Sizing a battery bank isn’t guesswork — it’s about balancing capacity, voltage, and daily consumption to match your energy needs. Undersize it, and you’ll drain the battery too fast. Oversize it, and you’ll waste money on unused capacity.
Here’s a quick, practical guide to get it right.
1. Know your daily energy use (Wh or kWh).
List all your loads — lights, refrigerator, inverter, and other appliances. Multiply watts by hours of use per day. For example, a 100W device running for 5 hours = 500Wh.
2. Determine usable battery capacity.
Batteries are rated in amp-hours (Ah), but only part of that is usable.
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Lead-acid: use about 50% of capacity (50% DOD)
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Lithium (LiFePO₄): use up to 90% safely
To convert:Watt-hours ÷ System voltage = Required Ah
3. Factor in autonomy days.
If you want your system to run during cloudy weather or outages, multiply your daily usage by 2–3 days. That’s your minimum storage requirement.
4. Match your system voltage.
Most small solar setups use 12V or 24V; larger systems go 48V for better efficiency. Make sure your inverter, charge controller, and battery bank share the same voltage rating.
5. Account for efficiency losses.
Real-world systems lose about 10–15% of power through wiring and inverter conversion. Add a little extra capacity for reliability.
Example:
You use 2 kWh/day on a 24V system →
2,000 Wh ÷ 24V = 83.3Ah.
With LiFePO₄ and 2 days of autonomy:
83.3Ah × 2 ÷ 0.9 = ~185Ah total capacity.
With the right sizing, your battery bank will deliver consistent, stable power — day and night — without overloading or early degradation.