Possible issue with Toyota Corolla 12V battery.

TumblingDice1 · 18-03-2026 06:58PM #1

Hi,

Just looking for some opinions here. I have a Corolla which is just over 1 year old. Recently, I have been getting messages on my Toyota phone app saying that the starter battery is heavily discharged and that there is a danger the car won't start, although this has never happened. When I check the battery voltage after resting overnight, the voltage is around 11.5-11,6v. This, when I look online, is indicative of a dodgy battery. I had the battery checked at the main dealer where I bought the car, and they said that the battery was fine, and to basically ignore the phone app messages.

Should I be concerned about this?

Thanks.

elperello · 18-03-2026 07:07PM

You might find this recent thread useful.

What the car dealers don't tell you when buying a new Toyota Hybrid car, and the 12 Volt battery. - Page 2 — boards.ie - Now Ye're Talkin' https://share.google/pJSgg0GNNy2hlzcrY

mk7r · 18-03-2026 07:21PM

I can guarantee you if the car was out of warranty the dealer would have been charging you for a new battery

odyssey06 · 18-03-2026 08:59PM

Give it some time in Ready mode and see if warnings stop.

Turn off radio, AC etc.

Hybrid car owners should switch on ‘Ready Mode’ for approximately 30 minutes every 15 to 20 days to keep the battery topped up.
- It’s important to note, that for Hybrid users the engine may not kick-in or omit any sound, however their dashboard’s ‘Ready Lamp’ will be illuminated when ‘Ready Mode’ is active.
- It is important to uphold car safety when in ‘Ready Mode’ and ensure all lights are turned off, the car’s position is secure with the brake on, and no passengers are in the vehicle.

https://www.toyota.ie/company/news/2020/maintaining-battery-life

TumblingDice1 · 24-03-2026 08:16PM

Hi,

Thanks to everyone who replied. That link that elperello supplied was educational. I always assumed that the 12v battery was charged by an alternator, I was never told otherwise! I have just done another check on the 12v battery and the situation is this:

When I drive the car 20-20 Km and leave "Ready"mode on, the voltage is around 13.7-13.8v. As soon as I turn off the engine, it drops immediately to 12.1-12.2v. When I check the next morning, It is down to 11.2-11.3v.

Maybe this is the new norm for hybrid batteries. Anyway, the car has not failed to start, so I'm just going to carry on without worrying about it for now.

Thanks again to all who replied.

zg3409 · 27-03-2026 10:51AM

I would bring a jump pack with you everywhere and check you have breakdown cover on existing car insurance or free with new car for a number of years. Below 12 volt is not normal and a sign 12 volt needs to be replaced.

elperello · 27-03-2026 02:24PM

https://www.boards.ie/discussion/comment/124344879#Comment_124344879

You can get a jump pack for about €60 in Lidl and they are very easy to use.

On the plus side though a family member has a Corolla hybrid just coming up 7 years old and no battery issues.

Another has a 172 Rav 4 hybrid which just needed a new 12 volt a few weeks ago

Esel · 28-03-2026 09:04AM

Is there any risk to ECUs etc. when connecting a jump pack or jump leads in this case?

elperello · 28-03-2026 10:11AM

https://www.boards.ie/discussion/comment/124346786#Comment_124346786

Not if the correct procedure shown in the vehicle's handbook is followed.

There is a dedicated connection point in the engine bay which reduces the chance of reverse polarity.

A power pack having only two crocodile clips also makes it easier to avoid errors.

TumblingDice1 · 29-03-2026 01:14PM

https://www.boards.ie/discussion/comment/124344879#Comment_124344879

Thanks, I have a jump power pack already. I agree that anything below 12v is not great. However, the main dealer checked it and came back with a printout saying the battery was in spec. However, as one poster said, it might have been a different story if the car was out of warranty!

yagan · 29-03-2026 01:36PM

I've an elderly aunt who's had recurring problems with a 2019 Corolla and now 2023 Yaris, I'm constantly having to drop around now with one of those recharageble jump starter packs as she doesn't drive much and then take it for a long drive to recharge the system. This will work for a couple of months and then I get the call again.

This has been her normal lifelong driving habit but the problems began with her first Toyota hybrid, the 2019 corolla. She's been driving Toyotas since the 80s and swears by them, so it's been hard for to accept that she needs to drive the newer ones more to top up the battery.

I've taken her cars to the dealership and have been told that all's good, but I did get one salesperson to admit that they have to have to have a starter pack handy for the new cars.

I do feel Toyota Ireland should have a warning about having to change driving habits for their newer hybrid system so people who expect reliability aren't misled.

TumblingDice1 · 30-03-2026 02:45PM

And now we have the Government telling us to drive as little as possible to save fuel!

selectamatic · 30-03-2026 03:03PM

https://www.boards.ie/discussion/comment/124348858#Comment_124348858

Has she tried the ready mode method for 20-30 minutes every fortnight or 3 weeks. It might save having to adjust driving habits and save ya having to jump it every so often.

yagan · 30-03-2026 03:50PM

https://www.boards.ie/discussion/comment/124351070#Comment_124351070

She never had to consider such a thing before her first hybrid, so I'm not getting involved.

It's Toyota who should be explaining this to her before committing to their newer hybrids.

Its not like she requires fuel efficiency for the twenty mins of driving she'll do a fortnight. A basic Sandero would do.

elperello · 30-03-2026 06:22PM

https://www.boards.ie/discussion/comment/124351188#Comment_124351188

You're right it is the dealers job to sort her out with some good advice apart from driving around in circles.

A small petrol would be ideal for her minimal usage.

Problem is the dealer hasn't got one to sell and he doesn't want to lose the sale.

If he's not honest with the customer he'll likely lose the next one though.

yagan · 30-03-2026 06:30PM

https://www.boards.ie/discussion/comment/124351550#Comment_124351550

Here's the thing, it has put me off ever buying such Toyota's, and I've owned a few in the past.

I see Corolla's from the 90s still used as a daily drivers but I can not see the current models having such longevity and reliability.

On a UK forum I've read people who drive their new toyotas regularly still have issues like coming back from a two week holiday and needing a jump start in the airport car park. It's absolutely insane that anyone should have to think about regularly carrying a jump start pack for a new car.

elperello · 30-03-2026 06:51PM

https://www.boards.ie/discussion/comment/124351569#Comment_124351569

Further back in the thread I mentioned two Toyota hybrids owned by family members who have had no issues.

The 12 volt battery lasted almost 9 years in one and the other one is going strong after 7 years.

They are both used daily but one was recently left for 12 days while on holiday and started no problem.

I'm wondering is it a software problem where the true condition of the battery is being misread ?

Are the batteries actually capable of powering up the cars systems but the computer is "saying no".

yagan · 30-03-2026 08:13PM

https://www.boards.ie/discussion/comment/124351605#Comment_124351605

I don't care, not my cars.

Took both cars to a Toyota dealership, they said everything was grand but still didn't inform mention anything about them needing to be driven. Very poor form for cars still in warranty.

I simply don't trust Toyota after seeing how the auld one was fobbed off.

Possible issue with Toyota Corolla 12V battery.

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