Ask them to squeeze your finger

Have your kid squeeze your finger as hard as they can.

That is what they have to stop a bike with.

Nobody thinks about this when they are shopping. Hand strength is the constraint that decides whether a brake works for a child, and it is the reason brake type matters more on a kids bike than on yours.

Here is the mechanical part, briefly.

A cable brake pulls a steel wire. Friction in the housing eats some of the effort, and whatever survives that trip reaches the pad. A hydraulic brake pushes fluid through a sealed line. Fluid does not compress, so almost everything the hand puts in arrives at the caliper.

Same kid, same squeeze, different amount of stopping.

The practical version is that a hydraulic brake works with one or two fingers. A small hand does not have to give everything it has.

Most kids electric balance bikes do not use them. Hydraulic systems cost more to build, they need bleeding rather than a cable adjustment, and on a product people expect to be cheap, that is usually the first thing cut.

We use Shimano hydraulic disc brakes on every Orion Electric Balance Bike model. The e16x, e20x-FS and e24X run them front and rear. The e12x runs a rear hydraulic disc.

One honest note. The brake system is covered for 12 months. Pads, discs, levers and fluid are wear items and are not, because they are supposed to wear.

Now the useful part. Go look at any other kids electric balance bike and find the brake type on the product page. If it does not say hydraulic, it is not hydraulic. Brands that fit them tend to say so. 

No short cuts here. We use top of the line Shimano hydraulic brakes because they simply work. At Orion, quality is everything.