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8636Re: [solectria_ev] Thermal Management System

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  • d. Bouton Baldridge
    Dec 3, 2012
    • 0 Attachment
      Hi Rex, you have done well getting 7 years and 22,000 miles. I have not been so fortunate with Pb.
      Ok not too sure of the miles maybe 3000. Since the main reason for a small pack was cost I also adopted a different attitude for the car. Being an early model the 30 -40 mile range on 90 ah  l/a is still pretty much possible with the 40 Ah lithium. Not needing to drive that much every a day any longer (retired) I wanted to find a solution to the problem of replacing packs every 18 months or 2 years. My goal was to get the overall cost of driving electric down, and replacing packs so frequently was the number one culprit. Since my lithium pack cost just a bit more than the Pb four years ago, I feel that my goal is proving to be successful. I have added the solar feature to not only reduce the cost more, but I wanted to prove to myself that it could be done without using supplemental power which now influences my driving as well. I will have driven 2.5 years without even plugging in. I drive only the distance that will allow me to recharge from the sun
      the next day, which is qute a challenge during the winter. So distance driving is for somebody else. Range anxiety is an issue all of us EVers  have to deal with in our public image. If you want to go long distances in an EV it can be done but at a steep price for a large pack, but how much do you really need? Those 3000 miles were hundreds of short trips like the average driver does every day; if an ICE were used they would be the least efficient and most polluting miles, not so with an EV. Hope this helps.
      Bouty



      ________________________________
      From: Rex Allison <ev64bug@...>
      To: "solectria_ev@yahoogroups.com" <solectria_ev@yahoogroups.com>
      Sent: Monday, December 3, 2012 11:33 AM
      Subject: Re: [solectria_ev] Thermal Management System

       
      I have one question for Bouty:
      How many miles do you have on your pack?

      One question for the group:
      Does anyone have the dimension for the inside of the front battery box?

      I'm really interesting in Bouty's configuration. After 7 years and 22,000 miles my poor old Pb pack is on it's last legs. I'm able to get 22 to 24Ahrs out of the pack which is enough for a round trip to work and a very short side trip. Since the pack is fairly weak it takes 1.5 to 1.6Ahr per mile.  I'm trying to hold out until summer for my switch to lithium when the weather is a little better and I have my battery monitor tested out. I'm interested in putting 49 40Ahr CALB "grey" cells (CA40BFI) for a couple of reasons:

      1.  If my measurements are correct the complete pack should fit in the front battery box in a 7x7 array. By moving the charger up front all the 156V wiring will be under the hood with a very short run between the pack and the controller.

      2. The pack cost
      is comparable to if not cheaper than the Deka equivalent. 40Ahr CALBs are around $55 each. 49 x $55 = $2,695 before tax and shipping.  13 Deka batteries would have to be $207 just to be comparable ($2,695 / 13 = $207 approx.)

      3. My car will be shedding 661lb. The CALB cells at 3.3lb each x 49 = 161 lb vs the 822lb (63.2lb x 13) of the current pack. I'm probably going to have to find the original springs for the Geo, otherwise the car will feel like it is permanently going down a hill.

      4. The "blue" CALBs (SE40AHA) already have fantastic C ratings and the "grey" cells have better cold weather performance. The max current of the force at around 240A dc should be no problem for the 40Ahr cells, they should be able to handle C6. There is some interesting test data on the cells: http://blog.evtv.me/2012/06/battery-jump-shift/

      I know the general consensus is that 60 Ahr or 100 Ahr is preferable, but I've been logging all my driving for the past 7 years, most days I use between 16Ahrs and 20Ahrs and only a few times did I even come close to 35Ahrs.

      ________________________________
      From: d. Bouton Baldridge <mailto:cfrkeepr%40yahoo.com>
      To: "mailto:solectria_ev%40yahoogroups.com" <mailto:solectria_ev%40yahoogroups.com>
      Sent: Sunday, December 2, 2012 7:26 AM
      Subject: Re: [solectria_ev] Thermal Management System


       
      Hi Wade,
       In my opinion, the balance thing has been greatly over blown and your readings are perefectly acceptable especially after using so much capacity having only +/-.1 v or so from the mean is fantastic. The big thing is avoiding going beyond the knees and your system seems to be working just fine doing that. As for the Ahmeter issue, It has been my experience that voltage is not a reliable means for determining capacity. In my case I have found the reaching the limiting voltage was caused by the pack warming up; for me it was the sun. Now that the ambient temperature is lower in the winter season my charge resets closer to zero, but in summer it stops on the plus side by .1 ah each cycle when the outside temp is above 80 degrees. My guess for you is that when you charge for a few hours, the pack temp increases higher than when you were driving and the voltage is slightly higher as a result this stops the charger earlier than
      the previous Ahour
      reading. I am not sure if this is happening as a function of breaking in or aging. But it was not an issue with lead since it woul be overcharged routinely and had the automatic reset.  I am a few months shy of 4 years and this slight precession is only an annoyance it has not seemed to impact the utility of my pack. Since I have a pretty long warm season I would just occasionaly reset the Ah meter to zero just so I wouldn't have to remember every time. Now that my cells are getting twice as old as any Pb pack would last, I am getting into new territory for longevity and at some point I might find some of these answers, but for now I am saying congratulation on your project FWIW,
      Bouty

      ________________________________
      From: Wade Perry <mailto:perrypeas%40gmail.com>
      To: mailto:solectria_ev%40yahoogroups.com
      Sent: Sunday, December 2, 2012 1:47 AM
      Subject: [solectria_ev] Thermal Management System

       
      Greetings all- I've driven over 1,000 miles on lithium now.

      I drove a fair bit today, it was mostly empty when I was coming back home
      from the last errand so I thought I'd take the long way home and discharge
      a bit more than I usually do. Until today the maximum I'd taken out is
      probably around 45 Ahr. I had set my limit around 50 to be safe.
      So after I got home I drove the block a few times with the heater on. Went
      well past 50. I measured pack voltage and some individual cells while I
      did this and felt fairly safe as I was getting down towards the bottom.
      Finally drove it around one last time in econ with no heater and it was
      around 57.5 when I was done. Then I ran the heater by itself to get it to
      59. Took the voltage on each cell.
      Made a new column to my battery balancing spreadsheet, it's here-
      https://docs.google.com/spreadsheet/pub?key=0An5nm8itUMMcdHhQV3RsSUdfbzRTQkFlNmtaSy05MHc&output=html

      The cells were springing back as I was measuring them. When I was done I
      went back and measured CK, where I'd started measuring the pack. it was
      .04 volts higher than I'd written down the first time. By the time I was
      finishing measuring, all the cells were coming in around 3.04 or 3.05. So
      they're reasonably well balanced.

      One cell stands out. JA. It measured 2.93 when its adjacent cells were
      measuring an entire ~0.10 volt higher. I haven't figured it out yet.
      Other than it happens to be the one that I noticed arrived from the
      factory at 4.23% below 50% SOC. You can see that on the sheet. It stood
      out at the time because all the other cells came in at 1 or 2% over 50.
      This was the only one that was below, and by a fair amount.

      Anyway then I ran the heater some more, watching JA in particular. It
      would have been cool to have a graph of all the cells at once. But they
      were falling off quite quickly. Some dipped down to 2.75 or so. JA dipped
      all the way down to 2.50. But I discharged down to a full 60.00 Ahr on my
      counter! Finished with a pack voltage of around 160. (which was
      undoubtedly springing up also. I didn't wait around to check but plugged
      in the charger so I can drive again tomorrow)

      This is great, because I had feared I was losing capacity permanently by
      charging below freezing. I'd hoped this wasn't the case, but was concerned
      because on especially cold days there'd be +1.00 or +2.00 Ahr still left on
      the counter when the charger shut off. Warmer days I'd be back to -0.14 or
      something like that. I'd been worried that I was gradually damaging the
      cells.

      Apparently I'm not. Or at least not to the extent I'd feared. This is
      with a battery box that's not even put together yet- the 60 Ahr cells are
      taller than the gels I took out, so when I finally do get things put
      together properly, I'll need to shim the cover over the battery box. Right
      now it rests on top of the cells, so there's probably a 1" space all
      around, letting cold air in. I did put in a 60watt incandescent light bulb
      back there to keep things warmer (and bright and cheery) in the battery
      box, whenever the car's plugged in.

      So. What I'd really like to do is hook up the Solectria heating mats to AC
      power, so I can be more setup for winter. I myself took it apart back in
      August, but obviously didn't pay much attention to what I was doing. I've
      searched this list repeatedly but can't find anything that talks about
      where the AC power hooks up to the heaters / sensors... Can anyone point
      me to a resource about this?

      Thanks for the help!

      Wade Perry
      1998 Force
      56 CALB CA 60 Ahr

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