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Discussion Starter · #1 ·
Hi all,

Well, I've finally got around to writing up the results of LOTS of
LiFePO4 battery testing I've been doing over the last few weeks. I've
been testing five different cells, an assortment of 18650s and 26650s
from PHET, Huanyu, Valence and A123Systems. So without further ado..

http://zeva.com.au/tech/LiFePO4.php

I've also included details of the test bench including circuit
diagram for the electronics and the source/project files for the test
software, in case anyone else wants to build their own "battery
tester on a shoestring"! Please let me know if you see any errors or
if anything requires further clarfiication. :)

Kind regards,

Ian Hooper
[email protected]

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Discussion Starter · #7 ·
Hey Sam

Ya outta let people on the EVDL in on the details of your application using
the TS cells. I am sure folks here would find it of interest.

(Hint... it is a long-range motor-bike. [the word scooter doesn't really do
it justice, but it is _legally_ a scooter] :^)

Roy


Sam Maynard wrote:
>I don't know precisely what the chemistry and construction differences are
>between Thundersky LFP's and A123, but the TS LFP cells can be safely
>floated at 4.25V per cell. Take the float regulator off and they relax down
>to about 3.85V. There is a steep voltage curve charging above about 90%
>SOC,
>where the cells quickly rise from about 3.3 V to 4.25V (make sure it's
>regulated or they will climb higher and be permanently damaged!), but most
>of the charge/discharge cycle is a nearly flat line between 3.2 and 3.3V,
>during which I haven't personally found the limit of how much they can
>absorb, having not hit them with more than 1C yet.
>
>"Never let your sense of morals prevent you from doing the right thing"
>-S



~~~~~~


Roy LeMeur

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Discussion Starter · #10 ·
The cells are about 10 milli-ohms and low-current charge voltage is
about 3.4 volts (at ~50% SOC.) This implies that you should be able
to put in almost 40 amps before you push the cell terminal voltage up
to 3.8 volts. 3.6 volts would take about 20 amps.

You noted a "strange voltage taper" on the Valance cells. These were
the largest cells, and just slightly larger than the A123 cells.
Perhaps the high current was an issue with these tests. Maybe the
voltage drop on the leads or connections was a problem.

We have charged these cells in the bike at over 1 C and they stay
under 3.4 volts until they are close to fully charged.

When you charge a single cell at just over 1C, it is not a big deal.
We charged the 374 volt, 25.3 A-hr pack (1210 cells) at 1.15 C at the
track using a Mazanita Micro PFC-50 plugged into the grid.

Bill Dube'

Just a thought.

Bill Dube'

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Discussion Starter · #11 ·
Ian,
=

Amatuers like me really appreciate stuff like this. Graphs and pictures mak=
e it so much easier to comprehend. Like "Consumer Reports" for EV's.
Um..please don't take this the wrong way but do you have any sort of busine=
ss relationship with any of these companies?
=

Last question: Does anyone have contact info for PHET?
=

Rich A.
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ilnews
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Discussion Starter · #12 ·
I would be surprised if he was associated with any of them. I've seen no
bias and we've covered a lot of topics. he's building his own controller
and hope to sell those

PHET: http://www.phet.com.tw/

Dan


Richard Acuti wrote:

>Ian,
>
>Amatuers like me really appreciate stuff like this. Graphs and pictures make it so much easier to comprehend. Like "Consumer Reports" for EV's.
>Um..please don't take this the wrong way but do you have any sort of business relationship with any of these companies?
>
>Last question: Does anyone have contact info for PHET?
>
>Rich A.
>_________________________________________________________________
>Boo! Scare away worms, viruses and so much more! Try Windows Live OneCare!
>http://onecare.live.com/standard/en-us/purchase/trial.aspx?s_cid=wl_hotmailnews
>_______________________________________________
>For subscription options, see
>http://lists.sjsu.edu/mailman/listinfo/ev
>
>
>

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