Lakesound

Cleantech: The Sixth Industrial Revolution

Jkessler,

Thanks for your response on the Valence batteries. That is great news! Perhaps Valence just didn't take my email inquiry seriously and gave me the shove-off. You must have found them to be cost effective. If they do really work, it seems like there would be a good market for them and Valence would be impoving their availability. Anyone from Valence or close to Valence care to comment?

Cleantech: The Sixth Industrial Revolution

To use your format:

Lead Acid 3, NiMH 1.5, Li-Ion 2.

My experience: Medical Electronics, portable defibrillators, power tools. While Lead Acids are poor for cycling and obviously heavy, they "like" to be kept fully charged. Emergency equipment users always want their equipment to be ready and fully charged. Keeping Lead Acid batteries on the charger works fine. However, all you have to do is leave SLA batteries fully discharged, on a very hot day, for 24 hours and they are permanently damaged.

Keeping NiMH batteries fully charged doesn't work well, hence the 1.5 year number which is pretty close to experience for a popular medical device. However, if you leave a NiMH battery at about 70 % state of charge, it lasts longer. You just can't leave it fully discharged nor always topped up. That becomes a hassle in real life. Your comments are spot-on. Real world users just don't treat batteries like they get treated in computer controlled testing environments.

Regarding Li-Ion batteries in computers, my experience is about 2 years for laptops, and maybe about the same for cell phones. However, they seem to degrade fairly gradually and gracefully and I've experienced no sudden failure to work. I also own a 36 volt DeWalt power tool set that uses A123 Li-Phosphate batteries. While they have amazing performance (I can cut through concrete blocks with the right blade), and the drill motor is stronger than an AC corded one, I have already had one of the battery packs fail (it just won't charge any more) in less than 2 years of use. This is very disappointing, as I really hoped these were going to be more reliable. My older DeWalt set with NiCd batteries just keeps on working. I hope my experience is not indicative of the reliability others have experienced.

A word about Valence- I got excited about their large format batteries and slick information on the web. I'd like to convert a boat to electric power. So I emailed them. It turns out these batteries must be "vaporware". A person got back to me and said that they had a minimum purchase of $500,000 (five hundred thousand dollars) and that would be only about 200 batteries. So, their 12 volt car battery size Li-Ion batteries are $2,500 each and you have to buy a half a million dollars worth. That, and they probably last only two years. It sure doesn't sound practical to me.

Like many others, I'm waiting to see if eestor (larger scale ultracapacitor technology) is really going to work in electric vehicles.

I'm interested to see what other reader's comment will be.