How a Smaller Charger Can Do More: Optimizing Battery Charging in MEWPs
Introduction
In the world of Mobile Elevated Work Platforms (MEWPs), battery-powered systems have undergone significant advancements, particularly with the adoption of lithium-ion batteries. While larger chargers have traditionally been the norm, especially for lead-acid batteries, newer lithium technology allows for more power in a smaller form. As reported by the US Office of Energy Efficiency and Renewable Energy (EERE), lithium-ion battery energy density has increased eightfold between 2008 and 2020, prompting a reevaluation of charging strategies in MEWPs.
Charging Dynamics of Lead-Acid Batteries
Lead-acid batteries, widely used in electrified MEWPs, undergo a three-phase charging process:
Bulk Phase
High power is delivered to the battery, rapidly increasing its charge level until a specific voltage threshold is reached.Absorption Phase
The charging rate gradually decreases as the battery voltage stabilizes. During this phase, the charge is absorbed more slowly to ensure the lead plates fully absorb the charge.Finish Phase
A lower current is used to maintain the battery at full charge, preventing overcharging and restoring the plates to maximum capacity.
This process is nonlinear, meaning that charging slows significantly as the battery approaches full charge. For instance, the final 20% of charging in a lead-acid battery can take as long as half the total charging time due to the absorption phase, where internal resistance mounts.
Streamlined Charging: The Lithium Battery Advantage
Lithium batteries differ significantly from lead-acid batteries in terms of charging dynamics, offering several key advantages:
Maximized Charging Rate
Lithium batteries can maintain a high charging rate for the majority of the charging cycle, with a brief cell-balancing phase at the end managed by the Battery Management System (BMS).Linear Charging Profile
Unlike the nonlinear nature of lead-acid batteries, lithium batteries charge linearly. This means that the increase in charge is directly proportional to the charging time, allowing for more predictable and efficient charging.Efficiency Across Charge Range
Lithium batteries operate efficiently, especially within the 10% to 90% charge range, minimizing energy loss and heat generation.
The Potential of Compact Chargers
The linear charging profile of lithium batteries allows for the use of smaller chargers while still maintaining efficient and effective charging. For example:
- Lead-Acid Batteries: A 24V 220Ah lead-acid battery pack in a scissor lift typically requires a 700W charger to recharge overnight from 0% to 100%.
- Lithium Batteries: An equivalent 24V 180Ah lithium battery can achieve the same overnight charge (from 10% to 90%) using just a 350W charger.
This is possible because lithium batteries do not require the prolonged absorption phase that lead-acid batteries do. A smaller charger can still complete the charge within the same time frame by efficiently utilizing the linear charging profile of lithium batteries.
Advantages of Adopting Smaller Chargers in MEWP Applications
Switching to smaller chargers for lithium-powered MEWPs offers several benefits:
Space Efficiency
Compact chargers like the XVE 550D are designed to fit in the limited space of compact MEWPs, making them an ideal choice for designs where space is at a premium.Versatility
Smaller chargers can be used with a wider range of battery sizes, from smaller 4x6V packs to larger 2x12V configurations, providing flexibility in fleet management.Cost Savings
By using a charger that matches the actual needs of a lithium battery, energy waste is minimized. This leads to lower operational costs and contributes to a reduced total cost of ownership (TCO).Simplicity and Portability
Smaller chargers are lighter and more portable, making them easier to handle and deploy across different environments.
Conclusion
The evolution of battery technology, particularly the rise of lithium-ion batteries, has enabled the use of smaller chargers in MEWPs without compromising performance. By understanding the differences between lead-acid and lithium battery charging profiles, fleet managers and OEMs can optimize charging strategies to improve efficiency, reduce costs, and enhance the overall sustainability of their operations.