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Thread: EarthX ETX36D Tear Down And Surprises

  1. #1
    cubflier's Avatar
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    Nov 2003
    Palmer, AK
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    EarthX ETX36D Tear Down And Surprises

    I recently opened up an EarthX ETX36D to further my learning about how these batteries work. The battery showed 10V which if you divide by 4 (the series pack count of a 12V LiFePO4) gives 2.5V which makes sense in that the battery must be teetering at the Over Discharge Protection limit. This first photos are how the inside of this EarthX is arranged. This LiFePO4 which is referred to as 4S2P for 4 in series 2 parallel.

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    Next I disassembled one of the packs in parallel to separate each LiFePO4 pouch cell. The next two shots show all that stuff after it was taken apart.

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    Testing the voltage of both packs showed cell #3 at 0V and all other cells at 3.33V which was different from what I expected.

    The BMS circuit board was very simple so I went drew up a schematic ( to the best of my ability) to see if I could understand what's going on.
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    It's a fairly simple circuit that serves to balance the cells and that's about it. There is no Over Discharge Protection at all. Both the EarthX Manual and Marketing literature on the ETX36D claim the following features:

    Exclusive Features:
    Over discharge protection (#1 killer of all batteries and other brands do not protect against this and void the warranty)
    Over charge protection (Other brands do not protect against this and void the warranty)
    Built in cell balancing technology (Other brands must use a special balancing charger in order to level the charge of each cell. Your vehicle is what charges the battery most of the time, if you do not have built in cell balancing technology, how is your battery balanced while using it?)
    Short circuit protection up to 1,000 amps (Other brands void the warranty if you short the battery)
    Excessive cranking protection (Lithium technology is different than a lead acid battery and needs to be protected from heat)

    This battery was purchased in 2013. I had always assumed that the features listed above applied. They do not. The important take away from this is if you have an ETX36D in your airplane that was purchased in 2013 there is very little in the way of the safe guards listed in the EarthX ETX36D literature. If you ever leave the master on it will possibly go flat on you. This is when they can get dangerous if you try to pump them back up. What I cannot say is whether EarthX made a change the BMS for this model of later years. I suspect this is case.

    In any event I was always curious what these batteries looked like inside and thought I would share what I discovered in case any of you had the same curiosity.

    If it looks might be

    If it looks is!!

  2. #2
    SJ's Avatar
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    Jan 2002
    Kansas City, USA
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    Very cool, Jerry! Thanks for sharing!

    "Often Mistaken, but Never in Doubt"

  3. #3
    Eddie Foy's Avatar
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    Dec 2014
    South Florida
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    Glad I am not the only one that likes to take stuff apart to see what makes it tick.
    "Put out my hand and touched the face of God!"

  4. #4

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    Jan 2003
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    that circuit board looks like a faillure looking for a place to happen.
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  5. #5

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    Sep 2003
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    Wave soldered epoxy-glass board with solid state components vs. bags of goop. Ill take the board. My battery is behind the firewall, so im waiting for cylindrical cells. I put a lipo model plane pouch batt in the middle of my 40foot hangar floor and whacked it. The result was not what I want between my legs. Your photos reveal pouches that look identical to model plane pouches. The fe tech maybe more forgiving of over/under volts, but I think they are just as fragile as model plane lipos. And modelers charge them in asbestos gloves. Even with external computerized balance boxes.
    What's a go-around?
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  6. #6
    courierguy's Avatar
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    Dec 2004
    Inkom, Idaho
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    The other day, I had my 17 AH 52 VDC ebike battery charging, my plugin Prius charging, and my 60 volt Greenworks electric chain saw also charging. Plus I have a second gen EarthX in the plane. And I had my Android phone on me, as always. I treat all of them with due care, but I guess I trust the tech, like most do nowadays, then again I also use plastic jerry jugs sometimes for carrying and pouring fuel out of, and those have been known to go off also. What is somewhat scary is how dependent I am on a daily basis on rechargable batteries of any kind. Also today just ran a bunch of self tapping metal screws, with the Dewalt impact driver. More and more common, are construction sites I'm craning on, and I notice the carpenters are using battery nail guns, or a regular nail gun but a battery compressor. These batteries are taking over it seems!

  7. #7
    Cub Builder's Avatar
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    Mar 2011
    North Central AR
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    Quote Originally Posted by Skywalker View Post
    ... I put a lipo model plane pouch batt in the middle of my 40foot hangar floor and whacked it. The result was not what I want between my legs. Your photos reveal pouches that look identical to model plane pouches. The fe tech maybe more forgiving of over/under volts, but I think they are just as fragile as model plane lipos. And modelers charge them in asbestos gloves. Even with external computerized balance boxes.
    The LiFePo4 chemistry is significantly different from the LiPo. It's less prone to over heating, and if overheated, will not decompose like a LiPo. The Phosphate based Cathode will not burn and is not prone to thermal runaway. Ref: this web site to read about the differences between the various types of Lithium batteries.

    -Cub Builder

  8. #8

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    Apr 2018
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    Hi Jerry,
    I see you are in Palmer, Alaska. EarthX just attended the Great Alaskan Aviation show in Anchorage this month and we bring with us the current internal components of the batteries, such as the BMS board, so inquiry minds can see what is inside the battery and we can help answer any questions you might have as we know this is a rapidly advancing technology. We also publish many fact sheets on our website to help educate consumers on this advancing world of lithium batteries and how it might apply to them.

    EarthX produced and sold its first batteries in November of 2011 with the 1st generation circuit board, which you have pictured. This generation had cell balancing. In the later part of 2013, we advanced to our 2nd generation circuit board which included not only the cell balancing technology, but also the over charge, over discharge, short circuit and excessive cranking protection. Fast forward to 2019, we are producing our 6th generation circuit board, with technology that wasn’t even available in 2011, and have 7 aircraft models, the ETX Hundred series, that not only have all the above features, but also LED battery fault monitoring and redundancies built into the BMS so there is no single point failure.

    EarthX is the first company in history to perform the DO-311a 12V lithium battery testing to achieve an approved, certified FAA TSO battery, the ETX900-TSO (the ETX36D series in part of our powersport line and not the aircraft line). I can promise you that 6 years from today, the advancement of our technology with the EarthX batteries will not be the same as today’s. As a pioneering company in this field, we are constantly investing in research and development so that we can and will continue to advance.

    We have been very fortunate to work with 30+ experimental aircraft manufacturers, and experimental engine manufactures over the past few years and together we are striving to have the best charging systems available. Currently, we are adding the certified aircraft manufactures to our list of excellent companies we work with so stay tuned….we will continue to advance.

    Kathy Nicoson
    Global Sales Director
    EarthX Lithium Batteries

  9. #9
    wireweinie's Avatar
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    Aug 2013
    Palmer, AK
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    Thanks for chiming in Kathy!

    Life's tough . . . wear a cup.

  10. #10

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    Apr 2015
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    Cool! Pleased to see another manufacturer monitoring our aviation forums.
    ACS stepped up to resolve an issue when I went public with my issue after exhausting efforts to resolve an issue privately on an order I had placed.
    Thanks flylow thanked for this post
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