Safety of lithium cells is crucial for battery makers

It’s no secret that demand for lithium batteries for EVs is going to be phenomenal in the coming years in India. It is estimated that by 2030, we will have more than 300 GW/hr of battery pack capacity requirements in the country. Most of the cells are imported and very few start-ups have ventured into this territory.

Log9 is among the early manufacturers of tropical ionised batteries. The company is working on two parallel battery chemistries — Lithium-Titanium-Oxide battery (LTO) and Lithium Iron Phosphate (LFP).

Hemant Charaya, Senior Vice President-Battery Cell Technology, explains the reason behind opting for these two chemistries. “Having a clear understanding of the types of chemistries that can function properly under the extreme climatic conditions of our country is the first step towards ensuring safety. Most parts of our country touch 42°C-45°C for a good period of five to six months, during which we cannot rely on the normal lithium-ion batteries. Our research indicated that these chemistries are best suited for tropical zones like India where fluctuations in temperature are quite high.”

Selection and application
An LTO is a heavy-duty Li-ion battery, which Log9 is currently using for commercial electric three-wheelers. According to Charaya, all batteries lose charge capacity over their life cycle, but an LTO battery typically loses much less than the rest. It has a much longer lifespan than any other battery chemistry, which will result in a significantly lower total cost of ownership.

“LTOs are good for heavy-duty applications as they offer comparatively higher duty cycles. For instance, an electric three-wheeler fleet operator who is running 2-3 shifts a day is always in search of quick charge batteries. Our LTO batteries can give a range of up to 150 km in just 30 minutes of charging,” he added.

On the other hand, LFP makes more sense for electric two-wheelers which Log9 is planning to launch towards the end of this year. This is a relatively cheaper chemistry. “Electric two-wheeler customers want 2-3 kW battery packs with a range of about 100 kms on a single charge, which LFPs can easily achieve. We are currently in an advanced stage of testing and targeting to bring LFP cells to the market by this year with the advantage of opportunity charging," he says. While LTOs can offer a capacity of 10,000 cycles, with LFPs, customers can get around 2,000-3,000 cycles.

Safety is in the design
For its LFP battery, Log9 is making considerable efforts on the design front to make its battery as immune as possible to fire risks. Temperature, voltage and current are the focus areas and two systems have been employed.

In Active Safety implementation, temperature sensors are used to analyse the condition of the battery and they are installed in-between cells. They monitor the temperature in real-time and if they detect temperature of any of the cells going above the threshold limit of 42°C-45°C, the sensor sends out warning signals immediately. Voltage Regulation: The packs are equipped with mechanical connector systems, an extra layer of protection, to automatically cut off the battery pack during overcharging or discharging.

Current Regulations: During charging of EVs, a flux of current going in might create a spark, which is enough to start a fire. "To curb the sudden fluctuation in current, Log9 has installed fuses in different locations of the pack, such as the wire harness, insta charge control kit, and vehicle integration kit," Charaya concluded. All this real-time data is stored in a telematics device connected to the cloud system on a live basis. These are then examined by the service or technical team who will take appropriate action. Under Passive Safety Implementation protocol, Pressure Release Valves are placed at different locations on battery packs. “If a cell undergoes a thermal runaway, there are a lot of hydrocarbon gasses that come out of the cell thereby increasing the internal temperature. PRVs help vent these gasses out,” Charaya explained.

These LFP battery packs will come with fire retarding materials and safe casing. “We are using an aluminium based casing, which also helps in cooling the battery pack. We are using temperature regulations primarily for our LFP batteries as LTOs are a safer chemistry in which thermal runaway incidents are negligible,” Charaya concluded.

This feature was first published in Autocar Professional's June 1, 2023 issue.