🔋 RC to Ah Calculator (Reserve Capacity to Amp Hours)

✅ Formula

$$Ah = \frac{RC \times 25}{60}$$Ah=60RC×25​

Since Reserve Capacity (RC) is tested at 25 amps, we convert minutes to hours.

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How to Convert RC to Ah (Step-by-Step)

1. Take RC value in minutes
2. Multiply by 25
3. Divide by 60

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Example Calculation

RC = 120 minutes$$(120 × 25) ÷ 60 = 50 Ah$$(120×25)÷60=50Ah

✔ 120 RC ≈ 50 Ah

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Quick RC to Ah Reference Table

RC (Minutes)	Approx Ah
90	37.5 Ah
100	41.6 Ah
120	50 Ah
140	58.3 Ah
160	66.6 Ah
180	75 Ah

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🔄 Ah to RC Calculator (Amp Hours to Reserve Capacity)

Sometimes batteries list only Ah rating. To estimate RC:

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✅ Ah to RC Formula

$$RC = \frac{Ah \times 60}{25}$$RC=25Ah×60​

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Example Calculation

Ah = 60 Ah$$(60 × 60) ÷ 25 = 144 minutes$$(60×60)÷25=144minutes

✔ 60 Ah ≈ 144 RC

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Quick Ah to RC Table

Ah	Approx RC (Minutes)
40 Ah	96 RC
50 Ah	120 RC
60 Ah	144 RC
70 Ah	168 RC
80 Ah	192 RC

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Important Technical Note

These calculations are estimates because:

• RC is tested at constant 25A load
• Ah rating is usually based on 20-hour discharge rate
• Temperature affects performance
• Real-world loads vary

So RC ↔ Ah conversion gives an approximate comparison, not exact manufacturer value.

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When to Use RC to Ah Calculator

Use conversion when:

• Comparing car battery capacity
• Replacing automotive battery
• Designing backup system
• Estimating emergency runtime
• Matching inverter battery size

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RC vs Ah – What’s the Difference?

RC	Ah
Measured in minutes	Measured in amp-hours
Automotive standard	General battery capacity
Emergency backup time	Total stored energy

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Final Summary

RC to Ah:

Ah = (RC × 25) ÷ 60

Ah to RC:

RC = (Ah × 60) ÷ 25

These formulas allow quick battery capacity comparison for automotive batteries.