Nimh batteries are well established in the electronics market: cameras, portable devices, flashlights, etc. They are marginal in the electric scooter and electric bike markets because of their cost and the fact that they are not yet suitable for high current drain situations.

The Nimh packs required by electric vehicles are made by putting many smaller cells in series. This allows for them to meet the voltage requirements. The current requirements require putting nimh packs in parallel and that causes problems with charging. If one has a large budget to build-in the proper intelligence to monitor individual nimh cells in a pack and to take appropriate steps in the event of cell failure, then nimhs can be used successfully in electric vehicle applications.

Nimh packs are best for light current draw electric bikes and scooters, They typically weigh about 60% of the weight of equivalent lead acid types.

Ditto the above about Nimhs for Li-ons and add they cost even more, are more finiky when trying to build multi-cell packs, and they can be dangerous under high current drain situations if the packs are not properly designed and constructed.

They are even lighter than Nimhs.

Sealed lead acid batteries are the corner stone of the electric vehicle market, but they are also its greatest limiter for expanding performance. Sealed Lead Acid batteries (SLA) haven't improved that much in a hundred years. They are heavy for the power they put out, and their recharge life is less than the Nimhs or Li-ons chemistries.

SLA are like car battereries except their is no liquid acid to spill and corrode. They use a 'paste' and the unit is sealed with nothing other than the terminals exposed.

If you want reliability, simple charging, and power at a cheap price, they are the only game in town. They take up a lot of space, however, and one gets into 'diminishing returns' by adding more and more batteries for more range. The extra weight eventually negates the extra power gain.

* pictures courtesy of http://www.electricrider.com

More to follow soon.