Can I just use one electric brake if two were supplied?

I have just received a new conversion kit (hub motor etc) and among the kit are two electric brakes that are both connected to the same connector . Overall four cables two per brake as per photo. The small motorbike I am putting the kit onto already has a fully functioning hydraulic front brake that works well and so I only want to add the back brake to the hub motor. Can I in that case just disconnect one of the brakes so that only one is left connected by its two cables. This is probably a no brainer but before I do anything I just wanted to check.
Also why are two electric brakes supplied when there is only one motor?
Thanks

Yes, you can only use one or none.

I find brake cutoffs useful though. Some owners take the magnet/switch out of the e-brake lever and find a way to mount them on the hydraulic levers.

Jessiedog1234567 said:

Can I in that case just disconnect one of the brakes so that only one is left connected by its two cables.

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Yes. The brakes are just switches - the two are connected in parallel, so disconnecting one has no effect on the operation of the other.

Jessiedog1234567 said:

Also why are two electric brakes supplied when there is only one motor?

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The idea is that applying either brake will kill power so the motor isn't bucking the brake(s). For PAS systems, this is important because motor operation is only indirectly tied to operator activity and power may be applied for a bit after you stop pedaling. With the ebrakes hooked up applying the ebrakes cuts the power immediately by overriding the controller PAS functionality. This ebrake behavior is often required by law as a necessary safety feature. Think aunt Zelda cruising on PAS in the park and hitting the brakes (or a brake) but the bike doesn't stop and just motors on ahead... so - a law for a broad real-world demographic.

That said, for a non-PAS systems you have a more conventional motorcycle circumstance and there is no particular reason to hook up the ebrakes if you have normal hand coordination or motorcycle muscle memory. Many folks never bother with ebrakes and simply turn off the throttle before hitting the brakes just like bikers have done for a century (!). So - your choice there... ( 1, 2, or none)

I would recommend using both of them if they are quality parts -- if for some reason you only apply one brake, the engine will still cut off (whichever one you use).

If they're cheap junk, like some ebrake levers are, I'd recommend just getting better ones -- good ones aren't that expensive. But this is all a matter of personal preference.

Thanks for all your advice.

I have been looking at an ebike sensor switch to go with the existing hydraulic front brake set up that is on the bike. It means that I could keep that system in place but the electric sensor switch uses a magnet and sensor so that when the brake lever is pulled it switches off power. This means that I can have two electric brakes operating , has anyone used these?

You didn't provide a link so no telling if that specific product has been used, but that's the general mechanism for all magnetic ebrakes - a magnet that goes on the side of the cable pull and a pickup to attach to the brake housing. Works fine if you can get the magnet and pickup arranged in your hydraulic brakes. I have purchased NOS Tektro ebrakes for about $5 a set on eBay and stripped off the pickups to use on newer mechanical brakes - so, same basic deal as what you show. The result is impervious to water and nicely reliable - arguably a step up from the switch-type ebrakes.

Another option is the TripWire sensor sold by Grin that fastens onto your brake line with a little cable that goes to a convenient part of your lever. This eliminates the need to squish a magnet inside the housing at the cost of a bit of exposed mechanism. See: http://www.ebikes.ca/product-info/tripwire.html.