How To Convert Milliamp Hours (mAh) To Watts?

Converting milliamp-hours (mAh) to watts requires knowing the battery’s voltage (V) and discharge time (t). The formula: Watts = (mAh × V) / (1000 × t). Energy in watt-hours (Wh) = (mAh × V) / 1000. Without voltage, mAh alone can’t determine watts, as power depends on both energy capacity and the rate of energy use over time.

Watt Hours to Milliamp Hours Calculator (Wh to mAh)

What’s the formula for converting mAh to watts?

The core formula is Watts = (mAh × Voltage) / (1000 × hours). First, convert mAh to amp-hours (Ah) by dividing by 1000. Multiply by voltage to get watt-hours (Wh), then divide by discharge time to obtain watts. For example, a 5000mAh 12V battery discharged in 5 hours yields (5000×12)/(1000×5) = 12W.

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Deep Dive: Let’s break it down step-by-step. A 10,000mAh battery at 3.7V stores (10,000/1000) × 3.7 = 37Wh. If discharged over 2 hours, it delivers 37Wh / 2h = 18.5W. Pro Tip: Always confirm the battery’s nominal voltage—Li-ion cells typically use 3.7V, while lead-acid systems are 12V. A common mistake is assuming all batteries share the same voltage. For instance, using 5V for a drill battery rated at 18V would miscalculate power by 72%!

Why is voltage necessary in the conversion?

Voltage determines the energy density of a battery. Since mAh measures charge capacity, multiplying by voltage converts it to energy (Wh), enabling power (W) calculation. Without voltage, mAh only reveals charge, not energy.

Deep Dive: Think of mAh as the volume of water in a tank and voltage as the pressure pushing it through a pipe. Power (watts) is the flow rate, dependent on both factors. For example, a 4000mAh phone battery at 3.8V holds 15.2Wh, but a 4000mAh 12V car key fob battery stores 48Wh—triple the energy! Pro Tip: Higher voltage batteries pack more energy per mAh. Always prioritize Wh ratings for solar or EV applications where energy density matters most.

How does time factor into the calculation?

Time determines how rapidly energy is drawn. Dividing watt-hours by hours yields watts, representing continuous power output. Shorter discharge times increase wattage demands on the battery.

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Deep Dive: Consider two scenarios: A 20,000mAh power bank at 5V (100Wh) discharged over 10 hours provides 10W, suitable for low-power devices. The same bank drained in 1 hour must deliver 100W—a 10x surge risking overheating. Pro Tip: Match discharge rates to battery specifications. Exceeding C-rates (e.g., 1C = full discharge in 1 hour) strains cells, reducing lifespan. For example, a 2000mAh battery rated for 0.5C safely provides 1A for 2 hours, but pulling 2A (1C) might void warranties.

Milliamp Hours to Watt Hours Conversion Calculator (mAh to Wh)

What’s the difference between mAh and Wh?

mAh measures charge capacity, while Wh quantifies total energy. Wh factors in voltage, making it universally comparable across battery types. mAh alone only works for same-voltage systems.

Deep Dive: Imagine two batteries: Battery A is 3000mAh at 3.7V (11.1Wh), and Battery B is 1500mAh at 24V (36Wh). Despite half the mAh, Battery B holds 3x more energy. Airlines restrict batteries by Wh (e.g., 100Wh max) because energy, not charge, determines safety risks. Pro Tip: When replacing batteries, prioritize Wh over mAh unless voltage is identical. A 5000mAh 12V battery outperforms a 10,000mAh 5V pack in energy (60Wh vs. 50Wh).

Can you convert mAh to watts without knowing voltage?

No—voltage is essential. mAh reveals charge, but watts require energy (Wh), which hinges on voltage. Guessing voltage introduces errors up to 300%, as seen in 1.5V AA vs. 3.7V Li-ion comparisons.

Deep Dive: Suppose you assume a 2000mAh NiMH battery (1.2V) is 3.7V like a Li-ion. The calculated watt-hours would be 7.4Wh instead of 2.4Wh—a 208% overestimation. Always check labels: USB power banks use 3.7V or 5V, while RV batteries range from 12V to 48V. Pro Tip: For devices listing wattage (e.g., 60W laptop), use mAh = (W × t × 1000) / V to find compatible battery capacities.

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