What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

With pics: EarthX EXT900-VNT in aft battery location

jliltd

Well Known Member
I have been following the Earthx discussions and have a friend whom I helped install an EXT680 on his RV-8 firewall after Oshkosh 2017. It has worked great for him.

My RV-8 had the aft battery location with a Concord AGM aircraft battery. The airplane was down for a few months while Barrett Performance went through the engine. The battery didn't fare so well sitting around and had to be replaced. I opted to try one of the newer vented battery versions of the EarthX, the EXT900-VNT. I chose this vented model because of my battery location and wanted any smoke that might arise to be contained and vacate the fuselage. I added the optional EarthX vent adapter kit that takes both vent tubes and combines them into one larger tube. Included with this option is a machined vent port to send any smoke overboard.

Since the new EarthX was much smaller than the Concorde I fit new spacers around the perimeter of the EarthX. I also re-purposed a stainless steel securing band and latch from an old Artex ELT to keep the battery in place. I cross-drilled a hole in the latch for a safety pin.

OyS2yel.jpg



I bonded two channel spacers under the stainless band with 3M tape to allow clamping down the battery within the suggested areas in the manual.

pL4eV7R.jpg



Here is another shot of the hold-down set up from the front:

DV9Ebyc.jpg



Here is a photo of routing the battery vent kit to the fitting in the belly of the airplane along with a photo of the exit vent fitting from below. It was convienient to use the optional vent kit. The special plastic tubing supplied by EarthX is designed for high heat and chemicals so it does tend to want to kink of bent too far:

OvL54Nd.jpg


3cyOrsk.jpg


Here is a photo of the end result prior to re-assembling the baggage shelf:

Rl809Fg.jpg


I attached the EarthX BMS lead wire (black wire coming out of battery) to my G3X Touch system's GEA 24 LRU so that I get an alert annunciation on the GDU 460 screen if the BMS trips.
Here is a post I did two years ago describing how to do this for the G3X system:
http://www.vansairforce.com/community/showpost.php?p=1203629&postcount=7

The original battery hold down plate also holds the remote transponder and traverses the rear elevator bellcrank and pitch servo.

I have been flying this now for a month and so far so good. The starter has become alive and almost gives the impression I could taxi with the starter alone.

Jim
 
Last edited:
Jim,

It looks like you may be missing a snap bushing on the second to last bulkhead for the right rudder cable passthrough.

That battery isn't going anywhere! :)

B
 
No such thing as a dumb question. If all redundancies and safety features on your charging system fail, such as: your regulator fails, and then your over voltage protection fails, and then you do not take the alternator off line manually, any battery can go to thermal runaway and for a LiFePo4 lithium battery this means it produce a lot of smoke. As this battery is located within the cockpit, this would not be a good situation so it is "vented" overboard.
 
Now that EarthX has a TSO'd model of the EXT900-VNT I might put one in my Husky with same optional vent system to a belly fabric cover. :D
 
Temperature of Gases Vented in a thermal runanway?

No such thing as a dumb question. If all redundancies and safety features on your charging system fail, such as: your regulator fails, and then your over voltage protection fails, and then you do not take the alternator off line manually, any battery can go to thermal runaway and for a LiFePo4 lithium battery this means it produce a lot of smoke. As this battery is located within the cockpit, this would not be a good situation so it is "vented" overboard.

Has anyone measured the temperature of the gases at the exit point of the battery case? Just curious as what temperature rating the vent lines would need to be to resist shrinking or melting?
 
Has anyone measured the temperature of the gases at the exit point of the battery case? Just curious as what temperature rating the vent lines would need to be to resist shrinking or melting?

From The Earth-X install instructions. It surprised me that both lines are for exhaust:

"Only EarthX approved or supplied tubing should be used. The tubing is chemical resistant and rated for 500°F (ETX900-VNT:1/4” ID, 5/16” OD Teflon tubing, ETX680-24-VNT: 3/8” ID 7/16” ODTeflon Tubing)."
 
Battery mount

Jim,

Excellent idea, I think that is a great way to easily get the battery in and out. Now I just need to find a suitable ELT mount or something similar to what you did.

This forum is great, so many excellent ideas!
 
Nice work Jim !!

Nice work Jim !!

I used the supplied long bolts but moved them to front and back instead of to the sides.
I cut the long U channel and used the extra lenghts under bolted part so the top part of the battery case (where there's a seam) is not under pressure.
The vent is just behind the battery.

For the ELT, I used a cut-out from the instrument panel as a base, screwed on some angles that are riveted to longerons.
 

Attachments

  • IMG_6354.jpg
    IMG_6354.jpg
    362.2 KB · Views: 147
  • IMG_6406.jpg
    IMG_6406.jpg
    312.1 KB · Views: 110
  • IMG_6407.jpg
    IMG_6407.jpg
    262 KB · Views: 110
The vented models are created by adding vent outlets to the standard plastic case?
 
Dan, the vents are already in place, from the factory.

Yes, that's obvious. I'll re-phrase.

Both the ETX900 and the ETX-900-VNT use the E-sized case. It appears the vented model is simply the standard plastic case with two hose fittings added to the top.

Is the VNT case molded plastic? If so, is there something buried inside the plastic case which provides "thermal runaway containment" as described in the literature?
 
A while ago I asked EarthX about the maximum temperature in case of a runaway battery. I don't remember the temp they gave me but it was in the 300-400 F degree range. At the time I was planning on an aluminum box for it. Later, I found that it would fit in the cowl cheek, out of the cockpit and away from engine heat.

I suppose that the plastic might withstand that or that perhaps once it vents, it quits generating heat. I have no idea what's actually going on with it then, so these are purely speculative thoughts.

Dave
 
Is the VNT case molded plastic? If so, is there something buried inside the plastic case which provides "thermal runaway containment" as described in the literature?


I also have a 680 and it seems they both share the same type plastic case.
I didn't open the VNT of course so I shamely don't know what type of "thermal runaway containment" is there inside as advertised.

Maybe EarthX could chime in here??
 
Last edited:
I also have a 680 and it seems they both share the same type plastic case.
I didn't open the VNT of course so I shamely don't know what type of "thermal runaway containment" is there inside as advertised.

Maybe EarthX could chime in here??

Hello Eric,

The ETX900-VNT is the same platform as the FAA approved certified TSO battery, the ETX900-TSO. Inside the plastic housing is a thermal runaway containment box with the cells sealed inside it which is why it is slightly heavier.
 
Thanks Kathy,
I presume that the containment box is metallic?
Any insulation?

Yes to metal box and not sure what you mean by insulated? But if you mean how hot the outside of the plastic housing could reach in the event of a thermal runaway? It will not exceed 300 deg F.

Please note the probability of a thermal runaway is extremely improbable. All systems in your aircraft would have to fail (regulator, over voltage protection, pilot not turning off charging system and continuing to fly with high amperage and 40+V's which exceeds your electronics protection limits) in order achieve thermal runaway. This scenario would also completely destroy all of your electronics, not just the battery.
 
Yes, that's obvious. I'll re-phrase.

Both the ETX900 and the ETX-900-VNT use the E-sized case. It appears the vented model is simply the standard plastic case with two hose fittings added to the top.

Is the VNT case molded plastic? If so, is there something buried inside the plastic case which provides "thermal runaway containment" as described in the literature?

Dan - I don’t think your question was answered.

Carl
 
Oh no, Kathy covered the fundamentals...metal box inside the plastic case, 300F max exterior temperature.

Kathy, can you share construction details? Based on exterior dimensions, a half pound total weight difference suggests (ballpark) 0.010" steel or 0.028" aluminum.
 
Back
Top