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Source: BMW
Source: BMW

BMW patent could ice the issue of lost heat

BMW has filed a successful patent for technology it hopes will end the issue of temperature-derived efficiency problems in its electric vehicles.

The company’s patent explains that its new method will build upon the current performance of automotive systems when faced with changes in temperature.

There is widespread concern, both in the industry and from the consumer, regarding the problems that adverse or improperly regulated temperature has on the physical range of electric vehicles.

Simply put, a cold battery will take longer to recharge, longer to produce power output, and some power will be wasted. Basic processes, such as regenerative braking, whereby the momentum used to stop the car puts energy back into the battery, are much less effective in cold weather. In fact, the battery can be damaged by this process, which limits the vehicle’s lifespan overall, and finally makes for a very unhappy and out of pocket customer. Regardless of the vehicle’s mechanical performance though, temperature is important to the driver’s comfort.  Energy from the battery must also be used to heat up the inside of the car, which further drains it.

According to MIT Technology Review, a customer might see a 35% drop in range capabilities if they operate in a cold environment.  That means that a car, touted as having a range of 250 miles, might only achieve 160 miles before the battery needs to be recharged. This drives up costs because a customer will either choose to spend more charging their vehicle or more on a model with a larger battery.  The former also puts strain on the charging infrastructure in such areas.

To combat some of these issues, manufacturers might choose various solutions. One is to place a heater on the battery itself. Typically, these heaters draw energy from the battery which, again, depletes it. The Nissan Leaf is a model which does so.

Other methods include improving the conductivity of an electrolyte battery.  However, this has downfalls, ranging from poor longevity to potential chemical instability. Finally, a manufacturer might choose to heat the passenger area differently. Tesla uses heated seats which makes passengers feel warm without the need to heat the entire vehicle’s cabin.  Automakers might also insulate the car using special coatings on windows.

Hot topic

BMW is attempting to deal with the problem using a different method. It wants to avoid adding extra parts to the powertrain – more components mean increased cost and greater weight – while still being able to control excess heat produced by the motor’s movement.

The company’s solution is to balance the thermal loads of the electric drive itself rather than add extra parts to the car’s mechanics. This basically means that using the change in temperature, and how it effects each part, in order to move the other parts of the electric drive. In doing this, the thermal stress that temperature fluctuations cause would be simultaneously controlled and reduced.

The idea is not limited to this function. BMW plans to manipulate the field-generating current and the torque-generating current in order to increase dissipating power and temperature. That temperature increase can then be used to heat the interior of the car.

The principle is very intelligent, and demonstrates that the company is serious about positioning itself as a competitor to Tesla.  Elon Musk’s highly successful Model S is the best-selling electric vehicle in Norway, but despite it popularity, it is not as adept as it could be to deal with the country’s typically colder weather.

However, BMW must be careful to make sure that the system operates safely. Any increase in temperature can be difficult to control once it gets out of hand. The powertrain’s parts need to be made capable to deal with thermal load stresses.

Finally, the patent identifies that the new system will include an onboard computer which will manage the process of balancing temperatures.

The problem of is unlikely to be solved overnight, and the numerous methods employed by different manufacturers suggest there is not yet a consensus on how best to approach it. But the fact that BMW is tackling the issue is proof of its commitment to the technology – and advances like these may yet give its models the edge.


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