A complete battery cycle includes both a discharge phase (using power) and a charge phase (replenishing it). This calculator models both sides so you can see whether your system recharges fully before the next discharge cycle begins — a critical question for off-grid solar and backup power setups.
Example: A Day in the Life of an Off-Grid Battery
Here is a typical 24-hour cycle for a 200Ah 12V LiFePO4 battery bank on a cabin with solar panels:
Morning (7 AM - 10 AM): Battery is at 30% SOC after overnight loads. Solar panels start producing as the sun rises. The charge controller pushes 15A into the batteries. Energy goes both to charging and to running the fridge and lights.
Midday (10 AM - 3 PM): Peak solar production. The controller ramps up to 30A. Batteries reach full charge by 1 PM. Excess solar is wasted unless you have a dump load or second use (water heating, device charging).
Evening (5 PM - 11 PM): Solar production drops to zero. The battery powers lights (60W), fridge (50W avg), TV (80W), and phone charging (15W). Total load: 205W. At 80% DoD, the 200Ah battery gives you about 9.4 hours of runtime.
Overnight (11 PM - 7 AM): Only the fridge runs (50W avg). This draws about 400Wh over 8 hours. The battery still has capacity left, reaching roughly 30% SOC by morning — right where the cycle started.
Battery Cycle Life by Chemistry and DoD
| Chemistry | 50% DoD Cycles | 80% DoD Cycles | 100% DoD Cycles |
|---|---|---|---|
| LiFePO4 | 5,000-7,000 | 2,000-3,500 | 1,500-2,000 |
| AGM Lead-Acid | 500-800 | 300-400 | 150-250 |
| Flooded Lead-Acid | 600-1,000 | 300-500 | 150-300 |
| Gel Lead-Acid | 700-1,200 | 400-600 | 200-350 |
| Li-ion (NMC) | 1,500-3,000 | 800-1,500 | 500-800 |
One "cycle" is a discharge to the specified DoD followed by a full recharge. Shallower cycles mean more total cycles. A LiFePO4 battery cycling daily at 50% DoD could last over 15 years.
Frequently Asked Questions
Need to size your solar array for full daily recharging? The <a href="/solar/solar-panel-and-battery-sizing-calculator">solar panel and battery sizing calculator</a> matches generation to consumption.
Modelling the complete charge-discharge cycle reveals whether your system is sustainable or slowly draining your batteries into an early grave. If the numbers above show your batteries never fully recharge, you need either more charging capacity (bigger panels, faster charger) or less load — there is no third option.
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Written and maintained by Dan Dadovic, Developer & Off-Grid Energy Enthusiast. On the energy side, Dan has hands-on experience with residential solar panel installation, DIY battery bank construction, off-grid power systems, and wind power — all from building and maintaining his own systems..
Disclaimer: Calculator results are estimates based on theoretical formulas. Actual performance varies with temperature, battery age, load patterns, and equipment condition. For critical electrical work, consult a licensed electrician.