8637Re: [solectria_ev] Thermal Management System
- Dec 3, 2012Hi Wade,
It is only a theory but I think that while you are charging at the higher rate steady state it tends to heat the cell electrolite higher than when you were driving; in my case the cells are heated by the high outside temps and cabin. A warmer cell increases the voltage and thus the charger reaches voltage limit before the entire Ah capacity is reached just slightly less. I have withnesses my cell arround 90 degrees F and the car acts like it is in power mode good acceleration and the converse is true when they are below 50 F, so I know that these cells behave this way. So your cells are colder before charging, I think.
From: Wade Perry <perrypeas@...>
Sent: Monday, December 3, 2012 4:30 PM
Subject: Re: [solectria_ev] Thermal Management System
Yes that was my understanding.
It's been below freezing recently, sometimes a fair bit below freezing,
like -15C. My kids are enjoying our backyard skating rink.
But I knew the cells wouldn't be as cold as the outside air because I've
been driving them, and recharging, both of which should generate some heat
within the cell itself. However they don't generate all that much heat
really even when you're pushing them, which a Force isn't really capable of
doing anyway, so I was nervous. The phenomenon that Bouty and Tom are
calling "precession" was getting me concerned. Especially because it
happened when it was COLDER. That's why I was so happy to get the full
60Ahr out... But the full capacity might be partly because I'm breaking
the cells in too.
Wolf a question for you- What do you think is the maximum voltage the
AC325 controller can handle? I have 56 cells in the car now, could I add
any more??? :)
Bouty- I don't understand why you should see a higher incidence of
precession when it's warmer, while I see a higher incidence when it's
On Sun, Dec 2, 2012 at 10:23 AM, Wolf <mailto:wolf%40wolftronix.com> wrote:
> I would not charge lithium ion batteries that are below freezing, you will
> electroplate metallic lithium and ruin the battery.
> Do a quick Google search on electroplating lithium when charging below
> On Dec 2, 2012 12:47 AM, "Wade Perry" <mailto:perrypeas%40gmail.com> wrote:
> > **
> > 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
> > 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.
> > 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]
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