Earthx under seat mounting?

[swpilot3]

I had an EarthX fail. It was because of heat. I installed it engine side on the firewall with just the open aluminum box they sell. So, there wasn't much thermal protection. I also had the BMS warning light wired up. I saw the light turn on, turned off the master switch and made a beeline for the airport.

The EarthX swelled up (bulging out of the case) and leaked out the bottom. No smoke that I was aware of. The stuff that leaked burned right through the high temp Mark II paint on the tunnel. Oddly enough, the battery kept putting out normal voltage. Only damage was to the battery itself and the paint.

I called EarthX and talked to them about it. They were very friendly and full of good advice and said the battery needs to stay under 140 degrees F. We agreed that the warranty didn't cover it since it was likely getting too hot due to my installation location. They gave me a great discount on a new one.

Knowing this is a somewhat common problem, they have since come out with a thermal battery box. https://earthxbatteries.com/shop/the...0-900-vnt-1200 It's mainly for making sure the battery isn't cooked after shutdown or during a hot climb.

During my build I was afraid of the Lithium batteries and didn't want them in the cockpit with me. That decision and lack of thermal protection caused my failure. I think these are wonderful batteries and the failure mode is benign. Just make sure they don't get too hot!

[svyolo]

I thought about the underseat location, and did I want to be right above a potential fire. But then I also thought about, do I want to be downhill of 50 gallons of gas. Unfortunately aviation is full of risks. Some of them unavoidable.

After quite a bit of research, I believe EarthX makes a good product, backs it up, and provides good service. Like most of companies that sell to us. My preference is to put it north of the firewall, in a ventilated box. I hope it works. My second choice is just south of the firewall, in a vented box.

All that being said, Lithium batteries are probably the second most tested and trusted batteries. Maybe third. I would say dry cells are number one. Either Lithium or Lead Acid are number 2. I was well trained in lithium battery fires for my last job. But there have been a few billion mobile phones sold with lithium batteries. So far, I have never seen a human running down the street, with a flaming laptop/cellphone/etc, with a flaming lithium battery. Yeah, it happens occasionally. But I have never seen it.

But I have watched a Jeep burn to the ground.

[Bcone1381]

The bold print was written by Bob Nuckolls.

What does 'reliable' mean . . . nothing ever breaks? Won't
happen. ASSUME that everything you bolt to your airplane
is going to break.

How will you KNOW that it has broken?

If in flight, how does failure influence likely
outcome of the flight?

Can the failure be pre-flight detected?

If loss of that feature raises your level of
discomfort to unacceptable levels (too much
risk) then what is your Plan-B for mitigating
that failure?

The lowest risk FLIGHT system is fabricated by a
builder who understands systems sifted for high
risk failure modes and flown by a pilot who is confident
in the builder's decisions for crafting a FAILURE
TOLERANT airplane.


Any single failure of an electrical system component on your airplane should be a ho-hum event. I am designing my electrical system with an EarthX, and it will have sufficient ability to power its downloaded electrical system for a longer duration than my fuel supply will provide. If I have an over voltage seneraio, the Crow Bar Protection device will pop the Alternator CB before the EarthX battery BMS has a chance to take the Battery off line.

[Bdflies]

"ASSUME that everything you bolt to your airplane
is going to break."

If I operated under that assumption, I'd have to give up flying.

Bill

[zkelley2]

Those lightweight cables are fine provided they are thick enough on principal. I would use the 100% aluminum charts to be safe since I've never seen a 10% copper chart. But to be clear the resistance of a length of wire has nothing to do with it's weight. Aluminum has a known resistance per length given a thickness. Aluminum not conducting electricity as well as copper, has a higher resistance.
For example, if you're using 10AWG ETFE(Milspec Tefzel), it has a rating of 32.9 amps continuous duty. 10AWG general aluminum wire is only rated to 30 amps. It starts to open up a bit at larger gauges. At 1 AWG there's 30 amps between them.

I think the biggest question you'd want to ask regarding non-aviation wire, is it insulated with Tefzel(almost certainly no)?

[Bdflies]

At one point, aluminum welding cables were promoted. They were light weight and the weldors loved them. When you have to string out 200’, or more, of 2/0 cable - every morning and evening - weight mattered! The infatuation was short lived. Sizing them up one size wasn’t the issue, the problem was that the lug ends would overheat and fail. Even with hydraulic crimpers and antioxide paste, the ends would fail. The ends would literally melt off. Welding can be high current, which makes a lot of heat in every component of the system. The lug ends were copper. Copper and aluminum have different thermal expansion properties. The constant current cycling loosened the ends, producing resistive connections. Resistance was felt as less current, so naturally the weldors would crank up the machines, which produced even more heat.
I know nothing about the termination systems used with the new "lightweight" cables. If it’s suggested to use standard copper lugs, even the good silver plated ones, I would be wary.

Bill

[alaskabearhawk]

The lightweight aluminum cables are copper-clad. I learned even in high school that electrons traveled on the outside of the wire. Seems like a good idea. I’m no metallurgy expert so I have no technical expertise in evaluating the manufacturing process, but it sure warrants further study.

[Bdflies]

Alaska is correct, to a point. The phenomenon is called 'Skin Effect', which occurs in AC circuits. The higher the frequency, the more pronounced the phenomenon. This doesn’t apply to DC circuits.

Bill

[alaskabearhawk]

I didn't know a thing about the term "skin effect" until Bd pointed it out, but now I do. In a nutshell it means squat for a DC circuit. Learn something new every day!

[Chris In Milwaukee]

Yep, it’s why radar waveguides, “wires” for radio frequency energy, are hollow rectangular tubes. All the action is on the inside surface.

P.S. - not related to lithium batteries. Carry on smartly

[zkelley2]

At one point, aluminum welding cables were promoted. They were light weight and the weldors loved them. When you have to string out 200’, or more, of 2/0 cable - every morning and evening - weight mattered! The infatuation was short lived. Sizing them up one size wasn’t the issue, the problem was that the lug ends would overheat and fail. Even with hydraulic crimpers and antioxide paste, the ends would fail. The ends would literally melt off. Welding can be high current, which makes a lot of heat in every component of the system. The lug ends were copper. Copper and aluminum have different thermal expansion properties. The constant current cycling loosened the ends, producing resistive connections. Resistance was felt as less current, so naturally the weldors would crank up the machines, which produced even more heat.
I know nothing about the termination systems used with the new "lightweight" cables. If it’s suggested to use standard copper lugs, even the good silver plated ones, I would be wary.

Bill

That's the same reason a bunch of mobile homes have burned down. They used cheap aluminum wire and terminated it incorrectly. 10 years later it causes a fire. Those welding cables were also terminated wrong. You have to terminate with aluminum, or use a alloy in the wire that has more or less the same thermal expansion rate as copper.

All the high voltage overhead lines everywhere are aluminum. Most all the airliners use aluminum wiring. Alloys are different and everything is engineering with aluminum in mind.