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.
From my experience with a new Lexus LBX that is frequently used on long journeys, it cannot be left parked in a garage for more than 3 weeks without the battery running flat. Very disappointing as battery not fit for purpose. Car is less than 12 months old and already required two assistance call-outs due flat battery. For a supposedly high spec new car model, surprised it does not have self-adjusting headlights for when driving on the continent.
Hi John,
Thank you for your honest feedback. We greatly value the voice of our customer.
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 will 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 have any further questions, please do not hesitate to ask.
Many thanks,
Lexus UK
I’ve experienced a number of flat 12v battery occurrences, wouldn’t it be a good idea to make the boot catch openable from outside so that you can get to the battery and use any chargeable devices that you may have stored in the boot readily available
Morning Colin,
We’re sorry to hear you’ve experienced some problems with the 12v battery.
Thank you for this product feedback, we’ll be sure to pass it on.
If you would like your car to be inspected, please get in touch with your local Lexus Centre: https://brnw.ch/21x12lg
Thank you.
With my 2023 RX450 there have been two occasions when the 12v battery was discharged and left the car totally useless. That was frustrating enough, but the ridiculous process required to access the battery compartment in the boot when the boot lid is inoperable from outside, makes my first Lexus ownership experience very disappointing. Firstly the manufacture fitted battery is insufficient for such a large car packed with electronic systems. Secondly the 12v battery would be better located under the front bonnet, as using a trickle charger connected to the battery means the boot cannot be fully closed and locked. This represents a security risk as the rest of the car can be accessed from the boot.
Good morning Mark,
Thank you for taking the time to share your feedback.
We’re sorry to hear you’ve experienced problems with the 12v battery, we’d recommend contacting your local Lexus Centre to arrange an inspection.
Thank you.
I have had exact same problem with my 2025 Rx 450 H plug-in. With my car there have been two occasions when the 12v battery was discharged and left the car totally useless. Super frustrating. I don’t get it why can’t the big battery if fully charged can be used to draw some trickle down charge to keep 12 v alive. I can’t image Lexus did not think of this minimalistic engineering. Disappointed as a first time Lexus user. Won’t be getting again
Good morning Mj,
Thank you for getting in touch to share your concerns.
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.
Read more here and pick up some tips that, if followed, can help ensure your Lexus remains in tip-top condition: https://mag.lexus.co.uk/12v-battery-care/
If you would like your car to be inspected or for further technical advice, please get in touch with your local Lexus Centre.
Many thanks,
Lexus UK
How about designing it, or retro programming so it actually has an off state, really off nothing is on, ie no electronics running , stone cold dead. Shutdown.
Zero 12V drain, zip, nada nein, ziltch current moving out. Just the battery internal resistance to worry about.
Just like we actually think of a car, when its OFF.
I am more than happy to do with out the app features available to me at a moments notice. Even the remote key.
I simply want it in my garage and OFF.
With a mechanical lock to open/close it if necessary.
Or having that honking great 400V battery charge the thing up properly, The 12V battery its ground zero for everything!
I have been a Lexus owner for 15 years or so and have been delighted. Just upgraded again to NX450h+ and my battery has drained twice in 4 months. I have taken the car into Lexus who have checked the battery and been told I do not drive enough miles this has not changed since purchasing this car. It feels like Russian roulette when I go outside to start th car now. Very very disappointed.
I live in Spain so cold weather is not a problem I bought the LBX new 23 months ago had the battery replaced my the lexus dealer I charge the battery every month I drive 15,000 kms a year and still have flat battery issues love the car but the most unreliable car I have ever owned including £200 bangers my wife refuses to drive it on her own I have a power starter in the car which I use when a flat battery issue arises nobody seems to be able to sort this problem I get fobbed off at my main dealer the car is not fit for purpose I wish we had the lemon law then I could return it would love to get rid of it but would loose a lot of money another dissatisfied customer
Good morning David,
Thank you for getting in touch to share your concerns.
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.
Read more here and pick up some tips that, if followed, can help ensure your Lexus remains in tip-top condition: https://mag.lexus.co.uk/12v-battery-care/
If you would like your car to be inspected or for further technical advice, please get in touch with your local Lexus Centre.
Many thanks,
Lexus UK
I purchased an LBX in August 2024 and have had to call out the AA 5 times to sort out a flat 12 v battery . The car is currently at my local dealer having it’s 4 th battery fitted! Basically the LBX in it’s current configuration is not fit for purpose. I purchased an LBX so that I could have trouble free motoring and now have Lexus Assist on my mobile phone favourites. If you want trouble free motoring the LBX is a model to avoid.
Good morning Stuart,
Thank you for getting in touch to share your concerns.
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.
Read more here and pick up some tips that, if followed, can help ensure your Lexus remains in tip-top condition: https://mag.lexus.co.uk/12v-battery-care/
If you would like your car to be inspected or for further technical advice, please get in touch with your local Lexus Centre.
Many thanks,
Lexus UK
I bought a new Lexus 450 – took delivery five days back and achieved 251 miles – today I found the car doors locked and called the AA
The engineer was very helpful and now the car is recharging the 12 volt v=battery – frankly for me this is a dangerous car as I could find myself in an awkward situation.
It now appears that these 12volt batteries can run down due to parasitic drawdown from the cars support system – this is not good to know!
Good morning Philip,
Thank you for getting in touch to share your concerns.
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.
Read more here and pick up some tips that, if followed, can help ensure your Lexus remains in tip-top condition: https://mag.lexus.co.uk/12v-battery-care/
If you would like your car to be inspected or for further technical advice, please get in touch with your local Lexus Centre.
Many thanks,
Lexus UK
LBX purchased just over 1 year ago. Supposed to be our car for retirement. Informed when purchasing that a recall was imminent for the 12v battery issue. We have now had four occasions where the 12v battery failed – of course one had to be a hospital appointment.
We now carry a portable battery pack and charge the 12v regularly to aviod surprises – like this week when the 12v stopped visiting our local builders merchant. It started, did a 6 mile hill journey parked and then failed to start when leaving! not impressed.
Love the car but this issue makes it unreliable and honestly we regret our purchase. We wold not recommend this car as it stands.
Good morning Iain,
Thank you for your honest feedback. We take the voice of our customers very seriously.
Please refer to our magazine for any future developments: https://mag.lexus.co.uk/
Many thanks,
Lexus UK
I’ve just driven 4 days with 5 hour round trips. Coming home recently a long orange battery sign on the centre dashboard of my 69 plate RC300h, showed +5 minute, then +4 minutes.
As I’ve also experienced the 12volt problems and had a new one fitted, I thought it was the 12v battery, especially as I was charging my phone and had the Aircon on,.
I stopped at the services left it a while and it’s been ok since. I don’t know if it effects it but I was in Eco mode.
I called my local Sheffield dealer who had no idea nor has the Leicester dealer and it’s not in the handbook. Sheffield said ‘no idea, you’ll have to bring it in, next slot is the 7th May😧. Perhaps I should drive round the corner and phone the AA. Servicemmm
Good morning Robert,
Thank you for your honest feedback. We greatly value the voice of our customer.
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 will 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 have any further questions, please do not hesitate to ask.
Many thanks,
Lexus UK
I have just read this article regarding the problems with the 12V battery on the Lexus and the disappointing responses by a Lexus representative. It’s clear the responses have been moderated by some Legal department. To say all cars suffer the same battery drain is a get out and untrue and a poor excuse for what is clearly a design fault.
In my case I bought a LBX special edition 2 years ago and have continuous 12V battery problems. I traded in a 2 year old Yaris Hybrid with effectively the same powertrain and battery and no battery problems for the 2 years. The type of journey I do and is unchanged so why so much trouble with the LBX.?
We are retired and 70 +. Our typical journeys are short , to the local Tesco, pick grandchildren up from school, weekly trip to church and the odd weekly visit to family and National Trust. Typical I would say of most retirees. However the LBX does not last a week without having to be recharged. I would like Lexus to explain to my 70+ wife that she has to get to know how to recharge the car with a battery charger and wait for the response.! Im shocked to see such a response, asking 70+ retired ladies with absolutely no knowledge of how cars work to open up the engine bay, try and open up the fuse box and put power leads on hopefully the right terminals ! Absolutely ridiculous!
I keep getting told and read that my journey distances are not long enough to recharge the battery. I would argue my usage is typically of the majority of retirees, therefore what they are saying is the car is not suitable for retired people? I can’t remember Lexus advising me of this when I bought the car? The sales information even now states that “ The Lexus LBX is well suited to short trips in town traffic’ My understanding is that this is clearly an incorrect statement and non compliant with ‘ The Consumer Rights Act 2015’
So Lexus you have a problem with the LBX. It is not like other hybrids even your own such as the Yaris . You have a serious design fault. The power loads together with Parasitic drain are too great for the 12V battery. What owners want is a solution and not any more excuses saying it’s like other cars. To ask owners to charge the battery , in my case at least every 2 weeks after paying £40k for the car is farsical..
in my case it’s going back in to Lexus Birmingham next week , It went in for an annual service 1 week ago when it was kept overnight to check and recharge the battery, . Six days later after daily use for shopping, school run, visits, battery was dead, all doors locked, somehow I managed to get boot open to climb in which was the only way of getting in.
So Lexus,…… pull you fingers out, get it sorted, and start to look after your Customers. Your reputation is quickly going downhill at the moment.
Hi Ian,
Thank you for your honest feedback. We take the voice of our customers very seriously.
Please refer to our magazine for any future developments: https://mag.lexus.co.uk/
Kind regards,
Lexus UK