[EVDL List]

Hi Bill etc,

Does this mean I can remove the pesky undervoltage 2.6V per cell alarm on my car while driving for my LiFePO4 batteries? (CALB 130ah)

maybe the manufacturer was just kidding about the undervoltage limit :-)

have a renewable energy day,
mark
www.REEVA.info community service RE & EV's

Message: 9
Date: Wed, 04 Jul 2012 18:08:05 -0600
From: Bill Dube <xxx@xxx.xxx>
Subject: [EVDL] "Zero volts = OK for LiFePO4" (was: A123 ALM 12V7
Batteries now charging)
To: Electric Vehicle Discussion List <xxx@xxx.xxx.edu>
Message-ID: <20120705022839.xxx@xxx.xxx-a49.g.dreamhost.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

The "zero volts" data was presented on this list many years ago. I
remember it well, but a brief search of the archives did not turn it
up. Very well documented tests were performed and results presented
on this list showing that LiFePO4 cells were not only unharmed by
discharging them to zero volts, the internal resistance actually went
down after discharging to zero volts, improving the specific power.

I know that A123Systems did extensive internal testing (unpublished)
on this effect and was on the verge of patenting the "discharge to
zero" process, but then found out that this was already in the public
domain. (I was the one that told them about the results presented on
the EVDL.)

If you don't want to take my word for the facts, and absolutely must
see the data yourself, do the search of the EVDL archives and find
the thread on the subject. Maybe 7 years ago?

Bill D.

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[EVDL List]

Bill was specifically discussing A123 batteries.

A123 has a different structure of the active materials
('nanophosphate' referring to the texture and structure of the actual
iron phosphate cathode), and damage at low voltage is generally caused
by mechanical changes in the active material crystal structure as a
function of SoC. So even if Bill is correct and A123 can survive to 0V
without damage, that doesn't mean other LiFePO4 batteries can.

I read some interesting references a few months ago about how Lithium
batteries actually work including the differences between LiCoO2,
LiFePO4, and other Lithium chemistries and the mechanisms by which
cells are damaged by cycling. I don't have the links, but I'm pretty
sure they were posted here or on EVTech.

-Morgan LaMoore

[quote] Mark Hanson <marke.xxx@xxx.xxx> wrote:
>
> Hi Bill etc,
>
> Does this mean I can remove the pesky undervoltage 2.6V per cell alarm on my car while driving for my LiFePO4 batteries? (CALB 130ah)
>
> maybe the manufacturer was just kidding about the undervoltage limit :-)
>
> have a renewable energy day,
> mark
> www.REEVA.info community service RE & EV's
>

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