In a blog post, Maxwell Technologies president and CEO David Schramm argues that ultracapacitors would be a perfect fit for GM’s eAssist second-generation light electrification technology (Earlier post.) The eAssist system is slated to be GM’s current default mild hybrid system for electrification applications of 20 kW power or less.
The e-Assist system uses a 115V, 0.5 kWh lithium-ion battery system built with Hitachi power-optimized cells, an electric induction motor-generator and regenerative braking capability to improve fuel economy.
…the eAssist concept makes sense. Automakers around the world are sure to adopt this kind of system in increasing numbers over the next few years. Maxwell ultracapacitors are a perfect fit for regenerative braking applications for several reasons, including:
Charge/discharge rate. Anyone who uses a mobile phone or other device powered by a lithium battery knows that it can take up to several hours to recharge the battery, so how much energy can such a battery absorb during the few seconds that it takes to stop a car? By contrast, ultracaps fully charge or discharge in a second or less.
Cold temperature performance. When temperatures approach freezing, batteries become sluggish, so they won’t be able to deliver much power to the battery or capture much regenerative braking energy in cold climates. Ultracaps operate normally down to -40ºC.
Operational lifetime. Batteries typically last only a few thousand charge/discharge cycles before they need to be replaced, whereas ultracapacitors can be expected to last the life of the vehicle.
Maxwell’s ultracapacitors products have demonstrated that they are ideally suited to applications that require repetitive, rapid, charges and discharges in millions of miles of service in public transit vehicles, and more recently in stop-start idle elimination systems produced by Continental AG for Peugeot and Citroën cars in Europe. We’re convinced that Maxwell ultracaps would also make the eAssist system more efficient and reliable, thus enabling GM to deliver a superior product to its customers, so we hope they will take us up on our offer to prove it.