Al (and all), Further to my last post on this subject, I thought I would forward to you -- and anyone else on the list who is interested in reading and learning more about this -- a post I made a few weeks ago on the "EVs for Sale" Discussion List, which sheds more light and technical battery detail and gives a better explanation of what I alluded to in my last post as to the reasons why it is inadvisable and would not be a good idea for me to drive one of my RAV4-EVs up to Winter Haven at this time of the year and with 6.5-going-on-7 year old battery packs.
In addition to the story I give in my post below about my more recent trip to the Keys, back in May of this year, there is another, older story I should add to that and tell you about here of a long-distance road trip I made with one of my RAV4-EVs two years ago, in August 2006, to Central Florida, Winter Park specifically, for the Central Florida premiere of "Who Killed the Electric Car?" ... thanks, by the way, to the great work of FLEAA founding member Hugh Webber (of Winter Park) who set up the showing, got us permission from the theater manager to exhibit two EVs up on the sidewalk/pedestrian plaza in front of the theater there in tony Winter Park Village, arranged charging for my RAV4-EV while there, and was in general a terrific host! Despite all that, and notwithstanding my truly gracious, exceptional host Hugh and the absolutely outstanding job he did on all counts in arranging the event, I decided after that trip that I will never, never, never again make another trip to inland Central Florida during the summertime, due to some very painful (for my batteries) lessons I learned about the considerable differences between the summertime climates of coastal Florida and inland Florida, respectively. Where I live, just 3.5 miles from the Atlantic ocean in South Florida, the summertime daytime high is generally in the 87-93 degree F range and rarely ever exceeds that. Well, I had absolutely no idea how hot inland Florida (away from the moderating influence of the ocean) gets in the summertime until I made that trip two years ago. The situation was exascerbated by a very narrow, fixed-timetable window I had for charging at a house of one of Hugh's neighbors, I believe it was, IIRC. As I recall, I think the house nextdoor that Hugh was renting at the time didn't have an accessible 240V outlet. Even at the neighbor's house, which *did* have an accessible 240V outlet, we had to snake my charging cable down through a tiny basement window to the dryer in the basement. The fixed-timetable window that we had for charging was from 11am to 4pm. At 11am that August morning, the ambient air temperature was already 101 degrees F. I was astounded and knew I was in for trouble but had no idea how bad it would get. We put the car on charge and then left in Hugh's gasser, in which he gave me the grand tour of Winter Haven and all the celebrities' homes there, downtown Orlando, then down to International Drive and all the popular upscale restaurants, bars, and nightspots there where Hugh operates his pedicab business. Very interesting tour, and very kind of Hugh to spend all the time showing me around! Well, we got back to the charging RAV4-EV around 3pm or so as it was approaching the end of the charge, and it was even worse than I feared -- the battery temps were up at 120 degrees F. This is just *murder*, absolute *MURDER*, to do this to your battery pack! It was then that I realized what this trip was really costing me in terms of the permanent damage and degradation it was going to do to my battery pack. Well, the horror just continued for another 24 hours. I drove back to my hotel in Winter Park, making sure to drive off the top 7% of the charge (highly exothermic with its high IR), and went and lay down in my air-conditioned room for an hour to try to cool my own body down, which was similarly heat-stressed. Meanwhile, I left the car turned on so that the battery fans could continue to run. In fact, I left the car turned on for the next 24 hours so that the battery fans could run continuously, but there was little-to-nothing that could be done to ameliorate the situation for the heat-stressed batteries. [Technical note: The battery fans run anytime that one of the three battery temperature monitors (one on each of the three rows in the battery compartment) is at 97 deg. F or above. But this is only the case when the car is turned on. Unlike the EV1, the RAV4-EV electronics do not wake up periodically when the car is turned off, check the battery temps, and turn on the battery fans if above the 97F threshold. This is one of the few serious deficiencies in the design of the car. There are a few other design deficiencies as well, but thankfully very few.] At 4:30pm, I drove the few blocks from my hotel up to Winter Park Village. It would take another 8 hours -- from 4:30pm to half past midnight -- with the car left turned on and battery fans running continuously -- for the battery temps to very slowly, gradually come down from 120F to 101F, which was still the ambient air temperature at midnight! Yes, it was still 101 degrees F at half past midnight, when we wrapped up the event. Hugh was well conditioned to the heat, but my body was suffering like my batteries, although probably not as much as them. I had to go to the pizza place next door to the theater every half hour to buy a huge king-size drink, full of ice, just to keep myself hydrated and from getting heat stroke. (I can only imagine what it's like for people who live in Las Vegas, Phoenix, Tuscon, and Baghdad, who have to live with 120 degree F temperatures every day for 3-4 months of the year.) Of course there was no way to get the battery temps lower than 101F, because the fans are just blowing ambient air over the batteries, and ambient was 101F, even at midnight, and you obviously can't get the battery temps below ambient. One way to think about what this does to your battery pack is to make an analogy with the human body. Every time you subject your battery pack to an extended heat-soaking above about, say, 105F, it is like the human body having a minor heart attack. The damage is permanent -- a permanent degradation. And such damage is additive and cumulative. Every time you have a minor heart attack, you weaken the heart a little bit more and further shorten the life of the heart, and thus the life of the human, a little bit, maybe like taking a few years off of your life every time you have a minor heart attack. Similarly with batteries, NiMH specifically in this case, every time you subject them to extended (6+ hours) heat-soaking above about 105F, you are probably taking something like, say, 3 months off the life of the batteries. What I have observed with the PEVE EV-95 NiMH batteries in the RAV4-EV is that the battery temps will typically rise to about 15 degrees F above ambient during charging, especially in the latter stages of the charge. Normally this is not a problem when we charge here at home (by programmed timer-charge) in the late-night/early-morning hours from 4am to 8am, which of course is the coolest time of the day, when the (summertime) ambient is around 78F or so. So the battery temps only get up to around 93F. No problem, no heat-soak stress at that temperature level. Charles Whalen Two 2002 Toyota RAV4-EVs in Delray Beach, FL ----- Original Message ----- From: "Charles Whalen" <[EMAIL PROTECTED]> To: "EVs for Sale DL" <[EMAIL PROTECTED]> Sent: Sunday, August 10, 2008 1:19 AM Subject: Re: Portrait of a damaged RAV4-EV pack / Electron, a perfect pack at 47K miles Doug, Once again, many thanks for this! Fantastic! Very useful! Great work! Keep 'em comin'. I have a lot of experience with charging RAVs in a year-round hot climate. In my opinion and experience, right around 88 degrees F is that threshold above which I believe you are doing some permanent degradation to your pack and shortening its life a little bit every time you charge it above that ambient temperature threshold. I try to avoid doing so at all costs. Sometimes that has been impossible due to tight, difficult circumstances of timing on long-distance road trips, with very limited opportunities to charge, during the hotter months. I have cringed at the heat-soak stress I have put on these packs on a few such occasions. With 6.5 year old packs, I now try avoid, as much as possible, doing any such long-distance road trips during the hotter months (which is 6 months out of the year here). The only reasons I have taken such long-distance road trips in the first place have been in support of the cause [i.e. to exhibit at important events and educate the public (which here knows nothing about EVs and has never seen them nor ever even heard of them)]. I loaned out my HHT/Scantool 13 months ago and have not yet asked for it back. It's actually out there somewhere on the west coast. But as of 13 months ago, the two packs were both split between 6 mOhm and 7 mOhm, one pack about 50-50 between 6 and 7 and the other pack creeping closer to 7, about a 2/3 to 1/3 split between 7 and 6, respectively. The 3.3 years I have had these cars has been a trial-and-error learning experience about battery care, listening to sometimes conflicting advice from many different RAV4-EV owners (who've owned their cars longer than I have owned mine), trying different things based on differing advice, and eventually developing my own ideas and beliefs about battery care the more I have come to understand these batteries. I have put the packs through some unintentional extended abuse during this learning process. It is a truly amazing testament to PEVE's quality, reliability, and durability that these batteries are just so darn good that they can take a fair amount of abuse over time and yet still hold up so well. It is an old adage in the EV community that most EV newbies kill their first pack in the learning process of coming to understand batteries, what constitutes abuse, and how to properly care for them. Lucky are those of us with RAV4-EVs that such is not the case with the extremely forgiving and abuse-tolerant PEVE EV-95s. That said, an extreme amount of abuse on a sustained, consistent long-term basis will definitely shorten the life of these batts, as can be seen from some of the examples you've given in your insightful IR comparative analysis. A newbie does have to make an effort to learn (during which of course there will be some inevitable mistakes leading to abuse) -- learn from others, learn from his/her mistakes, try to get the right formula for one's particular circumstances of climate and application, and do the best one possibly can to care for these batteries. This is especially critical in a year-round hot climate like South Florida, where I live. I've got climate working against me right from the start, putting me at a critical handicap, already shortening the calendar life just by the sustained elevated ambient. That makes battery care and doing the best to baby these packs even more important and critical. I think the most important and salient point and lesson about care of these particular batteries (as well as most other battery chemistries, to varying degress) is to try one's best to limit the amount and duration of heat-soak exposure. In a hot climate, this means really only charging at night, for starters. Then one also has to understand that NiMH, by the very nature and properties of its chemistry, has a high internal resistance in the top ~7% of the SOC and in the bottom ~10-15% of the SOC, and to try to avoid the worst of the exothermic potential and consequences in those two respective bands by taking the appropriate mitigation strategies. I will be interested to get my HHT/Scantool back at some point in the hopefully not-too-distant future to see how my two packs' respective conditions have held up over the last year and where they are now on IR. I took one extended 10-day trip down to the Keys in mid May this year for a very important big annual event down there (which last year had been held in March but this year they moved it to mid May), and after the 2-day event ended up spending the remaining 8 days down there setting up new charging stations. In the process, on several occasions I had no choice and had to charge during the day, during which time the ambient temperature was always around 95-98 degrees. Even though I didn't have my HHT with me and no way to take any measurements, I know these cars and these packs well enough by now -- and I could just see and feel how really inefficient the charging was and how it was struggling -- that I just knew I was murdering my pack. I was cringing. Even driving at those temperatures is a strain on the pack, especially after the big heat-soak of charging at those ambients. You're just piling more heat-soak on top of more heat-soak, for longer and longer duration. My range was way down throughout the entire trip. I pretty much had to leave the car turned on 24x7 for the entire 10 days down there for the fans to run, but of course even that didn't do much good, because the fans come on anytime any of the three battery temperature monitors are at 97 deg. F or above, and daytime ambient was right around that anway, and of course the fans can't lower the battery temps to anything less than ambient. It would take all the way until 3 am for the battery temps to finally fall under 97 deg. F and the fans to turn off. Then I'd come out at 6am and turn the key off. I absolutely hate doing this. My wife doesn't want me taking our RAVs on any more such long trips for events between May and October for exactly this reason ... because she too understands (from all of my explanations to her) the amount of heat stress this is putting on the packs and thus shortening their lives. She knows (again because I've told her) that it may well be a very long time before there are ever any more production BEVs on the market of this incredibly high caliber and quality and thus that we have to do everything we can to baby these packs. For me, it's a terrible dilemma and with great ambivalence that I make these long-distance trips for the cause, at least during the hotter months, because I know what it is costing me in terms of the permanent degradation it is doing to my battery packs and shortening their lives. But for everyday daily driving, there are no such problems, as we only charge from 4am to 8am, when the ambient is around 78 degrees, and the PEVE EV-95 pack does great at such ambient and suffers no such heat-soak stress. And we only need to charge our cars about twice a week anyway, to provide for all our daily driving. If I would just limit our use to this and not make these overly ambitious long-distance road trips during the hottest 6 months of the year, I'm sure these batteries would last 12-15 years if one takes the kind of care with them that we do. As I mentioned before, your IR comparative analysis that you are posting on this forum is the most useful thing I have seen and read on any EV list in many years! It's helping to further my understanding of these batteries and their ageing and degradation process under varying conditions. It's also giving me a good deal of peace of mind and great reassurance about the amazing quality, reliability, and durability of these PEVE EV-95 batteries. These particular batteries were and still are the absolute pinnacle and high-water mark that have yet to be matched, and I wonder if they ever will be. No wonder Chevron went after them with such a vengeance and shut them down and killed them. Given what I know about lithium batteries from my own and others' experience with them and what I hear on a daily basis from working with EE/battery engineers in the EV industry who work with lithium batteries, I think it will be a long time before we see any lithium batteries match the safety, quality, reliability, and especially the durability of these PEVE EV-95 batteries. Chevron did a terrific job for their shareholders and the rest of their oily brethren in their industry. These PEVE EV-95 batteries are the only batteries I've ever seen, worked with, experienced, read about, and heard about, from all my sources in this industry, that really represented, and still do represent, a serious threat to the oil industry and existing status quo petro paradigm hegemony. Charles Whalen Two 2002 RAV4-EVs in Delray Beach, FL _______________________________________________ Florida EAA mailing list [email protected] http://www.floridaeaa.org
