The 12-volt auxiliary battery is a quietly essential component of your vehicle’s electrical architecture. It provides the primary source of power for all low-voltage systems, including lighting, climate control, audio features and, where fitted, the starter motor. While modern vehicles incorporate significantly more technology than those of previous generations, the fundamental principle remains unchanged: the 12V battery is replenished through the operation of the powertrain.
This cycle of energy consumption and replenishment has underpinned automotive engineering for over a century. Renowned for its reliability, it is largely self-sustaining. Nevertheless, an understanding of the system and a few considered practices can help ensure the continued health and longevity of your vehicle’s 12V battery.
Common causes of 12V battery concerns
Most issues arise when the battery is not given sufficient opportunity to fully recharge. It takes a little time to reinstate the charge that was expended from the battery at start-up – longer if multiple electrical systems are operating simultaneously. Frequent short journeys can therefore gradually reduce the battery’s charge.
Low ambient temperatures also place additional demands on the battery. Cold conditions slow the internal chemical processes, making start-up more demanding and accelerating charge loss. At the same time, increased use of heating, ventilation and lighting further draws on the battery’s reserves.
Recommendations for preserving battery health
1) Regular operation
Where possible, aim to take your car on a 30-minute journey at least once a week. If this is impractical, or if the vehicle will remain unused for an extended period, a high-quality battery maintainer (also known as a trickle charger) is recommended to sustain optimal charge levels. Your local Lexus Centre can advise whether a mains-powered or solar solution is best suited to your needs.
2) Consolidate journeys
Repeated short trips can prevent the battery from fully recharging. Combining errands into a single journey helps mitigate this effect. Brief stops during a longer trip are unlikely to be detrimental, as a warm engine and cabin require less energy to restart and maintain.
3) Minimise unnecessary electrical load
When the powertrain is not operating, the battery is not being recharged and therefore electrical features such as lighting, ventilation and audio systems will continue to draw power. To preserve charge, ensure these systems are switched off before turning off the powertrain. This also reduces the load placed on the 12V battery during the next start-up.
4) Monitor battery condition
Periodically inspect the battery terminals for signs of corrosion and ensure all connections are secure and clean. These checks form part of your vehicle’s scheduled service programme at your local Lexus Centre, but the team there will also be pleased to provide guidance at any time.
12V batteries in electrified vehicles
Hybrid and fully electric vehicles are equipped with two batteries: a 12V auxiliary battery that supports low-voltage electrical systems, and a high-capacity traction battery that powers the electric motor(s).
In both cases, the 12V battery is only charged when the vehicle is in READY mode. For this reason, we recommend keeping the vehicle in READY mode whenever you remain in the vehicle while using electrical features – for example, when listening to the audio system while waiting.
If assistance is required
By following the guidance above, issues with the 12V battery are unlikely. Should a concern arise, however, reassurance is close at hand – expert assistance is always just a phone call away.
Breakdown cover arranged through Lexus 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 Lexus 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. Lexus 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?
Lexus approved accessory dash cams should not cause any drain on the 12V battery when the vehicle is 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 Lexus Link+ app drain the 12V battery’s power?
Yes, a very small amount of power is drawn from the 12V battery when owners use Lexus connected services. Refreshing the vehicle status in the Lexus Link+ 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 Lexus Link+ app?
The Lexus Link+ 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 the Lexus 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.
Lexus NX350h Takumi, 12 v battery failed 3 times. First time day after I bought the car, locked in car, new battery fitted. Next failure day after 100 mile journey AA jump started . Next, admittedly after being parked for two whole days, another jump start. Took car into Lexus, apparently all my fault, no problem with car. This is my fourth hybrid, 1 Toyota ,3 Lexus, never a moments problem with 12v battery until now. I cannot believe the 12v battery is antiquated lead acid type, and it amazes me that Toyota Lexus do not have a system in place that recharges the 12v battery by taking power from the large “Drive” battery when the vehicle is parked, this system is used in the vast majority of EV and Hybrid vehicles on sale today, why not Toyota Lexus ? Sorry to say this is a car I simply cannot rely on , so I have bought and use continually a Noco Genius 5 trickle charger and should I be let down away from home, a jump starter. My very last Lexus. Please don’t insult me by saying “If you are still experiencing issues with your 12v battery, we would recommend that you please visit your local Lexus Centre.” I have, and apparently it’s all my fault. Nothing Premium about a car that will not start.
Good morning Ken,
We are sorry to hear you have experienced ongoing issues with your 12v battery and have lost faith in Lexus. We appreciate you taking the time to give feedback, any other queries please do not hesitate to reach out.
Kind regards.
I sold my 13 year old, reliable, Seat Ibiza because I felt that due to age, it was likely to become less reliable.
I treated myself to a Lexus LBX as it suited my needs, namely, comfort, ease of driving and most of all, reliability.
I have had the car just over a year, and I have lost count of the number of times it has completely let me down due to the 12 volt battery. This doesn’t just happen when I haven’t used the car, I have frequently received notifications of low battery in the evening after driving my normal 70 mile round trip commute that same day. I have had to buy a portable battery starter but this isn’t always convenient to use. I was recently running late to go on-a 3hr trip to a wedding when it failed again. Having to open the bonnet and connect it up, I got dirt on my shirt and had to change, it was infuriating!
I have had the car checked twice now by Lexus for this battery problem during annual service and fault recall and both times was told that the battery was adequately holding its charge – clearly Lexus idea of “adequately holding charge” differs massively from customers who are locked out of their flat battery cars.
In fact in a recent Which? magazine report the LBX was cited as the worst car for reliability due to 12 volt battery discharge.
Lexus answer is drive it more, clearly this is not the answer. They also recommend purchasing and using a solar panel, but a look on Amazon reveals an immense array of types, sizes and powers – which is the right one ? If indeed this is the Lexus answer to this too common problem surely having paid £40,000 for a car this should be chosen and supplied by Lexus for every one of these unreliable models. Frankly though, this as a solution is appalling, being messy and inconvenient.
Frankly the car is unsuitable for purpose and it is a problem that Lexus need to find a proper working solution to.
This problem is so well documented that surely the Lexus staff should warn potential customers of this problem, knowingly selling a car with this problem is surely close to a crime
I feel considerable frustration and anger that a car that I had purchased as hopefully my last due to my advancing years, and is such a comfortable joy to drive should be such an unreliable purchase. If to make it operable I need a solar panel to trickle charge the battery surely Lexus should be supplying this to every failing vehicle as a matter of course as a temporary solution until the cure is found.
I am at an impasse, do I get rid of this unreliable car and find something that I can trust, obviously at a great loss to myself, or do I purchase the messy inconvenient solar panel, and if so will Lexus advise on exactly which one, or better still, as a gesture of goodwill, supply the correct item.
Good morning Alan,
We are sorry to hear you are experiencing issues with your 12v battery. Countermeasures for the 12v battery in the Lexus LBX have been put in place to try and limit customer dissatisfaction.
In regards to purchasing a battery maintainer, your local Lexus Centre should be happy to help you choose the correct one. Furthermore, if you would like to arrange another inspection, find your local Lexus Centre here: https://brnw.ch/21x48TN
Kind regards.
Hi Alan, in my car RX450h+ Takumi, I have done 6000 miles in 2 years from new, and similar to you have had the 12v battery problems, and was looking at this being probably my last car. The suggested advice (without any specific parameters) to drive more often, and for longer periods seems totally contradictive to the purposes of a hybrid. Since locked inside car with 12v failure, the emergency exit process is not intuitive, and certainly not for any passengers, I’ve used a battery monitoring approach which even with the replacement battery (still a simple small lead/acid item), shows a similar decline in battery power to the original. Issues raised over 18 months ago, and like you every battery check done is recorded as OK . . . what did your Annual Hybrid Vehicle Check record on your service? There is a section on this which advises on the 12v ‘health’. It makes interesting reading if like mine after 1 year it advises the 12v had ‘failed test’ but the overall Hybrid Health Check was actually a pass.
Very much a current on-going story, wish more could be encouraged share their problems as I only found out about this location earlier this year!
Good morning James,
We’re sorry to hear you’ve been experiencing problems with the 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. This article shares some tips that, if followed, can help ensure your Lexus remains in tip-top condition.
If you would like your car to be inspected again, please get in touch with your local Lexus Centre.
Thank you.
My NX just had second service having completed over 20,000 miles. 12 volt battery recorded as failed in service health check. Advice from garage is that they will recover car if I breakdown and provide replacement car for three days. This is my fifth Lexus and my faith in the mark is gone. Time for a change!
Morning John,
We’re sorry to hear you’ve lost faith in your Lexus NX.
Your local Lexus Centre are on hand if any problems arise or if you wish to replace the failed battery.
Thank you.
I bought a new LBX two months ago, no problems yet but as I am retired, come winter, I will only need to use the car once a week to do the weekly shop. Reading about these battery problems has me very worried that the car will let me down. I consider it a huge failure of Lexus to make such an unreliable vehicle. After reading the posts I really wish I hadn’t bought the car. The dealership knew about my low milage as the trade in was 17 years old and had under 50,000 miles on the clock! No mention that doing such a low mileage would make the LBX unsuitable for my needs. If this car does let down I will be very annoyed! Beware of an angry retiree with plenty of time to spend on social media, YouTube etc.
I will copy my post made three years ago on ClubLexus website.
Many others have made similar posts and some have been extremely helpful from Canada and California. Perhaps the Lemon law there enforces some reliable response from Lexus.
The platitudes above simply do not help. The Which and ThisIsMoney publicity may …
My initial experience
Next Lexus nightmare
Car packed , about to set off from South of Spain.
My wife in car.
I cannot open door to get in.
My wife cannot get out.
She presses SOS button.
Nothing happens.
Wife in tears. We bought the top grade Lexus on the grounds it was safe and did not break down.
Eventually I ring European Lexus Assistance
They will send out someone within 90 minutes.
Something resets on car and I can open the doors with emergency lever.
i realise the battery has become flat after loading car and my wife getting in.
At least my wife is out of the completely dead car.
After 90 minutes the helpful Lexus guy arrived and starts car with external battery
So we think everything sorted – but NO
The car demands the security code.
I try the Lexus password – have found frequent need for that whenever my wife trys to drive – it will not recognise her key and provide a profile.
But that password includes a symbol – @. – and symbols are greyed out on the security code screen.
i ask the Lexus mechanic to sort it – luckily ? He had not left.
But No -,he tells me I must talk to Lexus.
So back to the telephone. Talk to my dealer after 5th in the line for service. I can now understand that Lexus is so unreliable that dealers cannot cope.
Dealer takes info then tells me I must ring the dealer I bought the car from new,less than a year ago.
So I ring and speak to a helpful lad who tells me, after consulting Lexus database, that I must bring the car.
I agree to this after explaining it will take me 3 days to get there including almost 2,600 miles and a ferry crossing . He is sorry, nothing else he can do.
I try to ring Lexus UK for help. No one available and message terminated – try again. After 20 similar attempts I realise that Lexus are so unreliable that their help system is totally overloaded. It will be much quicker to ring The Mail and BBC.
So I set off to drive.
After first night I realise that I cannot switch off the movement alarm while on the ferry.
so I assume the alarm will go for the 26 hour crossing of the bay of buscar, and I will have a flat battery again when we arrive in the UK.
I am parked just inside the doors so can imagine the fun and games while 200 other vehicles try to pass to get off the ferry.
A least I can look forward to telling them all why not to buy Lexus.
I spent £80,000 buying what I thought was a top quality reliable car.
can anyone tell me that I made the right choice? Where do I go from here.???
At least explaining my experience in detail may help others to escape the Lexus Disaster..
I just hope that this really good car can at last be made SAFE.
Morning Joseph,
Thank you for taking the time to share your experience. We’re sorry to hear about the problems you and your wife encountered on your trip.
Lexus vehicles are designed to provide a seamless ownership experience, with sophisticated technologies working intuitively in the background to enhance convenience and comfort. Like any modern vehicle, however, many of these systems rely on a 12v battery.
Should that battery become fully discharged, features such as smart entry and certain electronic door functions may become temporarily unavailable. To support drivers in these situations, Lexus vehicles incorporate alternative methods of entering and exiting the vehicle. We hope you find the guidance detailed in this article useful for the future: https://mag.lexus.co.uk/lexus-wont-unlock/
If you have any concerns with your car currently, please don’t hesitate to get in touch and visit your local Lexus Centre.
Thank you.
Hi
I am contacting you regarding the 12v battery on our Lexus NX450+. We seem to be experiencing a problem with the charging of the battery.
We have recently driven from home in Cardiff to Cornwall which is a journey of 205 miles, fully in petrol mode. We have purchased and installed a battery monitor on our vehicle to monitor the status of the battery. On this journey the status started at 42% and remained at this level until the end of the journey. I’m a retired electronics / software engineer and have worked for a large European aircraft company, so have been interested in the charging procedure. I’m surprised that having travelled a considerable distance the car failed to charge the 12v battery at all. I guess the on board dc/dc converter set parameters designed by Lexus don’t allow the 12v battery to be charged under these conditions maybe due to emissions regulations?.
What concerns us, is having driven this length of journey and then leaving the vehicle parked for a period of time, would result in the car being flat on our return.
We contacted our local Lexus dealer with our concerns and booked the car in to check the 12v battery. They checked this and found it to be working as it should. However, they did say it was a low SOC and they suggested they have the car in overnight to charge the battery back to 100%.
We have purchased a trickle charger and have charged the battery to 100%.
We were about to book in, but they advised they could not provide us with a loan vehicle overnight which would leave us without a car. They had also suggested a 3-day period, but we would be in the same position of not having a car during this time.
We find this whole scenario totally unacceptable. We have gone to the expense of purchasing a battery monitor & charger and along with the initial expense of the car we are very disappointed with the whole experience. The lady at our local dealer, told us that there is a problem with all makes of hybrid. This is not something we want to hear or really interested in other manufacturers as it is an issue we are trying to resolve on our car and have lost confidence in leaving our car at the airport in November when we fly to Tenerife. Our confidence is that low, that we have booked a taxi for the journey as we did not want to come back to a flat battery.
Morning David,
Thank you for getting in touch. We’re sorry you’ve got some concerns with the 12v battery in your Lexus NX.
To give your local Lexus Centre sufficient time to complete a thorough investigation, we’d recommend leaving the car with them at a time that suits you.
Thank you.