I have purchased two "Yu Feng" trikes that were originally cleaners' carts in a shopping centre. They have a 500 watt 48 volt hub motor on one back wheel with a free wheel on the other side and use four 12 volt 20AHr SLA's for juice. They look pretty good with "mag" spoked wheels of 450mm diameter but a truly horrendous set of 'brakes' consisting of a bicycle style rim brake on the front and a very rudimentary and flimsy drum-and-band brake on the powered rear wheel (but NOT the other rear wheel!?)
As built, they are heavy, slow and under powered and loath ANY kind of slope, let alone a hill, so I put two of the powered wheels on one of them to try it out. Not surprisingly it was a lot better but still not approaching good, by any means, but at least it could get back up the hill to my place at a leisurely 7.5 kph.
I am looking at the feasibility of upping the power even further and getting one registered, but I know very little about this process and the kinds of things that matter and don't matter. I would appreciate any ideas, assistance or know-how about registerable trikes in general and the specifics of getting these sort of things registered.

That tray back is also a tip-tray (If you are strong enough to lift it up).

The speedo only works when the throttle is open but not when you are coasting and the 'Fuel Guage' is only a crude voltmeter.

The beautifully fabricated stainless steel cupboard on the back looks like something out of a hospital and would be ideal as a bain-marie to sell hotdogs or whatever and the dinky little trailer also has a tip tray complete will proper tailgate. The hospital cupboard/canopy can be replaced with another tip tray and with the trailer can carry two wheelbarrows full of stuff. Mind you, if it's something heavy like dirt you had better be prepared to put in some pedal effort. It's also possible to configure the trailer with the other hospital cupboard/canopy for a truly bizarre looking setup.
They have some glaring electrical design faults. There is nothing to stop you driving off with the battery charger plugged in and the battery charging point is a standard IEC (240vac) connector that is permanently live-wired to the battery. Plenty of scope for disaster!
The red trike now has a charging lockout relay but I still need to replace that connector before someone tries to plug it into 240volts.
The range, barebones (no canopy, etc), is about 20 Kms with both power wheels operating and one (slightly over weight) adult but you still have to pedal or push up steep hills. I'm not complaining, though, because they only cost me $300 for the lot, second hand, off course.