We are being led to believe the lithium ion battery is the future of electric vehicle technology. But the NiMH has a much better, longer and more reliable history. Most of the hybrids on the road use smaller capacity NiMH packs thanks to Chevron's control and suppression of the the larger capacity versions used in the RAV4-EV and EV-1.

For years after the Toyota Prius Hybrid first went on sale in 2000, Toyota never replaced a single battery for wear and tear. Long-range durability is intrinsic to the NiMH battery system used in Toyota hybrids and other hybrid models.

“When in service, the NiMH battery pack is kept in a partial state of charge, and is cycled through a range of partial charge levels as the vehicle is driven. By never fully charging or discharging the battery pack, the service life of the battery pack is greatly extended. The NiMH design lends itself very well to this constant state of partial charge operation,” said Toyota Product Communications Specialist David Lee.

The first Prius battery to tire out that Lee became aware of “came from a Prius with 175K miles on it,” he said. “I feel this is indicative of how long the battery packs can last.”

According to the 2010 Prius product information, Toyota warrantees the battery for ten years or 150,000 miles. Honda offers the same warranty for its 2010 Insight, a hybrid that also uses NiMH batteries. These long-term guarantees indicate the proven reliability and long-range durability of NiMH battery technology.

Sources:

http://pressroom.toyota.com/pr/tms/toyota/document/10_Prius_Product_Info_final.pdf

http://automobiles.honda.com/insight-hybrid/warranty.aspx

http://www.hybridcars.com/cars.html#battery

Interesting argument Joel, but I think I heard that before when people said "we don't need Stereo when AM radio has a much longer, reliable history" (end sarcasm). I own a Vectrix with NiMH and I can tell you first hand that they are only good enough for die hard EV fans who are willing to put up with short distances and long recharge times. For progress to happen, I mean serious adoption, we need much better battery technology. I am not saying that Lithium ion is the answer, just that NiMH is certainly not.

Li based batteries of one form or another are seen as the future because of energy density.Many of the Li based batteries have more Energy per unit weight than NiMH does.

The best NiMH batteries availible to purchase that I know of get up near ~90Wh/kg range of energy density.

There are Li based batteries availible to purchase that are above this ... some up near ~150Wh/kg.

This means more energy can be carried for the same weight... this is a desired effect for all protable energy sources ... cell phones , laptops , EVs , etc...

This energy density of batteries has historically always been the primary drawl back of any battery powered device ... 1 kg of gasoline just brings massive amounts of energy density compared to any battery technology.

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Your point on there being that there some benefits that NiMH offer I agree with... and so does anybody who knows enough about how different batteries function.

Unfortunately it isn't that simple ... for any battery application the designer has to weigh the pros and cons of every battery option availible to him/her... it is the balance and comparison of all these pros and cons that works out to a specific choice... even if whatever is choosen is not the best option in every way.

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The unfortunate aspect I see today is that the general public doesn't know enough about the specifics and just want it made overly simple... The public just wants to know what battery is better... if you even try to talk about the pros and cons you will loose your audience ... The general public opinion is that Li is better ... so the general public puts value on Li batteries so there is a marketing negative impact to use anything else but Li batteries.

Well I have a problem with batteries still create "Nitrogen and Sulfur Oxides regardless," whether its NiMH or Lithium Ion or Polymer plus that is considered no matter what a bad "Green House Gases" and which means not a BEV or Zero Emissions.

using batteries, which still use (coal plants and solar plus wind) still create GHG regardless .

BEVs are truly not greenhouse gas free unless they only use solar panel energy from the Sun .

Well I have a problem with Nitrogen and Sulfur Oxides, when Lithium produced these Green House Gases and along with BEV are zero emissions using batteries, which still use (coal plants and solar plus wind) still create GHG regardless .

BEVs are truly not greenhouse gas free unless they only use solar panel energy from the Sun .

The beauty of rechargable batteries no matter what kind they are... is that it pollutes less and is more efficient to use the large scale centrally located power grid... than a small scale , distributed , individual power system.

This is the same reason why we don't have individual house coal fired , gas fired, or oil fired, power plants for our electrical needs.

The mobile application in a vehicle is even worse than a stationary application at your house... it has to tolerate more harsh conditions , respond to fluctuations faster , fit in small size and weight constraints , and some of its produced energy has to be spent to move itself.

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That having been said... I look forward to continual progress with NiMH ... and thanks to all Hydrogen happy folks ... we see it happen ... Because the energy density of NiMH is related to the amount of hydrogen stored in the Hydride ... Modern NiMH even up in the ~90Wh/kg range only have Hydrides storing ~3% hydrogen by weight ... But thanks to the hydrogen pushing lovers... they have developed reversables hydrides that will hold up to ~7%.

Sanyo makes a 2,700 mAh NiMH AA battery that weighs 30g ... this is ~108 Wh / kg ... which is already pretty good and as a cell scale up in size its energy density improves... the weight needed for the case for the contacts begin to take up a smaller and smaller % ratio of the overall mass of the battery allowing a greater and greater % to be occupied by active battery material.... but in addition to tha scaling up effect that helps any battery ... NiMH like these can potentially double their energy density ... using modern techniques it should already be possible to build a NiMH battery that offer ~200 Wh / kg.

Thanks to the LSD ( Low Self Discharge ) Improvements in NiMH their historically bad self discharge rate is much less of a consern... the LSD-NiMH actually self discharge less than the Li based batteries do... ~15% SoC loss to self discharge in 12 months is only ~1.25% Self discharge per month... I don't know of a Li based battery that gets less than 4% per month.