It’s looking like the days of the old, mechanical power disconnect are numbered as Modern Racing has developed a better, safer, and more versatile version with its Solid-State Battery Disconnect.
The mechanical cable and push/pull lever employed to turn power off and on in race cars all over the world has been a reliable product and a mandated safety feature for many sanctioning bodies. It allows track and safety personnel the ability to shut the power down from the outside of the car, which can be necessitated by a variety of circumstances.
As necessity is often the mother of invention, an on-track incident involving Erica Enders at the NHRA event in Norwalk showed a fault in the design of the mechanical power disconnect system, and as Justin Elkes of Modern Racing was already working on something new to replace it, the near-tragic incident verified the need for something better and pushed development forward.
The Pro Modified machine Enders was driving at the time caught fire at the top end of the track and after the car came to a stop and Enders bailed out, a shorted out starter continued to turn the engine over. While that wouldn’t normally be an issue, especially with Enders having killed the ignition, the engine’s rotation continued to drive the mechanical fuel pump. The damaged fuel system then leaked fuel and fed the fire, but the NHRA Safety Safari was able to contain it. Once the car arrived back at Modern Racing for repairs and Elkes had a chance to assess the situation, he decided the time was right to make a change.
With the current mechanical design, it’s possible that a safety crew might not be able to reach the power disconnect if the back of the car is on fire. Another scenario is as a result of a crash, the mechanical disconnect components could be damaged and not function properly. Modern Racing believed it could add another layer of protection for everyone involved by building a better system.
“We had installed some solid-state disconnects on cars here that were industrial-based, and we liked getting rid of the mechanical switch, but we couldn’t find one made for the motorsports industry,” explained Elkes “There were none that had any logic in them and could take inputs. The concept also needed a switch able to handle the 24-volt cranking systems of the supercharged engines,” Elkes told us. “We just couldn’t find one that met all of our specs.”
In them midst of designing it, Elkes said that the NHRA approached Modern Racing about the situation.
“Looking at her incident and how it all unfolded, we needed to get these things in the cars,” he explained. “We had a prototype piece that we had been testing for some time and we did a presentation at St. Louis to them on how it works. There was a vote from the safety committee and chassis builders and it was unanimous to vote it in.”
The final product resulted in the Modern Racing Solid-State Disconnect. Unlike a mechanical setup, this unit employs solid-state technology with no moving parts. And, at just a half-pound, it weighs only a third of a traditional mechanical disconnect. It’s simple, rugged, and reliable construction is designed specifically for the harsh environment of motorsports.
“It has a billet 6061-aluminum CNC-machined case with hard-coat anodizing and is O-ringed for weatherproofing,” Elkes said. “The battery stud is captured in the case so you can’t break it off — we take a lot of the things we’ve seen in electronics and make them better.”
Internally, the MR power disconnect is rated for 300 amps continuous usage (up to 1200A surge) and is safe for 5V—30V with low-voltage protection built in.
Likely the most interesting feature is how the system allows for multiple triggers to cut the power. If you order the power disconnect master kit, it includes a driver’s switch, an exterior large button-style switch, and a fire-suppression pressure switch that will cut power when a change in the pressure of the fire-suppression system is detected.
“This new system allows for multiple triggers, meaning the fire-suppression system, driver, or track crew can activate the disconnect. This layered safety reduces the chance of another dangerous fire on or off the track,” Elkes said. “Currently it has one input, but you can wire several inputs in series and if it sees any one of those triggers, it’ll disconnect.”
While the driver would likely engage the fire-suppression system, which would then trigger the disconnect, you could wire it in series for an overboost or oil pressure situation, or even kill the power in case of a parachute deployment failure.
Modern Racing’s power disconnect is now a mandatory safety requirement for both the Pro Modified and Pro Stock categories. And while it has been fully sorted before coming to market, we’re sure teams and car builders will find new ways to utilize its expandability going forward.