Car battery: how to make it last and charge it

Faced with repeated breakdowns, our forefathers had a respect for their car’s battery that we don’t have. Wrongly so. Because the failures that pass for isolated cases actually hide a real epidemic. The German Automobile Club (ADAC) reports that the battery was the number one cause of breakdowns in 2017, just like in the good old days of carburetors and ignition switches. No less than 39% of the calls from motorists in distress were caused by insufficient electrical voltage, preventing the engine from starting or operating normally (restricted power, warning message on the dashboard). There is every reason to believe that this proportion is on the rise.

Accustomed to only worrying about their battery every five to seven years on average, when the time comes to replace it, motorists will conclude that an early failure is a sign of declining quality. In fact, the opposite is true: the introduction of the Euro 6 standard in 2016 has led manufacturers to fit their cars with reinforced batteries (see definition at the end of the article), made necessary by the widespread use of automatic stop-start systems, kinetic energy recovery and controlled alternators.

The battery is more stressed but less charged and suffers

Powerline Car Batteries

All three systems have the same objective: to save precious deciliters of fuel in order to save a few grams of carbon dioxide during certification tests. The aim is to avoid the ecological penalty that hits the buyer, as well as the fines to which the manufacturer is exposed if it does not succeed in reducing its average CO2 emissions below a certain threshold by 2021.

Why should your car’s battery suffer from this strategy? For the simple reason that the current that feeds it is produced by an alternator that is driven by the engine, at the cost of slightly higher fuel consumption. To reduce fuel consumption, manufacturers have decided not to have the alternator run continuously. The electronics determine when to drive it, depending on the current demand of the accessories and the battery charge rate.

Less battery charging to save fuel

The problem is that manufacturers seem to have pushed their fuel-saving strategy too far. This is what Abel Santirso, representative in France of the Swedish company CTEK, the world’s leading manufacturer of battery chargers, explains to Challenges.

“On recent vehicles, the ECU is programmed to stop driving the alternator as soon as the battery charge level reaches 85%. This threshold varies from one model to another, from one manufacturer to another, depending on the rule programmed into the BMS (or Battery Management System) computer chip connected to the negative pole. “The battery is never fully charged, as it could be on pre-Euro 6 vehicles that were constantly driving their alternator.” Compiling data from manufacturers, CTEK estimates that 40 percent of newer vehicles (Euro 6) that come into the shop for service need a battery charge.

40% of recent vehicles run on a weak battery

As a result, in the morning, your car battery is not always in top shape. This is especially true since its capacity to store current is rapidly diminishing as a result of hard work. This is demonstrated by the results of a study carried out by a major battery manufacturer (who will remain anonymous), which found that in a vehicle that was only six months old, the automatic stop-start system was already operating half as frequently as when it left the factory. This is due to a battery whose voltage is deemed insufficient by the computer that controls the system.

But this is an average time: “The battery capacity will degrade faster in hot regions and on a vehicle that is frequently driven in the city, where stops and starts are more frequent,” says Abel Santirso.

More and more on-board electronics

As if that wasn’t enough, the hardy 12-volt lead-acid battery has to meet the power demands of an increasing number of on-board accessories (displays, phone and wireless antenna, assist motors). “On average, there are about 110 ECUs per vehicle,” says Abel Santirso. “The simple act of remotely locking the doors of a recent Volkswagen Golf consumes 25 amps. A quarter of an hour later, a host of electronic systems related to engine management and infotainment are still awake and drawing a significant amount of current.”

Another example: on vehicles equipped with an electric parking brake, the ECU is programmed to check the tension of the brake cables. “On a typical family sedan such as a Volkswagen Passat, this action can consume up to 35 amps,” says A. Santirso. This check takes place at regular intervals, or when a sensor detects a movement. For example, when a truck passes by, due to air displacement.

“This significant current consumption adds up to others and leads, for example, the German manufacturer Daimler to warn its customers: the engine start is no longer guaranteed beyond fifteen successive days of stopping because the battery power may not be sufficient.” This applies to a perfectly healthy battery. Some drivers of recent vehicles – and not only Mercedes – have had the unpleasant surprise to find their battery flat after a four-day stay.

It’s no coincidence that BMW has reintroduced the battery gauge to the dashboard or that Mercedes’ mobile app displays an alert if the voltage drops.

Even at a standstill, a car consumes power

As Abel Santirso reminds us, electronic systems “pull” on the battery without the motorist being aware of it. This is so true that manufacturers are putting in place procedures to protect the vehicle’s battery during maintenance operations.

At Volkswagen, for example, the diagnostic unit (VAS 6161 controller) prompts the technician to connect an external power supply as soon as he or she begins any maintenance work. In the jargon of the trade, this is called “stabilizing the battery”. “If software updates or flashing actions need to be performed on a vehicle, the diagnostic device reminds the technician to use a battery charger with a charging current of at least 70 A to avoid any problems,” says Audrey Garousse, of Volkswagen France’s Press & Public Relations department. On a 2015 Volkswagen Golf, with a 1.4 TSI gasoline engine, CTEK’s people found that just plugging the case into the diagnostic socket consumed 33 amps of current. On a Volkswagen Passat, operating the rear brake calipers to change the brake pads consumes about 55 amps. And so on (the list is long, see our box).

Our cars are more and more voracious in running

Swedish battery charger manufacturer CTEK has measured the current levels in two representative vehicles: a compact family sedan with a gasoline engine and a large SUV with a diesel engine. In the Volkswagen Golf 1.4 TSI, operating the central locking system consumes 24.20 amps, compared to 27.1 amps in the BMW X4, not only because of the lock motors but also because of the various electronic devices. Pulling the door draws 7.1 amps and 10.5 amps respectively; turning on the ignition, between 26.5 amps and 32.8 amps; rolling down the power window, between 35.7 amps and 40.4 amps; operating the parking brake, between 36.1 amps and 30.6 amps; turning on the lights, between 30.7 amps and 27.68 amps; and plugging in a diagnostic case, between 33.1 amps and 29.98 amps. The most disturbing thing is that these actions, once accomplished, still induce a residual consumption during several minutes. Remember that when properly charged, a battery given a capacity of 70 ampere-hours (Ah) can theoretically deliver a current of 70 amperes for one hour.

The same is true of BMW, where the technician’s work on the on-board electronics can only start if an external charger is connected to the battery. The same goes for Ford, where the IDS diagnostic tool requires “permanent power or, if necessary, a full charge” of the battery when the technician begins his maintenance operations. “The objective is to return a vehicle that will not present any risk of “return on repair” linked to the battery’s load during maintenance”, explains Olivier Gallic, Head of Press Service at Ford France. In other words, the aim is to prevent the customer from running out of battery power on the way home.

At Peugeot, we consider that the risk only exists after downloading a large update from the on-board computer. The connection of an external charger is only recommended in this case, provided of course that the battery’s good health has been guaranteed by a prior diagnosis. In fact, all manufacturers include the battery on the list of components systematically checked during periodic maintenance. Depending on the diagnosis, the technician will either charge the battery or replace it.

Mechanics are too quick to replace the battery

Abel Santirso believes that this diagnosis is not always done properly and that batteries in good condition are discarded prematurely. “CTEK has estimated that 85.2 percent of the batteries disassembled by repairers and destined for recycling do not suffer from any defects.”

Why such a mess? Because the diagnostic tools conclude too quickly that the battery needs to be replaced.

“Modern vehicles are very energy-intensive. Yet their BMS only charges the battery to a very small range of its capacity, never more than 85%,” recalls A. Santirso. “This has the effect of quickly depleting the battery’s charge potential. At first, the driver doesn’t notice anything. Then he notices that the automatic stop-start system works less early and less often. Then, some on-board equipment refuses to work and the on-board computer generates an error code to declare the battery non-compliant, because it is unable to take the charge. In some extreme cases, the engine ends up going into a degraded operating mode: power and rpm are limited, simply because the computer judges the battery voltage to be too low, for example to manage the opening of the EGR valve. The customer then goes to his repairer who concludes too quickly that the battery needs to be replaced. Whereas its reconditioning is possible.”

Abel Santirso is referring to the so-called “intelligent” battery chargers that CTEK has made a specialty of. Available in a range of versions for both professional and private users, these devices are capable not only of regulating the charging voltage (in order to limit the heating of the electrolyte), but also of splitting the process into several analysis and desulphation phases.

This operation consists in detaching the sulphate crystals which agglomerate on the lead plates and gradually reduce the battery’s capacity. Note that sulfation starts as soon as the voltage drops below 12.42 volts, very precisely. Therefore, a battery that is not fully charged will sulphate faster and lose capacity quickly.

Every 3 months, give your battery a nightly charge

Anyone can perform this treatment by plugging in a so-called smart charger at home. “I recommend desulfation once a year and nightly charging every three months or so. Our studies have measured that this regimen limits capacity loss to 4.6 percent after 1,080 hours of operation, the equivalent of two and a half years of city traffic. Without treatment, capacity loss averages 40 percent in two and a half years.” CTEK thus promises to increase the life expectancy of a reinforced AGM battery threefold, which can cost up to 400 euros to replace. This is partly because a technician is required to “pair” the new battery with the car’s electronic management system.

According to CTEK, workshops are gradually equipping themselves with intelligent chargers: more and more of them are offering battery maintenance as part of their services. “In Germany, when a vehicle comes to the workshop, the technician systematically diagnoses the battery, without the customer having to ask. In France, this is not yet the case everywhere,” laments Abel Santirso. However, this kind of discipline would make it possible to prevent rather than cure a drop in the battery’s condition, in order to usefully extend its lifespan.

Between 200 and 400 euros to replace a battery

Are the necessary precautions taken in independent garages and in the fast repair networks? Norauto tells us that they take advantage of the times when the engine is started during the service to carry out diagnostic operations and thus spare the battery. When they drag on, an external charger is connected. Finally, diagnostic tools use “patented algorithms” to distinguish between batteries that are good to save and those that are good to throw away.

In the end, everything depends on the goodwill of the mechanic and on the seriousness of the training he receives. Unfortunately for the consumer, it seems very delicate to require his mechanic to connect an external power supply to the battery of his vehicle. At the very least, he should get into the habit of asking for a systematic diagnosis of his battery, without waiting for the first signs of weakness. Better still, the modern motorist will have to adopt the habits of our grandfathers who used to plug in the battery at night. Watch out! The old charger of yesteryear – you know, that big metal cube that delivers a strong and constant voltage – will not do the trick: it risks damaging a modern battery, whether it is reinforced or not.

What is a reinforced battery?

In an AGM (Absorbent Glass Mat) battery, the acid in the electrolyte does not circulate freely but is retained by thin sheets of glass mat which act like blotters between more numerous lead plates. This improves electronic exchanges as well as resistance to vibrations, which in turn improves endurance and power output. The drawback is that AGM batteries can no longer tolerate the high voltages suddenly applied by a traditional battery charger. You know, that red tin box that’s been lying around in the garage since the days when poorly tuned carburetors, worn platinum screws and hesitant capacitors made cold starting acrobatic.

In an EFB (enhanced flooded battery), the conventional liquid electrolyte is retained but circulates between better insulated positive and negative plates, for better heat resistance. The EFB battery is less expensive than the AGM battery: for this reason, the former is preferred by manufacturers of mass-market models, while the latter is more likely to be found on high-end models.

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