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

7 hours ago, DV21VSV said:

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. 

I had thought of putting a 12v bluetooth monitoring on the Battery. But if the Battery has such a low volage capacitance I am concerned it will exasperate the problem.

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14 hours ago, forkingabout said:

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

No.

15 hours ago, W1P30UT said:

ts 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

.... 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

........

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

......

If you have done some shorter journeys ..... this may well be because of a low battery warning."

And this is exactly what I have concluded from observing my Battery monitor data. Two hours driving per week with 2 journeys day of 12 minutes is not sufficient. 

We have been stressing that the essential criteria for Battery management was time not mileage but that should be quality time, ie the 'one hour per week in Ready mode'.  Ideally that should be for one hour and not an accumulated hour.  3x20 minutes or 2x30 minutes will probably be acceptable. 

"Just pop in to the shop Dear, I have to stay in the car for an hour."

Job done,  both happy.😀

Funny but true. 
This is exactly the concept of all vehicles, petrol, diesels, hybrids or Battery electric and they all will suffer the same faith if you start stop driving them. 
This is the reason why on many delivery vehicles drivers keep engine running or on even if they arrive at their destination, to preserve Battery charge, stop and start frequently kills your Battery. 
For example, after new battery replacement it is best to use the car for longer time between on and off, 30 min or more each time.
If this is not possible , then solar charger, smart charger or ready mode once a week are necessary to extend the life of the new battery, otherwise it will slowly but surely degrade quickly and let you down. And if anyone argue, but all my previous cars had no issues at all , I will agree, but ask yourself a question., did all of them had connected services, huge screens and everything digital and electronic inside? 
It’s not just Toyota these days but all car brands suffer same problems. 

Anyone seen this? Not a great situation really.

https://www.honestjohn.co.uk/askhj/answer/189428/my-new-hybrid-keeps-showing-low-battery-warnings---should-i-reject-it-

Emergency services,[cops] are useing these models,how do they cope,a second Battery? I'll ask at upcomeing service.

5 minutes ago, loz8 said:

Emergency services,[cops] are useing these models,how do they cope,a second battery? I'll ask at upcomeing service.

The Police Corolla Touring Sports have a special Police equipment specification with many modifications.

https://media.toyota.co.uk/toyota-works-with-the-police-to-produce-new-corolla-patrol-car/

https://mag.toyota.co.uk/toyota-corolla-police-car-a-force-for-good/

3 hours ago, fred88 said:

Anyone seen this? Not a great situation really.

https://www.honestjohn.co.uk/askhj/answer/189428/my-new-hybrid-keeps-showing-low-battery-warnings---should-i-reject-it-

The Question appears to be based on the classic ICE model with no knowledge of the new methods for a modern HEV.

No mention of the actual profile,  how were the long drives in relation to the short?  Was the radio used on ACC mode?  That used to be necessary in ICE to avoid overheating the coil or burning fuel unnecessarily.

The advice is as we have all said, Ready mode and a charger.

If you want the radio on when parked up, stay in Ready mode, switch AC off.

15 minutes ago, loz8 said:

Emergency services,[cops] are useing these models,how do they cope,a second battery? I'll ask at upcomeing service.

I bet they don't switch off from start until end of shift.

Probably do have a secondary Battery for all the extra gear.

32 minutes ago, Roy124 said:

Probably do have a secondary battery for all the extra gear....

Yes, maybe, or just a better Battery and a much larger capacity. Surrey Police have Odyssey batteries The biggest system they have in place is to be able to leave the vehicle in the 'Ready' mode but un-drivable. (You can't put it into Drive because as soon as you put your foot on the brake, it kills everything.) This way the vehicle will keep the lights flashing for hours, (with the ICE keeping the Battery charged when necessary) but no-one can nip into the vehicle and drive it away. 

2 hours ago, Wooster said:

The biggest system they have in place is to be able to leave the vehicle in the 'Ready' mode but un-drivable. 

A run lock system - vehicle cannot be driven away without the key.

I wonder, if you put the car in P, will it let you take the car out of P without the key present?

Perhaps Toyota should remove the 'Accessory' option from the Start/Stop button. That would stop all this unnecessary angst.

I wonder how the police charge the second Battery fo all there extra kit?.

N. I am using Battery monitor via bluetooth & for the last 9 or 10 weeks solar charging using 3 solar panels.

So I now for the present do not need to use mains charging it may change in the winter months only time will tell.

Today I have changed back to my Yuasa 45Ah Battery this was removed to cary out a desulphation process process that takes about 4 or 5 hours 10 weeks ago since then its used a simlar solar charging process.

Note the old MuTlu will never regain its lost capacity but it still works well with solar charging setup above.

I can't speak for every make/model but I never heard of an extra Battery being fitted.   Some manufacturers do 'tweak' models for emergency services and that may include larger batteries, enhanced alternators, etc..

The key is to keep the Battery charged by using what is referred to above as a run lock system.   Driver presses a hidden button, exits and locks vehicle leaving the engine running (or a hybrid in ready mode, I suppose).   If anyone breaks in, pressing the brake (auto) or clutch (manual) stops the engine.

There have been some interesting and helpful comments on this topic. Our car was collected by the dealer last Friday and returned on Monday. They applied a software update to stop background software activities when the car is parked. I can't be very specific as a report was not provided on the return of the car. So far it seems better. I'm monitoring the resting Battery voltage each evening after a drive and on the morning before a drive. For example last night after a 50-mile journey it was 12.1v and this morning 11.9v. I'll update the post if any further problems arise.

On 5/23/2024 at 6:45 PM, Pannett said:

For the second time. our Corolla wouldn't start today (Thursday). Fortunately the car was at a garage with a booster pack, so we were able to start the car and drive it for a while to charge the battery. Last Saturday we did about 60 miles, then on Monday we did 4 miles and Tuesday we did 18 miles. The car  stood for three days and then would not start.  This is worrying: for example if we go on holiday and leave the car at the airport car park for a period of time, it's highly likely that the car won't start on our return. The car is awaiting a call from the dealer to do some overnight testing of the battery, but does anyone know of a fix? If not, I am considering rejecting the car because it is not acceptable that this problem occurs and could be serious if we are on the Moors with our dog in the boot and no 'phone signal to call for help.

Looks like the inevitable , the 12v Battery is at the end of it's life

On 6/8/2024 at 8:10 AM, W1P30UT said:

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.

I'd dispute the 'most normal use cases'. I can't remember the last time I sat in a car and listened to the radio with the engine off. I'd either get out and do whatever it is I drove there for or I'd drive off and go somewhere else.

I'm not saying it's wrong but I think you're overestimating the significance of your predicament. You are a corner case. Even worse you are apparently choosing to remain so even though several people have told you how to fix the problem.

Don't leave the vehicle in Accessory Mode. Leave it in Ready Mode instead. Problem solved.

I have never felt comfortable leaving any vehicle in Accessory Mode. I think my Dad once told me that the ignition circuits were a drain on the Battery. He was possibly wrong. But either way I've known since the 1980s that sitting in a car and listening to the radio is bad for the Battery.

I really think you're blowing this up into a bigger deal than it really is. Millions of hybrid/EV owners are happy with the current system and/or have learnt to work with it. Why can't you?

Used to wait in the car listening to the radio for an hour or so while the kids had various after school lessons. Mind you that was pre-hybrid days!! But I'm sure others must be in a similar position today.

On old cars I was told not to leave the ignition on because it would burn out the coil. Is there an equivalent issue with a Corolla Hybrid in Ready mode?

38 minutes ago, fred88 said:

Used to wait in the car listening to the radio for an hour or so while the kids had various after school lessons. Mind you that was pre-hybrid days!! But I'm sure others must be in a similar position today.

On old cars I was told not to leave the ignition on because it would burn out the coil. Is there an equivalent issue with a Corolla Hybrid in Ready mode?

No, its akin to having the engine running in a conventional ICE. The ICE will just cut in and out when the Battery needs more juice.

5 hours ago, AndrueC said:

I think my Dad once told me that the ignition circuits were a drain on the battery. He was possibly wrong.

He was correct but it would depend if the old mechanical contact breaker points in the distributer were closed or not and that would depend on the position of the engine as it comes to rest. If closed a current would flow which I would estimate in the 3 amp region. Even then it would take many hours to discharge the Battery but the coil would get hot and possibly suffer in the long term.

No such issue with any modern engine hybrid or not. 

Listening to the radio with the key in accessory mode was fine as it only powered the radio. You could listen all day if you wanted without issues.

On older cars Aux pretty much just powered the radio, but on modern cars the whole computer system has to be powered on, and the screen of the infotainment system alone probably uses more power than a standard single-DIN head unit!  

Some cars, esp. the bigger SUVs, have 2 12v batteries (One starter type and one caravan-esque deep-cycle/leisure type) to power the infotainment system without the engine.

Even a modern vehicle info system should be able to be powered for many hours from a fully charged 35Ah Battery. Just think of a large screen laptop that has something like a 100Wh Battery vs the 400+Wh of even a small 35Ah car Battery. The standard laptop could run for anywhere from around 4 or 5 hours to 15 or more dependent on what tasks it was doing. On the car battery and it goes into days...

I'd bet these issues are addressed in future models as the battery technology and charge management is addressed. 

Here is a brief update. The car was returned on 10th June after the software update and I've been monitoring the resting voltage on most days since then. The value typically drops by 0.1v overnight, which reassures me that the larger drops before the update have been fixed. I do like the car immensely, particularly the impressive performance and economy, so rejection is now off the cards. I was irritated before the fix about our Corolla because our Octavia PHEV gave us 2 1/2 years of software issues and the car should have been rejected early on in its ownership, but we liked the car so much otherwise that we hung on to it.  I'll check the resting voltage less often, wait in the car whilst my wife shops leaving it in park, carry the booster pack 'just in case' and go out a bit more. Now there is just the faulty key fob to fix, so the car is being collected tomorrow. Then my wife and I will be happy!