Need to convert between Ah and Wh for your battery calculations? Our Ampere Hour ↔ Watt Hour Converter makes it easy to transform battery capacity measurements with just a few clicks. Simply enter your value, voltage, and system efficiency to get instant conversions and practical equivalents. Whether you’re working with solar systems, electric vehicles, or portable devices, understand your battery’s true energy capacity in the units you need.

Ampere Hour ↔ Watt Hour Converter

Ampere Hours (Ah):

Voltage (V):

Common voltages: 3.7V (Li-ion), 12V (Lead acid), 24V (Systems)

System Efficiency (%):

Typical range: 85-98% depending on system type

Common Battery	Voltage	Typical Capacity
Li-ion Cell	3.7V	2-3 Ah
Lead Acid	12V	7-200 Ah
LiFePO4	3.2V	20-300 Ah

Basic Concepts

Ampere Hours (Ah)

Ampere Hours measure electrical charge capacity, indicating how many hours a battery can provide a certain current. For example, a 10Ah battery can theoretically provide 1 ampere for 10 hours, or 2 amperes for 5 hours.

Watt Hours (Wh)

Watt Hours measure actual energy capacity, combining current and voltage. This gives a true picture of stored energy regardless of voltage. A 120Wh battery can provide 120 watts for one hour, or 60 watts for two hours.

Why Convert Between Ampere Hours and Watt Hours?

Practical Applications

Comparing Different Batteries
- Different voltages
- Different chemistries
- Different manufacturers
System Design
- Power requirements
- Runtime calculations
- Equipment compatibility

Understanding the Ampere Hour ↔ Watt Hour Converter

Input Parameters

Voltage

Common Values:
- 3.7V (Li-ion cells)
- 12V (Lead acid)
- 24V (EV systems)
- 48V (Solar systems)

Efficiency

Typical Ranges:
- 95-98%: High-end systems
- 90-95%: Standard systems
- 85-90%: Basic systems
- Below 85%: Check system health

Conversion Formulas

Ah to Wh

Watt Hours = Ampere Hours × Voltage × Efficiency Example: 10Ah at 12V with 95% efficiency = 114Wh

Wh to Ah

Ampere Hours = Watt Hours ÷ (Voltage × Efficiency) Example: 120Wh at 12V with 95% efficiency = 10.53Ah

Frequently Asked Questions – Ah/Wh Converter

Q: Why do I need to convert between Ah and Wh?

A: Converting between Ah and Wh is essential when comparing batteries with different voltages or when matching batteries to equipment requirements. Wh provides a true measure of energy capacity regardless of voltage, while Ah is voltage-dependent.

Q: Which is better for comparing batteries – Ah or Wh?

A: Watt-hours (Wh) is generally better for comparing batteries, especially when they have different voltages. For example, a 10Ah 12V battery (120Wh) has more energy than a 10Ah 6V battery (60Wh). Wh gives you the true energy capacity.

Q: How do I know what efficiency value to use?

A: For most modern systems, use:

95-98% for high-end lithium systems
90-95% for standard lithium systems
85-90% for lead-acid systems
80-85% for older or basic systems When in doubt, use 90% for a conservative estimate.

Q: Why does my battery not last as long as the calculated time?

A: Several factors affect actual battery runtime:

Temperature (cold reduces capacity)
Age (batteries lose capacity over time)
Load variations (higher loads reduce efficiency)
Discharge rate (faster discharge reduces available capacity)
System losses (wiring, connections, etc.)

Q: Can I use this calculator for any type of battery?

A: Yes, this calculator works for all battery types, including:

Lithium-ion
Lead-acid
LiFePO4
NiMH
NiCd Just ensure you use the correct voltage and efficiency values for your specific battery type.

Q: Should I include inverter losses in the efficiency value?

A: Yes, if you’re planning to use an inverter, you should factor in its efficiency:

High-end inverters: 94-96% efficiency
Standard inverters: 90-93% efficiency
Basic inverters: 85-89% efficiency Multiply the inverter efficiency by your battery system efficiency for total system efficiency.

Q: How does temperature affect the calculations?

A: Temperature significantly impacts battery capacity:

Optimal temperature is usually 20-25°C (68-77°F)
Capacity typically drops 1-2% per degree below 20°C
High temperatures reduce battery life but don’t affect immediate capacity Consider these factors when planning your system.

Q: What’s the difference between rated capacity and usable capacity?

A: Rated capacity is the theoretical maximum, while usable capacity is what you can actually use:

Lead-acid: Usually 50% of rated capacity
Lithium-ion: Usually 80% of rated capacity
LiFePO4: Usually 80-90% of rated capacity Always design systems based on usable capacity.

Q: Do I need to convert units for solar system calculations?

A: Yes, solar system calculations often require both Ah and Wh:

Solar panels are rated in Watts
Batteries might be rated in Ah
Inverters use Watts This makes the converter essential for solar system design.

Q: How accurate are the conversion results?

A: The mathematical conversion is 100% accurate, but real-world performance varies due to:

Operating conditions
System losses
Battery age and condition
Temperature variations Always include a safety margin in your calculations.

Q: Should I oversize my battery system?

A: It’s generally recommended to include a 20-30% safety margin when sizing battery systems to account for:

Future capacity loss
Unexpected loads
Temperature effects
System inefficiencies

Q: How often should I recalculate my battery capacity?

A: Recalculate when:

Battery shows signs of aging
System loads change
Operating conditions change
After significant temperature changes
Yearly for critical systems

Q: Can I use this calculator for EV range calculations?

A: Yes, but remember to:

Include motor efficiency
Factor in driving conditions
Consider temperature effects
Add safety margin for accessories More detailed EV calculators might be needed for precise range estimates.

Q: How do I account for battery degradation?

A: For long-term planning:

Lithium-ion: Assume 20% capacity loss over 1000 cycles
Lead-acid: Assume 50% capacity loss over 500 cycles
LiFePO4: Assume 20% capacity loss over 3000+ cycles Adjust your calculations accordingly for system age.

Enjoyed this Ampere Hour ↔ Watt Hour Converter? Then be sure to check out our other lithium battery guides.