Ebay Offroad E-Bike Builders?

[Arby]

Hi, I currently own an 'offroad' Burisch bike which is great for my flat commute which is predominantly off-road. The issue is that I can only cruise at about 18-19mph but I'd like to increase this to 25-28 mph so I can reduce my 17 mile commute time. I've seen a few small e-bike buiders on e-bay that seem to offer what I'm looking for at a sensible price. These are
Wing E-bikes: http://www.ebay.co.uk/itm/Electric-Bike-Carrera-Vengeance-eBike-2015-1000w-Very-Fast-48V-12ah-battery-/131512575057?
and
Hammer_Ebikes: http://www.ebay.co.uk/itm/Fast-Electric-Bike-30-mph-1000W-48V-battery-Disk-Brakes-Suspension-Forks/151682451753?_trksid=p2060778.c100276.m3476&_trkparms=aid=222007&algo=SIC.MBE&ao=1&asc=31033&meid=7c7b616582444d49b2293fc6273720cb&pid=100276&rk=1&rkt=4&sd=151667564738

I was wondering if anyone on this site has had any experience with either of these?

 

[Deleted member 4366]

Battery consumption increases rapidly with increasing speed. At 25-28 mph, you can expect a range of 10 to 15 miles with those batteries.

 

[Fordulike]

d8veh is spot on. I was running something similar with a 15Ah battery, and travelling at 26/27mph would only see up to 20 miles.
The voltage sag near the end of battery capacity was ghastly, so the top speed started tapering off at around the 15 mile point. You will need to factor that into your new bike.