X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 19 Jan 2011 23:01:03 -0500 Message-ID: X-Original-Return-Path: Received: from mail-qw0-f52.google.com ([209.85.216.52] verified) by logan.com (CommuniGate Pro SMTP 5.4c1) with ESMTPS id 4792139 for lml@lancaironline.net; Wed, 19 Jan 2011 20:48:35 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.216.52; envelope-from=afm528@gmail.com Received: by qwi4 with SMTP id 4so57532qwi.25 for ; Wed, 19 Jan 2011 17:48:00 -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=CYk0Dbd3ALjRI1Q6u95zmucoLfa3YIApK+fpsyXi86vZeeUD1XAMy6TjOm/WTp9juJ LIB4qZnpaXyYml8l0iYmcpjBsvZ0D8tpofu27/F13jdxjFY35lr2MwqC0RlCRjfj+1xI OdF6nzDsUcQ9LHKcZ/qp7ISW9NtEdHcVV/Rbw= MIME-Version: 1.0 Received: by 10.224.47.149 with SMTP id n21mr1263656qaf.188.1295488079882; Wed, 19 Jan 2011 17:47:59 -0800 (PST) Received: by 10.224.2.210 with HTTP; Wed, 19 Jan 2011 17:47:59 -0800 (PST) Received: by 10.224.2.210 with HTTP; Wed, 19 Jan 2011 17:47:59 -0800 (PST) In-Reply-To: References: X-Original-Date: Wed, 19 Jan 2011 17:47:59 -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=0015175117eecfed01049a3d52e6 --0015175117eecfed01049a3d52e6 Content-Type: text/plain; charset=ISO-8859-1 I cannot claim first -hand experience, but modern EV gurus claim there is not much benefit to load balancing. I do not want to start an argument, but it is frustrating for people to say they don't like ideas based on out-of-date or incomplete data. I am building an experimental aircraft to test and learn new things, for the pure joy of experimenting. Please don't try to stifle experimentation without doing your research. Just my two cents. On Jan 19, 2011 4:32 PM, wrote: > > Concerning home-packaged lithium batteries, Hamid wrote: > > <> > > I have to agree with Hamid here. I spent a very long two years as a battery engineer in the mid 1990's and learned a bunch of stuff. Among these was the requirement to balance the individual cells during the recharging process (which happens at the beginning of every flight, right after you start the engine). Screwing it up results in overcharging some cells and undercharging others. Lead acid is rather robust in this regard, as it turns out, but lithium is another story. In fact, the R/C model guys charge each cell individually and discharge them in series. (They also do this in fireproof bags, but that's the more twitchy Li-Po chemistry). I think it's the overcharging of an individual cell that results in fires, but excessively rapid discharge could also do it, I suppose. (Maybe due to a short in the packaging???) > > WARNING! I KNOW NOTHING ABOUT MODERN BATTERIES! But I do know that lithium batteries can catch fire and lead acid batteries don't. So I'd be reluctant to take a chance here -- let the professional research lab do it. > > I also understand that this technological reticence is why I installed a 1940's Lycoming in my 360. Modern stuff is generally better but we each draw the safety / efficiency / experimental line in different places, I suppose. > > - Rob Wolf > > > --0015175117eecfed01049a3d52e6 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

I cannot claim first -hand experience, but modern EV gurus claim there i= s not much benefit to load balancing.=A0

I do not want to start an argument,=A0 but it is frustrating for people = to say they don't like ideas based on out-of-date or incomplete data.= =A0=A0 I am building an experimental aircraft to test and learn new things,= for the pure joy of experimenting.=A0 Please don't try to stifle exper= imentation without doing your research.

Just my two cents.

On Jan 19, 2011 4:32 PM, <rwolf99@aol.com> wrote:
>= ;
> Concerning home-packaged lithium batteries, Hamid wrote:
>=
> <<You can not just take a bunch of cells and put them in series/= parallel to make a pack and put it in your airplane to replace the lead aci= d battery. You need to charge balance the pack and pay attention to the cha= rging voltage and over-charge/over-discharge. Better to pay some reliable c= ompany to do the integration and testing than do it yourself and risk an in= -flight fire. The $100 you saved by doing it yourself will feel the most ex= pensive $100 in your wallet as you are dealing with an in-flight fire.>&= gt;
>
> I have to agree with Hamid here. I spent a very long two yea= rs as a battery engineer in the mid 1990's and learned a bunch of stuff= . Among these was the requirement to balance the individual cells during t= he recharging process (which happens at the beginning of every flight, righ= t after you start the engine). Screwing it up results in overcharging some= cells and undercharging others. Lead acid is rather robust in this regard= , as it turns out, but lithium is another story. In fact, the R/C model gu= ys charge each cell individually and discharge them in series. (They also = do this in fireproof bags, but that's the more twitchy Li-Po chemistry)= . I think it's the overcharging of an individual cell that results in = fires, but excessively rapid discharge could also do it, I suppose. (Maybe= due to a short in the packaging???)
>
> WARNING! I KNOW NOTHING ABOUT MODERN BATTERIES! But I do kno= w that lithium batteries can catch fire and lead acid batteries don't. = So I'd be reluctant to take a chance here -- let the professional rese= arch lab do it.
>
> I also understand that this technological reticence is why I = installed a 1940's Lycoming in my 360. Modern stuff is generally bette= r but we each draw the safety / efficiency / experimental line in different= places, I suppose.
>
> - Rob Wolf
>
>
>
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