Why Can Plug-In Hybrid Cars Be Plugged-In and Recharged While Conventional Hybrids Cannot?
One of the key differentiators between plug-in hybrid cars and conventional hybrid cars is their ability to be plugged in and recharge from an outlet. This distinction is not merely a marketing gimmick but a fundamental aspect of the technologies underlying these vehicles. To understand why, we need to delve into the core functionalities and design principles of both types of hybrid vehicles.
The Concept of Plug-In Hybrids
A plug-in hybrid (PHEV) is a hybrid vehicle that can be charged from an external power source. This design feature allows the vehicle to run exclusively on electric power for a certain distance, before switching to a combination of gasoline and electric power. The ability to recharge from an outlet is what distinguishes plug-in hybrids from their conventional counterparts. This feature is not just convenient but also crucial in maximizing fuel efficiency and reducing environmental impact.
Conversely, conventional hybrids are designed with a smaller battery that serves to buffer the internal combustion engine (ICE). The battery is used to store energy produced during regenerative braking and to assist the ICE during acceleration. The goal here is to improve fuel efficiency and overall vehicle performance by optimizing the use of both electric and gasoline power. However, the battery in a conventional hybrid is much smaller, typically around 15 kWh, which is not sufficient to support the vehicle for extended periods of electric-only operation.
Design and Functionality
The primary reason for the distinction in battery capacity is the intended use of the vehicle. Plug-in hybrids are designed to operate as pure electric vehicles (EVs) until the battery is depleted to a pre-set level. Once the battery is charged to a lesser capacity, the vehicle switches to a mode where it uses both the electric battery and the ICE to function. This is in stark contrast to conventional hybrids, which rely on the ICE to always be present and active, drawing power from the battery only when necessary.
Another key factor is the EV range. Conventional hybrids, such as the Ford Fusion, run on electric power at low speeds, but the ICE is always at the ready. The Ford Fusion has a battery capacity of just 1.4 kWh, which is insufficient for any significant pure-EV range. On the other hand, plug-in hybrids can run on electric power for much longer periods. For instance, the Chevrolet Volt, a plug-in hybrid, has a 14 kWh battery, providing a much longer range before the ICE is needed.
Alternative Design in Conventional Hybrids
While conventional hybrids do offer some alternative modes, such as the electric-assist hybrid, these are not as extensive as in plug-in hybrids. In a typical electric-assist hybrid like the Ford Fusion, the battery capacity is still limited and the ICE is designed to kick in quickly to ensure that the vehicle can maintain its performance. During long downhill stretches or at low speeds, the ICE may be powered off to save fuel, but this is not the same as operating as a pure EV for extended periods.
To illustrate this, consider the experience of a Ford Fusion hybrid rental vehicle in hilly Los Angeles County. The ICE would cut out during long downhill stretches, allowing the vehicle to run on electric power. However, this is a temporary and limited solution compared to the consistent electric operation of a plug-in hybrid. In my own 2015 Chevrolet Volt, the vehicle runs as a pure EV at any speed until the battery level reaches a pre-set threshold, at which point it operates as a conventional hybrid.
Conclusion
The ability of plug-in hybrid cars to be plugged in and recharged from an outlet is rooted in their design philosophy. These vehicles are built to optimize the use of electric power over longer periods, offering a more sustainable and efficient driving experience. Conventional hybrids, while still offering improved fuel efficiency, are designed with a smaller battery to serve a different purpose, primarily as a buffer for the ICE. This fundamental difference in design means that plug-in hybrids can offer true EV operation for a more extended period, something that is not possible with conventional hybrids.
Understanding this distinction is crucial for anyone considering purchasing a hybrid vehicle. It highlights the trade-offs between the two types of hybrids and the sacrifices made in terms of battery size and weight in conventional hybrids to maintain a consistent performance and reliability.