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8625Re: [solectria_ev] Thermal Management System

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  • Tom Hudson
    Dec 3, 2012
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      Thanks for the info, Wade. I'm lucky in that my Force was upgraded to NiCD in 2001, so
      all the components are fine up to 250V. I may try a conservative "pack emptying" run at
      some point soon just so we know what we can expect out of the pack in a pinch, but for the
      time being it's good to know it's working as it should. I might put in a simple reset
      button somewhere for the Ah meter to deal with the "precession" business.


      On 12/3/2012 2:56 PM, Wade Perry wrote:
      > Hi Tom.
      > The cells cannot be "undercharged", in any sense that would cause them
      > damage anyway. Totally different from Lead. In fact it's better to
      > undercharge them a bit, or as Bouty says "stay away from the knees".
      > Charging to 3.4v is good. Very conservative, you'd probably be fine
      > charging to 3.5v, and get a little extra capacity on the top end.
      > (although there's risk of exceeding the operating voltage of the
      > controller, which is theoretically 190v, if you interrupt the end of a
      > charge and try to drive without letting the cells settle down to resting
      > voltage)
      > I'm charging up to ~192v right now when the charger enters the Constant
      > Voltage phase of the charge. I'd thought that was a little low but based
      > on my "pack emptying" experiment and getting a full 60 Ahr out, why change
      > anything? (Of course that last Ah wasn't really usable for much, but I did
      > make it to 60!) I do plan on setting my new charger to go to 196v though.
      > Congratulations by the way on your own transplant. Very impressive and
      > very neatly done! (I'm envious actually- looking at the snarl of wires
      > beside my own pack)
      > Wade
      > On Sun, Dec 2, 2012 at 9:58 AM, Tom Hudson <tdhudson@...> wrote:
      >> **
      >> The Ah "precession" is something I have been very curious about. Our car
      >> is up to 2Ah now
      >> after charging, and it's pretty cool out in the garage (in the 50s). So
      >> it's not real
      >> warm, which seems to be what you're indicating causes the charge to
      >> terminate before the
      >> Ah counter reaches zero.
      >> What is your charge profile setup? Mine charges to 3.4V per module
      >> (190.4V) at 20A then
      >> switches to 190.4V until the current drops below 1A, then the charger
      >> turns off. I'm
      >> wondering if this is similar to what you're using to charge your pack, and
      >> want to make
      >> sure I'm not chronically undercharging or something. I was tempted to
      >> change the charge
      >> so that it used a lower termination current, just in case stopping at 1A
      >> was too early and
      >> causing undercharging.
      >> At least I know that others see a similar precession on charge, so I'm
      >> less concerned than
      >> I might be, but I'd like to know what your charge profile does. You are
      >> doing very well
      >> with your pack and I could do worse than emulate you!
      >> -Tom
      >> On 12/2/2012 9:26 AM, d. Bouton Baldridge 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@... <mailto:perrypeas%40gmail.com>>
      >>> To: solectria_ev@yahoogroups.com <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
      >>> [Non-text portions of this message have been removed]
      >>> [Non-text portions of this message have been removed]
      >> --
      >> Thomas Hudson
      >> http://portev.org -- Electric Vehicles, Solar Power & More
      >> http://klanky.com -- Animation Projects
      >> [Non-text portions of this message have been removed]
      > [Non-text portions of this message have been removed]
      > ------------------------------------
      > Yahoo! Groups Links

      Thomas Hudson
      http://portev.org -- Electric Vehicles, Solar Power & More
      http://klanky.com -- Animation Projects
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