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8629Re: [solectria_ev] Thermal Management System

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  • Wade Perry
    Dec 3, 2012
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      Thanks Bouty.
      I would never have considered a "smaller" pack size had it not been for
      you. And as it turns out I don't need the extra range. :)
      One difference- these CALB CA cells can handle anything the Force could
      ever throw at them, I usually drive quite aggressively in "Normal" and use
      the "Power" setting when I need to. Got the little car up to 117km/hr last
      night, that's a record! 72.7 mph.
      Given the lighter pack size of the 60s, plus the current they're capable of
      delivering, I think I might have the fastest stock Solectria Force
      transplant to lithium in the WORLD. (that is until someone decides to do
      the 40Ah CALB CA version- ahem)

      On Sun, Dec 2, 2012 at 8:26 AM, d. Bouton Baldridge <cfrkeepr@...>wrote:

      > **
      > 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 <perrypeas@...>
      > To: solectria_ev@yahoogroups.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
      > [Non-text portions of this message have been removed]
      > [Non-text portions of this message have been removed]

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