Outdoor enclosure for 48-volt Lithium battery

Hi All
After 43 years, I have decided to upgrade my power system.
I am switching from a 12-volt system to a 48-volt system.
My new Battery is a Discover Helios 48-volt lithium battery.
It has 16,000 watts and a 314-amp-hour capacity; it supports 10K continuous use and comes in a large, weatherproof enclosure that can be installed outdoors.
A built-in internal heater can keep the battery at the correct operating temperature.
This battery works from- 13°F to 131°F, but below 47F the internal heater would run.
In a warm climate, this would not be an issue. In northern Montana, it would be a big deal; I'd use power just to keep my battery warm overnight when I'm not even using it.  During a typical winter day, we never get near 47F. This means the battery heater would be running 24-7... not acceptable.
Although considered completely safe for an indoor installation, with double internal shut-down switches in case of thermal runaway, I cannot bring myself to install this inside our old cabin.
So, I have constructed a fire retardent brick vault, insulated, cement-lined, attached to the outside of the cabin.
Two 1.25" holes for the large power cables and two three-inch holes are drilled through the cedar logs to allow air to circulate from the cabin. Shorty core is only 6-7 feet from the wall; warm air is not lacking.
I will have a temperature probe inside the box to monitor temperatures, and if needed, I can use a muffin fan to force warm air through the box.
I still need to put metal on the roof, but for now the new battery room is ready for the 300# battery to be moved in.