low energy consumer but constantly draining the Battery are the connected services and possibly the poor network connection all around the country. Since introduction of 5G standard in 2020, and later removing 3G masts doing calls or using mobile internet has worsened a lot. Poor signal drains phone batteries faster therefore no surprises if it actually makes things worse for all these cars with modern tech inside. 

@TonyHSD I think it's important to consider the difference between power and energy, remebering that it's the latter that we need to limit in order to preserve the Battery charge.

Sure, folding the mirrors draws a lot of power, but it's over in 3 seconds. It's not really a high energy consumer unless repeated a few times every day (not forgetting the other activity generated by unlocking the car like priming the brake servo etc.).  So, it all depends on use case: if you're using the car a few times every day then the mirrors are going to be the higher consumer, whereas someone like me, who will often fold them up once and leave the car standing for several days, will most certainly need to worry more about the background activity........e.g. keyless entry.😄

Stuart, good point about high energy consumers which bears out what I have observed.  Frequent restart cycles,  even if Ready mode gives you an hour a week, reduce Battery energy 

So my new Corolla is with the garage for the second time to investigate the low 12v Battery warning. The car is driven regularly, with some long journeys, and still I get this warning. As a courtesy car I got one of the managers approximately six month old Corolla. Guess what? 12v Low Battery warning on that too!

Here's the latest update from Toyota.

"We cannot fault the Battery itself in terms of drains or charging concerns, he has guided me in explaining that if you are sat with the radio on with ignition off then naturally there will be a draw on the vehicle as a whole and the 12v Battery would be subject to this, granted if its small increments at a time then in theory it shouldn’t be depleted allot however its important to  explain that small journeys or shorter increments over time with maybe sitting stationary the vehicle 12v Battery would be lower than when constantly used and thus wouldn’t ever return from full charge state as hybrids communicate differently compared to none hybrid cars and this impacts how the 12v battery responds vs switching to electric mode. If the vehicle feels it has enough 12v battery charge to not require more charge and stays in electric mode stationary for regular periods and the isn’t used for any substantial journeys, then this can create low battery queries on the dash based on regular like events. However, we have noticed that those who do regular journeys and moderate mileage over 12 months and by moderate in my experience over 6/7k a year we don’t have any 12v battery concerns but again everyone using their car is different. I think in this instance if you have done some shorter journeys and then been local this may well be because of a low battery warning."

In short, don't do local short journeys. I can't say I am happy with owning a car that support regular short journeys. What do people think?

Do you still leave the vehicle in accessory mode to listen to the radio? 

35 minutes ago, W1P30UT said:

Here's the latest update from Toyota.

"We cannot fault the battery itself in terms of drains or charging concerns, he has guided me in explaining that if you are sat with the radio on with ignition off then naturally there will be a draw on the vehicle as a whole and the 12v battery would be subject to this, granted if its small increments at a time then in theory it shouldn’t be depleted allot however its important to  explain that small journeys or shorter increments over time with maybe sitting stationary the vehicle 12v battery would be lower than when constantly used and thus wouldn’t ever return from full charge state as hybrids communicate differently compared to none hybrid cars and this impacts how the 12v battery responds vs switching to electric mode. If the vehicle feels it has enough 12v battery charge to not require more charge and stays in electric mode stationary for regular periods and the isn’t used for any substantial journeys, then this can create low battery queries on the dash based on regular like events. However, we have noticed that those who do regular journeys and moderate mileage over 12 months and by moderate in my experience over 6/7k a year we don’t have any 12v battery concerns but again everyone using their car is different. I think in this instance if you have done some shorter journeys and then been local this may well be because of a low battery warning."

In short, don't do local short journeys. I can't say I am happy with owning a car that support regular short journeys. What do people think?

If you’re unhappy with the car, sell it and buy a non hybrid. I’ve just done the same with my previous 5 month old car (Sportage hybrid) as it was too big for my lifestyle (and it had a number of annoyances) and bought the Corolla as it’s perfect for me. Life is too short to be stressing about a car. Move on. 

4 hours ago, W1P30UT said:

Here's the latest update from Toyota.

"We cannot fault the battery itself in terms of drains or charging concerns, he has guided me in explaining that if you are sat with the radio on with ignition off then naturally there will be a draw on the vehicle as a whole and the 12v battery would be subject to this, granted if its small increments at a time then in theory it shouldn’t be depleted allot however its important to  explain that small journeys or shorter increments over time with maybe sitting stationary the vehicle 12v battery would be lower than when constantly used and thus wouldn’t ever return from full charge state as hybrids communicate differently compared to none hybrid cars and this impacts how the 12v battery responds vs switching to electric mode. If the vehicle feels it has enough 12v battery charge to not require more charge and stays in electric mode stationary for regular periods and the isn’t used for any substantial journeys, then this can create low battery queries on the dash based on regular like events. However, we have noticed that those who do regular journeys and moderate mileage over 12 months and by moderate in my experience over 6/7k a year we don’t have any 12v battery concerns but again everyone using their car is different. I think in this instance if you have done some shorter journeys and then been local this may well be because of a low battery warning."

In short, don't do local short journeys. I can't say I am happy with owning a car that support regular short journeys. What do people think?

First thought is wondering who at Toyota (?) - or what (AI?) - wrote this garbage.   A candidate for a Crystal Mark from the Plain English Campaign it isn’t.    Auto-translated I suppose. 

Second thought is that if this the reality of owning a hybrid (Toyota and probably others too) then so be it;   the problem could be considered as not being with the cars but with dealer sales people who don't make this clear to potential buyers.   Diesel cars fitted with DPFs (so since 2009ish) aren't suited to regular short journeys either;   but do car sales people still sell them without asking potential customers about their intended use (rhetorical)?

This problem is becoming common with new hybrids. I had similar with 2021 chr. I got a voltmeter and was horrified at the voltage capacitance.  Check the voltage at end of day and again next morning. I was getting up to 0.5v drop and after 2 days car failed to start. AA told me the problem is getting worse. Now I have a trickle charger as recommended by the toyota dealer service manager. The toyota 12v batteries can't even support a radio with engine switched off for over 4 minutes. The engine restarts because of the voltage drop. It can't support a next base 2k Dashcam in service with engine running cos that needs 13V. As I see it they have microdesigned the 12v Battery to only be able to supply engines run daily and to support the heavy demands of the cars engine and security monitoring systems. My next step is to buy Battery monitor with bluetooth feed to mobile that records voltage 24/7. They only cost £20. 

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13 hours ago, Neptuneblue said:

If you’re unhappy with the car, sell it and buy a non hybrid. I’ve just done the same with my previous 5 month old car (Sportage hybrid) as it was too big for my lifestyle (and it had a number of annoyances) and bought the Corolla as it’s perfect for me. Life is too short to be stressing about a car. Move on. 

 

Thanks, I am happy with the car. I am not satisfied with the 12v low Battery issue. My car is just over 1 month old. Why should I take a financial hit of depreciation for Toyota not designing a car to work with most normal use cases, or warn prospective buyers of the limitiation.

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9 hours ago, SDR said:

First thought is wondering who at Toyota (?) - or what (AI?) - wrote this garbage.   A candidate for a Crystal Mark from the Plain English Campaign it isn’t.    Auto-translated I suppose. 

Second thought is that if this the reality of owning a hybrid (Toyota and probably others too) then so be it;   the problem could be considered as not being with the cars but with dealer sales people who don't make this clear to potential buyers.   Diesel cars fitted with DPFs (so since 2009ish) aren't suited to regular short journeys either;   but do car sales people still sell them without asking potential customers about their intended use (rhetorical)?

 

Agreed it's a garbage statement. They should make this limitation clear to prospective buyers.