The Ni-MH battery technology has gained wider acceptance among hybrid vehicles, with the likes of Toyota successfully leveraging it across its various models
The battery technology for electric vehicles has witnessed considerable advancements over the past several decades. It is pretty well documented in public domain how lead acid and nickel-metal hydride (Ni-MH) batteries emerged as mainstays for electric vehicles across the globe and how both these battery technologies subsequently lost out its market relevance owing to the advent of much-better-performing lithium-based batteries in the EV space. The battery technology space is an ever-evolving one and it is a ‘given’ that newer and better performing technologies would mark its presence in the market. This is not to overlook the importance of lead acid and nickel-metal hydride (Ni-MH) battery technologies that had served the needs of all kinds of electric vehicles be it hybrid electric vehicles, plug-in electric vehicles and battery electric vehicles for a long time.
Interestingly, nickel-metal hydride batteries may have not been quite a success for battery electric vehicles, but have gained huge popularity among hybrid vehicles. Globally, Toyota Motor Corporation has been successfully leveraging the nickel-metal hydride battery technology for its hybrid vehicles across various models such as Prius, Camry Hybrid, etc. “Nickel-metal hydride batteries offer higher energy density as well as higher charge/discharge cycles resulting in high durability,” remarked Vikram Gulati, Country Head & Senior Vice President, External Affairs, Public Relations, Corporate Social Responsibility & Corporate Governance, Toyota Kirloskar Motor.
He elaborated on NiMH’s other attributes that paved the way for its wider deployment across hybrid vehicles. “Nickel-metal hydride batteries carry no toxic content and can be efficiently recycled. NiMH batteries and lithium-based batteries carry different advantages and are leveraged based on criterion such as thermal management, energy density and specific application requirements,” he noted.
Ashim Sharma, Partner & Group Head, Nomura Research Institute elucidated on the wider deployment of nickel-metal hydride batteries for hybrid vehicles. “One of the key battery requirements in hybrid vehicles is longevity owing to multiple change and discharge cycles on during the course of operation. Such NiMH batteries can be used for 1,000+ cycles if used carefully – for instance it has 80 % depth of charge and no extensive stress due to extensive power demand and all these factors contributed to its wider usage in hybrid vehicles. Further, the smaller form factor as compared to other battery technologies has led to increased adoption of NiMH batteries,” he said.
NiMH batteries were considered a better and an improved version of nickel-cadmium (NiCd) batteries – a technology that did not found prominent usage among EVs. “Nickel-cadmium batteries have major limitations for EVs such as low energy density and carries toxic content. More importantly, nickel-cadmium batteries have regulatory restrictions and it is difficult to recycle and dispose on account of which it was not considered a good option for EVs and ended up being widely deployed in consumer electronics application,” Gulati pointed out.
However, NiMH batteries have certain deficiencies that limited its popularity only among hybrid vehicles. “Nickel-metal hydride batteries make a good case for hybrid vehicles but they are not considered the most ideal solution for battery electric vehicles since they offer limited discharge current (0.2C-0.5C) as well as limited lifecycle. NiMH batteries are prone to thermal runaways under overcharging and this necessitates the need for leveraging complex circuit protection systems and advanced trickle charging algorithms to avoid overheating. These factors affect the performance of EVs, in terms of acceleration performance and fast charging capabilities that are considered crucial as compared to battery electric vehicles,” Sharma explained in a threadbare manner.
Every battery technology will carry some deficiency or the other, which eventually leads to the arrival of a new technology in the market. Similarly, owing to certain deficiencies nickel-metal hydride batteries may have failed to gain mass market acceptance among battery electric vehicles, but there is no denying the fact that these technology managed to retain its relevance among hybrid vehicles.