X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 24 Jan 2011 07:57:11 -0500 Message-ID: X-Original-Return-Path: Received: from mail-yw0-f52.google.com ([209.85.213.52] verified) by logan.com (CommuniGate Pro SMTP 5.4c2a) with ESMTPS id 4823173 for lml@lancaironline.net; Sat, 22 Jan 2011 21:33:43 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.213.52; envelope-from=afm528@gmail.com Received: by ywf9 with SMTP id 9so1845053ywf.25 for ; Sat, 22 Jan 2011 18:33:08 -0800 (PST) DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=PYfgptJ/s+1vRYlApSVApsor4MDF4H0EeRedpEUxPY//aH2GkfA8LtS+GLyta3dZQ5 Z7sAjvuTAaR8okobMm1cxUTbl4rpoI5Sg13fQrSZkIG+3FgDvrRfjmvREBB0vUV/uZ4i x5yr1ru4jivjoS1U+EHLy//BZ8VHbYNnp+0S8= MIME-Version: 1.0 Received: by 10.151.41.9 with SMTP id t9mr2807303ybj.113.1295749986778; Sat, 22 Jan 2011 18:33:06 -0800 (PST) Received: by 10.236.105.235 with HTTP; Sat, 22 Jan 2011 18:33:06 -0800 (PST) In-Reply-To: References: X-Original-Date: Sat, 22 Jan 2011 18:33:06 -0800 X-Original-Message-ID: Subject: Re: [LML] Re: Lithium Batteries From: Michael McMahon X-Original-To: Lancair Mailing List Content-Type: multipart/alternative; boundary=0015174ff446ae0038049a7a4d1d --0015174ff446ae0038049a7a4d1d Content-Type: text/plain; charset=ISO-8859-1 Thanks Wolfgang, the PowerPoint has lots of great data points all in one place. Michael On Sat, Jan 22, 2011 at 4:32 AM, Wolfgang wrote: > You are right about balancing and it's details . . . . but the details of > battery types being tossed around on the list are all to vague. > > LiPo - Lithium Polymer - this describes a Lithium battery and it's > mechanical construction, a polymer sheet separator used as a stage for the > chemical reaction. This can described Lithium Graphite, Lithium Carbon, > Lithium Manganese or Lithium Iron (LiFe), all of which can also be called > Lithium Ion batteries. > > LiFe - Specifically describes a Lithium Iron battery, usually constructed > with a Polymer sheet separator. > > The attachments will provide more details. > > Wolfgang > > > > ----- Original Message ----- From: "Hamid Wasti" > To: > Sent: Friday, January 21, 2011 11:35 AM > Subject: Re: [LML] Re: Lithium Batteries > > > > Michael McMahon wrote: >> >>> >>> I do not want to start an argument, but it is frustrating for people to >>> say they don't like ideas based on out-of-date or incomplete data. >>> >>> It is even more frustrating when people proposed ideas based on >> incomplete data. Your "EV guru" friends are correct, you do not HAVE to >> cell balance a pack, but only as long as you are willing to live with >> the limitations imposed by that choice. Do you know what those >> limitations are? >> >> When you have a number of cells of any chemistry in series in a battery >> pack, they all receive exactly the same current when charging. Some >> cells are a little more efficient than others so they get fully charged >> before their colleagues in the string. If at that point they continue to >> receive charging current, they will over-charge. Some chemistries are >> able to handle this over-charging. Other chemistries like LiPo are very >> intolerant of this over charging and quite literally blow up. Cell >> balancing attempts to make sure that the charge on each of the cells in >> the string is identical so they all get fully charged at the same time, >> maximizing the charge that the pack can hold. That maximum number is the >> one everyone throws around and that is the number you will expect to get >> from your battery pack. >> >> As I mentioned, you do not HAVE to cell balance. For a LiPo or LiFe >> pack, you can just monitor the voltage on each individual cell and stop >> charging when one of the cells gets fully charged. Over time, the >> discrepancy in th charge state between the most efficient and the least >> efficient cell in the string will keep increasing, with the usable >> capacity of the entire pack being controlled by the charge in the least >> efficient cell. Taking this to the theoretical extreme, at some point >> the pack will not be able to deliver any energy because one cell will be >> fully charged and another will be fully discharged. In real life, you >> will declare the pack useless and stop using it before you get to that >> point. If you are willing to live with this diminishing capacity, then >> cell balancing is indeed not required. Just remember that your pack is >> no longer going to have the same capacity as the pack that has cell >> balancing and you must design the rest of your system to account for that. >> >> Quoting the late Paul Harvey: Now you know the rest of the story. >> >> Regards, >> >> Hamid >> >> >> >> > -- > For archives and unsub > http://mail.lancaironline.net:81/lists/lml/List.html > > --0015174ff446ae0038049a7a4d1d Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Thanks Wolfgang, the PowerPoint has lots of great data points all in one pl= ace.

Michael

On Sat, Jan 22, 2011 = at 4:32 AM, Wolfgang <Wolfgang@micom.net> wrote:
You are right abo= ut balancing and it's details . . . . but the details of battery types = being tossed around on the list are all to vague.

LiPo - Lithium Polymer - this describes a Lithium battery and it's mech= anical construction, a polymer sheet separator used as a stage for the chem= ical reaction. This can described Lithium Graphite, Lithium Carbon, Lithium= Manganese or Lithium Iron (LiFe), all of which can also be called Lithium = Ion batteries.

LiFe - Specifically describes a Lithium Iron battery, usually constructed w= ith a Polymer sheet separator.

The attachments will provide more details.

Wolfgang



----- Original Message ----- From: "Hamid Wasti" <hwasti@lm50.com>
To: <lml@lanc= aironline.net>
Sent: Friday, January 21, 2011 11:35 AM
Subject: Re: [LML] Re: Lithium Batteries
<= br>

Michael McMahon wrote:

I do not want to start an argument, =A0but it is frustrating for people to = say they don't like ideas based on out-of-date or incomplete data.

It is even more frustrating when people proposed ideas based on
incomplete data. Your "EV guru" friends are correct, you do not H= AVE to
cell balance a pack, but only as long as you are willing to live with
the limitations imposed by that choice. Do you know what those
limitations are?

When you have a number of cells of any chemistry in series in a battery
pack, they all receive exactly the same current when charging. Some
cells are a little more efficient than others so they get fully charged
before their colleagues in the string. If at that point they continue to receive charging current, they will over-charge. Some chemistries are
able to handle this over-charging. Other chemistries like LiPo are very
intolerant of this over charging and quite literally blow up. Cell
balancing attempts to make sure that the charge on each of the cells in
the string is identical so they all get fully charged at the same time,
maximizing the charge that the pack can hold. That maximum number is the one everyone throws around and that is the number you will expect to get from your battery pack.

As I mentioned, you do not HAVE to cell balance. For a LiPo or LiFe
pack, you can just monitor the voltage on each individual cell and stop
charging when one of the cells gets fully charged. Over time, the
discrepancy in th charge state between the most efficient and the least
efficient cell in the string will keep increasing, with the usable
capacity of the entire pack being controlled by the charge in the least
efficient cell. Taking this to the theoretical extreme, at some point
the pack will not be able to deliver any energy because one cell will be fully charged and another will be fully discharged. In real life, you
will declare the pack useless and stop using it before you get to that
point. If you are willing to live with this diminishing capacity, then
cell balancing is indeed not required. Just remember that your pack is
no longer going to have the same capacity as the pack that has cell
balancing and you must design the rest of your system to account for that.<= br>
Quoting the late Paul Harvey: Now you know the rest of the story.

Regards,

Hamid




--
For archives and unsub http://mail.lancaironline.net:81/lists/lml/L= ist.html


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