Depth of Discharge (DoD) is the percentage of a battery's total capacity that has been used. If you have a 10 kWh battery and you use 5 kWh, the DoD is 50%. A DoD of 100% means the battery is fully empty.

Every battery chemistry has a maximum recommended DoD. Exceeding this regularly will dramatically shorten the battery's cycle life. Understanding these limits is essential for correctly sizing a solar battery bank and predicting replacement costs.

                    Quick Answer: For a 5 kWh daily load, tubular lead-acid needs a 10 kWh battery (50% DoD limit), while lithium LiFePO4 needs only a 5.6 kWh battery (90% DoD). The lithium battery costs more upfront but requires half the physical capacity and lasts 4-6 times longer.
                

DoD Limits by Battery Chemistry

Different battery chemistries tolerate discharge differently. The table below shows the maximum recommended DoD and the resulting cycle life for common solar battery types.

Chemistry	Max Recommended DoD	Cycle Life at Max DoD	Cycle Life at 50% DoD	Cycle Life at 30% DoD
Flooded Lead-Acid (C10)	50%	1,200 cycles	1,200 cycles	~2,500 cycles
Tubular Lead-Acid (C10)	50%	1,500 cycles	1,500 cycles	~3,000 cycles
AGM / Gel Lead-Acid	50%	600-800 cycles	600-800 cycles	~1,500 cycles
Lithium LiFePO4 (LFP)	90%	6,000 cycles	8,000+ cycles	10,000+ cycles
Lithium NMC	80%	3,000-4,000 cycles	5,000+ cycles	6,000+ cycles

Key Insight: Lead-acid batteries do not gain cycle life by discharging shallower than their rated DoD — they are designed to be discharged to 50%. Going shallower (e.g., 30% DoD) does extend life but is rarely economical. Lithium, on the other hand, sees a dramatic cycle life improvement at shallower DoD levels.

The Core Formula: Actual Capacity from DoD

Nominal Battery Capacity (kWh) = Usable Energy (kWh) ÷ DoD

Nominal Battery Capacity (Ah) = (kWh × 1000) ÷ Voltage ÷ DoD

Example: You need 5 kWh of usable energy per cycle:

Chemistry	DoD	Nominal kWh Needed	Ah at 48V
Tubular Lead-Acid	50%	5 ÷ 0.50 = 10 kWh	10,000 ÷ 48 = 208 Ah
Lithium LiFePO4	90%	5 ÷ 0.90 = 5.56 kWh	5,560 ÷ 48 = 116 Ah
AGM Lead-Acid	50%	5 ÷ 0.50 = 10 kWh	10,000 ÷ 48 = 208 Ah

                    Real-World Impact: To deliver 5 kWh daily, you need a 208 Ah (48V) tubular battery bank costing ~$1,800, or a 116 Ah (48V) lithium battery costing ~$2,800. The lithium bank is physically smaller, weighs 60% less, and lasts 4x longer.
                

10-Year Cycle Life Comparison

Let's examine what happens over a 10-year period with daily cycling (one full charge/discharge per day, or 3,650 cycles total).

Chemistry	Cycles at DoD	Lifespan (daily cycles)	Replacements in 10 Years	10-Year Hardware Cost
Tubular Lead-Acid (50% DoD)	1,500	4.1 years	3-4 replacements	$6,000-8,000
AGM Lead-Acid (50% DoD)	800	2.2 years	5 replacements	$7,500-10,000
Lithium LiFePO4 (90% DoD)	6,000	16.4 years	0-1 replacements	$2,800-5,600
Lithium NMC (80% DoD)	3,500	9.6 years	1 replacement	$4,000-6,000

The cycle life difference is the single most important factor in total cost of ownership. A tubular battery bank that cycles daily will need replacement every 4 years, meaning you pay for it 3-4 times over a decade. A lithium bank likely lasts the full 10 years without replacement.

Global Market Context: DoD in Practice

Battery DoD limits are universal, but how they affect system design varies by market:

Market	Dominant Battery Type	Typical Usable DoD	Common System Voltage
India	Tubular Lead-Acid	50%	24V / 48V
Pakistan	Tubular Lead-Acid	50%	24V / 48V
South Africa	Lithium LiFePO4	80-90%	48V
USA	Lithium LFP / NMC	80-90%	48V
UK / Europe	Lithium LFP	90%	48V
Australia	Lithium LFP	90%	48V

Warning: Many lead-acid battery warranties specify a maximum DoD. For example, a tubular battery warrantied for 1,500 cycles at 50% DoD may only be warrantied for 750 cycles if discharged to 70% DoD. Exceeding the rated DoD voids the warranty and accelerates plate sulfation.

How Round-Trip Efficiency Compounds DoD Effects

DoD is not the only factor. Round-trip efficiency (RTE) determines how much energy is lost as heat during charging and discharging. This loss effectively increases the DoD required to deliver a given amount of usable energy.

Actual DoD = Usable Energy ÷ (Nominal Capacity × RTE)

Example: A 10 kWh tubular battery (50% DoD, 80% RTE) delivering 4 kWh usable: 4 kWh ÷ (10 × 0.80) = 50% DoD. With 5 kWh usable: 5 ÷ 8 = 62.5% DoD — exceeding the safe limit.

A 5.6 kWh lithium battery (90% DoD, 95% RTE) delivering 4 kWh usable: 4 ÷ (5.6 × 0.95) = 4 ÷ 5.32 = 75% DoD — well within limits.

Related Guides

Size your battery with correct DoD limits

Open the Battery Sizing Tool →

How Solar Metrix Pro Helps: The Battery Backup Sizing Calculator in the sidebar above handles the math. Enter your day and night loads, backup hours, and system voltage. It instantly compares tubular lead-acid vs lithium capacities, energy waste, and recommends the best chemistry for your needs.
                

Open All Solar Tools in Pro Suite →

Data sources: Battery manufacturer datasheets (Luminous, Exide, Trojan for lead-acid; BYD, Pylontech, CATL, EVE for lithium). DoD cycle life figures based on C10 (lead-acid) and C5 (lithium) test standards at 25°C ambient. Actual cycle life varies with temperature, discharge rate, and maintenance. Pricing indicative Q2 2026.

Last updated: July 2026 | Browse all guides

Battery Depth of Discharge: Why 50% DoD Matters