# Nickel-based batteries: Engineering and performance Why tough beats efficient in harsh, remote places Source page: https://www.materialinsights.org/energy/e_nickel_batt/sg-eng/ What this tab covers Engineering and operating performance: round-trip efficiency, whether power and energy can be scaled separately, footprint and siting, and safety. Nickel batteries are robust rather than efficient: they survive abuse and temperature extremes, but are heavier and less efficient than lithium-ion, so they have been displaced from most grid roles. #### Round-trip efficiency Unfavourable Lithium-ion reaches about 85 to 90% (Sandia). Nickel-based cells are lower because charging ends in gas-producing side reactions, and nickel-iron is the least efficient of the three because its iron electrode evolves hydrogen; University of Southern California researchers raised iron-electrode charging efficiency to 97% in laboratory cells, which shows how much commercial cells lose. No recent independent system-level round-trip figure was found, so investors should rely on project test data.^[9](https://www.sandia.gov/app/uploads/sites/273/2021/12/3_Passell_Howard_SNL_NECPUC_Session1_3-19-2021.pdf)^[12](https://ecs.confex.com/ecs/227/webprogram/Paper50646.html) Lithium-ion benchmark About 85-90%^[9](https://www.sandia.gov/app/uploads/sites/273/2021/12/3_Passell_Howard_SNL_NECPUC_Session1_3-19-2021.pdf) Advanced NiFe iron-electrode charging efficiency (lab) 97%^[12](https://ecs.confex.com/ecs/227/webprogram/Paper50646.html) #### Power and energy decoupling Unfavourable Power and energy are set by cell design and cannot be sized separately, like other solid-electrode batteries. NiCd and NiMH can deliver high power for short periods, which suits uninterruptible power supplies and engine starting. Extra hours mean extra cells, so the marginal cost per kWh does not fall with duration. #### Footprint and siting flexibility Mixed Energy density is well below lithium-ion, so systems are larger and heavier for the same energy. The main siting advantage is tolerance of heat and cold without much climate control, which matters for remote telecom, rail signalling, solar sites and substations; Saft says its solar NiCd typically needs maintenance only once every four years (manufacturer claim).^[1](https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-cadmium.pdf)^[11](https://sabik.com/wp-content/uploads/2024/10/sabik_marine_datasheet_saft_sunnicd_batteries_20201.pdf) Saft NiCd maintenance interval Typically every 4 years^[11](https://sabik.com/wp-content/uploads/2024/10/sabik_marine_datasheet_saft_sunnicd_batteries_20201.pdf) #### Safety and thermal runaway risk Mixed The water-based alkaline electrolyte does not burn, so thermal runaway of the lithium-ion kind is rare, though overcharged cells release hydrogen and need ventilation. The bigger hazards are the caustic electrolyte and, for NiCd, cadmium exposure in manufacturing and disposal. Under EU Regulation 2023/1542, cadmium in portable batteries is capped at 0.002% by weight and mercury in all batteries at 0.0005%; NFPA 855 governs stationary systems in the US.^[5](https://www.sgs.com/en/news/2023/09/safeguards-11523-eu-issues-new-regulation-on-batteries-and-waste-batteries) EU cadmium limit, portable batteries 0.002% by weight^[5](https://www.sgs.com/en/news/2023/09/safeguards-11523-eu-issues-new-regulation-on-batteries-and-waste-batteries) EU mercury limit, all batteries 0.0005% by weight^[5](https://www.sgs.com/en/news/2023/09/safeguards-11523-eu-issues-new-regulation-on-batteries-and-waste-batteries) #### Sources 1. [Mineral Commodity Summaries 2026: Cadmium](https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-cadmium.pdf) US Geological Survey, 2026 2. [SafeGuardS 115/23: EU issues new regulation on batteries and waste batteries (summary of Regulation (EU) 2023/1542)](https://www.sgs.com/en/news/2023/09/safeguards-11523-eu-issues-new-regulation-on-batteries-and-waste-batteries) SGS, 2023 3. [Energy Storage Overview (H. Passell, NECPUC Energy Storage Webinar Series, 19 Mar 2021)](https://www.sandia.gov/app/uploads/sites/273/2021/12/3_Passell_Howard_SNL_NECPUC_Session1_3-19-2021.pdf) Sandia National Laboratories, 2021 4. [Saft Sun+ (Sunica) nickel-cadmium batteries for solar systems: datasheet (undated; file name suggests 2020; hosted by distributor Sabik Marine)](https://sabik.com/wp-content/uploads/2024/10/sabik_marine_datasheet_saft_sunnicd_batteries_20201.pdf) Saft, distributed by Sabik Marine 5. [Properties of nickel-iron batteries with high-performance iron electrodes (Yang, Manohar, Prakash and Narayanan, University of Southern California; 227th ECS Meeting conference abstract)](https://ecs.confex.com/ecs/227/webprogram/Paper50646.html) The Electrochemical Society, 2015 ## Other sections - [Summary](https://www.materialinsights.org/energy/e_nickel_batt/index.md) - [Overview](https://www.materialinsights.org/energy/e_nickel_batt/overview/index.md) - [Correlation](https://www.materialinsights.org/energy/e_nickel_batt/correlation/index.md) - [Science and technology](https://www.materialinsights.org/energy/e_nickel_batt/sg-sci/index.md) - [Economics](https://www.materialinsights.org/energy/e_nickel_batt/sg-econ/index.md) - [Impact and additionality](https://www.materialinsights.org/energy/e_nickel_batt/sg-impact/index.md) - [What to track](https://www.materialinsights.org/energy/e_nickel_batt/tracking/index.md) - [Relationships](https://www.materialinsights.org/energy/e_nickel_batt/links/index.md)