Depth of Discharge (DOD) describes how much of a battery’s stored energy has been used.
Example：
If a 10 kWh battery uses 5 kWh → DOD = 50%
If it uses 9 kWh → DOD = 90%
The higher the DOD, the more the battery has been discharged.
A battery’s lifespan is closely linked to DOD.
Lower DOD = longer lifespan
Higher DOD = more stress on batteries
For example:
Lead-acid batteries：recommended DOD 30–50%
Lithium (LiFePO4) batteries：can safely reach 80–95% DOD
This is why lithium batteries last much longer than lead-acid.
Cycle life means how many times the battery can fully charge and discharge.
| Tip baterie | Recommended DOD | Ciclul de viață |
|---|---|---|
| Plumb-acid | 30–50% | 300–600 cycles |
| NCM Lithium | 70–80% | 800–1,500 cycles |
| LiFePO4 | 80–95% | 3,000–6,000+ cycles |
LiFePO4 batteries are popular for solar systems because they maintain long cycle life even at high DOD.
100% SOC = 0% DOD
20% SOC = 80% DOD
Example：
If the battery is 20% full, the DOD is 80%.
For home energy storage and solar systems：
Stable chemistry
Very long cycle life
Safe for deep discharge
Deep discharge greatly shortens lifespan
Not ideal for daily solar cycling
When choosing a battery, look for:
Rated DOD (e.g., 80%, 90%, 95%)
Cycle life at that DOD
Warranty terms
Daily usage scenario
If you use the battery every day (solar system, backup system)，choose a lithium battery with high DOD and long cycle life.
Usable energy = 10 kWh × 90% = 9 kWh
If the DOD was only 50% → usable energy = 5 kWh
Higher DOD gives more usable power and better efficiency.
Depth of Discharge (DOD) is a key factor in choosing the right solar battery.
A higher DOD means more usable energy, but only lithium (especially LiFePO4) can handle high DOD while still keeping long lifespan.
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