Jerry,

A big part of the weight of the Currie electric system is the original SLA battery. I live in the far Northern Rockies, we don't have many flat areas on the roads here. I'm quite impressed with the torque of the Currie non-hub motor. I'm adding a second battery this spring and it will be LIFEPO4. When the SLA batteries in the stock Currie case die, they'll get replaced with non-SLAs; whether it will be with more LIFEPO4s or NIMH will depend in part on how well my first LIFEPO4 battery performs. If you don't want to budget for a ready-made electric bike right now, you might buy a LIFEPO4 battery or a High C NIMH or NICAD battery pack for your Currie system.

The regenerative feature on the BIONX system is nice, but don't expect it to really recharge the battery much. As for BIONX batteries, depending on the model of BIONX kit you buy, you may be stuck spending close to $1000 USD to replace them with another BIONX pack when they're depleted. (There is a person on ebay who rebuilds BIONX packs. His services are discussed on the V is for Voltage forum.)

Although some of the extremely high-powered hub motors may produce a fair amount of torque, most ready-made ebikes in the US keep the hub motors installed well under 750W and the speed under 20 MPH. That's because high-powered, ready-electric bicycles sold in the US (motors over 750W or able to travel faster than 20 MPH) must meet moped/motorcycle safety standards set by the National Highway Safety Administration. (The US Congress exempted "low powered" electric bikes from these standards in 2001--low powered electric bicycles--defined as motors under 750W and speed 20 MPH or less--only have to meet the safety standards for consumer bicycles set by the Consumer Product Safety Administration.) At present, conversion kits sold in the US aren't governed by these safety standards, but I don't expect that to be the case much longer as more and more powerful hub motors are exported from China.

Good luck. Buy as much battery power as you can afford and try to avoid systems that may have proprietary designs that make it difficult to replace batteries since even LIFEPO4s fail with time.