A.J.: Sorry for the delayed response. The only edge that lead acid has over NiZn is initial cost, and even there NiZn shouldn't cost too much more, once it is in mass production. Lead acid is a lot heavier than NiZn. The real battles will be between NiZn, nickel-cadmium, and nickel-metal-hydride.
In just about every respect, NiZn is better than NiCd.
Compared to NiMH, NiZn has some plusses and minuses. Both have similar gravitational energy densities, while the volumetric energy density of NiMH is about 20% better than NiZn. In other words, you get the same amount of power relative to the weight, but a NiMH battery is somewhat smaller than a NiZn battery of the same capacity.
NiZn has a big edge over NiMH in three categories:
1.Its power density (as opposed to energy density) is about twice that of NiMH. That measures the instantaneous power that the battery can deliver. This would give NiZn a big edge in electric vehicles or hybrid gas/electric vehicles - when the light turns green, you need a lot of power to get the car rolling.
2. Cost - because its materials are inherently cheaper, a NiZn battery should cost about one third that of a NiMH one. This is very significant; I saw an estimate somewhere that the NiMH battery in Toyota's new hybrid car is costing the company around $10,000 each.
3. The third advantage, which NiZn holds over lead acid and NiCd as well as NiMH, is that it is environmentally the "greenest". The metal hydrides, lead, and cadmium in the older battery types are nasty things that one doesn't want leaching into the water supply from landfills.
NiMH has an edge over NiZn in terms of number of cycles. NiMH can do 500-1000 deep cycles and as many as 20,000 shallow ones, whereas the comparable figures are 600+ deep and 11,000+ shallow ones for NiZn. That means that NiZn wouldn't last as long as NiMH, but given that it is so much cheaper, even replacing them more frequently, the cost of NiZn will still be well below that of NiMH. |
