Looking at the data sheet, Novec 7100 or HCFC-225  would be a better choice than 7200.
Novec 7200 is flammable, while 7100 or HCFC-225  isn't. HCFC-225 has a boiling point a few degrees below the cell electrolyte while 7100 has a boiling point _just_ below that of the electrolyte in the cells. (You would rather the coolant boil first, and remove the heat, than the electrolyte, and cause the cells to vent.)

Not a new idea at all. It has been tossed around for quite some time. Halotron (R123) was proposed for this exact propose awhile back. Other, less ozone depleting, substances have been considered, but flammability becomes an issue generally associated with low ozone depletion. However, corrosion is an issue that has to be taken into account, but is often forgotten until it makes itself painfully obvious. When you constrain the coolant to passages, instead of covering the entire battery, corrosion can be controlled by reducing the materials exposed to the coolant.

The ideal solution is reducing the internal resistance of the cells, which reduces the need for cooling and increases efficiency. That will eventually be the optimal solution, I suspect.

Bill D.

On 12/13/2017 2:47 AM, brucedp5 via EV wrote:

New approach to electric-car battery cooling: immerse cells in coolant
Dec 8, 2017  Mark Stevenson

XING Miss R Lithium-Ion Battery Pack

XING Modular Battery System

Regardless of how your vehicle is powered—whether it be an
internal-combustion engine or a battery pack powering an electric motor—most
powertrains have a common enemy: heat.

For Taipei-based XING Mobility, heat is a major concern for its
high-performance Miss R model as its battery cells need to rapidly discharge
to generate its maximum quoted output of 1,000 kilowatts (1,341-horsepower).

The more rapidly you discharge a battery, the more heat it generates—and
XING believes it has a solution to keep its fast-discharging battery pack

Instead of snaking coolant through lines and chambers within the battery
pack's case, XING is taking a wholly different approach by immersing its
cells in a non-conductive fluid with a high boiling point.

According to Charged EVs, the coolant is 3M Novec 7200 Engineered Fluid, "a
non-conductive fluid designed for heat transfer applications, fire
suppression and supercomputer cooling."

“The use of Novec Engineered Fluids to immersion-cool EV batteries is a
breakthrough application, addressing the critical performance needs of the
market in a new and disruptive way,” said 3M’s Michael Garceau to Charged

XING's batteries take the form of 42 lithium-ion-cell modules that can be
put together to build larger battery solutions.

For the XING Miss R, the complete battery houses 4,200 individual 18650
lithium-ion cells encased in liquid-cooled module packs.

While XING plans to use the battery packs for its own vehicles, it said it
will also sell the battery solutions to other OEMs looking for energy
storage solutions.

READ MORE: Could water be the secret to faster electric-car battery

“The industrial vehicle market is primed for a conversion to electric
drivetrains due to functional needs, increasing emissions requirements and
public noise reduction,” said XING co-founder and CTO Azizi Tucker.

"The XING Battery System is an opportune solution for small- to
medium-volume vehicle makers, catering to a huge variety of shapes, sizes
and power requirements.”

XING also plans to offer other off-the-shelf components for fledgling EV
makers, such as torque-vectoring gearboxes, electric power kits, and
magnetorheological dampers.

The company projects its Miss R model should be capable of sprinting to 100
km/h in 1.8 seconds, reaching 200 km/h in 5 seconds, and hitting a top speed
of 270 km/h (168 mph).
[© 2017 Green Car Reports]

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