Tel:+44(0)121 748 4600 Fax:+44(0)121 730 2745 Email: Search
The Independent Automotive Aftermarket Federation

12-volt batteries, the EV battery of choice!

Date: Thursday 29 February 2024

As it previously made clear, whether an EV incorporates an internal combustion engine (ICE) with a 48-volt or 350-volt battery in hybrid form, or uses a 400-volt plus battery as a fully battery powered variant, a ‘traditional’ 12-volt battery is also fitted. The revelation comes however, in the fact that in common with their ICE powered counterparts, the number one cause of EV breakdown also turns out to be failure of this battery! But why?

Since the UK launch of the Tesla a decade ago, and following changes in government legislation, many other vehicle manufacturers (VM) have added full EVs to their product ranges.

As a result, they and their partners have invested hundreds of millions of pounds to develop the electric motors, control systems and high voltage (HV) battery packs to make the move from relying on an ICE, to using fully electric propulsion achievable.

However, as stated earlier, in the quest to develop these new technology vehicles, not everything is new, as 12-volt systems remain integral to EVs to enable them to perform vital functions. These include not only powering the lighting system, both internal and external, but the central locking, alarm, and other security features. It also powers the vehicles onboard computer and diagnostic systems and plays a role in starting the main HV battery pack.

These systems put significant load on the 12-volt battery and whereas in vehicles incorporating an ICE after providing a big burst of electrical energy to power the starter motor, it is recharged by an alternator and managed by the vehicle’s electronic control units (ECU), a process that has been refined over many years, in an EV, the 12-volt battery is performing a much more cyclic function, being charged by the high voltage battery and discharged by the 12-volt systems that rely on it.

Irrespective of whether the vehicle is an EV or incorporates an ICE, the maintenance of its 12-volt battery is down to the parameters set in the ECU’s battery management system, and this is where there is a potential conflict of interest.  

It’s well known that discharging a standard 12-volt SLI (starter, ignition & lighting) battery beyond 50% will reduce its life expectancy.  However, largely due to the fact that range anxiety is one of the key barriers to EV uptake, VMs want to maximise the range capability that they can offer drivers. To do this the battery management system has to make a compromise between charging the 12-volt battery to keep it in top condition, or providing for the vehicle’s optimum range, which can result in an undercharged 12-volt battery, affecting its useable life.

A further impact on the life of the 12-volt battery comes with the advanced technology inbuilt into an EV. Its inherent connectivity and the plethora of apps it can run, such as to remotely ’wake it up’ and activate the 12-volt system, for example, can require 5,000 activations per day, which can seriously discharge the 12-volt battery and leave the driver with a lifeless car.

Although the VMs work hard to update their systems when they find these issues, in the meantime they provide a welcome opportunity for the aftermarket because, despite many workshops being wary of working on EVs, it should be encouraging for them to know that the most likely cause of a breakdown, is due to one of the components that they are most familiar with.

Therefore, before surrendering an EV to the franchised dealer network, workshops should first assess the condition of the 12-volt battery and if that’s the issue, providing they use the correct protocols for working on a HV vehicle, installing a replacement not only solves a problem for the owner, but it also makes a profitable job for the business.

As a result of its findings and to further assist the independent service and repair sector, Ecobat Battery has proactively updated its application data on its online Battery Finder, as well as its Numax and Lucas data on MAM Autocat, to provide all the necessary application links to these vehicles.

For further details, please visit Ecobat Battery at: