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Electric Unicycle Charging Time Calculator: Hours From Wh, Volts and Amps

By EUC ReviewPublished 4 min readHow we research

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Charging time comes down to how many amp-hours the battery holds and how many amps the charger pushes. Enter your wheel's watt-hours and pack voltage from the maker's spec sheet and the charger's output current (printed on the charger), and the calculator gives the hours from any starting charge. We checked the method against ten published charge times for eight wheels; it lands close to the makers' figures, mostly within 5%.

Electric unicycle charging time

Wh

Nominal 86.4V, so 17.4 Ah

A

Printed on the charger as output amps. Stock chargers we read run 1.5A to 10A.

1 matches the charge times makers publish; 2 would mean the last 20% charges at half speed.

%
%

Charging time

4.6 hours

20% to 100%

To 80%

3.5 hours

from 20%

Charger power

302 W

100.8V x 3A at the top

Amp-hours = watt-hours / nominal voltage. Up to about 80% the charger runs near its rated current; above that it tapers, so the last stretch is slowed by the taper factor. Use the charger's rated output current, not its input.

How the calculator works

  1. Amp-hours = watt-hours / nominal pack voltage.
  2. Charge to add = amp-hours x (end % minus start %).
  3. Hours = charge to add / charger amps, with the part above 80% multiplied by the taper factor.

With the defaults (1,500 Wh, 100.8V pack, 3A charger, 20% to 100%, taper 1) that is 1,500 / 86.4 = 17.4 Ah, then 17.4 x 0.8 / 3 = about 4.6 hours. The calculator also shows the time to 80% and the charger's power at full voltage.

Where each default comes from

Nominal voltage: 3.6V per cell

Each pack class is named by its full-charge voltage (4.2V per cell), but amp-hours are worked from the nominal voltage. Molicel rates its 21700 P45B cell at 3.6V nominal, so the calculator uses 3.6V per cell: 72V for an 84V pack, 86.4V for 100.8V, 108V for 126V, 115.2V for 134.4V and 129.6V for 151.2V. Some makers use 3.7V: King Song lists the 151.2V F18 at 133.2V nominal. Using 3.6V gives about 3% more amp-hours, so the estimate errs slightly long. Our battery voltage guide explains the classes.

Battery: 1,500 Wh on a 100.8V pack

A mid-size pack in the middle voltage class, as a starting point. Replace both with your wheel's figures.

Charger: 3A

InMotion's V14 Pro ships with a 3A charger. Stock chargers on the wheels we read run from 1.5A (InMotion E20 and V8S) to 10A (King Song F18). Use the output current printed on your charger, not the input rating.

Charge from 20% to 100%

Our assumption: a typical top-up from a reserve, close to the 15% reserve our range calculator keeps by default. Set it to 0% to compare with a maker's full-charge figure.

Taper factor: 1

Lithium-ion chargers run at a constant current, then hold a constant voltage near full while the current falls away, so the last stretch can be slower. The taper factor lets you model that, but the default is 1 (no slowdown) because that is what the makers' own figures show: in every case below, the published charge time is close to amp-hours divided by charger amps, within about 5% in most rows (the V8S's page gives both 6 and 6.5 hours). If your charger takes noticeably longer than the maker's figure, raise the taper to 1.5 or 2.

Checked against makers' published charge times

WheelBatteryPack (nominal)ChargerCalculator, 0 to 100%Maker's figure
InMotion E20240 Wh13S (46.8V)1.5A3.4 h3.5 h
InMotion V9750 Wh84V (72V)2A5.2 h5 h
InMotion V8S728 Wh84V (72V)1.5A6.7 h6 h (6.5 h elsewhere on the page)
InMotion V11Y1,500 Wh84V (72V)2.5A8.3 h8 h
King Song 16X Pro1,554 Wh84V (72V)1.5A / 2.5A14.4 h / 8.6 h14 h / 8.4 h
King Song 16S Pro840 Wh16S (57.6V)2A / 5A7.3 h / 2.9 hAbout 7 h / about 3 h
InMotion V14 Pro2,400 Wh134.4V (115.2V)3A6.9 h7 h
King Song F182,664 Wh151.2V (129.6V)10A2.1 hAbout 2 to 3 h

The 84V rows are identified from the 84V charger output each maker lists. The E20 (13 cells in series, 54.8V charger) and the 16S Pro (67.2V charger, so 16 in series) sit outside the calculator's pack list; their rows were worked by hand the same way. Makers do not say what charge level their times start from; their figures fit a full 0 to 100% charge at the charger's rated current.

Faster chargers

A higher-current charger cuts the time in direct proportion, within what the wheel accepts. Makers set those limits: InMotion recommends no more than 5A for the V9, lists a 10A maximum for the V11Y and advertises up to 16A on the V14 Pro (its FAQ says 8A and 16A chargers are not included), and King Song quotes about 3 hours for the 16S Pro on a compatible 5A charger. Use only a charger the maker approves for your wheel. The CPSC tells consumers to use the charger provided with the device and not to use "universal" chargers unless they have been tested and approved for it.

Charging habits the CPSC recommends

The CPSC's advice for micromobility batteries is to be present while charging, never charge while sleeping, and unplug the charger when the charge cycle is complete. Our guide to battery safety and UL 2272 covers certification, and our guide to winter riding and battery storage covers charging and storing a pack in the cold.

Frequently asked questions

How long does it take to charge an electric unicycle?

From a few hours to over half a day, depending on battery size and charger. Makers quote 3.5 hours for the 240 Wh InMotion E20 on its 1.5A charger, 5 hours for the 750 Wh V9 on 2A, 14 hours for the 1,554 Wh King Song 16X Pro on 1.5A and about 2 to 3 hours for the 2,664 Wh King Song F18 on its 10A charger.

How do I calculate electric unicycle charging time?

Divide the battery's watt-hours by the pack's nominal voltage to get amp-hours, then divide the amp-hours you need to add by the charger's output amps. A 750 Wh, 84V wheel holds about 10.4 Ah, so a 2A charger takes about 5.2 hours from empty, close to InMotion's 5-hour figure for the V9.

Can I use a fast charger on my electric unicycle?

Only one the maker approves, at or below the current the wheel accepts. InMotion recommends no more than 5A on the V9 and lists 10A as the V11Y's maximum. The CPSC warns against universal micromobility chargers that have not been tested and approved for the device.

Is it faster to charge an electric unicycle to 80%?

Yes, simply because there is less to add, and the last stretch of a lithium-ion charge can slow as the charger holds a constant voltage. The calculator shows the time to 80% separately; raise the taper factor above 1 if your charger slows noticeably near full.

Can I leave my electric unicycle charging overnight?

The CPSC advises against it: be present when charging micromobility products, never charge them while sleeping, and unplug the charger when the charge cycle is complete.

Sources

  1. INMOTION E20 Electric Unicycle, INMOTION
  2. INMOTION V9 Electric Unicycle, INMOTION
  3. INMOTION V8S Electric Unicycle, INMOTION
  4. INMOTION V11Y Electric Unicycle, INMOTION
  5. KingSong 16X Pro Electric Unicycle, KingSong
  6. KingSong 16S Pro Electric Unicycle, KingSong
  7. INMOTION V14 PRO Electric Unicycle, INMOTION
  8. KingSong F18 Electric Unicycle, KingSong
  9. INR-21700-P45B (Low impedance), Molicel
  10. CPSC Urges Consumers to Not Buy or Use "Universal" Chargers with Micromobility Products Due to Fire Hazard, U.S. Consumer Product Safety Commission

Cover photo: Free phone charger image, CC0 1.0, via rawpixel. Cropped.

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