Maxwell's Ultracapacitor-Based Engine Start Module

Fleets with heavy and medium duty diesel trucks depend on the Maxwell Engine Start Module (ESM) for reliable starting, no matter how cold the climate. The Maxwell ESM is by far the leading ultracapacitor-based engine starting product on the market today and offers unmatched capability in truck starting.

What Our Customers Say



"With the ESM, everything will last longer—the alternators, the starters and the batteries. That’s all part of that ROI. You’re saving on not having service calls, not having jump-starts, and you’re not replacing components as often and you’re saving on that labor."

- Bill Turner, Fleet Manager | Holroyd Company, Washington State



"I have absolutely no fear of my truck not starting whatsoever. I know when I turn the key, I’m going to have 1,800 cold cranking amps."

- Mike Deffely, Owner Operator | Oregon



"It was a peace-of-mind purchase. Even when it’s cold out I can let the truck sit and just start it right up. I don’t have to worry about keeping the truck warm. I would recommend the ESM to other drivers."

- Ryan Forrest, Professional Driver | Sam Forrest and Sons, Michigan

FREE WHITE PAPER: How Ultracapacitors Improve Starting Reliability for Truck Fleets

Today’s trucks demand more energy from batteries than ever before, and batteries alone are no longer keeping up. To solve the frustrating problem of discharged batteries that can’t start the truck, fleet managers and operators are turning to ultracapacitor engine start technology for Class 6–8 trucks. In this free white paper, you will learn:

  • The most common diesel engine starting issues fleets face today
  • The business advantages of using ultracapacitors for starting, including the ability to dedicate battery energy to power electrical loads while the ultracapacitors provide faster, more reliable starts, even when batteries are severely discharged
  • The performance difference between ultracapacitors and batteries in a wide range of temperatures
  • How the ultracapacitor is installed and connected with existing Group 31 batteries


Download the paper now to learn how fleets improve uptime and gain competitive advantage by using ultracapacitors for engine starting.

Download Now

We start diesel engines like nobody else.

Leave hotel loads to lead-acid batteries and truck starting to us. With the Maxwell ESM, fleets and owner operators can expect better starting performance over batteries alone.

Today, Maxwell’s ESM reliably starts over 6,000 trucks across North America and counting, thanks to our robust ultracapacitor technology. Effectively eliminate the expense of no-start downtime and bolster bottom line profits.

Don’t let discharged or weakened batteries jeopardize profits or performance.

The Maxwell ESM takes over engine cranking for trucks with engines up to 16 liters in displacement and delivers faster cranking with quicker starts. Unlike a battery, which is susceptible to extreme cold and hot temperatures, our ultracapacitor-based ESM performs down to –40°F and up to +149°F (–40°C to +65°C).

Our starting technology gives drivers the confidence that their trucks will start.



The Maxwell ESM provides higher voltage at lower temperatures—the opposite of a battery.

Kenworth and Peterbilt Trucks with ESM Starting

Kenworth T680s and T880s and Peterbilt 579s and 567s offer the Maxwell ESM as a factory-installed option. Click below to learn how to order your new Kenworth or Peterbilt truck with Maxwell’s ESM.

Save on Operating Costs and Increase Uptime

How many jump-starts do you pay for in a year? What is the cost of fuel spent on idling? How often do you replace batteries? Maxwell’s payback calculator takes these factors into account and helps you determine how quickly the ESM can pay for itself in your truck or fleet. Many customers have told us that the ESM pays for itself in about one year thanks to the savings on jump-start costs, fuel spent on idling, and tare weight reductions.


Longest-standing, Award-Winning Engine Start Technology

Since 2011, Maxwell has led the way in ultracapacitor-based engine starting technology for the trucking and heavy equipment industries. Our ESM has been recognized for its unique ability to effectively eliminate jump-starts and provide fleet managers and owner operators with an alternative to the lead-acid battery, which has not been able to keep up with the growing energy demands of today’s trucking industry.

Easy to Install, 24/7 Customer Support

Retrofitting your fleet with the Maxwell ESM is as easy as replacing one Group 31 battery in the battery box and adding a cable. We provide worry-free ownership of your new ESM including a 24/7 technical support line. Customers can call (888) 890-3337 for ESM installation assistance from a Maxwell technical support team member.

Get the Specs

The Maxwell ESM product line includes the ULTRA 31/1800 and ULTRA 31/900 for Class 3 – 8 trucks and 24 volt versions for heavy duty vehicles and equipment with engine sizes up to 15 liters.



Where to Buy

The ESM is available at hundreds of locations across North America. Use our interactive map to locate a Maxwell dealer near you.