Battery Depth of Discharge Chart
How deep you can safely discharge each battery chemistry, how DoD affects usable capacity, and practical guidelines for maximizing cycle life.
Approximate usable capacity from a 100Ah battery. Always verify manufacturer specifications.
Approximate values only. Always verify manufacturer specifications.
DoD by Chemistry
Different battery chemistries have different safe discharge limits. Exceeding these limits causes accelerated degradation, capacity loss, and in extreme cases, permanent damage. The table below shows typical recommended DoD limits for common chemistries.
| Chemistry | Typical Max DoD | Usable from 100Ah | Notes |
|---|---|---|---|
| LiFePO4 (LFP) | 80–100% | 80–100 Ah | Can handle 100% DoD; 80% recommended for optimal cycle life |
| NMC (Lithium) | 80–90% | 80–90 Ah | Slightly more sensitive than LFP to deep discharges |
| Lead-Acid (Flooded) | 50% | 50 Ah | Deep discharges cause sulfation and rapid capacity loss |
| AGM (Sealed) | 50–60% | 50–60 Ah | Slightly better than flooded; still limited by chemistry |
| Gel (Sealed) | 50% | 50 Ah | Similar to flooded; deep discharge damages gel electrolyte |
Values are typical recommendations. Always check manufacturer specifications for your specific battery model.
Usable Capacity
Usable capacity is the amount of energy you can actually draw from a battery. A 100Ah battery at 50% DoD only provides 50Ah of usable energy. This is why battery bank sizing must account for DoD limits — a nominal 200Ah lead-acid bank provides only 100Ah of usable capacity at 50% DoD.
Lithium batteries (LiFePO4 and NMC) offer significantly more usable capacity from the same nominal rating. A 100Ah LiFePO4 battery at 80% DoD provides 80Ah — 60% more usable energy than a lead-acid battery of the same rating. This is one of the primary reasons lithium batteries have lower effective cost per usable Wh over their lifetime.
| Nominal Capacity | LiFePO4 (80% DoD) | Lead-Acid (50% DoD) | Difference |
|---|---|---|---|
| 50 Ah | 40 Ah | 25 Ah | +60% |
| 100 Ah | 80 Ah | 50 Ah | +60% |
| 200 Ah | 160 Ah | 100 Ah | +60% |
| 300 Ah | 240 Ah | 150 Ah | +60% |
DoD and Cycle Life
The relationship between DoD and cycle life is nonlinear. Deeper discharges cause disproportionately more damage. A battery that lasts 5,000 cycles at 20% DoD might only last 1,500 cycles at 80% DoD and 500 cycles at 100% DoD. This trade-off is a key factor in battery system design.
LiFePO4 Cycle Life
At 80% DoD: ~3,000–5,000 cycles
At 50% DoD: ~5,000–7,000 cycles
At 20% DoD: ~7,000–10,000+ cycles
Calendar life: 10–15 years typical
Lead-Acid Cycle Life
At 50% DoD: ~300–500 cycles
At 30% DoD: ~600–1,000 cycles
At 20% DoD: ~1,000–1,500 cycles
Calendar life: 3–5 years typical
The optimal DoD depends on your application. For daily-cycled solar storage, a shallower DoD (50–80% for LiFePO4) extends battery life. For emergency backup that rarely cycles, a deeper DoD may be acceptable since cycle count is low.
Practical Guidelines
When sizing a battery bank, always calculate based on usable capacity (nominal capacity × DoD limit), not nominal capacity alone. A system requiring 100Ah of usable energy needs a 200Ah lead-acid bank or a 125Ah LiFePO4 bank.
Include a safety margin of 10–20% on top of the DoD-limited usable capacity to account for capacity degradation over the battery's life, temperature effects, and load estimation errors.
For systems with a BMS, set the low-voltage cutoff to match the manufacturer's recommended DoD limit. The BMS will disconnect the load before the battery reaches an unsafe discharge depth.
Common Mistakes
Sizing from Nominal Capacity
Using nominal capacity without accounting for DoD limits leads to undersized battery banks. A 200Ah lead-acid bank at 50% DoD only provides 100Ah usable. Size from usable capacity, not nominal.
Applying Lithium Rules to Lead-Acid
Lead-acid batteries cannot tolerate the same DoD as lithium. A 50% DoD that is fine for LiFePO4 will cause rapid sulfation and capacity loss in lead-acid. Use the correct DoD limit for your chemistry.
Ignoring Degradation Over Time
Batteries lose capacity as they age. A 100Ah battery at 80% DoD provides 80Ah when new, but only 60–70Ah after several years. Plan for end-of-life capacity, not just Day 1 capacity.
No Safety Margin
Designing right to the edge of usable capacity leaves no buffer for load estimation errors, temperature effects, or capacity degradation. Add 10–20% safety margin to all sizing calculations.
Try It
Use the Battery Sizing Calculator to size a battery bank with proper DoD limits, or the Degradation Estimator to see how DoD affects cycle life over time.
Open Battery Sizing CalculatorFrequently Asked Questions
What is depth of discharge (DoD)?
Depth of discharge is the percentage of total battery capacity that has been used. A 100Ah battery discharged to 50Ah is at 50% DoD. It is the inverse of state of charge: DoD = 100% − SOC. Battery manufacturers specify maximum DoD limits to protect cycle life.
How does DoD affect battery lifespan?
Deeper discharges accelerate degradation. A LiFePO4 battery rated for 5,000 cycles at 80% DoD may last 3,000 cycles at 100% DoD. Lead-acid batteries are even more sensitive — regularly discharging below 50% DoD can cut cycle life by 50% or more.
Can I discharge a LiFePO4 battery to 100% DoD?
Technically yes, LiFePO4 can handle 100% DoD without immediate damage. However, regularly discharging to 100% DoD reduces cycle life compared to limiting discharge to 80% DoD. Most system designers recommend an 80% DoD limit for optimal longevity.
What is usable capacity?
Usable capacity is the amount of energy you can actually draw from a battery given its DoD limit. A 100Ah battery with an 80% DoD limit provides 80Ah of usable capacity. Always size battery banks based on usable capacity, not nominal capacity.