How To Prevent A Flat Or Dead Battery On Your Porsche

How To Prevent A Flat Or Dead Battery On Your Porsche

Stop risking a breakdown or damaging your Porsche’s electronics.
Unexpected battery failure is an all too common occurrence. Germany’s ADAC (Allgemeiner Deutscher Automobil-Club) organsation estimates that 40 percent of all roadside breakdowns are battery-related and that only a few starter batteries reach the average age of five years.

What is even more perturbing are the findings of a German manufacturer of high-quality starter batteries that estimates factory defects account for only 5 to 7 percent of all warranty claims during the warranty period; driving habits and lack of battery maintenance are the main causes behind the remainder.

In this article, we’ll take a look at how best to maintain your Porsche’s starter battery to avoid being left stranded at the roadside and then risking damaging your car’s electronics when forced to jump-start a flat lead-acid, or in some cases lithium-ion, battery.

Porsche Battery Charger

Why do Porsche batteries go flat?

 The modern Porsche with its digital motor electronics (DME), infotainment screens and advanced driver assist systems (ADAS) is a technological masterpiece and one that relies heavily on a fully charged lead-acid or lithium-ion battery to perform at its best.

However, with many Porsches tucked away, unused, in garages for extended periods the alternator never gets the opportunity to “top-up” the battery. Even with the car switched off it would be quite normal for a parasitic current draw to permanently drain about 50- to 85-milliamps in a modern Porsche, with older cars with fewer electronics drawing less.

Thus, a fully charged “flooded car” battery discharge rate could quite easily be about 0.25 percent per day at 10°C (50°F), 1 percent per day at room temperature, and 1.5 percent per day at 30°C (86°F).

Whilst modern Porsches do have battery management systems that shut down non-essential electrical systems to preserve the battery, there are certain functions, such as Porsche’s “Hands Off” anti-theft system, that have to operate continuously.

And the age-old practice of starting and running a car for a “few minutes” now and again to charge the battery, is also not a good idea. The alternator is only meant to ‘top-up’ the battery, and with the starter motor drawing between 100 to 130 amps, idling the car for 15 minutes might only put back three or four amps. Therefore, the battery never really gets recharged. So each time you start and leave it to idle, the battery’s state of charge (SOC) reduces.

If the battery SOC is allowed to regularly drop to critical levels (typically below about 12.4V in a flooded battery) sulfation will take place. The buildup of lead sulfate crystals is the number one cause of early battery failure in lead-acid batteries.

Porsche battery sulphation

The solution to this problem is to ‘trickle-charge’ your Porsche’s battery frequently and without starting the engine.


Why does trickle-charging your Porsche battery prevent breakdowns?

The principle of maintenance-trickle-charging is quite simple. The intention is to maintain the battery’s state of charge by regularly charging the battery at low currents. This is ideal for cars that are garaged for extended periods, but also important for cars used for short trips or driven infrequently.

A huge benefit of this form of battery maintenance is that the battery is always fit for service, and, by never allowing the battery to fully or “deep-discharge”, sulfation is kept at bay.

To get the job done you need what is commonly known as a trickle-charger. Trickle-chargers come in many formats, with wide-ranging features and even wider-ranging prices and quality. Some even serve as portable chargers that do not need to be plugged into the mains! In this day of electrification where lightweight energy-dense lithium-ion batteries are being offered as an option on high-performance variants such as the Porsche GT3, some trickle chargers even feature a function to charge a Li-ion starter battery.

One such charger widely viewed as the gold standard in cost-effective trickle-chargers, the CTEK Charge-o-mat MXS 5.0 battery conditioner, optimizer, and trickle charger is compatible will all models of Porsche 911, 924, 928, 944, 968, 964, 993, 986, 987, 981, 718 Boxster, Cayman, 996, 997, 991, 992, Panamera, Macan and Cayenne.

Porsche & CTEK MXS5.0 battery charger

When charging a Porsche starter battery the CTEK charger also does not need to be connected directly to the battery terminals, instead, it can charge via an adapter that plugs into the cigar lighter socket so you never get your hands dirty.

It is designed to protect vehicle electronics, in particular the Porsche audio equipment, is non-sparking, reverse polarity protected, and short-circuit proof. It’s also equipped with a raft of other handy features such as its automatic desulfation functionality.

Through effective temperature compensation the rate at which the battery charges is also always optimized, irrespective of climatic conditions. This gives you the confidence that your battery is always in tip-top condition and ready for use regardless if the air temperature is -10°C or +30°C. By maintenance charging your Porsche’s battery, you are also extending its functional lifetime, thereby saving on an expensive early replacement.

With high energy density and lightweight Li-ion starter batteries finding their way into an increasing number of road cars, it is important to note that typical battery chargers, or trickle chargers, are unsuitable and should NOT be used to charge these types of batteries.

However, for owners of Porsches thus equipped CTEK has developed the CSFree portable battery charger, maintainer, and booster. This multifunctional portable handheld battery charger can be used to maintain the charge in your battery, or even boost-charge a 12-volt lead-acid or Li-ion car battery when completely flat.

CTek portable battery charger

It is simple to use. Just charge it up using the mains power adaptors and being portable it’s easy to transport in the glovebox of your Porsche. What is more, it will hold its charge for up to 12 months allowing you to put your Porsche (or any other vehicle) into storage knowing that a flat battery will not prevent you from starting your car when needed. 

And if your car won’t start, the revolutionary adaptive boost technology will safely power up your car battery from flat and get you going within 15 minutes. Unlike many other “battery boosters”, the CSFree charger is designed to circumvent damaging the battery or vehicle's electronics by only providing the required charge.

Furthermore, this flexible charger can also be used as a power bank to run other electrical devices, such as mobile phones and laptop computers.

For long term vehicle trickle and maintenance battery charging, the charger will need a permanent main power supply.


How to maintenance-charge and trickle-charge your Porsche 12v battery

Whilst charging the battery by connecting the charger’s cables directly to the battery poles is the conventional method of charging or boosting the car’s battery, Porsche has simplified the process by allowing customers to charge through the cigarette-lighter or a socket located in the footwell. This also reduces the risk of damaging sensitive vehicle electronics and is by far the easiest way to facilitate effortless maintenance-trickle-charging.


Up until about 2015 Porsche wired the cigarette-lighter with a direct, unswitched and permanent connection to the battery to allow owners to directly connect a charger through the socket.

However, on some later vehicles, the auxiliary power socket is only live for 30 minutes after the ignition is switched off before shutting down. This also applies to vehicles equipped with a footwell socket where the connection remains live (ie connected to the battery) for 30 minutes after the ignition is switched off.

Porsche battery charging through an auxillary socket

In this instance, the procedure for connecting a charger requires that the charger be plugged in and the charger turned on at the mains within a couple of minutes of the ignition being turned off (and definitely within 30 minutes). Once the charger is connected to the socket and switched on, the automatic disconnection is overridden.

Porsche’s focus on making maintenance trickle-charging as easy as possible is an indication of the importance it places on owners of its prestigious vehicles keeping the 12-volt starter battery in peak working order, at all times.

Here at FrazerPart we fully support Porsche’s efforts in ensuring your vehicle’s battery is fully maintained. This reduces the chances of you being stranded at the side of the road and running the risk of damaging the car’s electronics when ‘jump-starting’ it. For these reasons we stock the highly regarded CTEK MXS 5.0 and portable CTEK CSFree trickle chargers, that are compatible with the full range of Porsche vehicles.

To order give us a call at +44 151 66 50 911 or order directly off our website at


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