How the calculator models a battery
Three efficiencies, multiplied, never added
The flight-time estimate does not apply a single weather penalty. It computes a temperature efficiency from the pack temperature, an altitude efficiency from the air density at your field elevation, and a wind efficiency from the wind and turbulence model, then multiplies the three. The product, capped at 100%, is the share of the pack the model treats as usable:
The efficiency stack:
Usable capacity % = temperature efficiency × altitude efficiency × wind efficiencyMultiplication is why bad conditions compound. A cold day at altitude in wind is not three small losses added together; each factor shrinks what the others leave behind.
Voltage follows the same product in the model: a pack working at 65% efficiency also sags further under load, which is why a cold pack can hit a low-voltage warning while the percentage gauge still looks comfortable. The gauge counts charge; the motors feel voltage.
Temperature: the biggest single factor
The efficiency curve the calculator applies to a LiPo pack
Cold slows the chemistry inside the cells. Internal resistance rises, capacity that is technically still in the pack cannot come out fast enough to use, and efficiency falls off well before the pack is physically damaged. Heat restores output briefly, then costs it again as the cells are stressed. The curve below is the one the site calculates with, interpolated between these points:
| Pack temperature | -20°C | -10°C | 0°C | 5°C | 10°C | 15°C | 20-25°C | 30°C | 35°C | 40°C | 45°C |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Efficiency | 30% | 45% | 65% | 80% | 90% | 98% | 100% | 85% | 75% | 65% | 50% |
Cold (below 5°C)
At 0°C a third of the pack is already out of reach, and at -10°C more than half is. The calculator flags cold packs explicitly because the voltage sag arrives before the capacity gauge suggests it should.Optimal (15-25°C)
The severity model rates 15-25°C as optimal flight conditions with no derating. The efficiency plateau sits at 20-25°C; 15°C already returns 98%.Warm (26-34°C)
Output slips to the mid-80s and the severity model classifies this band as thermal stress. Shorter flights, and packs age faster when worked hard in heat.Hot (45°C and up)
The severity model calls 45-60°C an equipment damage risk and recommends avoiding flight. A pack left in a parked car reaches this band without any flying at all.Getting the most out of a cold pack
Temperature optimisation is mostly logistics, not settings
- • Start warm. The model derates by pack temperature, not air temperature alone. A pack carried at room temperature and flown promptly starts near the top of the curve even when the air is cold; a pack that sat in a cold car boot starts at the bottom.
- • Keep packs insulated in transit. An insulated bag holds the warmth from home. It does nothing once the pack is in the drone and the wind is moving over it, so fly the warmest pack first.
- • Budget by the curve, not the label. At 0°C, plan on roughly two thirds of the rated time before wind and altitude take their share. The worked example below shows the arithmetic.
- • Watch voltage, not just percent. Cold packs sag under load and recover when the load drops. A low-voltage warning early in a cold flight is the pack telling the truth; the percentage readout catches up later.
- • Let a cold pack warm up before charging it. Bring it back to room temperature first. Charging a cold-soaked pack is hard on the cells, and the charge it accepts is not the charge it can give back.
Altitude and wind take their share
The other two factors in the stack
Altitude efficiency comes from air density: thinner air gives the propellers less to push against, so the motors spin faster and draw more for the same lift. The model derives it from the ISA density at your elevation, the same physics covered in Understanding Air Density.
Wind is priced separately because it is a power problem, not a capacity problem: holding position against wind and correcting for gusts raises the current draw. The model's graduated wind penalty starts at 8 mph and grows toward the drone's rated wind limit, and turbulence raises the draw further because the flight controller is constantly correcting. This is why a breezy day shortens a flight even with a warm pack at sea level.
Worked example:
A drone rated at 34 minutes, flown at 0°C at sea level in calm air: 34 × 0.65 ≈ 22 minutes of usable pack. Move the same flight to -10°C and the temperature factor alone leaves 34 × 0.45 ≈ 15 minutes, before any wind or altitude factor is applied.
Charging best practices
What happens on the charger decides what happens in the air
- • Charge to the chemistry's full voltage: 4.2 V per cell for LiPo, 4.35 V per cell for LiHV. Charging a LiHV pack on a LiPo profile leaves its extra capacity unused; charging a LiPo pack on a LiHV profile overcharges it.
- • Use the manufacturer's charger and rate unless you know why you are deviating. Smart batteries manage their own balance and limits; generic chargers need the cell count and charge rate set correctly every time.
- • Charge at room temperature. A pack that comes in cold from a flight or hot from a summer flight should rest first. Room temperature is also the top of the efficiency curve, so a pack charged warm and flown soon after gives back the most.
- • Do not leave charging packs unattended, and charge on a non-flammable surface. Most packs live out their whole cycle life without incident, and the ones that fail tend to fail on the charger.
- • Retire damaged packs. A swollen, punctured or crash-bent pack has internal damage that no charger setting fixes. Its capacity and its safety margin are both gone.
Storage and cycle life
Packs age fastest sitting still, fully charged
A LiPo pack stored at full charge ages noticeably faster than one stored at a partial charge: the high cell voltage that helps in the air accelerates degradation on the shelf. The standard storage target is about 3.8 V per cell. Many smart batteries discharge themselves toward a storage level after a set idle period; with manual packs, use the charger's storage mode after the last flight of a trip rather than topping everything back up.
- • Depth of discharge sets cycle life. The chemistry comparison on this site puts LiPo at 150-300 cycles and LiHV at 300-500. Deep discharges spend those cycles faster. Land at 3.4 V per cell under load and never drain a pack below 3.0 V per cell; below that, cells take permanent damage.
- • Store cool and dry, not cold-soaked. Room temperature or a little below is the target; a freezer is not a storage strategy, and a hot garage in summer sits in the model's damage band.
- • Check stored packs periodically. A pack that has self-discharged well below storage voltage, or swollen in storage, should not go back into service.