It might be within spec, but I said earlier that I hadn't heard of a NiMH EV pack going more than 30,000 miles. I also didn't say that was why they were returned. Just that all reports showed a replacement every 30,000 miles or so. And of the EV plus reports I looked up on the web last night, it seemed that 3 of 5 that had a history that I looked at on the web last night had a replecement in their history.
I don't like NiMH due to intolerance to discharge, self discharge, heat generation and poor cyclic life compared to NiCd. That's all. I **never said** the Honda EV+ was a bad car, just that NiMH are not a mature battery yet. I should know, I shipped a few thousand packs last year. And dealt with the returns and the fires. Those were consumer NiMH batteries with peak detecting chargers with timers and thermal protection too. So I have a little experience with NiMH. Additional comments inserted below. <snip> > > You are making a mountain out of a molehill. > > The 27,000 mile EV+ NiMH battery pack was still > *within spec*, according to the report on hondaev.org. > I remember that incident because it was so unusual. > Instead of replacing one battery module that had a > weak cell, Honda chose to replace the entire battery > pack. Speculation was that Honda wanted to do > advanced mortality studies on the remaining batteries > to project how many more years they might last. > > The EV+ lease returns were primarily because > Honda ended its lease program, *not* because of > battery problems, as you have apparently assumed. > Even if there were three NiMH battery pack replace- > ments, that would be *less than 1 percent* of the > 360 EV+s that were built and leased by Honda -- > a very respectable battery mortality rate compared > to Lead-Acid or any other battery chemistry. <Again, I looked at perhaps 5 reports and saw 3 replacements. Scheduled or not. An all by 36,000 miles that's a 60% replacement rate.> > > Incidentally, the Matsushita NiMH batteries used > in the EV+ were very similar, if not identical, to the > NiMH batteries used in the RAV4EV. As the > Hondaev.org site clearly points out in the opening > paragraph: > > >> * To date, about 1200 Toyota RAV4 on the road > in fleet operation have had zero battery pack > replacement[s]. The batteries have virtually > zero defects, considering the number of cells, > and they do not suffer apparent degradation. << > > Please stop confusing the little "AA" NiMH > batteries that you use in your hobby experiments > with state-of-the-art NiMH EV traction batteries. > *They are worlds apart!* > <Not my hobby experiments. A consumer product. With more shipped than probably the EV-1, EV+ and RAV4EV combined. See above.> > Regardless of whether you are talking about > Matsushita, Ovonic or Saft NiMH EV batteries, > all of these batteries meet or exceed USABC (U.S. > Advanced Battery Consortium) Midterm life cycle > standards. Each manufacturer's battery is slightly > different, but in the case of the Saft 109 ah NiMH > mentioned earlier on this thread, these modules > have delivered in excess of 1,250 cycles to 80 > percent DOD (depth of discharge) at C/3. That > is a VERY respectable number! <C/3 is also a silly discharge rate. The heating of NiMH happens at higher currents. With a 300V pack, C/3 on a 100Ah pack is about 10kW. Or highway cruise. Full acceleration is more like 90kW -60kW or 3C to 2C, I would think. 1250 cycles is better than lead at 80%DOD. But who here does a steady state discharge at C/3? Which is 20-30 amps for most batteries.> > The primary challenge for NiMH is to get > enough of these batteries into production to > bring the price down to a projected cost of > $250/kWh. In a RAV4 EV, that would equate > to a $7,100 battery pack (plus dealer profit) > that may very well last for 8 to 10 years! <I would love to see them get cheap like lead. Then they could become the next lead battery. Lighter and with improved #cycles, but retaining intolerance to full discharge and still requiring advanced charging and thermal management. I will still buy NiCD for long life though.> ***end of comment insertion*** > > Regards, > > Dave Goldstein > President, EVA/DC and > Program Development Associates > Gaithersburg, MD > > -- > > -- vze3v25q@verizondotnet
