X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 20 Jan 2011 16:18:11 -0500 Message-ID: X-Original-Return-Path: Received: from [69.146.254.20] (HELO crmtest.arilabs.net) by logan.com (CommuniGate Pro SMTP 5.4c2a) with ESMTP id 4820284 for lml@lancaironline.net; Thu, 20 Jan 2011 07:37:34 -0500 Received-SPF: none receiver=logan.com; client-ip=69.146.254.20; envelope-from=kevin@arilabs.net Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01CBB89E.BA07A6F6" Subject: RE: [LML] Re: Lithium Batteries X-MimeOLE: Produced By Microsoft Exchange V6.5.6944.0 X-Original-Date: Thu, 20 Jan 2011 05:36:56 -0700 X-Original-Message-ID: <3E1C96B95693C640B0AC2F59D2500F3B0FE055@crmtest.arilabs.net> X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [LML] Re: Lithium Batteries Thread-Index: Acu4Vr1BamrQi6UwRU65FPEZfovH8AARhTYg From: "Kevin Stallard" X-Original-To: "Lancair Mailing List" This is a multi-part message in MIME format. ------_=_NextPart_001_01CBB89E.BA07A6F6 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hey Michael, =20 I've worked first hand with lithium ion batteries in a hybrid electric environment. You can't over charge them or bad things happen. I've seen it first hand. I don't know what battery chemistry that your modern EV gurus are using, and perhaps there are Lithium chemistries (i.e. LiFe stuff we've been talking about) that don't care about a bit of over charging, but the fact is that there are cells that will discharge faster and recharge slower than others. I think the Toyota is using NiMH, those don't do bad things when that happens. =20 Also, balancing can take quite a bit of time and can be impractical. One of the options is to limit charge and discharge to protect the cells. There may be other strategies in use to avoid problems with over charging or over discharging cells. But again, they may be using chemistries that aren't susceptible to damage. =20 There is nothing keeping you from finding out yourself, go for it, and if you feel so inclined post your results. Nobody here is saying don't do it. Come to think of it, take some video, it would be fun to watch. No one wants to destroy your fun, if we're wrong (and that is likely) there is some joy in proving that as well. I don't think anybody here knows what happens when a LIFe battery is overcharged, I certainly don't. =20 =20 Kevin =20 =20 ________________________________ From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Michael McMahon Sent: Wednesday, January 19, 2011 9:01 PM To: lml@lancaironline.net Subject: [LML] Re: Lithium Batteries =20 I cannot claim first -hand experience, but modern EV gurus claim there is not much benefit to load balancing. =20 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: >=20 > Concerning home-packaged lithium batteries, Hamid wrote: >=20 > <> >=20 > 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???) >=20 > 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.=20 >=20 > 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. >=20 > - Rob Wolf >=20 >=20 >=20 ------_=_NextPart_001_01CBB89E.BA07A6F6 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hey = Michael,

 

I’ve worked first hand with = lithium ion batteries in a hybrid electric environment.  You can’t = over charge them or bad things happen.  I’ve seen it first = hand.  I don’t know what battery chemistry that your modern EV gurus are = using, and perhaps there are Lithium chemistries (i.e. LiFe stuff we’ve = been talking about) that don’t care about a bit of over charging, but = the fact is that there are cells that will discharge faster and recharge slower = than others.  I think the Toyota is using NiMH, those don’t do bad things when that = happens.

 

Also, balancing can take quite a = bit of time and can be impractical.  One of the options is to limit charge = and discharge to protect the cells.  There may be other strategies in = use to avoid problems with over charging or over discharging cells.  But = again, they may be using chemistries that aren’t susceptible to = damage.

 

There is nothing keeping you from = finding out yourself, go for it, and if you feel so inclined post your = results.  Nobody here is saying don’t do it.  Come to think of it, take = some video, it would be fun to watch.  No one wants to destroy your fun, = if we’re wrong (and that is likely) there is some joy in proving that as = well.  I don’t think anybody here knows what happens when a LIFe battery is overcharged, I certainly don’t. =  

 

Kevin

 

 

From: = Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Michael McMahon
Sent: Wednesday, January = 19, 2011 9:01 PM
To: = lml@lancaironline.net
Subject: [LML] Re: = Lithium Batteries

 

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, <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 acid battery. You need to charge balance the pack and pay attention to = the charging voltage and over-charge/over-discharge. Better to pay some = reliable company 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 expensive $100 in your wallet as you are dealing with an in-flight = fire.>>
>
> 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
>
>
>

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