Varg ridden at 6,700 m = 22,000 ft above sea level

[Theo]

It happened on the Los Ojos del Salado active volcano, located in the Argentina-Chile border.
Here is the video:

Here is an article in which you can see better that sort of blanket on the battery that reminds me of the ones used on space vehicles: according to an AI, it's called Multi Layer Insulation.
The temperature there, these days, is roughly -10 C / -25 C: 15 F / -10 F.
The air pressure is roughly two fifth of the one at sea level but, according to that AI, the air density is something more, closer to 50%, because it's also very cold. Less dense air also means less heat lost via conduction with air. Combine this will less heat radiation thanks to the aforementioned blanket and the cold battery problem becomes less serious.
The winds are strong there: from 20 to 70 knots.
The tenuous air isn't a problem for an electric motor but it is for the rider, who has way less oxygen to breathe.

 

[Theo]

A more extended video:

Something I've found pretty interesting:
• The inverter and the VCU are airtight and assembled at sea level (so with a lower external pressure they tend to expand) but their engineer connected to the bike to make sure they were allright.
• At 13:40 and 17:54 he deflated tyres, I think because with a lower external pressure they become overinflated: 1 bar at sea level for example means 1 bar more than the air pressure at sea level, which is roughly 1 bar, so the absolute pressure of the tyre is 1 bar + 1 bar = 2 bar; when the same tyre is brought to a place where the atmpspheric pressure is 0.4 bar, than the tyre behaves like it were inflated at 1.6 bar at sea level (since 2 - 0.4 = 1.6).
• I guess the fork had the same pressure problem but he wasn't jumping big so the spring effect of the air pressure was probably negligible anyways. Bleeding it would have probably solved issues.
• Stark suggested charging to heat up battery; notice how for my MX 1.0 the manual says not to charge a battery below 4°C.
• They tested a Varg on a dyno at subfreezing temperatures before attempting that.