• The MNRE said that the present specifications for batteries provide for use of Lithium Ferro Phosphate (LFP), but it has now decided to include all Lithium-based batteries

• The energy density of the batteries should be 120 Wh/Kg and the C rate for charging should be a minimum of C/4, said the MNRE

New Delhi: The government has released performance parameters for Lithium batteries to be used in solar street lights and study lamps under off-grid and decentralised solar PV applications programme of the Ministry of New and Renewable Energy (MNRE). In a notification released on December 16, the MNRE said that the present specifications for batteries provide for use of Lithium Ferro Phosphate (LFP). However, the ministry has now decided to include Lithium batteries of chemistry other than LFP.

"Ministry after having detailed stakeholder consultation has decided to specify minimum performance parameters for batteries to be used for Solar Street Lights and Solar Study Lamps in place of specifying LFP. Accordingly, all Lithium-based batteries, fulfilling following performance parameters, shall be used for Solar Street Lights and Solar Study Lamps under the off-grid and Decentralised Solar PV Applications Programme of the Ministry," said the MNRE notification.

Qualifying conditions

According to the MNRE notification, the energy density of the batteries should be 120 Wh/Kg. The C rate for charging should be a minimum of C/4 and for discharging, it should be up to 1C. The charge-discharge cycles of the batteries should be a minimum of 2,000 cycles at C/10 rate at 25 degree Celsius. The thermal runaway should be a minimum of 120 degree Celsius, depth of discharge should be at a minimum of 85 percent at 25 degree Celsius, and temperature of operation should be 10 to 50 degree Celsius, with thermal management system for ambient temperatures lower and higher than the given range.

How do Lithium batteries differ from LFP batteries?

There are significant differences in energy when comparing Lithium-ion and LFP batteries. Lithium-ion has a higher energy density at 150/200 Wh/kg versus LFP at 90/120 Wh/kg. So, Lithium-ion is normally the go-to source for power hungry electronics that drain batteries at a high rate.

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On the other hand, the discharge rate for LFP outmatches Lithium-ion. At 25 degree Celsius, LFP batteries have voltage discharges that are excellent when at higher temperatures. The discharge rate doesn't significantly degrade the LFP battery as the capacity is reduced.

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