What is battery cycle life?

Battery cycle life is the charging and discharging use a battery can sustain before reaching a defined capacity threshold under stated conditions. Full-equivalent cycles combine partial discharges: two assumed 50% discharges total one equivalent cycle [S1]. Check the counting method, retained-capacity threshold and warranty conditions rather than treating a cycle figure as years of service. Checked October 2026.

Last checked 19 October 2026

What does battery cycle life mean for your site?

Battery cycle life describes accumulated charge and discharge use before capacity falls to a specified threshold under stated test conditions [S2], [S3]. Why it matters for your site: repeated daily dispatch needs a lifetime assumption that matches the proposed operating schedule.

Read the cycle figure alongside depth of discharge, temperature, charging rate and the capacity remaining at the test endpoint. A specification without its conditions is insufficient for comparing proposals. SAM’s battery-life model treats depth of discharge and cycle count together, and models calendar ageing separately [S2].

How do partial discharges become full-equivalent cycles?

Full-equivalent cycles add partial-cycle use relative to a capacity reference [S1]. An illustration, not a quote: assume a constant 200 kilowatt-hour (kWh) reference capacity, where kWh measures energy.

• Discharge 100 kWh, recharge, then discharge another 100 kWh.
• Total discharged energy = 100 + 100 = 200 kWh.
• Equivalent cycles = 200 ÷ 200 = 1.

The inputs and fixed reference are assumptions. This discharged-energy illustration must not be confused with a counter that totals charging and discharging energy together. Request the precise definition used in monitoring and contractual throughput limits.

What does the end-of-life threshold actually mean?

It describes a defined endpoint, rather than an instruction that the battery stops immediately. For example, the Energy Technology List’s commercial storage criteria specify at least 10,000 cycles before reaching 60% of rated capacity [S3]. Those are listing criteria, not typical product life or warranty terms for your site.

Use depth of discharge for the operating window and battery warranties and degradation for the contract checklist. Have your solicitor check the actual warranty’s measurement method and remedy.

Next step

Bring the proposed dispatch schedule to cut energy costs and the site check, then get matched with an installer that covers your area.

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