Battery lifespan (cycles vs DoD) estimator

Estimate how cycle life changes with Depth of Discharge (DoD). Pick a chemistry preset or enter your own reference point.

Inputs

Number of cycles at the reference DoD
Higher k => cycles drop faster as DoD increases
E.g., 0.25 cycles/day ≈ full cycle every 4 days
Model formula: cycles = C_ref × (refDoD / DoD)^k
This is an empirical model widely used for quick estimates. Presets provide conservative default reference numbers — adjust the reference cycles or exponent if you have manufacturer/test data.

Preset notes

Presets are conservative typical references — they are starting points, not guarantees. Always check manufacturer's datasheet for exact cycle-life curves.

Practical tip

Operating at shallower DoD greatly increases cycle life. Using a larger battery bank to reduce average DoD is usually more cost-effective long-term.

How to Estimate Battery Lifespan Based on Depth of Discharge (DoD)

The battery lifespan (cycles vs DoD) estimator helps you understand how deeply discharging your battery affects its total usable life. Depth of Discharge (DoD) is one of the most influential factors in determining how many charge–discharge cycles a battery can complete before its capacity drops below a usable level. Whether you use LiFePO₄, Li-ion, or lead-acid batteries, understanding DoD allows you to make smarter design decisions for solar, RV, or backup systems.


🔋 What Is Depth of Discharge (DoD)?

Depth of Discharge (DoD) measures how much of a battery’s stored energy has been used relative to its total capacity. A 100 Ah battery discharged to 50 Ah remaining has a 50% DoD. A lower DoD means you’re using only a portion of the battery before recharging, while a higher DoD means you’re nearly depleting it before recharge. Each cycle slightly degrades the internal chemistry, and the depth of that discharge determines how quickly degradation accumulates.

For example, cycling a LiFePO₄ battery between 80% and 20% (a 60% DoD) may last over 5000 cycles, whereas draining it from 100% to 0% (a full 100% DoD) could cut lifespan in half. The same pattern holds true for other chemistries, though the sensitivity to DoD differs between battery types.


📈 The Relationship Between DoD and Battery Cycle Life

Most batteries follow an inverse or power-law relationship between cycle life and DoD, often expressed as: Cycles = Cref × (DoDref / DoD)k. Here, k is an exponent that captures how strongly a given battery type reacts to deep discharges. A high k means that deeper cycles reduce life more dramatically.

For instance, LiFePO₄ chemistry typically has a lower k value than lead-acid batteries, meaning it tolerates deeper discharges better. This is one reason LiFePO₄ batteries are becoming the preferred choice for solar and off-grid storage, where daily cycling is common.


⚡ Example: LiFePO₄ vs Li-ion vs Lead-Acid

  • LiFePO₄ (LFP): Usually delivers 3000–6000 cycles at 80% DoD, and more than 7000 cycles at 50% DoD. Known for excellent thermal stability, long life, and high efficiency — perfect for solar and energy storage systems.
  • Li-ion (NMC/NCA): Typically 1000–2000 cycles at 80% DoD. These batteries power electric vehicles, laptops, and power banks. They offer higher energy density but degrade faster at deep discharges.
  • Lead-acid (AGM/Gel/Flooded): Generally 300–800 cycles at 50% DoD and may last only 200–300 cycles at 80% DoD. Best for backup applications with infrequent discharges rather than continuous daily use.

🧮 How to Use the Calculator

  1. Select your battery chemistry (LiFePO₄, Li-ion, or Lead-acid) from the dropdown.
  2. Enter your target DoD (%), typically between 10–100%, depending on your system usage.
  3. Input the manufacturer’s reference cycle life at a known DoD (for example, 4000 cycles at 80% DoD).
  4. Adjust the exponent (k) value to match your chemistry’s typical behavior — a higher number increases DoD sensitivity.
  5. Optionally, enter cycles per day to estimate total years of service life.
  6. Finally, apply a safety margin (e.g., 80–90%) to reflect real-world conditions such as temperature, aging, and irregular charging.

Once the inputs are set, the calculator instantly predicts how many cycles your battery should last under your chosen operating pattern. The resulting curve clearly shows why lower DoD dramatically extends lifespan — a core insight for solar designers and battery system planners.


📅 Estimating Battery Life in Years

To estimate lifespan in years, multiply the predicted number of cycles by the frequency of use. For example, a 4000-cycle LiFePO₄ battery used once daily (1 cycle/day) would last about 10.9 years. If used every other day (0.5 cycles/day), it could exceed 20 years.

However, environmental and operational factors often reduce this theoretical figure. High ambient temperatures, sustained overcharging, or frequent operation at extreme voltage levels can shorten life dramatically. That’s why applying a conservative safety margin (like 85%) yields a more practical estimate.


🌞 Why Shallower DoD Extends Battery Life

Every discharge–recharge cycle causes minor wear to a battery’s internal materials. Shallower cycles mean less stress per use, allowing for many more cycles over the battery’s lifetime. Even though the energy per cycle is smaller, the cumulative energy delivered over thousands of shallow cycles often surpasses that of fewer deep cycles.

For example, a LiFePO₄ battery cycled at 40% DoD may last over 8000 cycles. That’s roughly double the life of cycling at 80% DoD — proving that conservative energy use significantly improves system ROI. Many professional solar installers intentionally oversize battery banks to ensure daily cycling stays under 50% DoD, balancing upfront cost with long-term performance.


🌡️ Other Factors Affecting Battery Lifespan

While DoD is a primary variable, several secondary factors also play a major role:

  • Temperature: Elevated heat accelerates electrolyte degradation and internal resistance growth. Batteries kept below 30°C typically last 20–30% longer.
  • Charge Rate (C-rate): Fast charging creates heat and internal stress. Slower, balanced charging extends longevity.
  • Voltage Limits: Avoid both overcharging and deep undervoltage — both extremes harm cells irreversibly.
  • Balancing & BMS: A quality battery management system (BMS) maintains equal cell voltages, preventing early failure.
  • Storage Conditions: Store batteries partially charged (around 40–60%) if not in use for long periods to reduce calendar aging.

🔧 Practical Tips to Maximize Battery Lifespan

  • Limit routine discharges to 50–70% DoD for daily use systems.
  • Keep the battery environment cool and well-ventilated.
  • Use chargers and controllers matched to your chemistry’s voltage range.
  • Install temperature-compensated charging for lead-acid systems.
  • Perform periodic capacity tests to monitor degradation trends.
  • Avoid leaving batteries at 100% charge for extended periods unless necessary.
  • Design solar systems with reserve capacity to handle seasonal variation.

🧠 Real-World Example

Suppose you have a 48V 200Ah LiFePO₄ bank (9.6 kWh usable) and use 5 kWh per night — a 52% DoD. The calculator might predict 6000 cycles. At 1 cycle/day, that’s about 16.4 years. If instead you used only 3 kWh per night (31% DoD), the lifespan could exceed 9000 cycles, translating to over 24 years of operation — nearly a decade longer, with less total stress and better long-term performance.