Watch Tesla’s battery thermal management in action while Supercharging

By Steve Hanley

Posted on April 18, 2017

Early Tesla Model S adopter and YouTuber KmanAuto set out to prove his theory that the Tesla battery thermal management system kicks in to full cooling mode when battery temperatures exceed 113º F (45 C). The exercise put a spotlight on the rarely seen relationship between charging power and battery temperature in a Tesla.

The video begins with KmanAuto’s Model S 90D plugged into Tesla’s high power Supercharger station while having a battery state of charge of 47.5%. Outside temperature was reported to be around 63º F (17 C). By plugging into his Tesla’s diagnostic port, Kman was able to obtain battery activity data using a 3rd party app called TM-Spy.

Supercharging began at 94 kilowatts of power, with battery temperature holding steady at just over 112º F (44.4C). As charging continued, the car’s cooling fans were in operation but the air conditioner remained inactive. As battery temperature reached 113.1º F (45C), the Supercharger began to reduce charging power by nearly 25% to 72 kW in order to keep operating temperatures within safe thermal limits. Kman also noted that the vehicle’s cooling fans began to noticeably increase in speed during that time.

In circumstances when outside temperature and battery state of charge is at an optimal state, Model S and Model X owners should be able to charge at 90 kW – battery packs on early generation Model S were able to sustain a max 90 kW charge – and as high as 135 kW to at least a 60% SOC. Tesla’s most recent Superchargers are rated at a max output of 145 kW.

Kman noted that charging power decreased to 64 kW but as battery temperature stabilized at 113.3º (45.17 C), the charge rate began to increase. As the vehicle approached a 60% SOC, battery temperature remained steady at 112.5º F (44.72 C) and charging power reached 81 kW. KmanAuto speculates that those numbers represent what the battery charging system is capable of maintaining under normal conditions. Beyond the 60% SOC point in the process, charging power once again began to decline, which he notes is typical.

KmanAuto’s video supports the conventional wisdom that lithium ion batteries prefer to be kept below 113º F (45 C). That’s the point at which Tesla has programmed the cooling system to go to maximum thermal cooling mode.

Source: KmanAuto via Teslarati forum

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Top Rated Comments  (view all)

Discuss: Model S

Pat Free     1 likes  2 months ago

There seams to have zero headroom left for when even faster SuperCharger v3 up-date will come... (Well Greater than 350KW tweeted by Elon in Dec). Understand this is on a 90D Model S limited to unclear peak and sustained power levels. I'm targeting a Model X 100D that was said to be limited to 120KW fast charging (1.2C) so far. I'm now waiting for Elon to clarify his entire SC v3 plan, especially after he recently tweeted that all Model S & X will also move to the new better 2170 battery modules by the end of 2017. I would not like to order a current X 100D model, with previous 18165 battery modules now (That will never benefit free-for-life Supercharger refills despite its price was not set lower to account for this loss in January, and whose price will now un-expectively increase on April 24th instead of the opposite expected to share the -5% to -30% battery price deceases experienced recently), ..... Then see Tesla announcing a new 100D+ Model X with new better 2170 battery modules up to 30% more effective, means lighter and possibly cheaper, and that could charge 3X to 5X faster in the second half of this year, while old models based on 18165 may remain blocked at 120KW or less forever. I understand this 3X-5X faster charging may come at the expense of a reduction of Tesla 8Y unlimited millage warranty on the battery, but this could be OK if in the same time Elon commits for ex. a maximum <$10K new battery replacement option price guarantied for at least 15 years, down the road.
For me this SC v3 3X-5X faster charging is a critical capability for my long vacation trips up to 6 times per year, so I'll wait until I know which way to go to best benefit these new SC v3 on Model X with at least a 100KWH battery pack.

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