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
We have just been informed that our 12volt battery is flat and we need to take it for a 30 mile drive. We are in Spain on holiday and not back for another 6 days. This is the 3rd time it has happened to us with Toyota cars. What should we do.?
Hi Cathryn,
We are sorry to hear this.
Thank you for your question.
We recommend, where possible, aim to take your car on a 30-minute journey at least once a week. The speed isn’t as important as the duration of the journey. However, 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.
If you have any concerns, please don’t hesitate speaking to your local Toyota Centre again.
Thank you.
My wife’s car was only two years old, and the battery had to be replaced. Recently we were away on a cruise and after ten days got a email to say that that the battery was low! Car still under three years old, with a fairly new battery. Thank goodness that was the car we had left at home and not taken to the airport. Moral here is never take these cars to park at an airport.
Clearly on reading all the comments here that Toyota have specified at smaller battery than they should have put on these cars. They should recall all cars concerned and supply a higher rated battery. I have a friend who had the same problem.
My wife’s previous Yaris never has this problem over her four years of ownership. Doubtful if her next car will a Toyota!
Agree. These batteries aren’t reliable, which is annoyong as reliability was why most of us bought a toyota.
Good morning Michelle,
We are attentive to the situation which you have highlighted. To provide a bit of reassurance, less than 1% of our entire customer base encounters issues with their 12 volt Battery. All modern cars drain the 12v battery when they are switched off. This is due to the onboard electrical systems. If the 12v battery is not given a chance to recharge often enough, it can go flat. We pride ourselves on performance and reliability so to ensure there is a continuation and we live up to our own standards, we have introduced a higher performance battery for some of our models if and when needed.
If you continue to experience issues, please visit your local Toyota Centre.
Thank you.
Hyundai/Kia EV’s have solved this problem by allowing the main traction battery to charge the auxillary while the vehicle is inactive such as stored in your garage for a few weeks. I do not know why Toyota does not allow this self charging capability in their EV’s saying that you must drive the car for 30 minutes at least once a week so the auxillary battery will charge. A Toyota EV’s auxillary battery will only charge when the dashboard says “READY” after turning on the vehicle. Toyota’s recommendation is to use a trickle charger (low amperage, around 2 amps) to recondition the auxillary battery if the car is left in the garage for a few weeks. The problem is that if the voltage of your auxillary battery goes below 12.4 volts, most likely there has been some damage to your auxillary battery. I had a Toyota RAV4 Prime and the auxillary battery had to be replaced three times. On my Kia EV6, this has never been a problem as the traction battery will charge the auxillary battery whenever needed….the Kia does not need to be driven for 30 minutes. I also now own a Toyota C-HR and I check the voltage output of the auxillary battery regulary which is a pain in the behind.
Agree this battery issue is completely destroying my new car joy. After a battery failure at 5 months, Im constantly worried the 12v battery will fail again. I have functions like the check seat alert that i want to disable but can only turn off once they alert triggers when the engine goes off. Going away gor 2 weeks is stressfull as i dont know if my car will stsrt when i return.
Good morning Michelle,
We are sorry to hear you are experiencing issues with your car.
If you are concerned about your vehicle, we would recommend contacting your local Toyota Centre to book in an inspection.
Thank you.
I agree with Michelle. I have had the car for 2 months. The battery should work even if I leave it sitting. THIS IS A NEW CAR!!!!! Why isn’t Toyota addressing this problem???? There needs to be a recall – and we should not be advised to go out and buy a trickle battery.
GRRRRR
Since buying my Yaris Cross Hybrid two years ago, I have had numerous battery warnings. In late May 2026 I had the car serviced and raised this issue. The dealership tested the battery and it was fine and was told the App is known to erroneously generate low battery warnings. No warnings since until the 15 July. On the 6th July I had driven to my partners house about I hour away. The vehicle was unused until the 15th July. The car started fine and I drive for about 1.5 hours. Within 20 minutes of arriving at my destination I got a low battery charge warning from the App. How can this happen ?Again a day later and the car starts fine.
Toyota need to sort out the App !!!!
Good morning Keith,
We are sorry to hear you are unhappy with the MyToyota App.
After a trip ends, the algorithm may take up to 24 hours to process the data and issue an alert. If the vehicle is driven sufficiently during that time, the alert may still appear but can usually be disregarded.
Our developers are continuously refining the algorithm to improve accuracy and reduce false alerts. In the meantime, if you remain concerned, we suggest visiting your local Toyota Centre. They can check the battery for you and discuss further options, including the use of a solar or trickle charger as mentioned above.
If you have any other questions, please don’t hesitate to get in touch, we’re always happy to help!
Thank you.
We have had to replace our battery 3 times in 10 months making us feel anxious every time we go to start the car. Definitely wouldn’t buy another Toyota hybrid.
Good morning Sue,
We’re sorry to hear that you are experiencing ongoing issues with your 12v battery.
Here in this article are some tips that, if followed, can help ensure your Toyota remains in tip-top condition. If you would like your car to be inspected, please get in touch with your local Toyota Centre.
Find your local Toyota Centre here: https://brnw.ch/21x48TK
Kind regards.
Tips don’t help! Replace the batteries and fix any DCM and software issues that are involved. Toyotas are supposed to be reliable!
Left my BZ4X parked up at Airport parking while on an 11 day holiday. Parked on 21 June, plugged in solar trickle charger. 8 days later (29 June), received warning message from Toyota app that my Starter Battery had a Low Charge.
A little difficult to comply as I wouldn’t return for a further 3 days.
One day later (30 June) I receive an email from Toyota providing a WARNING: STARTER BATTERY CHARGE IS LOW.
Both these communications strongly suggest an actual “measurement” had been made and the battery level had been recorded. Terminology like “Warning Lights” and “Your BZ4X has detected the starter battery is low” are highly misleading.
After digging around a bit, I found this contained in the battery warning email from Toyota in the FAQ section:
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.
Here’s a key pertinent question: What “other factors” besides the frequency of the vehicle’s use are measured? Is there any mechanism actually measuring battery drain? If there are no other actual “measurements” being taken, as I’m using a Solar powered Trickle-Charger, the warning should include a caveat that this is based solely on the number of days between starts and not an actual battery measurements. A Solar Panel trickle-charger should prevent this. One further concern however: When the solar trickle-charger is plugged into the OBD-II slot, there is no control panel confirmation (or any other method I’m aware of) that the trickle-charge is actually working. In my case, happily, the solar charger apparently did work, and my vehicle started after sitting for 11 days, without incident.
I’ve personally experienced a dead-battery situation on my Toyota BZ4X before. I was away on a 2 week trip and could not start the vehicle upon return. In this case, the car was left parked at home, and if I’d known of this issue in advance I would have been able to have a family member start the vehicle weekly. However, they would not be able to drive it for the requisite 30 minutes, so not sure if it would have prevented the battery drain anyway.
In this earlier incident, I returned on a Saturday, could not trickle-charge or even jump-start the vehicle. I had to call out Toyota’s breakdown service. The mechanic said the battery was so dead that a trickle charger wouldn’t revive it and concluded the battery was faulty. My dealership could not see me till the Monday, but insisted they had to put the vehicle on trickle-charge for 24 hours instead of replacing the battery. All of this assuming I would/could happily go several days without the use of my vehicle.
As I travel abroad often, I wanted to ensure this situation did not recur. The service department at Toyota advised me to purchase a solar panel trickle charger that can be plugged directly into the vehicle’s OBD-II Port. Theoretically, it would continuously “float-charge” the battery as long as the panel in your window gets sunlight. As a back-up precaution, I also purchased a Boost Jump Starter Pack that can revive a completely dead battery without the use of a second vehicle.
In general, such a limitation is unexpected from such a high-end luxury vehicle. Furthermore, I’ve read enough online to realize this is not an isolated incidence. Toyota should be incorporating solutions, like a built-in solar charger into their Hybrid and EV models NOW instead of expecting their customers to purchase work-arounds at their own expense, or experience the failure for themselves. This is a known vulnerability and we expect better from Toyota.
Good morning Anthony,
We are sorry to hear that you have experienced issues with your Toyota bZ4X, we value the voice of our customer and would like to thank you for taking the time to share your feedback.
If you experience any further issues in the future, please don’t hesitate to visit your local Toyota centre.
Thank you.
Driving 2024 C-HR PHEV, bought second hand from Toyota dealership. After 2 months of ownership, I received the 12v battery low charge warning in app and booked dealer visit immediately. On day of visit car would not start and AA had to help me get going. Dealer charged battery overnight and following day said it flagged up errors but Toyota policy is to do a battery drain test which was fine and asked to collect car, so no new battery.
Somewhat surprisingly I was told that I am not braking enough which is why battery is flat . . . . surely that is completely wrong if I read above article by Toyota UK correctly, plus numerous forum discussions on this topic. I have no intention of changing my careful driving in numerous HEV’s which includes allowing the car to brake when I lift my foot of accelerator approaching junctions or other cars when I always feel the regenerative braking kick in.
Am I missing something? Above states that ‘it is important to note that the 12V battery is only trickle-charged when the powertrain is turned on – also known as READY mode’. It is not braking that charges the battery right? I also see reference to ‘The 12V battery in a Toyota C-HR hybrid is charged automatically through a DC-DC converter connected to the main hybrid high-voltage battery pack’.
To put this in perspective, the car is driven almost daily and the day before the error message appeared in the app I had done a 100 mile round trip.
I am pretty sure I will get same issue again in a couple of months time.
Absolutely love the car but this is a bit of a curve-ball!
Good morning Simon,
We’re sorry to hear you’re experiencing a problem with the battery in your Toyota C-HR. All modern cars drain the 12v battery when they are switched off. This is due to the onboard electrical systems. If the 12v battery is not given a chance to recharge often enough, it can go flat.
In this article you can pick up some tips that, if followed, can help ensure your Toyota remains in tip-top condition.
If you experience any further issues, we would recommend you visit your local Toyota centre to have your car re-inspected.
Thank you.
Problem z niedoladowanym akumulatorem 12V dotyczy również mojej Corolli. Problem jest na tyle poważny dodatkowo dotyczy wielu użytkowników hybryd Toyoty że firma powinna poważnie zająć się tym tematem a nie angażować w łatanie problemu swoich klientów. To nie jest dobry pomysł marketingowo. W moim przypadku Problem szczególnie pojawia się zimą przy ujemnych temperaturach. Wedlug mnie aplikacja zamiast informować mnie o niskim napięciu akumulatora 12v powinna mieć możliwość skorzystania w takim przypadku w pierwszej kolejności z zapasu energii w baterii hybrydowej. Ilość enerii w tej baterii zimą jest dużo wyższa jak w okresach cieplejszych gdzie udział jazdy na napędzie elektrycznym dochodzi do 60 a nawet 70%. Letnie naładowanie baterii hybrydowej to od 40 do 60 %. Zimą jazdy elektryczniej szczególnie w mieście na krótszych odcinkach to góra 20%..A bateria naładowana znacznie wyżej niż latem nawet 80%. Czyli reasumując jest wtedy spora ilość energii w samochodzie, którą w takim przypadku można rozsądnie wykorzystać. Myślę że chodzi o zmiany w programie zarządzającym energią.
My Toyota Yaris GR sport is only two years old. The battery died and was replaced. I travel a lot and constantly receive low battery emails. I have a solar panel which doesn’t seem to provide enough or any charge at all as I’ve jest received another low battery email- nothing I can do as I’m away on summer holiday. I bought this Toyota for reliability. This issue is a great deterrent. Why has Toyota not yet resolved this!?!
Good morning Elisa,
We are sorry to hear you are experiencing issues with your car.
We would recommend visiting your local Toyota centre for a battery inspection.
Find your local Toyota Centre here: https://www.toyota.co.uk/
Thank you.
May I know my 2019 RAV4 Design Hybrid (Gen 5) need beam deflectors travelling to European? Thank you very much.
Good morning William,
All of our new cars with LED headlights have a flat beam pattern so will not need deflectors when driving in Europe. Older models have a ‘kick up’ on the left which would head directly into the view of oncoming drivers.
Our technical team have advised that you visit your local Toyota Centre or MOT centre to have the beam pattern checked on a beam analyser before heading abroad. The use of stick on beam deflectors is not advised as LED type headlamps can let off a lot of heat and generally cause the stickers to melt on the lens. However, some European laws do require these beam deflector stickers to be present though so worth purchasing anyway.
Many thanks.