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After owner outcry, Tesla reverses decision to limit Model S Launch Mode

Tesla Model S (charged EVs)

Many Tesla owners rave (in a good way) about the over-the-air software updates that the company uses to add new features or fix bugs. However, some were less pleased when Tesla used over-the-air capability to limit an existing feature called Launch Mode.

Launch Mode is an electronic system that helps the driver to achieve maximum acceleration – many ICE performance cars have a similar feature. Some of them also have a system that limits power output if drivers blast off too frequently, in order to prevent excessive wear on the powertrain.

Some time ago, Tesla quietly installed such a limiter on some versions of Model S. The issue came to light after a couple of Tesla Motors Club forum users noticed that their use of Launch Mode had been limited, and a Tesla spokesperson confirmed it, saying that the car’s computers “automatically track Launch Mode usage and continually estimate fatigue damage,” and that “depending on how Launch Mode is used, the computer may eventually limit the available power during Launch Mode to protect the powertrain.”

Which components of the powertrain are being stressed by Launch Mode? For some insight into this question, we asked Charged technology editor Jeffrey Jenkins. He noted that the power electronics could be part of the problem. “The bond wires that connect a semiconductor die to the outside world are subject to fatigue failure from thermal cycling, but that’s usually only a problem in semiconductors that are run close to their amperage limit and/or which aren’t cooled well.”

MORE: A closer look at the semiconductor switch

However, the best guess is that there’s an issue with the battery pack, judging by the fact that the Model S P100D with Ludicrous Mode never had the limiter. The discharge rate of the battery might be a factor – drawing maximum current from a smaller pack stresses the individual cells and components more than drawing it from a larger pack.

Be that as it may, in response to owner dissatisfaction with the limiting software, Tesla has decided to scrap it. President of Sales and Service Jon McNeill told the Tesla Motors Club forum that the offending software will be removed by the next software update, in about three weeks.

“Based on your input, we have decided to remove all software performance reductions tied to frequent max power usage,” said McNeill. “We had put these reductions in place to proactively protect the powertrain from wear and tear. Instead, we will monitor the condition of the powertrain and let our customers know if service is needed so that we can take proactive steps, such as by replacing parts if necessary, to maintain the vehicle’s performance.”

Any necessary parts replacements will be covered by the warranty.


Sources: Tesla Motors Club, Green Car Reports, Electrek


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