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40Ah or 60Ah cells?

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  • theoldcars@aol.com
    One other consideration when considering 40 or 60 Ah cells. Keep in mind on the 40Ah cell you should not charge them at rates exceeding 12 amps for long cycle
    Message 1 of 1 , Dec 3, 2012
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      One other consideration when considering 40 or 60 Ah cells.

      Keep in mind on the 40Ah cell you should not charge them at rates exceeding
      12 amps for long cycle life. With the 60Ah cells 18 amps or less is going
      to be within the CALB recommend charging. Just as in driving lower charge
      rates are going to extend your service life.

      If you use a lot of regen the above is another reason you may want to have
      a larger cells.

      Keep in mind the CA 40 by CALB is cycle life based on a 1/3 C rate charging
      and discharging. CALB does not provide what 2C cycle life information so I
      would assume its not good news.

      Also watch the regen in a higher SOC. My Force would regen on a full lead
      pack.

      Don Blazer


      In a message dated 12/3/2012 3:38:25 P.M. Pacific Standard Time,
      perrypeas@... writes:

      Rex-
      I don't think the "general consensus" includes 60Ahr. Yet. I only know of
      two transplants that are less than 100 Ahr. (Bouty & me) Would like to be
      enlightened about any more out there...
      I see you running through the same thought process as I did. 40Ahr is
      definitely small. But you of all people should know, having driven
      electric for so long in the first place, and even tracked your Ahr usage.
      I didn't have that benefit, and I can tell you it wasn't wrong.
      The only thing I'd recommend is to consider putting in as high a voltage as
      you can. 56 cells is really fun- the "sport" version of the Solectria
      Force. Plus it results in greater range too- the higher voltage means the
      Ahr counter moves slower.
      Also the 60s are a different shape than the 40s. Taller and skinnier. I'm
      not sure what the height of the front box is, but with the smaller
      footprint you could definitely fit more of them in.
      If you do a "high-voltage" transplant using CA 40s, you'd have a very light
      and zippy car.

      Putting all the cells in the front is also a good idea, and I wish I had
      that too. When there's snow on the roads I really notice the lack of
      traction. I have a hard time getting going in front of my house. I have
      one gel cell in the front still just to give me some weight up there. I'm
      thinking that after a year of this, when I have the sense that the cells
      really are not going to drift and have some experience with it, I may move
      them up to the front where they're very difficult to actually measure (or
      as many as I can fit up there).

      I remember reading Bouty's email with disbelief that he hadn't even checked
      the voltage on the cells for 18 months! How irresponsible! Is he trying
      to wreck his batteries?
      Now I'm quite a ways down that road myself.

      Wade



      On Mon, Dec 3, 2012 at 9:33 AM, Rex Allison <ev64bug@...> wrote:

      > **
      >
      >
      > 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 <cfrkeepr@...>
      > To: "solectria_ev@yahoogroups.com" <solectria_ev@yahoogroups.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 <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



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