Here's the vendor datasheet for the batteries: https://www.samsungsdi.com/upload/ess_brochure/201902_Samsung%20SDI%20ESS_EN.pdf https://www.samsungsdi.com/uplo

Here's the vendor datasheet for the batteries: https://www.samsungsdi.com/upload/ess_brochure/201902_Samsung%20SDI%20ESS_EN.pdf https://www.samsungsdi.com/upload/ess_brochure/201902_Samsun... It doesn't say the specific chemistry but it shows a chart estimating 6000 100% charge/discharge cycles at 1C until it hits 80% capacity. So for this system that'd be 16 years of full cycles till it wore down to being "only" a 240MWh system. In reality they'll probably cycle it less aggressively than that (95/5 or 90/10) to meet the expected 25 year lifetime of the overall system.