Keep your cool... but not too cold!

The Molicel cells chosen stated operating range is  -40°C to 60°C.  That's a pretty good range, but really operate best and are "happiest", make full cycle lives and operation to spec when they are around the same temperature us humans like 22°C.  Here are some typical operating temperatures

Unvented Hangar: -10°C - 60°C

Flight(pilot limited): 10°C - 50°C

Sitting outside: -20°C - 50°C

Typical operating range: 10°C - 30°C

So while the operating range is workable, it's not "that" far from the absolute limits.  And those limits are hard limits.  The battery pack will definitely be temperature sensitive and requires active temperature control, especially cooling under high loads in flight.  The simplest/lightest active cooling system is air-cooled.   The nose batteries should receive good airflow from the existing motor cooling inlets.  I am less concerned about them.  The wing-mounted batteries will be sitting inside styrofoam in a cavity carved from the leading edge of the wing.  They will be well insulated (which is a very good thing), but unless some accommodations are made, they would not receive any airflow in flight.  To remedy this, the layout of the pack will accommodate channels where outside air from a NAC duct under thewing can flow through the battery packs in flight to cool them.

Air will flow in three channels formed by the batteries themselves and a baffle.  There's an outside channel between the outside batteries and the walls of the foam cavity, between the first and second rows of batteries, and an inner channel formed by the baffling which will slide into a hot-knife-cut-notch in the foam cavity.

To help determine appropriate cooling and operating parameters several temperature sensors (up to 15) will be installed in the battery packs and monitored during test flights to determine the best-operating conditions and limits.  Those limits will inform normal operating limits.

The temperature sensor is a DS18B20.  These are uniquely identifiable solid-state digital sensors.  They operate from -55 to 125°C and ±0.5°C Accuracy from -10°C to +85°C, so pretty perfect for these operations.  They use a "1-wire" bus-style protocol, so they can all be "ganged" together sharing a single communication wire to a microcontroller that can collect and display the information to the pilot.  That will likely be its own future post.

They can be purchased with some environmental and water resistance.  One potentially layout could be...

Each Motor - 2

Each Controller - 2

Each forward battery - 2

4 per wing battery - 8

Outside Air Temp - 1

Total count 15