The two 24V products are basically an extension of the existing 12 V engine start products. We rearranged the connection of the ultracapacitors inside the same Group 31 form factor to provide from 24 volts up to 28.5 volts to the starter, based on temperature. There’s an internal DC/DC converter, and a computer board that monitors battery input voltage, the temperature, and adjusts the output voltage.

—Jeff Brakley, senior business portfolio manager at Maxwell

The two models of the Maxwell 24-volt, ultracapacitor-based ESM will be generally available in May. The third terminal connects to the starter solenoid. Click to enlarge.

When subjected to extended periods of non-use or low temperatures, diesel engines are often difficult to start. As with Maxwell’s 12-volt ESM, the 24-volt product completely takes over the engine cranking and starting function by remaining fully charged, even if battery voltage drops significantly. Maxwell’s 24-volt ESM cranks and starts an engine when batteries can’t.

Unlike the 12V ESMs, the 24V system will largely be an OEM play, Brakley explained. The 12V product goes into a battery box in a truck that has from two to four 12V lead acid batteries to provide power for starting and other loads. In that situation, the Maxwell 12V ESM can simply replace one of the existing 12V batteries and be isolated to the starter. The other batteries remain for the other loads.

A 24V application typically has two 12 volt batteries in series to get the 24 volts. The Maxwell 24V ESM is thus an add-on that needs to be designed into the vehicle. Depending on the target equipment, Brakley observed, the ESM doesn’t even have to go into the battery box.

In addition to serving a new market with the 24V ESM solution, Maxwell is also gaining experience with that configuration of the technology that may prove useful if the on-road trucking industry begins to shift to a 24V starting system, as is being discussed, he added.

Unlike batteries, which produce and store energy by means of a chemical reaction, ultracapacitors store energy in an electric field. This electrostatic energy storage mechanism enables ultracapacitors to charge and discharge in as little as fractions of a second, perform normally over a broad temperature range (-40 degrees Celsius to +65 degrees Celsius/-40 degrees Fahrenheit to +149 degrees Fahrenheit), operate reliably in up to 1 million or more charge/discharge cycles and resist shock and vibration.

Maxwell offers ultracapacitor cells ranging in capacitance from one to 3,400 farads and multi-cell modules ranging from 12 to 160 volts.