BATTERY POWER  The Lithium-Ion Manganese battery power pack is lightweight, technologically advanced, and safe.  EcoBike battery packs are UL and CE approved, exceeding safety and quality standards in the U.S. and E.U.  EcoBike batteries are specially designed and manufactured for the EcoBike by a subsidiary of Lenovo / IBM ThinkPad.  These batteries deliver the maximum consistent output and longevity.  EcoBike batteries have been tested and proven, with over 100,000 units manufactured and a failure rate of less than 1%.
Both land management regulators and mountain bike trail access advocates have argued for bans of electric bicycles on outdoor trails that are accessible to mountain bikes, citing potential safety hazards as well as the potential for electric bikes to damage trails. A study conducted by the International Mountain Bicycling Association, however, found that the physical impacts of low-powered pedal-assist electric mountain bikes may be similar to traditional mountain bikes.[68]

In a friction drive motor, a small, solid wheel rotates against the side of the tire in order to drive it. The first motorcycles used the same concept, with a motor mounted above the front wheel. The problem is that the drive rubs at the side of the tire. It's inefficient, and it quickly wears the sidewall away. Tires need to be replaced every couple hundred miles. For this reason, you'll seldom see electric bikes with this type of drive anymore.
Even though it’s a hefty amount of money to fork over upfront, LaLonde says you’ll likely save money in the long run. If you use public transportation, do the math to see how much you could save over time. If you choose an e-bike over a car, you’re foregoing auto maintenance, gas, insurance, parking fees, and potential tickets, LaLonde adds. “So while there’s sticker shock for a first-time bike buyer, it can still be cost-effective.”

E-bikes use rechargeable batteries, electric motors and some form of control. Battery systems in use include sealed lead-acid (SLA), nickel-cadmium (NiCad), nickel-metal hydride (NiMH) or lithium-ion polymer (Li-ion). Batteries vary according to the voltage, total charge capacity (amp hours), weight, the number of charging cycles before performance degrades, and ability to handle over-voltage charging conditions. The energy costs of operating e-bikes are small, but there can be considerable battery replacement costs. The lifespan of a battery pack varies depending on the type of usage. Shallow discharge/recharge cycles will help extend the overall battery life.
Thanks to clever engineering, the Electric Brompton folds up identically to the non-powered variety. It is heavier than a standard Brompton of course, but quite light by e-bike standards. It has small , suitcase-style additional wheels that come into play once folded up, and the way the weight is balanced means it is quite straightforward to trundle along in that state.  
Because e-bikes are capable of greater speeds for longer periods of time than standard bikes, you want extra control. Wider tires provide traction and some bump absorption with little penalty. You also want strong brakes to slow you (and all that extra weight) easily. It's worth looking at the quality of the brakes and investing in bikes with better ones if you can.