EVB Technology (HK)Limited, as member of the Gold Peak group, benefits from the wide range of battery chemistries and types manufactured by the group to offer confidence in its products. The selection of the two chemistries provided by EVB comes from extensive research into the characteristics of potential options to locate a beneficial mix of price, performance, stability and overall safety.

CHEMICAL CONSTRUCTION

EVB’s NiMH History

EVB became one of the original licensees of the full Ovonic Nickel Metal Hydride (NiMH) manufacturing license (AB-2) in 1993 in the same year the company employed its first EV project with Solectria. The license was upgraded to AB-5 in 1998 to reflect the expanding nature of EVB’s business. Furthermore, EVB and its parent company, Gold Peak, are research partners of Ovonic on the constant effort to improve the overall performance and manufacturing capability of NiMH cells.

Advantages of NiMH

Nickel Metal Hydride (NiMH) is a reliable, safe and stable chemistry used for nearly 30 years in the electric vehicle industry. The chemical combination of NiMH provides a good operating temperature range for use in different geographical locations

Advantages of LiFePO4

The choice of Lithium Ferro Phosphate (LiFePO4) for EVB’s lithium option is derived from the research into the lithium chemistries at the molecular level and their performance. LiFePO4’s cathode molecular structure is divine structure offering the one of the highest stability in the lithium family. One key point is Phosphates (PO4) do not undergo structural disordering and oxygen release while de-lithiating. A key result of this structural integrity is the stable midpoint voltage of LiFePO4 cells.

Again comparing the LiFePO4 chemistry to the other lithium options, the chemistry provides a balanced performance with a high cycle life and safety. Another key aspect of LiFePO4sometimes overlooked is the general cost of the individual elements. Using commonly found Fe and PO4, LiFePO4 minimizes potential cost spikes, a key element when planning for the future.

For further information, please refer to our presentations: Introduction of Lithium Ion Rechargeable Battery and Lithium-ion Batteries Technology Introduction.

CELL CONSTRUCTION

Prismatic vs. Cylindrical

EVB selected the prismatic option mainly on the ability of the prismatic format to transfer heat to the surface in a more efficient manner than a cylindrical format. As the package of cells increase, the heat transfer efficiency becomes more important. Heat is major enemies to the overall performance and life of a cell.

The Stainless Steel Can

EVB uses a stainless steel can for cells to protect against corrosion from the chemical impact of the electrolytes when used. In addition to the protection against chemical impacts, the stainless steel can is robust against mechanical and environmental impacts. Finally, the ruggedness of stainless steel permits the cell wall to be constructed thinner compared to other common material, which aids in better heat dissipation for the cell.

Why Black?

Black is the best color option for dissipating heat for infrared wavelengths; the common wavelength of the heat generated in a cell. The color black dissipates the same amount of heat as it absorbs unlike other colors of the spectrum with varying amounts of absorption versus dissipation ratios.

A good introduction to the concept of the color black being a good heat dissipator can be found here.