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
Very disappointing / frustrating … As a long standing Toyota customer (6 cars to-date), to be told that it’s my problem if my Yaris Cross battery goes dead whilst I am on holiday or I don’t drive the car for around 10 days – really! So I’m told to buy a solar trickle charger, plug it in via an in-bonnet connector whilst at the airport or parked on the road near my house!?! I’ve always been impressed with Toyota engineering but this is crazy, plus since Oct 25, all new Yaris Cross cars have been fitted with a larger 12v battery to overcome the known engineering deficiencies with the Cross design! Why can’t Toyota be honest with their customers and help fix the problem?
Morning Martin,
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 a free inspection of the 12v battery in your car, please get in touch with your local Toyota Centre.
Thank you.
I took my Corolla to Lindops in Wrexham after it failed to start and I had several messages before saying there was. Problem. Lindops said my battery was good. At the time of my visit 4 other people in there complained about the same thing and were given the same answer! Don’t think I’ll be buying another Toyota
My poorly performing Yaris Cross auxiliary battery is only just about healthy enough not to be replaced under warranty but with winter coming and no access to mains power near the parked vehicle, keeping it viable is now becoming a real challenge other than by multiple unnecessary journeys just to constantly top it up. Buying a car and then having to buy multiple accessories just to keep it functional is simply unacceptable, and the fact that all such models are being produced with larger capacity auxiliary batteries shows the issue is known and accepted as needing a remedial response – so will you not please offer replacement on request with a higher capacity battery where the individual circumstances clearly warrant it?
Good morning,
We are sorry to hear you are experiencing issues with your vehicle.
We would recommend revisiting your local Toyota Centre to discuss options for your Yaris Cross Hybrid.
Thank you.
I bought a new Yaris Cross late August 2025. This is my 4th new Toyota. No mention was made, by the saleswoman, about the 12V battery issues, of which Toyota was fully aware. Hence the uprated amp.hour battery fitted from October 2025
On Saturday 3rd October 2026, my car would not start. I tried to contact the York dealership for guidance re jumpstarting but they are closed on Saturdays! Plans for the weekend ruined! I made contact Monday, and mentioned ” under warranty” which caused panic. Later, I was horrified to read all the 12V battery issues!
I also suffered with the “wrong piston rings” (massive oil consumption after about 40k miles) which damaged the lambda sensor, of my Toyota Corolla. Again, Toyota did not accept responsibility until long after I sold the car.
Come on, Toyota. Massive Chinese competition, yet you treat customers so badly with YOUR design faults, YOUR attempts to fob off/ blame customers, for YOUR KNOWN AND ACCEPTED defects.
My car is booked in to upload safety software (TSS) lost when the 12V battery lost all charge plus a battery check. I’m sure I’ll be back in touch with Toyota Customer Services immediately afterwards, requesting the upgraded 12V battery .
I have serious health problems, especially in winter, so I need my car to be 100% reliable, especially in cold weather.
Good morning Mike,
We are sorry to hear you are experiencing issues with your cars.
Please get in contact with our Customer Relations team who will be happy to discuss any concerns you may have.
0344 701 6202
cr@toyota.co.uk
Kind regards
I am going away for six weeks last year when I did this battery died and had to be replaced. I understand you can buy a smart solar trickle charger. Huge variation in price on internet. Do they work and is so which one for 2026 Yaris Cross
Good morning,
We’d recommend getting in touch with your local Toyota Centre who can advise on the best options available for your Yaris Cross Hybrid.
For details of your closest Centre, please click here: https://brnw.ch/21x5S2E
Thank you.
This is my sixth Toyota and my last. To allow a car with a known fault to be sold is not what I expect from Toyota. I have bought six because they have always had a reputation of reliability. Toyota seems to have dropped their standards now to the likes of VW. Telling customers that it is their fault that the battery dies, is what I would expect from another company. We are on our third battery now. Reading the replies from Toyota that “we are sorry that you are experiencing this … but tough” certainly reflects the care that Toyota are putting into this issue.
Good morning David,
We’re sorry to hear you feel this way. We will share your feedback internally but if you are experiencing any further problems with your car, we’d recommend getting in touch with your local Toyota Centre.
Thank you.
My 22 plate Yaris cross has the same problem as everyone else, car not starting after a week of not using or as yesterday only doing short journeys for about 10 days. I know the battery is ok, as it was checked by Toyota last month, so for you to keep telling people to get a battery check is frankly insulting. It’s obviously a known fault that has been going on for years and I’ve called the AA 3 times but have now bought a battery jump starter. Please do not tell me to get a battery check, what I would rather have is the bigger battery which you are now fitting to the Yaris cross. I assume you won’t answer this message or offer the upgraded battery but I live in hope.
Good morning Martin,
We are sorry to hear you are experiencing ongoing issues with your 12V battery.
If you get in touch with your local Toyota Centre, they can discuss different options available for your car. Additionally, please refer to the relevant article for our recommendations regarding maintaining your battery health.
Kind regards.
When I purchased my 2021 rav4 PHEV in May this year, it had a brand new battery. I charged the car overnight when I got home and had to call the AA out the next morning as I couldn’t unlock the car with the fob. The AA have since been out on a monthly basis when the car has been left charging overnight. It’s got to the point that I unplug the charger as soon as the app notifies me that the EV battery is at 100%
My daily commute is roughly 48 miles each way, at least an hour in the morning and 1.5 to 2 hours in the evening.
Every time the AA come out they say the 12v battery had completely discharged. When the car was serviced last week I was advised the battery was ok, but could do with a charge, this was after a 50 mile drive to get there.
I’ve never received a ‘Starter Battery Low Charge’ on the app. When/how will this issue be resolved?
Good morning,
We are sorry to hear you are still experiencing issues with your RAV4 PHEV.
We would recommend revisiting your local Toyota Centre for another inspection if you are still experiencing issues.
We apologise for the inconvenience and disappointment caused.
Thank you.
Hi Toyota – this is obviously a major issue. Why not have a ‘holiday’ setting/switch that switches off all ancillary 12v drain. OK I might have to unlock the car manually with the key on the first occasion when I return, but that’s a lot less trouble than getting a jump or having to trickle charge. You’re welcome.
Good morning,
Thank you for your feedback, we appreciate you taking the time to share your thoughts.
We will ensure your comments are passed on to the relevant teams and taken into consideration.
Thank you.
I think it is disgraceful that in this day and age that Toyota are fitting a 12v battery that is clearly of a very poor standard and not fit for purpose. I am going on a cruise for 16 days and my Yaris Hybrid will be parked in a secure underground car park for that period so a Solar Trickle Charger is out of the question. I therefore have the stress of not knowing if my car will start on my return. My car is also normally parked in my garage when I am at home. I would have thought that with Toyota’s technical ability you would be able to fit a trickle charge from the drive train battery bank to the starter battery.
Makes one think twice about purchasing another Yaris Hybrid.
As a long standing Toyota Yaris hybrid customer for my wife’s car 2021 , the auxiliary battery is dead after standing in an airport car park after 2 weeks . Previously, we had a 2014 Toyota Yaris hybrid and that was fine .
I have spoken to the local TOYOTA DEALER WHO replaced the battery shortly after we purchased the car and recommended we drive down the motorway for an hour, surely this is a design defect that needs to be addressed. Buying a solar charger is also a bonkers idea , I am laughing at the thought of including this in your marketing and sales strategy.
As I am an electrical engineer, I am able to sort this by buying a jump start unit and charging my auxiliary , but a lot of drivers not be in this position, Toyota you need to be honest and get this sorted. Unfortunately, my wife’s confidence in Toyota has diminished and probably will not buy another Toyota car .
It appears that I have also been caught out by the battery issue as everyone else here. Holiday booked from 21st September – 1st October arriving home to have a flat battery. Abe to jump start & drive for 2 days only to receive a low battery warning on Sunday 4th. I am advised to purchase a solar trickle charger & have the 12v battery replaced at considerable cost. Never an issue with my old diesel Yaris over 14 years only to upgrade & end up stuck after an 11 day holiday. Come on Toyota – sort it out. Reliability doesn’t exist with the current issue & I will be rethinking options. Awful situation that is entirely avoidable.
It is absolutely ridiculous that the battery in the car goes flat within 2-3 weeks of the car not being used. How do Toyota justify this as a ‘good design feature’??? I have never had this problem with any previous (conventional) car, and nor was this ‘design fault’ made clear to me when I purchased my Corolla two years ago.
Either Toyota need to include a battery with the car that will last whilst people are away on holiday (not an uncommon occurrence) or they should build in some form of (solar?) charging facility into the car itself.
To expect customers to purchase a separate charging facility is totally unacceptable. And my local Toyota dealer has provided no information or recommendation as to what might be best.
Having spent over £30000 on a car why do I now have to spend more so that it will work properly?
I am very disappointed with Toyota over this, and expect much better from them.
Good morning,
We are sorry to hear that you are experiencing issues with your vehicle.
We would recommend arranging an inspection with your local Toyota Centre, who will be able to assess the vehicle and discuss the most appropriate options available to you based on their findings.
Thank you.