The 12-volt auxiliary battery is the unsung hero of your car’s electrical system. This fundamental component provides the sole source of power for all low-voltage electrical features, from the lights and starter motor (where fitted) to climate control and audio systems. Modern vehicles contain much more technology than even those of a decade ago. Yet despite having to provide the energy for these increased demands, all the 12V battery requires to maintain a virtuous electrical cycle is to be effectively recharged by the powertrain.
This method of expending and reinstating electrical energy has been used in vehicles for more than 100 years. It is extremely reliable, and in the majority of circumstances entirely self-sustaining. However, a little knowledge and the following handful of tips will help owners support the health of their car’s 12V battery.
What are the primary causes of 12V battery issues?
Most problems occur when the 12V battery has not been given the chance to properly recharge. It takes a little time to reinstate the charge that was expended from the battery at start-up – more if there are lots of additional electrical systems in use at the same time. Consistently short journeys are therefore likely to slowly deplete the battery’s reserves.
Cold weather is also tough on the battery. Low temperatures slow the chemical reactions inside the battery cells, which make it harder to start the engine and easier for the battery to lose charge. In addition, cold weather usually means greater reliance on electrical systems for heating, ventilation and lighting – all of which draw power from the 12V battery.
Recommendations for maintaining 12V battery health
1) Frequent use. Where possible, aim to take your car on a 30-minute journey at least once a week. If this is not possible or you plan not to use the car for a prolonged period, use a quality battery maintainer (also called a trickle charger) to keep the charge level topped up. Toyota Centre staff will be able to advise on whether a mains- or solar-powered option is the best for your circumstances.
2) Combine trips. Constant short trips will get your battery down, so try reducing their frequency by combining errands. And if these journeys require a couple of short stops, don’t worry too much. Less battery energy is required to start an already warm engine; and similarly, less energy is required to maintain the climate of an already warm cabin.
3) Avoid wasting energy. Remember that if the powertrain is not active it is not charging the battery. In that case, electrical accessories such as lights, ventilation and the audio system will all nibble away at the level of charge. So make it a habit to switch off these accessories before turning off the engine. Not only will this preserve the charge but it will stop the battery having to power the systems back up at the same time as starting the powertrain.
4) Check the battery’s condition. Regularly inspect your battery for corrosion around the terminals and ensure the cables attached to them are tight and clean. Your local Toyota Centre will check these connections as part of your car’s regular service programme, but will also be happy to offer advice outside of this schedule.
What about electrified vehicles – do they have a 12V battery?
Yes, they do. Hybrid and full electric vehicles are equipped with two batteries: a 12V auxiliary battery for the same low-voltage electrical features as any other car, and a much larger traction battery that powers the electric motor/s to drive the vehicle.
In both vehicle types, it is important to note that the 12V battery is only trickle-charged when the powertrain is turned on – also known as READY mode. We therefore recommend that drivers use READY mode whenever they are inside the vehicle using electrical features, such as listening to the radio while waiting to collect a family member.
What to do if you have a problem
Owners who follow the recommendations listed above are unlikely to experience a problem with their car’s 12V battery. However, if an issue does arise, be assured that expert help is never more than a phone call away.
Breakdown cover arranged through Toyota Roadside Assistance offers year-round support, 24 hours a day. Delivered in partnership with The AA, the UK’s number one provider, this breakdown cover includes jump starts, towing and emergency roadside assistance. In addition, the nationwide network of Toyota Centres is also available for advice or assistance.
FAQs:
How can I make sure the 12V battery is in good condition after it has been parked for an extended period of time?
Consider using a quality battery maintainer to keep the charge level topped up. Toyota Centre staff will be able to advise on whether a mains- or solar-powered option is the best for your circumstances.
How do I put my vehicle in READY mode?
READY mode only applies to full hybrid or full electric vehicles. First, ensure the transmission is in PARK and that the handbrake or e-brake is engaged. Then apply the foot brake and press the vehicle’s START button. Green READY lettering (see image below) will illuminate on the dashboard to confirm that this mode is now active.
NB: Remember that if the powertrain is not active, low-voltage accessories like the lights, ventilation and audio system will all draw power from the 12V battery.
Will using a dash cam affect the 12V battery?
Toyota approved accessory dash cams should not cause any drain on the 12V battery when both the vehicle and dash cam are switched off (and parked). However, when the dash cam is active, ensure the powertrain is either running or the vehicle is in READY (not ACCESSORY) mode to prevent draining the 12V battery.
Does using connected services on the MyToyota app drain the 12V battery’s power?
Yes, a very small amount of power is drawn from the 12V battery when owners use Toyota Connected Services. Refreshing the vehicle status in the MyToyota app can wake the vehicle, so make sure to follow our battery maintenance recommendations if you regularly refresh your vehicle’s status.
What should I do if I’ve received a ‘Starter Battery Low Charge’ alert from the MyToyota app?
The MyToyota app does not directly monitor the charge level in the 12V battery (starter battery) but is programmed to predict its health and alert owners as a result of other factors, such as the infrequency of the vehicle’s use. The alert is therefore a calculated suggestion that the battery would benefit from the vehicle being driven for at least 30 minutes.
NB: Notifications can take 24 hours to clear from the app after the vehicle has been driven.
Is the 12V battery covered by Toyota’s manufacturer warranty?
Yes, the 12V battery is covered by our manufacturer warranty for up to three years or 60,000 miles, whichever comes first. This includes any failure caused by defects in manufacturing or assembly.
NB: The 12V battery is not covered under the following warranty products: Toyota Battery Care, Toyota Hybrid Battery Cover, Service Activated Warranty or Approved Used Warranty.
Useful links:
Winter driving tips
How to get the most out of a hybrid electric vehicle
From what I can see by reading all 8 pages of comments here, there is not one actual answer from Toyota…
How can that be satisfactory?
Since 2012, my wife, my daughter and I have owned 12 Toyota vehicles (Aygo x2, IQ, Yaris x2, Avensis, Auris x3 and Corolla x3). We have never had any reason to consider reliability issues, until these ‘low starter battery’ alerts began in July 2026.
Here I am now replacing my Corolla’s battery as a precaution before leaving for a holiday, as my dealership just trot out the same statements that appear on these pages…how about an honest discussion with an informed and experienced human being, Toyota?
Good morning David,
We are sorry to hear you are experiencing issues with your 12V battery.
We would recommend arranging a visit to your Toyota Centre to discuss your concerns.
Kind regards.
I use my new Yaris Cross infrequently and the battery is often flat when I come to use it. The local dealer replaced the battery (when the car was a few months old) but the problem has persisted.
I’ve got a jump-starter that has got me out of trouble, but having to use this on a brand-new modern car is a bit of a joke. Using a solar charger isn’t really an option either in a UK winter and mounting one on the dashboard is a break-in risk.
Is there anything in the Toyota sales material https://www.toyota.co.uk/new-cars/yaris-cross#/ that warns potential customers of this problem? And does Toyota consider that cars sold with this problem are fit-for-purpose?
Good morning,
As part of our continuous product development activities, higher-capacity and charge acceptance batteries have been introduced on a number of models over time, including the Yaris Cross Hybrid from October 2025. These actions reflect our ongoing commitment to monitoring vehicle performance and implementing improvements where appropriate.
If you’re concerned and wish to arrange an inspection of the 12v battery in your car, please get in touch with your local Toyota Centre.
Thank you.
I bought a new RAV 4 plug in hybrid last year I am retired and regularly take 2 and 3 week holidays and arrive home only to have to call out the AA to start the car. Toyota have changed the battery for a higher capacity one and charged me £90! for a solar panel as i cannot use a trickle charger as the car is parked on the drive.
My neighbour has a Kia hybrid and friend a hyundi hybrid. Both have a button which diverts power from the drive battery to start the car when the 12v battery is flat. Why on earth can’t Toyota, as a world leading car manufacturer recognise this long standing battery problem and offer the same solution as their competitors?
After spending £47000 on a new car I do not expect to have to call out the AA every time I return from holiday or after leaving it in an airport car park.
Good morning John,
If you are still experiencing issues with your new 12V battery and the solar charger, please get back in contact with your local Toyota Centre who should be happy to help.
Kind regards.
I bought my Yaris cross new in Jan. 2024. At that time ai new I would be away for 5 weeks. I specifically asked the salesman if that would be a problem.re the battery. The answer was an emphatic “No”.Two subsequent periods away have resulted in the E mail telling me my battery level is low. I am away again for a few weeks and requested my daughter to drive it for the suggested time..Now she can’t get into the vehicle so it is sitting on my drive unusable until I return. Never have I had a such a problem in 50 years of owning cars from bangers to new models. I am deeply unimpressed with Toyota ,the salesman,car and company.
Good morning Keith,
If your vehicle’s 12V battery is flat, you can still gain access using the manual key. Once inside, we recommend contacting Toyota Roadside Assistance for support with starting the vehicle safely. We would also recommend visiting your local Toyota Centre for a vehicle inspection once your car is up and running.
For further guidance on manually unlocking your Yaris Cross, please refer to this article: https://mag.toyota.co.uk/toyota-wont-unlock/
Thank you.
I’m just about to take delivery of a new Yaris Excel.
One of the reasons for buying a Toyota was it’s reputation for reliability. The posts here suggest otherwise.
My dealership did advise that the battery has been upgraded. So, please can it be confirmed what the Ah value will be on this 2026 model.
Thanks.
Good morning Andrew.
Congratulations and thank you for choosing Toyota. Is it the Yaris Hybrid Excel or Yaris Cross Hybrid Excel you’re driving?
Thanks.