Michael,

Private note.

I would charge my A123 26650 cells fully, and heat them up to 70 Celsius (160 F) and maintain that temperature all day in my drag bike. I did this for _years_ will no issues. The cells would reach a peak temperature of 90 to 100 Celsius (212 F) at the end of each run. We would wait 20 minutes until they returned to 70 C, then recharge. We did this routinely.

The calendar life is very much a function of temperature, and I was very much chewing away at the calendar life by heating the cells. Not "instant death" like you describe by any means.

The specific cell chemistry makes a huge difference as not all li-ion cells, or even all LFP cells, have the same chemistry.

The formula 1 "KERS" cells are _designed_ to run continuously at 75 Celsius. They are LFP.

Bill D.


On 8/7/2017 5:59 AM, Michael Ross via EV wrote:
The surest way to destroy a pack of LFP cells is to fully charge them and
let then get hot as in over 100F.

Can you tell us the number of cells and their parallel series
configuration? Then specific recs can be made.

You may want to consider cutting of charging before fully charged state is
reached and never let them sit in a hot place if you have charged them to a
high SOC.

The problem is the positive electrode becomes very reactive with the
electrolyte when fully charged and temperature sets off a destructive
process.

I speak from experience, but also researching it. There is a long and
interesting video on YouTube of professor Jeff Dahn a long time battery's
researcher, discussing his. Try searching Jeff Dahn Waterloo lithium or
similar. It was a lecture he gave at Waterloo University. Dahn is an
electrochemistry at Dalhousie University in Novelty Scotia.

On Aug 7, 2017 3:00 AM, "Matthew Quitter via EV" <ev@lists.evdl.org> wrote:

Thanks guys... but if the charger is turning off at a fixed voltage how do
I get more power into the pack?


On 7 Aug 2017, at 05:02, Bill Dube via EV <ev@lists.evdl.org> wrote:

I agree. Voltage on LFP cells is useless for determining the SOC.
The voltage is very constant except at near 100% SOC and at 0% SOC.
You really need information about the middle, and voltage doesn't give
any clue about that.
You need to count the amp-hours, like with an E-meter or a Cycle-Analyst.

Bill D.

On 8/6/2017 7:00 PM, Willie via EV wrote:


On 08/06/2017 07:38 PM, Matthew Quitter via EV wrote:
Hi Guys,

My 1238-6501 Curtis controller gives very different SOC % for similar
voltages.

For example I've recorded a pack voltage of 82.2 and had the Curtis
show
22%, 31%, 43%.

The pack is made up of 25 Thundersky 160Ah batteries.
With LFP cells, you can't accurately infer SOC from voltages in the
middle of the range.  The voltage/SOC curve is too flat.
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
Read EVAngel's EV News at http://evdl.org/evln/
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/
group/NEDRA)

_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
Read EVAngel's EV News at http://evdl.org/evln/
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/
group/NEDRA)
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
Read EVAngel's EV News at http://evdl.org/evln/
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/
group/NEDRA)


-------------- next part --------------
An HTML attachment was scrubbed...
URL: 
<http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20170807/e16e792e/attachment.htm>
_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
Read EVAngel's EV News at http://evdl.org/evln/
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)



_______________________________________________
UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
http://lists.evdl.org/listinfo.cgi/ev-evdl.org
Read EVAngel's EV News at http://evdl.org/evln/
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)

Reply via email to