Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rating: Thread Rating: 33 votes, 4.82 average. Display Modes
Old 07-03-2013, 20:45   #2266
Registered User
 
deckofficer's Avatar

Join Date: Feb 2011
Location: Northern and Southern California
Boat: too many
Posts: 4,197
Images: 4
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by FlyingCloud1937 View Post
So is that Marketing 101, besides the facts?

L
Yep, a product trying to find a home.
__________________

__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
http://tbuckets.lefora.com/
deckofficer is offline   Reply With Quote
Old 07-03-2013, 20:55   #2267
Marine Service Provider

Join Date: Oct 2011
Posts: 1,205
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by deckofficer View Post
Yep, a product trying to find a home.
Dude if nothing else I love your passion.

I once had a Carrol Shelby modified A gas, at green valley , North Dallas..hehe.

This is a 2008 photo but looks as if I can remember to be the same/similar car.





It's not the same, we had a 427, this clearly is a Hemi.

lloyd
__________________

__________________
FlyingCloud1937 is offline   Reply With Quote
Old 07-03-2013, 21:50   #2268
Registered User
 
deckofficer's Avatar

Join Date: Feb 2011
Location: Northern and Southern California
Boat: too many
Posts: 4,197
Images: 4
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Well this is a big drift. You happen to know I'm a fellow gearhead? We can take it to Any Classic Car Enthusiasts on Board ? so as to not clutter this thread.
__________________
Bob
USCG Unlimited Tonnage Open Ocean (CMA)
http://tbuckets.lefora.com/
deckofficer is offline   Reply With Quote
Old 07-03-2013, 22:02   #2269
Marine Service Provider

Join Date: Oct 2011
Posts: 1,205
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by deckofficer View Post
Well this is a big drift. You happen to know I'm a fellow gearhead? We can take it to Any Classic Car Enthusiasts on Board ? so as to not clutter this thread.
it's a big drift, but it's also the glue that brings us together.

in any event i'll wonder on over.

lloyd
__________________
FlyingCloud1937 is offline   Reply With Quote
Old 10-03-2013, 16:01   #2270
Registered User
 
ebaugh's Avatar

Join Date: Dec 2011
Location: On the boat
Boat: DeFever 44
Posts: 525
Well the preliminary NTSB report on the Boeing battery is out. 48 pages, complete with lots of pictures. See it here:

http://www.ntsb.gov/investigations/2...787_3-7-13.pdf

I have not read every word...but it looks like a metal bolt punctured one of the cells, shorting the battery to ground. If a cell of this chemistry is shorted, the end result is not especially surprising. I did not see what would have caused this yet, did the cell overcharge and bulge into the bolt? Or did the bolt just work it's way through?

My conclusion, metal cases maybe more fireproof, but also are conductive, so I'm not so sure that's the best answer for a battery case, apparently even a well engineered one. At least this one cost enough to be well engineered. LiFePO4 would not generate near this amount of heat, even in a similar worse case scenario based on the chemistry. The data I have indicates the max is maybe 350F for LiFePO4, so wood seems good enough? My wife bakes fish on cedar in the oven at higher temps.

A quick search said a conservative estimate shows you need about 500F, or more to start a wood fire. See:

http://www.doctorfire.com/wood_ign.pdf

Mine are in a wood box, so unless anyone else thinks otherwise, Im still happy.......
__________________
ebaugh is offline   Reply With Quote
Old 10-03-2013, 16:17   #2271
Registered User

Join Date: Jun 2011
Posts: 41
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
LiFePO4 would not generate near this amount of heat, even in a similar worse case scenario based on the chemistry. The data I have indicates the max is maybe 350F for LiFePO4, so wood seems good enough? My wife bakes fish on cedar in the oven at higher temps.
Be careful wither assumptions like that, the temperature will depend on how much heat can be dumped to the outside environment. If you put a shorted battery on a table in free air and it reaches an internal temperature of 350F it will get much hotter if you surrounded all sides with a foot of styrofoam, the heat can't move without a much higher difference in temperature (heat transfer by radiation, conduction and convection are all driven by a difference in temperature). Putting the batteries in a sealed box will reduce free convection compared to no box, and wood is less thermally conductive than metals so any heat generated inside will increase the temperature moreso than a metal case. The temperature the wood would reach is dependent on the specifics of what environment it is in and how many watts you think the battery would produce in the worst case scenario you are planning for, so it might work fine, but a metal box (particularly aluminum for its better thermal conductivity) would do better at reducing peak temperatures given the same geometry.

Andy
__________________
durundal is offline   Reply With Quote
Old 10-03-2013, 16:22   #2272

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 12,107
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Where are your reading that as saying a metal bolt punctured anything?
__________________
hellosailor is offline   Reply With Quote
Old 10-03-2013, 16:39   #2273
Registered User
 
bill good's Avatar

Join Date: Oct 2006
Location: Brisbane Australia
Boat: Crowther windspeed 36' cat Goldrush
Posts: 700
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

EBAUGH You are the only person to have found the short was due to a metal bolt. Please give more information as there are a lot people looking for the root cause. Yes there are lots of data to go thru but the risk that the two battery events under investigation has at this stage are lessons for all Li-Ion users. Houses made of wood still burn down & boats are still destroyed by fires. The risk appears hopefully is less for DIY boat owners with more resourses than Aerospace companies like Boeing with scientist & engineers looking for answers.
__________________
bill good is offline   Reply With Quote
Old 10-03-2013, 18:21   #2274
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
A shorted battery will only reach a few hundred degrees? With the energy available in an LFP the temperature will easily reach whatever temperature is needed to melt away the parts involved in the short. Thousands of degrees in milliseconds if necessary. That's the magic of electricity.

A wooden battery box would be my last choice.
__________________
daddle is offline   Reply With Quote
Old 10-03-2013, 19:11   #2275
Senior Cruiser
 
Opie91's Avatar

Join Date: Apr 2009
Location: CT
Boat: C&C 34
Posts: 765
Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by ebaugh View Post
My conclusion, metal cases maybe more fireproof, but also are conductive, so I'm not so sure that's the best answer for a battery case, apparently even a well engineered one. At least this one cost enough to be well engineered. LiFePO4 would not generate near this amount of heat, even in a similar worse case scenario based on the chemistry. The data I have indicates the max is maybe 350F for LiFePO4, so wood seems good enough? My wife bakes fish on cedar in the oven at higher temps.
You might want to rethink your conclusion. Airplanes have been flying around with metal battery cases for years.
__________________
Opie91 is online now   Reply With Quote
Old 10-03-2013, 20:23   #2276
Registered User
 
ebaugh's Avatar

Join Date: Dec 2011
Location: On the boat
Boat: DeFever 44
Posts: 525
I attached a couple of screen prints from the NTSB file. The one with the scan of the cell is clear evidence the cell was punctured. The other one shows where.
Attached Thumbnails
Click image for larger version

Name:	image-1000184955.jpg
Views:	119
Size:	335.7 KB
ID:	56626   Click image for larger version

Name:	image-1015082550.jpg
Views:	111
Size:	226.2 KB
ID:	56627  

__________________
ebaugh is offline   Reply With Quote
Old 10-03-2013, 20:32   #2277
Registered User
 
ebaugh's Avatar

Join Date: Dec 2011
Location: On the boat
Boat: DeFever 44
Posts: 525
The supposition that the ground connection took a bunch of current is the middle of this page.
Attached Thumbnails
Click image for larger version

Name:	image-2799455593.jpg
Views:	96
Size:	295.8 KB
ID:	56631  
__________________
ebaugh is offline   Reply With Quote
Old 10-03-2013, 20:41   #2278
Registered User
 
ebaugh's Avatar

Join Date: Dec 2011
Location: On the boat
Boat: DeFever 44
Posts: 525
Quote:
Originally Posted by durundal View Post

Be careful wither assumptions like that, the temperature will depend on how much heat can be dumped to the outside environment. If you put a shorted battery on a table in free air and it reaches an internal temperature of 350F it will get much hotter if you surrounded all sides with a foot of styrofoam, the heat can't move without a much higher difference in temperature (heat transfer by radiation, conduction and convection are all driven by a difference in temperature). Putting the batteries in a sealed box will reduce free convection compared to no box, and wood is less thermally conductive than metals so any heat generated inside will increase the temperature moreso than a metal case. The temperature the wood would reach is dependent on the specifics of what environment it is in and how many watts you think the battery would produce in the worst case scenario you are planning for, so it might work fine, but a metal box (particularly aluminum for its better thermal conductivity) would do better at reducing peak temperatures given the same geometry.

Andy
I understand your points. My wood box does have "vents", that would ventilate some heat outside the box.

Maybe you are better off with no enclosure? The max free air temps are not much higher than that oil temperature?

An issue outside the engine room for sure, but mine are between 2 gensets, in a 20 ft by 15 ft by 5.5 ft engine room.
__________________
ebaugh is offline   Reply With Quote
Old 10-03-2013, 21:01   #2279
Registered User
 
ebaugh's Avatar

Join Date: Dec 2011
Location: On the boat
Boat: DeFever 44
Posts: 525
Quote:
Originally Posted by bill good View Post
EBAUGH You are the only person to have found the short was due to a metal bolt. Please give more information as there are a lot people looking for the root cause. Yes there are lots of data to go thru but the risk that the two battery events under investigation has at this stage are lessons for all Li-Ion users. Houses made of wood still burn down & boats are still destroyed by fires. The risk appears hopefully is less for DIY boat owners with more resourses than Aerospace companies like Boeing with scientist & engineers looking for answers.
I posted what refers to the "bolt" already. Maybe it was something else, but something punctured the cell.

Wood will burn. But I think a poor battery connection, with high resistance, can cause a heat, potentially a fire regardless of the battery chemistry. Probably in excess of the temps shown in the attached document from Los Alamos. There is no free lunch with 15 kW of stored energy. Just not sure the battery type is the biggest risk?

It may be a fallacy that the temps can't ever reach more than any specific point as shown on the attached overcharge graphs. Which is where some of my assertions lie. But short out any battery and heat is generated no matter the chemistry. The good thing, probably no different than lead acid, is the adjacent cells should not pour coal on the fire for LiFePO4. As you can see the Boeing chemistry is the worst shown in the second graph. And in fact at some point does add additional heat to an already bad situation.
Attached Thumbnails
Click image for larger version

Name:	image-1852615269.jpg
Views:	75
Size:	300.6 KB
ID:	56632   Click image for larger version

Name:	image-4263620506.jpg
Views:	69
Size:	285.2 KB
ID:	56633  

__________________
ebaugh is offline   Reply With Quote
Old 10-03-2013, 21:17   #2280
Registered User
 
ebaugh's Avatar

Join Date: Dec 2011
Location: On the boat
Boat: DeFever 44
Posts: 525
Quote:
Originally Posted by Opie91 View Post
You might want to rethink your conclusion. Airplanes have been flying around with metal battery cases for years.
You are correct. Even my old Piper had one. I'm still not sure it's a great idea. Part of the design issue for Li of any chemistry is it will produce huge current until empty. Many of the airplane batteries are much smaller capacity (<100 Ah, probably 55 or 60) than a marine Li bank, and are somewhat self limiting based on size. The LA just won't keep going as long in a shorted condition. They just quit. But a 400 (or sometimes much larger) Ah bank calls for different considerations regardless of chemistry.
__________________

__________________
ebaugh is offline   Reply With Quote
Reply

Tags
battery, lifepo4, LiFePO4 Batteries, sailing

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LiFePO4 Batteries - Okay Tear Me Apart ;-) jallum Electrical: Batteries, Generators & Solar 395 03-12-2015 13:19
Voltage drop under load, amps read 99% ?? VVD Electrical: Batteries, Generators & Solar 25 28-06-2011 16:25


Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 16:51.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.