Practical battery & energy tools
Battery & Runtime Calculators
Calculate battery runtime, capacity, charging time, energy, power requirements and battery combinations with practical browser-based tools for everyday electronics, backup systems, vehicles, solar setups and portable power.
Calculations run locally in your browser. Nothing you enter is uploaded.
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Battery physics is the same everywhere. Your region only sets the mains-electricity context, terminology and optional cost currency.
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Quick-start scenarios
Load a common setup with example values, then edit every assumption.
Battery calculator directory
No tools match your search. Try “runtime”, “Ah”, “UPS”, “phone” or “solar”.
Battery quick reference
What is Voltage (V)?
Electrical potential difference — the “push” that moves current through a circuit.
What is Ah?
Amp-hours represent electric charge capacity. They describe energy only when combined with voltage.
What is Wh?
Watt-hours represent stored or consumed energy. Wh = V × Ah.
What is mAh?
One-thousandth of an amp-hour. Common for phones and small electronics. 1000 mAh = 1 Ah.
What is C-rate?
The relationship between capacity and charge/discharge current. 1C discharges the rated capacity in about one hour.
What is Depth of Discharge?
The proportion of battery capacity that has been used. Many chemistries last longer at lower depth of discharge.
What is Efficiency?
The percentage of energy retained after conversion and system losses (inverter, charger, wiring, heat).
What is Usable Capacity?
The portion of stored energy you can safely draw, after applying depth-of-discharge and efficiency limits.
Battery chemistry overview
General educational comparison. Always follow the manufacturer specifications for your specific cells.
| Chemistry | Typical use | Rechargeable | Relative energy density | Cycle life (general) | Common nominal voltage |
|---|---|---|---|---|---|
| Lithium-ion (Li-ion) | Phones, laptops, EVs, power banks | Yes | High | Moderate–high | 3.6–3.7 V/cell |
| LiFePO₄ (LFP) | Solar, RV, backup, e-mobility | Yes | Medium | Very high | 3.2 V/cell |
| Lead-acid (flooded) | Automotive, inverters, UPS | Yes | Low | Low–moderate | 2 V/cell (12 V packs) |
| AGM | UPS, backup, vehicles | Yes | Low–medium | Moderate | 2 V/cell (12 V packs) |
| Gel | Deep-cycle, solar | Yes | Low–medium | Moderate | 2 V/cell (12 V packs) |
| NiMH | AA/AAA rechargeables, some tools | Yes | Medium | Moderate | 1.2 V/cell |
| Alkaline | Remotes, clocks, low-drain devices | No | Medium | Single-use | 1.5 V/cell |
Safety first: Follow battery and charger manufacturer specifications. Do not charge physically damaged, swollen or leaking batteries. Use compatible chargers and protection systems. High-current battery-bank wiring may require a qualified electrical professional. These calculators are planning tools and do not replace product specifications.
Common calculation examples
12 V 100 Ah at 100 W
1,200 Wh stored. At 90% usable × 90% efficiency = 972 Wh → about 9.7 hours of runtime.
20,000 mAh power bank
At 3.7 V: 20,000 × 3.7 ÷ 1000 = 74 Wh of stored energy (before conversion losses).
500 Wh at 20 V
500 ÷ 20 = 25 Ah. Voltage is required — mAh alone cannot describe energy.
EV: 60 kWh at 15 kWh/100 km
60 ÷ 15 × 100 = about 400 km theoretical range before real-world adjustments.
How to use HowMuchBattery.com
- 1
Choose a calculator
Pick the battery, runtime, charging, capacity or conversion tool that matches your question.
- 2
Enter battery information
Enter values such as voltage, Ah, Wh, mAh or battery quantity.
- 3
Enter your load or requirement
Enter device watts, charging current, desired runtime or related information.
- 4
Adjust assumptions
Where available, configure efficiency, depth of discharge or other relevant factors.
- 5
Calculate
The application performs the calculation directly in your browser.
- 6
Review the explanation
See the formula, intermediate values and interpretation.
- 7
Save or share
For detailed reports, copy, print, save or share the calculated result.