The most common mistake in solar installations is undersizing the battery bank. Here's a straightforward method our engineers use in the field.
Step 1: List your loads. Write down every device, its wattage, and daily hours of use. Example: 5 LED bulbs × 10W × 5 hours = 250 Wh/day.
Step 2: Add them up. A typical rural home might total 1,500–2,500 Wh/day.
Step 3: Account for system losses. Multiply by 1.3 to cover inverter efficiency, cable losses, and battery round-trip efficiency.
Step 4: Factor in autonomy days. How many days without sun? In most South Asian climates, 2 days of autonomy is standard. Multiply daily Wh by autonomy days.
Step 5: Convert to Ah. Divide total Wh by system voltage (usually 12V, 24V, or 48V). For a 3,000 Wh requirement at 12V: 3,000 ÷ 12 = 250 Ah.
Step 6: Apply depth of discharge. Lead-acid batteries should not be discharged below 50% regularly. Double the Ah: 250 × 2 = 500 Ah bank. Two SOLO 150 Ah batteries in parallel (300 Ah) would need a third for headroom — or step up to a 48V configuration.
Pro tip: Tubular plate batteries like the SOLO 150 Ah Deep Cycle handle partial state-of-charge cycling better than flat-plate designs.