This guide explains what Depth of Discharge (DoD) means, how it affects your battery’s cycle life, and what you can do to maximise the lifespan of lithium and AGM batteries in your solar or off-grid setup.
? What Is Depth of Discharge (DoD)?
Depth of Discharge (DoD) refers to how much of a battery's total capacity is used before recharging.
A 100% DoD means the battery has been fully discharged (completely emptied).
A 50% DoD means half the battery's capacity has been used before charging begins.
⚠️ The more deeply you discharge a battery each cycle, the fewer total cycles it will last.
? What Is Battery Cycle Life?
Cycle life is the number of charge/discharge cycles a battery can go through before its capacity drops to about 70–80% of its original value.
One cycle = one full charge and discharge (or a combination adding up to 100%)
Cycle life is directly affected by DoD and battery chemistry (AGM vs Lithium)
? AGM vs Lithium: DoD & Cycle Life Comparison
| Battery Type | Recommended Max DoD | Typical Cycle Life at Recommended DoD | Notes |
|---|---|---|---|
| AGM | 50% | ~500–600 cycles | Deeper discharges (e.g. 80%) drastically reduce life |
| Lithium (LiFePO₄) | 80–90% | ~2000–5000 cycles | Can tolerate deep discharges with minimal impact |
Key takeaway:
Lithium batteries offer much higher cycle life, even with deep discharges — making them ideal for regular, high-demand use.
⚙️ Example: How Usage Patterns Affect Lifespan
Let’s say you have a 100Ah battery:
| Usage | DoD | What Happens Over Time |
|---|---|---|
| Use 50Ah daily and recharge | 50% | Longer lifespan (especially for AGM) |
| Use 80Ah daily and recharge | 80% | Shorter lifespan for AGM; still safe for Lithium |
| Fully drain to 0% regularly | 100% | Very damaging for AGM; Lithium can handle it occasionally but not ideal |
? Tips to Maximise Battery Life
Avoid 100% discharges, especially on AGM batteries
Recharge batteries promptly after use
Use a battery monitor or app to track state of charge
Set low voltage disconnects on your inverter/controller to prevent over-discharge
For Lithium batteries, aim to cycle between 10–90% for optimal longevity
? Monitoring DoD with Solar Controllers & Apps
Most modern solar charge controllers and lithium batteries with built-in BMS offer:
State of Charge (SoC) and DoD readings
Real-time voltage tracking
Cycle history and performance trends
Connect via Bluetooth (e.g. Victron, Renogy, or DCS) to your smartphone to track this data and prevent excessive cycling.
? Conclusion
Understanding and managing your battery’s Depth of Discharge is key to extending its life and performance. Whether you're powering a 4WD, caravan, off-grid cabin or camping setup, aim for conservative discharges (especially on AGM), or invest in lithium for deeper, longer-lasting use.
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