Porsche invents a way to start a car with a flat battery without outside help
Porsche engineers have developed a system that could make a car with a depleted 12-volt battery ready to start again. It uses heat from a petrol-fired auxiliary heater to generate electricity, allowing the battery to be charged without an external charger or jump-start. The idea is clever, but its practical value depends on one important question: how do you start the heater when the battery is already flat?
Turning heat into electricity
Porsche patent application DE102025116604A1 describes a system that combines a fuel-fired auxiliary heater with a thermoelectric generator.
The generator uses the Seebeck effect, in which a voltage develops between two sides at different temperatures.
In Porsche's design, a petrol burner heats one side of the generator, while the other transfers heat to cooler body components. The temperature difference allows electricity to be generated to charge the car's 12-volt battery.
In cold weather, a greater temperature difference could help the generator operate. Such a system is particularly useful in winter, as low temperatures reduce a lead-acid battery's starting capability and make an internal combustion engine harder to start.
The biggest problem is starting the heater itself
The core idea behind the patent is to use fuel in the car's tank to generate electricity when the battery no longer has enough energy to operate the starter motor.
Unlike a conventional generator, the thermoelectric system does not need moving mechanical parts to generate electricity.
Unfortunately, its efficiency is relatively low. To generate a significant amount of electrical energy, the system needs a sufficient temperature difference and time.
An even more important issue is operating the auxiliary heater. The fuel pump, control unit and burner ignition system all need electricity. The design must therefore ensure that enough energy remains to start them even when the starter battery can no longer start the engine.
Porsche has not disclosed the generator's power output, the time needed to recharge the battery or the system's cost.
Could Porsche's system become a winter option?
Webasto and Eberspächer already offer fuel-fired auxiliary heaters in the European market. These use a burner that operates independently of the engine to heat the cabin or coolant.
Porsche's idea would add the ability to generate electricity.
However, a conventional jump-start battery is considerably simpler and cheaper. Porsche's system could offer advantages primarily in situations where a car is left standing in the cold for long periods without access to external charging.
The patent's greatest value lies in finding a new use for existing technology. If Porsche can ensure that the heater operates even with a heavily depleted battery and generates enough electricity within a reasonable time, the system could reduce winter starting problems.
For now, however, it remains a patent application. Porsche has not confirmed any test results for the technology or its introduction in any production model.
