VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-10
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #21  
Old 08-05-2014, 09:57 AM
ppilotmike's Avatar
ppilotmike ppilotmike is offline
 
Join Date: Jan 2010
Location: Denver, CO
Posts: 1,692
Default Earth X

I was intrigued to see the Earth X batteries at OSH this year, and actually experience the difference in size and weight (which is amazing). I even bought a small battery for my motorcycle, to see how well it performs. However, I'm concerned about the fire risk. Maybe it's less of an issue if it's located behind the baggage compartment in the 10 (Van's planned location for the 680). I would love it, if someone with a lot of "scientific method" experience would put a match, corrosive fog and maybe an axe to one (or a couple) of these batteries to see how they hold up. The other thing I worry about besides fire, is cranking ability and how long they would hold up in an emergency depletion situation (i.e. lost alternator). It seems like the vendors of these batteries don't have much information to provide the consumers...
__________________
Mike Rettig
EAA Chapter 301, President www.eaa301.org
VAF Dues Current: as of 01/13/17
RV-10 (41PX Reserved) Fuselage
F-14 (Pedal Plane - Daughter's Project) "Flying"
http://www.mykitlog.com/mikrettig
Reply With Quote
  #22  
Old 08-05-2014, 10:03 AM
Mike S's Avatar
Mike S Mike S is offline
Senior Curmudgeon
 
Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 13,593
Default

Quote:
Originally Posted by rocketbob View Post
--- make a thin stainless battery box to enclose the battery. Problem solved.
Not necessarily solved, but mitigated greatly.

After all, we do build thin aluminum boxes that we fill with gasoline.

Lots more gasoline than lithium by a huge margin. And the gas is a lot easier to ignite than the Li.

No, I am not flipping on my position about having a LI FE battery in the cabin, I am just trying to get folks to think about the safety factors involved. There are ways to deal with things, such as what Bob suggested.
__________________
Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
Reply With Quote
  #23  
Old 08-05-2014, 10:14 AM
rocketbob's Avatar
rocketbob rocketbob is offline
 
Join Date: Jun 2006
Location: 8I3
Posts: 2,860
Default

Quote:
Originally Posted by Mike S View Post
Not necessarily solved, but mitigated greatly.

After all, we do build thin aluminum boxes that we fill with gasoline.

Lots more gasoline than lithium by a huge margin. And the gas is a lot easier to ignite than the Li.
And run said gasoline thru fuel line just a few inches from a glowing red hot exhaust.

Mounting a LiFePO4 on the firewall wasn't possible in my rocket due to room constraints but I enclosed them in 0.015" stainless battery boxes I fabbed in the tunnel between my feet. There is no way for a flame to propagate and the battery cables pass thru small Garolite blocks I machined to make the boxes as gas-tight as possible in the event of a smoldering battery fire.

http://www.mcmaster.com/#8557k412/=t5cu5a
__________________
Bob Japundza A&P IA
N55BC RV-6 borrowed, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Don't believe everything you read on the internet. -Woodrow Wilson
Reply With Quote
  #24  
Old 08-06-2014, 09:34 PM
Wayne Gillispie Wayne Gillispie is offline
 
Join Date: Apr 2009
Location: USA
Posts: 1,494
Default

I will put two in the back in place of my 925L/680 as soon as they go bad and you guys test fly them some more. I will install two thermistor temp sensors inside them similar to what I have at the cowl exit now(runs 180-230F).

As the kids get bigger, this will help a lot.
__________________
Good judgment comes from experience, and a lot of that comes from bad judgment.
Reply With Quote
  #25  
Old 08-07-2014, 10:28 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 3,992
Default

Quote:
Originally Posted by ppilotmike View Post
<snip> It seems like the vendors of these batteries don't have much information to provide the consumers...
Marketing is making us fall in love with the product. Love is hard to quantify. Hard facts and data are what will keep us within the envelope. If we don't have them there are risks. Sorry if this sounds preachy, but it is only intended to stimulate the experimental brain and think about the consequences, like Bob as done. I will likely use this product, but only after some quantified information is gained. Until then caveat emptor applies.

A123 battery company worked with DOE for many years and has a well quantified and controlled product. In experimental we become our own development engineers. They have mitigated many of the issues, but do the companies that copy their product do the same? A123 has had many groups test their batteries in adiabatic (insulated) thermal runaway conditions precipitated by elevated temperatures, and over voltage charging. They still exhibit the runaway failure mode, but the peak temperatures are much lower than other chemistries, and seldom cause the adjacent cell to fail in a cascade manner. Can the other vendors say that?

When it comes to this product, "i don't know" is not a very good answer with the severity potential of this failure. Earth-X says 140F is the limit environmental temp. Is under cowl under that? Always? I have not seen the listing of what happens if the alternator puts out 16 volts continuously (16.3 vdc is the crowbar trip voltage). And we don't know who supplies the cells, nor exactly what the BMS does.

RocketBob has take two steps to reduce the risks, 1 - lower temp environment, and 2-containment structure if the possible happens. We should all continue to take a cautious approach and study to be aware of the risks. Within that environment - lets make these things work!

BTW We talk about gasoline, but heating gasoline in a container won't make it release its energy internally, it needs oxygen, and ignition. The same can not be said of these batteries. If the Li battery - all of them -are heated then they will reach a point of internal self heating. Bad ones will reach 1300F, good ones maybe only 700F. Which one are we buying?
__________________
Bill

W&B done
Doing paperwork.
Beginning G3X calibrations.
Reply With Quote
  #26  
Old 08-07-2014, 10:51 AM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 3,246
Default

Well, let's say the thing is self-heating at 700 deg. F. Even if it's contained, where would be a safe place to have that?

I thought of two places, neither practical: in the wingtip or on the ground.

I sure wouldn't want it ahead of the firewall because that's where there are lots of important items.

And I certainly wouldn't want it in the cabin.

If it were mounted behind the baggage compartment, I'd be afraid of the integrity of the fuselage.

These batteries are very attractive. I'd like to see some more experience and data, though.

Dave
Reply With Quote
  #27  
Old 08-07-2014, 11:38 AM
Wayne Gillispie Wayne Gillispie is offline
 
Join Date: Apr 2009
Location: USA
Posts: 1,494
Default

Here is a LiFePO4 fire last summer...

http://www.thepolypost.com/news/lith...9bb30f31a.html

This company put one in the G650...

http://www.securaplane.com/products/...e-technologies

Concorde is working them too...

http://www.concordebattery.com/lion.php

Put in a Odyssey 925L for now and enjoy the extra baggage later. Be patient and keep pounding rivets or take some more trips.
__________________
Good judgment comes from experience, and a lot of that comes from bad judgment.
Reply With Quote
  #28  
Old 08-07-2014, 11:43 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
Posts: 3,992
Default

Quote:
Originally Posted by David Paule View Post
Well, let's say the thing is self-heating at 700 deg. F. Even if it's contained, where would be a safe place to have that?

I thought of two places, neither practical: in the wingtip or on the ground.

I sure wouldn't want it ahead of the firewall because that's where there are lots of important items.

And I certainly wouldn't want it in the cabin.

If it were mounted behind the baggage compartment, I'd be afraid of the integrity of the fuselage.

These batteries are very attractive. I'd like to see some more experience and data, though.

Dave
Good questions all, Dave. In a best case scenario, one cell goes bad, and cooks, it does not spread to the other cells, it melts part of its case and is contained in a steel box with a vent to the outside. An alarm goes off and we take action. In the best best case all is kept inside the battery itself. There are 6-9 cells in the battery. So the exotherm of one cell is small compared to the whole. It maybe that mounted on the firewall, with blast cooling, in an appropriate box is the final recommendation and minimal change. We just don't know yet, so let's be careful out there. Data will help us all. A certified component with FAA validation might not need the same scrutiny.

In a vision of the final best case the BMS measures the internal resistance, temperatures, and voltages. It manages all the above so the the "battery pack" is a drop in replacement and it can tolerate anything within a defined set of operating conditions. When this is the case, hopefully a battery company will use this as advertising material to sell their products. An "I do know" approach. With good questions they will all get there, or the best ones will.
__________________
Bill

W&B done
Doing paperwork.
Beginning G3X calibrations.
Reply With Quote
  #29  
Old 08-07-2014, 01:23 PM
NovaBandit's Avatar
NovaBandit NovaBandit is offline
 
Join Date: Feb 2011
Location: Hastings, MN
Posts: 570
Default

(Cross Posted from the "other" discussion)
I've gathered some more data, based on some of the concerns raised in this discussion. The main issues brought up are
1: Safety
2: Performance and capacity
3: Weight and Balance.

Warning! Info dump to follow!


1: Safety
I looked at a few scientific research papers on the safety of LiFePo4 battery cells, and I was actually able to understand some of the words! After uncrossing my eyes, I actually searched something asked for in this discussion; what do these cells do when they are abused. I found some interesting videos:

https://www.youtube.com/watch?v=8IBapfB0Imo - Full Destruction of a charged cell

https://www.youtube.com/watch?v=TiTqY4FY1yk - Penetration Test 1

https://www.youtube.com/watch?v=XZf2pKzBErk - Penetration Test 2

https://www.youtube.com/watch?v=XymqQ-YlfJ0 - Over Charge


Also, here is some information from Wikipedia, which I know is NOT a infallible source:
http://en.wikipedia.org/wiki/Lithium...battery#Safety

And Finally, from http://www.mpoweruk.com/lithiumS.htm :
Phosphate based technology possesses superior thermal and chemical stability which provides better safety characteristics than those of Lithium-ion technology made with other cathode materials. Lithium phosphate cells are incombustible in the event of mishandling during charge or discharge, they are more stable under overcharge or short circuit conditions and they can withstand high temperatures without decomposing. When abuse does occur, the phosphate based cathode material will not burn and is not prone to thermal runaway. Phosphate chemistry also offers a longer cycle life.
Recent developments have produced a range of new environmentally friendly cathode active materials based on Lithiated transition metal phosphates for Lithium-ion applications.


2: Performance and Capacity
Some of the questions brought up relating to this were the operating temperatures that a LiFePo4 battery would encounter on the firewall of an RV10. I had asked the EarthX rep this question at Osh, and his response was this: "The operating range of the EarthX battery is wider than a comparable Odyssey SLA battery". This looks to be mostly true, as the Odyssey manual lists the range without a protective metal case to be only good to 113°F, but 176°F with an added shield. I'd imagine that you could add a similar, or even the same shield to the EarthX to get even more temperature range.

Also, a few of our fellow RV10 pilots are going to stick some temperature probes on the firewall in a few places to see what the requirements really are. As it stands today, it doesn't sound like temperature is going to be an issue.
Odyssey Operating Temperature Range
PC545, PC680, PC925, PC1200 and PC1700 without metal jacket: -40°C (-40°F) to 45°C (113°F),
PC545, PC680, PC925, PC1200 and PC1700 with metal jacket: -40°C (-40°F) to 80°C (176°F),

EarthX Operating Temperature Range
Operating Temperature* -30°C (-22°F) to +60 °C (140°F)
Storage Temperature -40°C (-40°F) to +60 °C (140°F)


EarthX Discharge Versus Temperature
We use a similar Cold Cranking Amp test standard (SAE test performed at 0°F, but 3
second discharge time) as the lead acid battery manufacturers. As such, our battery with a
similar CCA rating as a lead acid battery should provide the same cranking performance
at 0°F. But, below 0°F an equivalent lead acid battery will outperform a lithium battery
(From http://earthxmotorsports.com/wp-cont...l_111017_G.pdf)

As far as capacity, the EarthX battery that I am considering has 12ah. According to Skytec's specs, the 149-NL starter that I'm going to use has a draw of 125-185 amps. The 12ah battery will give me almost 4 minutes of solid cranking at the highest spec'd starter draw. As far as electrical emergency capacity, between whatever is left in the starter battery (say after 2 minutes of engine crank) and a 6ah TCW backup battery, I'll have 12ah, which at 6 amps of draw (rough estimate) gives me two hours of endurance buss time. And that is if both the primary and secondary alternators fail.

3: Weight and Balance
Taking the suggestion of a few people in this discussion, we figured out an example weight and balance for a generic RV10, found the arms of the battery tray and the firewall, and ran the numbers with a 26lb battery in the tail, and a 4lb battery on the firewall. Even with the battery on the firewall and 26lbs removed from the tail, it's difficult to get the plane into a CG past the forward limits. Pretty much any weight you carry in the plane pushes the CG back. So, worst case scenario would be a light pilot on low fuel. Even with the stock battery in the stock location, you'll be forward of the CG limit. Adding ~40 lbs in the baggage area will keep the plane within CG in this light configuration, and have the benefit of being removable when carrying capacity is needed. If even a single 65lb person is in the back seat, this extra weight isn't needed.

The real problem is hitting the aft CG before you hit gross weight, because, as I stated before, pretty much every pound you add pushed the CG rearward. Because of this, I personally would prefer to have a CG as far forward as possible to give me more options.

Basically, having the battery in the tail only moves the cg aft 1" in a single pilot no fuel scenario
but allows you to carry 30lbs more baggage in a full gross scenario.

The one thing these numbers don't include are the weight and CG changes from removing the large #2 power cable from the tailcone to the firewall.

Thehe WnB spreadsheet I've used for my numbers is here:
http://www.edandcolleen.com/files/RV...htBalance.xlsx
Thanks to Justin Twilbeck for throwing this together for me. (It even has a calculation for the loading needed to cause a tailstrike! Good stuff!)
__________________
Ed Kranz
RV-10 N829EC - Flying
First Flight: 8/29/15
KSGS - Fleming Field, South Saint Paul, Minnesota

YouTube.com/GoodPlaneLiving
-- Build Timelapse and Travel Videos . . GoodPlaneLiving.com -- Build and Travel Blog
Reply With Quote
  #30  
Old 08-07-2014, 01:31 PM
Mike S's Avatar
Mike S Mike S is offline
Senior Curmudgeon
 
Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 13,593
Default

Ed, you have been busy doing your homework-----good.

Now that you have a better idea of what you are getting into, "go forth and conquer" as my favorite pseudo mother would say.

Good luck.

And, thanks again for hosting the RV 10 cookout
__________________
Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

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

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 04:57 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.