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
Agree with the above – having purchased a 3 year old Toyota this year to have something reliable – this issue means it’s not. It’s driven at least weekly and often a good distance. Having to also charge it takes me back to a previous car, which I had to disconnect every time to avoid battery drain.
Toyota’s solution is an alert – but this does not FIX the problem of what is widely reported as an underpowered battery for the job. Alerts are delayed, meaning I received one the day AFTER driving for 4 hours mostly on the motorway. So I never know if my most recent journey has re-charged it. Half a day off-work to see a dealer is not attractive and a Toyota webpage on HOW you might connect a trickle charger, preferably without disconnecting the battery, is much needed.
Good day, Toyota.
I have had intermittent problems with the status of my 12V battery since buying the car several years ago. My AA man (called out 3 times for the battery) has told me that there is a known 12V battery fault with the Yaris, and I should ask Toyota to replace it. I have returned it to the dealership multiple times and they said ‘the battery is fine’. What should I do now ?
Good morning Siobhan,
We are sorry to hear that you are experiencing ongoing issues with your 12V Battery. We would recommend speaking to your local Toyota Centre about alternative options available for your Yaris.
Additionally, please refer to the relevant article for our recommendations regarding maintaining your battery health.
Kind regards.
I had a Toyota auris TS hybrid 160,000 miles 10 years of owner ship. 20 mile to work 20 mile back everyday 20,000 a year. Bought a 2023 Corolla TS hybrid 2 years of ownership 40,000 miles of my driving on the clock, battery issue on the app after tracker fitted through Toyota. Took the car to get checked out of warrenty and battery needs replacing £220 from dealership or £80 from Halfords with fitting. Has Toyota gone downhill in quality? Anyone else getting issues even with high mileage.
Toyota Corolla Touring Sport. My car is just 8months old and is used daily and many many times on journeys of 150 miles. Twice recently (the day after I had completed journeys of 150 miles) I received an email saying the starter battery charge is low and I should be in touch with my local Toyota. On ringing them I was told they would need the car for 24 hours and i cannot be without my car at this present time (I have a family member who is very ill and I need to travel frequently to Suffolk) and it was best that I ring roadside assistance who referred me back to my dealer. I am a more mature female who drives many miles on my own and after this experience I have no confidence whatsoever in your assistance procedure if I were to breakdown whilst driving on my own. Having read previous complaints on this same issue I agree that Toyota have a real problem with this issue. I was so pleased with my car but this has now left me extremely worried and questioning if I have made the right decision.