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Maxwell Technologies introduces ultracapacitor-based engine start module for medium-duty diesel trucks

ESM 31-900_Left Angle_NoBG
New medium-duty ESM. The third terminal connects to the starter solenoid. Click to enlarge.

Maxwell Technologies, Inc. is expanding its ultracapacitor-based Engine Start Module (ESM) product line (earlier post) to provide the same benefits to class 3 through 6 medium-duty trucks that it has been offering previously to class 7 and 8 heavy-duty diesel trucks.

Maxwell’s ESM ULTRA 31/900 assumes the starting responsibility for the truck and effectively eliminates cranking problems that come from weak or discharged batteries. Consistent with Maxwell’s current award-winning ESM product, the ESM ULTRA 31/900 delivers the quick-burst power trucks need to crank their engines in extreme cold, down to -40°F.

The new ESM is rugged and lightweight (16 lbs, 7.3 kg). It delivers reliable starts and allows extensive use of lift-gates and buckets while the engine is off without fear of the truck not starting.

The ESM ULTRA 31/900 is basically the same product as the heavy-duty version, but with half of the ultracap content taken out, according to Jeff Brakley, Senior Product Manager, Engine Starting Group, Maxwell. The heavy-duty product has 12 3000F ultracapacitors; the medium-duty version has 6—“more than sufficient power” to crank a medium-duty diesel, Brakley said.

The ESM ULTRA 31/900 is a no-acid, lead-free energy storage solution that weighs less than one-fourth of the Group 31 lead-acid battery it replaces in the battery bay of the truck. It stays fully charged even when the truck’s lead-acid battery is as low as 9.5V; the ESM charges off the lead-acid batteries in the truck.

Unlike the batteries, the ESM has three terminals. A positive and negative terminal for connection to the remaining batteries, and a third that connects to the starter solenoid of the engine. The ESM unit also has a controller inside, along with a voltage convertor and temperature monitor.

ESM diagram. (Heavy-duty version shown). Click to enlarge.

Basically, the existing batteries minus 1 power all other vehicle loads and the the alternator will continue to recharge the batteries, but the ESM controls all power to the starter solenoid.

Consistent with the current ESM product, the new ESM ULTRA 31/900 provides the following features and benefits:

  • 900 cold cranking amperes (CCA), or a three-second crank;

  • Reliable starting for diesel engines up to 9.9 liters at temperatures -40°C to 65°C (-40°F to 149°F);

  • Low maintenance operation and life-of-the-vehicle reliability;

  • Industry standard Group 31 battery form factor for easy integration with battery systems;

  • Built-in quick charging system (15 minutes or less);

  • Extended battery life, full compatibility with existing battery systems; and

  • Four year unlimited warranty.

Maxwell is showing the new ultracapacitor-based ESM ULTRA 31/900 at the Work Truck Show, 5-7 March in Indianapolis.



I've read trucker blogs that say these capacitor ESMs, while not cheap, can always start a diesel in the coldest weather.


When will those ultra caps units be coupled with HEV-PHEV-BEV batteries to capture more deceleration energy?


I wonder how they manage the capacitors' self discharge characteristic.

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