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.
