{"id":10734,"date":"2026-10-30T06:10:12","date_gmt":"2026-10-30T06:10:12","guid":{"rendered":"https:\/\/www.herewinpower.com\/blog\/battery-pack-voltage-capacity-energy-v-ah-wh-explained\/"},"modified":"2026-10-30T06:10:12","modified_gmt":"2026-10-30T06:10:12","slug":"battery-pack-voltage-capacity-energy-v-ah-wh-explained","status":"publish","type":"post","link":"https:\/\/www.herewinpower.com\/ja\/blog\/battery-pack-voltage-capacity-energy-v-ah-wh-explained\/","title":{"rendered":"Battery Voltage, Capacity and Energy: How to Read V, Ah and Wh"},"content":{"rendered":"
\"A<\/figure>\n\n\n\n

Two suppliers quote a battery for the same drone. Quote A reads 44.4 V, 20 Ah, 888 Wh. Quote B reads 22.2 V, 40 Ah, 888 Wh. The energy figure matches to the last digit, so it’s tempting to treat the two as interchangeable and pick on price.<\/p>\n\n\n\n

Don’t. Your ESC and flight controller may take one and reject the other, and neither quote tells you how long the drone stays up. Voltage, capacity and energy describe the same pack from three angles, and each answers a different question \u2014 almost none of which the other two can cover.<\/p>\n\n\n\n

Read them in order \u2014 voltage, then Ah, then Wh \u2014 and the two quotes stop looking interchangeable. Two more things fall outside those figures entirely: the current a pack can supply, and whether it physically fits your aircraft.<\/p>\n\n\n\n

Battery Voltage, Capacity and Energy: What Each Figure Means<\/h2>\n\n\n\n

The three figures on a battery label are three different measurements, not three names for the same thing. Voltage describes the electrical level of the pack, and it’s the first compatibility check against the equipment the pack directly powers. Capacity, in amp-hours (Ah), measures electric charge, while energy, in watt-hours (Wh), combines the two \u2014 and it’s the only one of the three that lets you compare packs built at different voltages.<\/p>\n\n\n\n

The handy pack-level expression is Wh \u2248 nominal V \u00d7 Ah<\/strong>. That single relationship is why two packs can carry identical energy yet still not fit the same aircraft.<\/p>\n\n\n\n

\n\n<\/colgroup>

Figure<\/p><\/th>

What it describes<\/p><\/th>

The question it answers<\/p><\/th><\/tr>

\u96fb\u5727 (V)<\/p><\/td>

The electrical level of the pack<\/p><\/td>

Will it match the ESC and flight controller input range?<\/p><\/td><\/tr>

Capacity (Ah)<\/p><\/td>

Electric charge the pack holds<\/p><\/td>

How much charge is available under stated test conditions?<\/p><\/td><\/tr>

Energy (Wh)<\/p><\/td>

Nominal energy, voltage \u00d7 capacity<\/p><\/td>

How do packs of different voltage compare on one scale?<\/p><\/td><\/tr><\/tbody>\n<\/table>\n<\/figure>\n\n\n\n

If the voltage doesn’t match the equipment’s specified range, stop there. A higher Ah or Wh figure cannot make an electrically incompatible pack work. A fourth question sits outside the three figures altogether: how much current the pack can deliver. It never appears in V, Ah or Wh, so the datasheet and specification sections come back to it.<\/p>\n\n\n\n

Battery Voltage: What V Tells You<\/h2>\n\n\n\n

During a flight, the voltage at the ESC input changes as the pack discharges and the load changes, so it is never simply the nominal voltage printed on the label.<\/p>\n\n\n\n

That printed number is the nominal voltage \u2014 a reference value close to the middle of the discharge curve, used to label and compare packs, and one a multimeter will rarely show you. Off the charger the pack sits higher at its fully charged voltage, and each burst of load pulls it lower still (voltage sag under load<\/a>).<\/p>\n\n\n\n

The pack’s window follows from the cell. A common 3.7 V nominal LiPo cell charges to 4.2 V, and its usable lower-voltage limit depends on the cell and the manufacturer’s discharge specification \u2014 often around 3.0 V per cell. Multiply by the series count and a 6S pack runs from about 18 V to 25.2 V under a 22.2 V label, while a 12S pack built on the same 3.7 V cell runs from about 36 V to 50.4 V under a 44.4 V label. Those figures apply to a 3.7 V nominal LiPo cell; other cell types use different nominal and charge voltages. The difference between the nominal label voltage and a meter reading is normal, since actual pack voltage changes with state of charge, load, temperature and cell characteristics.<\/p>\n\n\n\n

A pack is a stack of cells, and the per-cell nominal voltage is what shifts the pack’s headline figure. The S count tells you how many cells are connected in series, while the pack’s nominal voltage depends on the nominal voltage of the cells used. So treat 44.4 V as the value for a 3.7 V cell, rather than as a fixed property of “12S.”<\/p>\n\n\n\n

This is where the label can trip you up. A battery labelled 44.4 V may look compatible with a “48 V” system, but the label alone isn’t enough, because the equipment has to accept every voltage the pack visits, from full charge down to cutoff. So compare the pack’s maximum charged voltage with the equipment’s stated maximum input voltage, not one nominal label with another<\/strong>. A 12S pack sits at about 50.4 V off the charger, which means equipment rated only up to a 48 V input would be pushed past its rating by a pack sold as 44.4 V. Even when the electronics survive, a higher bus voltage changes how the propulsion system operates, so the motor, propeller, current and thermal limits still need checking. The low end matters too, because the pack’s low-voltage cutoff, along with any warning threshold the flight controller sets, decides how much of the charge you can use before the aircraft reacts. Check both ends of the range against the equipment datasheet, and confirm the charger matches the pack’s per-cell charge voltage, since a setting meant for a higher-voltage chemistry can overcharge a standard pack.<\/p>\n\n\n\n

Datasheets also tend to name packs by cell count rather than voltage, which is why 6S and 12S turn up as often as 22.2 V and 44.4 V. The S stands for cells in series, but it fixes only the number of cells in that string \u2014 the actual nominal voltage depends on the cell type, and packs run 3.65 V, 3.7 V and 3.8 V nominal cells, with LiHV cells charging higher still. Read the S count alongside the stated nominal and maximum charge voltage, not instead of it.<\/strong><\/p>\n\n\n\n

Battery Capacity: What Ah Tells You<\/h2>\n\n\n\n

Amp-hours count charge, and that number is easy to read as a promise. Rated capacity is a declared value, measured under stated conditions: IEC 61960-3 tests it through a defined discharge at 20 \u00b0C, and regulatory definitions likewise describe it as the capacity measured under a stated load, temperature and voltage cutoff. If a supplier hands you an Ah figure with no test conditions attached, you still don’t know what that number means in practice \u2014 a 20 Ah rating does not mean the pack will deliver 20 A for exactly one hour in every application.<\/p>\n\n\n\n

Real-world use rarely matches the test conditions exactly. At a high discharge rate the voltage sags toward the cutoff sooner, so less charge is delivered before the pack reaches its limit. In the cold, internal resistance rises and the same early cutoff follows \u2014 the low-temperature UAV battery guide<\/a> covers why capacity drops in cold conditions. Over hundreds of cycles capacity fades, so the label describes the pack when new. Three factors matter most in practice:<\/p>\n\n\n\n