As pointed out by recent coverage from foreign media, the National Highway Traffic Safety Administration (NHTSA) is currently handling and investigating the severe defects in the battery design of Tesla’s Model S, which leads to coolant leakage that would trigger malfunction or fire, and Tesla might have noticed such issue as early as 8 years ago.
The internal letter provided by the three former Tesla employees who were interviewed by Business Insider indicates that Tesla had discovered the leakage of its battery cooling device back in 2012, which the company had described as a critical quality issue, and was reported to the executives of the company, though the subsequent development is unknown due to the promotion phase of the product at the time. Simultaneously, when inspecting the copy of the letter and the relevant documents, The Times pointed out that Tesla was still installing this specific cooling system between 2012 and 2016.
NHTSA has pointed out accordingly that it will launch an investigation according to the facts and existing information, and also reminded automotive manufacturers to notify the administration within 5 days of recalling for any defects discovered on relevant safety equipment. Tesla never seemed to have notified on the issue.
The temperature range for the operation of lithium ion battery is usually between 15 and 45°C, though battery releases heat amidst charging and discharging, thus the functional safety and lifespan of battery cells, to the overall safety of smartphones, electric vehicles, and energy storage system, are partially dependent on temperature. Tesla had installed coolant pipes outside of the battery for Model S in the past to reduce the temperature of the battery.
Though as indicated by the internal letter, the softer aluminum material used for the end connection parts is prone to cracks and small openings from the abrasion derived during welding and subsequent usage, and leads to coolant leakage. As pointed out by Business Insider, third party verification agency IMR Test Labs had notified Tesla in 2012 that the cooling pipes the company purchased from a Chinese company are prone to cracks and small openings, and Tesla had implemented two tests targeted at the components of the battery cooling system, which confirmed on the defects.
Experts of battery accident commented that the ethylene glycol of coolant is flammable, thus the coolant may trigger fire or aggravate the fire after vehicle collisions. Formed with multiple batteries and a battery management system, the battery unit of electric vehicles is usually installed beneath the center of the two axles, which makes it part of the chassis structure, and despite its adequate impact resistance, safety remains to be a priority.
The electric vehicles of Tesla have sustained at least 14 fire incidents around the world since 2013, with most of them occurring after collisions. In accordance with the potential fire hazard from electric vehicles, the National Transportation Safety Board (NTSB) has expressed that the special investigation report targeted at electric vehicle collisions and the overheating of batteries will complete soon, and the board of NTSB pointed out that investigation of fire incidents from electric vehicles will take into account if the severe collisions are caused by machine or material defects.
NHTSA was investigating the potential issues in the batteries of Tesla during November 2019, though the administration has yet to disclose if the coolant leakage is an independent or comprehensive investigation.
The investigation scope from NHTSA in the future will cover the 63,000 units of Model S that were sold between 2012 and 2016. Tesla has yet to respond to the cooling system nor the concealment of critical information, and all will be revealed from the further investigation of NHTSA.
(Cover photo source: Tesla)