8625Re: [solectria_ev] Thermal Management System
- Dec 3, 2012Thanks 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
> 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)
> 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!
>> 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
>>> From: Wade Perry <perrypeas@... <mailto:perrypeas%40gmail.com>>
>>> To: email@example.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
>>> 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.
>>> 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-
>>> 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
>>> because on especially cold days there'd be +1.00 or +2.00 Ahr still left
>>> the counter when the charger shut off. Warmer days I'd be back to -0.14
>>> something like that. I'd been worried that I was gradually damaging the
>>> 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.
>>> 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
>>> 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
>>> 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
http://portev.org -- Electric Vehicles, Solar Power & More
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