Validation testing plays a significant role in vehicle development for Karma Automotive (and any OEM). Our thermal engineering team traveled to Stovepipe Wells in Death Valley with 2020 Karma Revero GT vehicles. Rigorous testing against extreme conditions commenced for three-days to gather data in multiple areas, including: air conditioning (HVAC) cooling, battery functionality, and powertrain temperatures.
Stovepipe Wells may be the most aptly named place in the world, truly revealing the harshness of a desert environment. The austere and rugged landscape offered the ultimate proving grounds as temperatures hovered at 115°F.
The first of three tests verified the performance of our Revero GT’s all-new HVAC cooling system. The vehicles were parked in the midday sun for 30 to 60 minutes to elevate the cabins temperatures to 73°C (163°F). This process is known as “heat-soaking,” and is used to analyze how quickly the air conditioning can cool down the interior cabin.
Following a soak, the Revero GT’s were driven on highway 19 to Stovepipe Wells. Along the way, the team experienced variable driving grades and long, steep climbs for 16-miles to an elevation of 4,090 ft. before descending back down. This drive was repeated three times to ensure that the additional load placed on the on-board generator and powertrain had minimal impact on the vehicles ability to cool itself and its occupants.
“The vehicles HVAC system worked very well under severe heat conditions and took minimal time to cool down the interior. We worked very hard to improve and optimize the original HVAC system. Over the past two years, we’ve tested at Death Valley, our HVAC system has shown improved performance” said Juan Gallardo, Thermal Engineering Test and Control Engineer.
The second test was designed to create maximum strain on our new 28-kWh battery, while driving in Stealth (pure-electric), Sustain and Sport modes. These tests were executed to monitor the batteries coolant system temperatures.
Heat is a major concern for high performance battery cells. The more rapid a battery is discharged; the more heat is generated. The combined discharge and hot ambient temperatures can cause uneven battery pack temperatures. Elevated temperatures cause different discharge and charge behaviors, which leads to reduced performance. In order to remedy this issue, our battery system cools the battery pack cells in a 50/50 liquid solution. This cooling process helps to insulate the battery cells to maintain stabilized temperatures and deliver optimal performance.
During final test verifications, engineers drove the Revero GT vehicles at both normal driving speeds and in Sport mode for 20 minutes through Stovepipe Wells, before stopping and idling the vehicle. This cyclic procedure of stop and go acceleration delivers additional strain to the on-board generator, powertrain, and HVAC systems.
According to Gallardo, testing was successful with no indications of battery overheating or degradation issues. He also mentioned that the air conditioning continued to run cold all the way up the climb.
This post was edited 10/15/2019 13:58:36