https://www.faa.gov/hazmat/packsafe/lithium-batteries

Spare lithium ion and lithium metal batteries, including power banks and battery charging cases, must be carried in carry-on baggage only. When a carry-on bag is checked at the gate or at planeside, all spare lithium batteries and power banks must be removed from the bag.

Size limits: Lithium ion (rechargeable) batteries are limited to a rating of 100 watt hours (Wh) per battery. These limits allow for nearly all types of lithium batteries used by the average person in their electronic devices. With airline approval, passengers may also carry up to two spare larger lithium ion batteries (100–160 Wh) (above 100 Wh up to 160Wh with special permits)

Now here the important bit, yes you can convert mAh to Watt Hours, but the battery limits pertaining to aircraft is taken from watt-hour NOT milli-amps. It does not matter what milli-amps your battery is.

So as long as you are at Maximum capacity allowed: 100Wh you are ok.

https://www.easa.europa.eu/en/domains/passengers/dangerous-goods

Personal transportation devices

Small lithium battery powered personal transportation devices, also known as hoverboards, self-balancing devices or gravity boards, were one of the most sold devices recently. However, there have been incidents where these items or their batteries overheated, caught fire and even exploded.

Passengers are not allowed to carry these batteries in their checked bag, as batteries have a rating of 100 Wh or more.