Battery Depth of Discharge Explained (Easy Guide)
Depth of Discharge (DoD) tells you how much of your battery’s capacity you’ve used. A battery drained to 50% DoD still has half its energy left. Understanding DoD helps you make your batteries last longer and size your off-grid system correctly.
Depth of Discharge Chart (Simple)
| Battery Type | Safe DoD | Lifespan Impact | Notes |
|---|---|---|---|
| LiFePO4 (LFP) | 80–100% | Very low impact | Longest lifespan |
| Lithium-Ion (NMC) | 80% | Moderate wear | Less stable |
| AGM / Lead-Acid | 50% | Major impact | Short lifespan |
| Gel | 50–70% | Moderate impact | Sensitive to charging |
LiFePO4 batteries allow deep discharges without damaging the cells — one of their biggest benefits for off-grid use.
3 Things DoD Tells You About Your Battery
1. How Much of Your Battery You Can Safely Use
LiFePO4 battery with 100Ah capacity:
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80% DoD = 80Ah usable
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90% DoD = 90Ah usable
Lead-acid only allows ~50Ah usable.
2. How Long Your Battery Will Last
Lower DoD = longer lifespan.
Example:
A LiFePO4 battery rated for 6,000 cycles at 80% DoD may reach 8,000+ cycles at 50% DoD.
3. How to Size Your System Correctly
If your cabin uses 1,200Wh/day, and your 100Ah battery gives ~1,200Wh usable at 100% DoD, you’d need:
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100Ah battery: 1 day of storage
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200Ah battery: 2 days of storage
Best DoD Practices for Off-Grid Systems
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Use LiFePO4 for deep discharges
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Keep DoD between 20%–80% for longest lifespan
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Avoid draining to 0%
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Use an MPPT controller with proper voltage settings
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Keep batteries in temperature-safe spaces
Recommended Gear
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LiFePO4 batteries (100Ah–300Ah)
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MPPT charge controllers
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Battery monitor / shunt meter
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Proper wiring & fusing