It is difficult or perhaps even impossible to determine the SOC on
LFP from voltage measurements alone. At least to do it with any
accuracy. You can measure the temperature on each cell in addition to
voltage to _perhaps_ get a better handle on the SOC, but still you
can't get a very accurate SOC.
From a practical point of view, it is easier and cheaper to count
the amp-hours in a single place, than to make very precise voltage
and temperature measurements on every cell in a high-voltage pack.
That is why it is done that way universally in OEM cars.
Bill D.
At 10:15 AM 8/8/2017, you wrote:
paul dove via EV wrote:
Sure you can. Voltage is the only way to discern SOC.
You just can't measure accurately under load. You have to measure
open circuit voltage.
www.mdpi.com/1996-1073/9/11/900/pdf
This paper mainly discusses the higher-voltage Li-Ion cells, which
have a larger voltage change between full and empty.
For the LiFePO3 cells being discussed here, the voltage change is
much smaller. As Bill says, the change is so small that it can't be
reliably measured outside of laboratory conditions and precisions
instruments. Other factors, such as age, temperature, manufacturing
variations, and the accuracy of the equipment play a larger factor.
--
Where ignorance is our master, there is no possibility of real peace.
-- Dalai Lama
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
_______________________________________________
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)
