Replacing a battery at the end of its life seems a simple matter. However, the operation requires great care to avoid unpleasant surprises.

Manufacturers’ battery specifications have evolved over the years, in much the same way as engine oils. Gone are the days when all you had to do to replace a 12-volt battery was remove a bracket, free up two terminals and install the first battery whose dimensions matched the compartment.

Those days are gone, because vehicles need specific batteries to operate, and the wrong choice can lead to problems that customers won’t soon forget.

“You know, many of the batteries affected by the pandemic have not been replaced,” says Nicolas Vallières, Senior Market Manager at NAPA Auto Parts.

“The need to replace the battery is a question of age, but also a factor of use. In addition to cars that have been little used during the pandemic, all those that only make sporadic trips over short distances could also show early battery fatigue.” According to him, even before early signs of weakness appear, workshops should put in place a systematic battery check protocol.

“Why not take a few minutes at every oil change to check the condition of the battery using a specialised tool? Customers can point to early signs of battery wear, such as difficulty starting or the loss of certain accessories. But an analysis of the electrical system may reveal fault codes on these batteries, which are heavily used not only for starting, but also for powering all the comfort and safety accessories found in modern vehicles.”

Some vehicles will simply switch off energy-hungry accessories if the battery is no longer able to meet demand, without anything lighting up the dashboard.

As a general rule, Vallières recommends paying particular attention to batteries that are more than five years old.

“There’s no longer a season to experience problems with a battery,” adds Billy Thomas, training specialist at Bumper to Bumper. We think of our harsh winters, but the battery takes a beating in the heat of summer too. Like his colleague, he notes that accessories are power-hungry and that battery health should be at the top of the list of items to check on customer vehicles.

“There’s nothing worse for consumer confidence than a car that refuses to start on a cold winter’s morning the day after a visit to the local workshop,” says Thomas.

In his opinion, a complete check of the charging system will reveal not only the condition of the battery, but also that of the alternator and starter motor. We can also identify voltage losses resulting from a wiring problem, for example. Corroded terminals or loose cables can cause a variety of problems.

Time to replace

The battery must also undergo a charge, resistance and sulphation test to determine whether it is still usable. Wilson Almeida, Technical Training Manager for the Del Vasto Group continues: “Once tested, if the battery does need replacing, the workshop manual and the search software will indicate exactly what type of part to choose and the replacement protocol. Some models have two batteries, so you need to know which one to replace first.”

The search software will indicate the type of battery: conventional lead-acid or AGM, with fibreglass separators – increasingly common in modern cars – and the power required. “It is possible, within certain parameters, to offer customers a more powerful battery than the one being replaced, from 300 to 400 CCA for example,” says Vallières.

But putting in a battery whose power exceeds the vehicle’s electrical capacity to please a customer who wants to start like a house on fire is a mistake that could cause major problems.

Like his colleagues, he recommends offering these customers batteries that meet the specifications of their vehicle, but of a higher quality. The extra cost is absorbed by greater durability and better warranty cover. “Don’t choose for the customer, offer quality.”

In some cases, the lead-acid battery can be replaced by its AGM equivalent, but never vice versa. Here too, the operation cannot be carried out blindly. Substitutions can only be made if the manufacturer indicates this in the digital workshop manual.

An intelligent room

Billy Thomas, like his colleagues, insists that when it comes to replacing a battery, you can’t do just anything. It’s hard to see consumers simply replacing the faulty battery in a shopping centre forecourt with a battery bought in a high street shop, and for good reason.

“You have to understand the battery management system (BMS). More and more often, this system has to be reprogrammed to accept the new part and adjust the charging system accordingly. The whole system has to adapt to this new battery, whose charging capacities are no longer the same. It’s not a minor detail, and you need to be vigilant and professional. Sometimes the replacement is very simple, sometimes it requires a high level of technical expertise.”

The three experts consulted agreed on the importance of following the processes indicated in digital maintenance manuals before carrying out a replacement, even if the operation seems routine.

Finally, Almeida reminds us of the importance of installing replacement batteries at full load.