Lithium Iron Batteries

Discussion in 'Instruments / Avionics / Electrical System' started by Terrh, Oct 20, 2019.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Oct 20, 2019 #1

    Terrh

    Terrh

    Terrh

    Well-Known Member

    Joined:
    Nov 12, 2016
    Messages:
    73
    Likes Received:
    10
    Location:
    Windsor, ON, Canada / Detroit, MI, USA.
    I'm not sure how commonly aware of these the aviation community is. Here's my automotive experience, in the hopes that it can help some of you on here.

    I'm sure most of you would do unspeakable things to take 20lbs of dead weight out of your airplane, so I thought I should share this.


    I put one of these in my sports car last spring and I don't think I'll ever buy a lead acid battery again. It's a motorcycle Lithium Iron (LiFePO4 - not Lithium Ion) battery I bought on amazon for about $90. YTX14L-BS was the biggest one I could find.

    It cranks/starts my 6cyl no problem despite being designed for a motorcycle, I'm sure that a pair of them would crank just about anything. It is definitely a much smaller capacity than a regular car battery, I'm sure if you left the headlights on for 20 minutes it wouldn't start the car. I did that once and had to jump the car.

    They are designed to work with a regular charging system, don't need special hardware. It's all internal to the battery.

    I had my battery in the trunk before, and a 0GA cable ran from the front to the back of the car. The old cable weighed 6.2lbs. The old battery, an Optima Redtop, weighed 43.5lbs. Battery mount and misc. hardware was another 3.1lbs.

    Total old setup weight 52.8lbs

    The new battery is so light I thought the box was empty when it arrived. It's 2.2lbs.

    I mounted it in the front, and so could use a much shorter and lighter cable, .8lbs. so 3 pounds total, almost 50! pounds lighter. This is the easiest 50lbs I've ever taken out of anything, ever.

    I just looked up cessna 152 batteries and they're 30lbs, 160CCA, 8.5AH@ 24V. Works out to 204WH
    The battery I bought is rated at 250CA (no CCA rating given), 64WH@ 12V. Using a pair would give you 128WH @ 24V, and weigh 4.4 LBS. Since most of you guys are using smaller engines than what a 152 uses, that should be plenty of battery - I just used 152 numbers since it was something to compare with.
     
    cheapracer likes this.
  2. Oct 20, 2019 #2

    cheapracer

    cheapracer

    cheapracer

    Well-Known Member

    Joined:
    Sep 8, 2013
    Messages:
    5,393
    Likes Received:
    3,655
    Location:
    Australian
    Thanks for the detailed, technical weight specs, your time is appreciated.
     
  3. Oct 20, 2019 #3

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,064
    Likes Received:
    2,355
    Location:
    Port Townsend WA
    If you leave the lights on and it runs completely dead does that ruin the battery? (it kills a lithium ion running dead once usually)
     
    MadRocketScientist and SVSUSteve like this.
  4. Oct 20, 2019 #4

    SVSUSteve

    SVSUSteve

    SVSUSteve

    Well-Known Member

    Joined:
    Aug 21, 2007
    Messages:
    3,889
    Likes Received:
    938
    Location:
    Evansville, Indiana
    I decided to go with NiCad since it ended was the lightest way I found to meet the Ah requirements (6.9 lbs for 81 amp hrs 24v; 4.53" L x 2.13" W x 8.82" H) and not have to worry about the in-flight fire risks associated with lithium batteries. They aren’t cheap (in fact, they probably cost more than the instruments in a stripped to the bare bones day VFR only bug smasher) but they have performed well in aerospace applications. Although I am guessing that there are smaller versions available for less money.

    It’s one thing to cut corners or simply go with the cheapest or lightest option available when you can pull over if the battery tries to kill you. It’s a whole different degree of risk assessment when it might take several minutes to get somewhere that you can safely get out of the aircraft.
     
    Last edited: Oct 20, 2019
  5. Oct 20, 2019 #5

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,649
    Likes Received:
    3,281
    Location:
    Memphis, TN
    On the biplane forum, one of the members left it on a couple of times and his seems ok. More than a few are running them. They do seem to loose power when cold. But one guy does a warm up crank; just cranks the engine. Internal temp goes up and ready for regular start. Kind of crazy but works for him. Some will warm up with the charger if they are having low start power. Most don’t seem to have any problems. A different member did have one go bad, but I think it was warranted. I have only handled them except for my RC planes. It’s just a little box. Makes an Odyssey look like a big brick.
     
  6. Oct 20, 2019 #6

    Vigilant1

    Vigilant1

    Vigilant1

    Well-Known Member Lifetime Supporter

    Joined:
    Jan 24, 2011
    Messages:
    4,071
    Likes Received:
    1,813
    Location:
    US
    The LiFePO4 batteries contain lithium, but are extremely unlikely to catch fire (esp compared to "lithium ion batteries," which have various specific chemistries). They aren't perfect (require a specific type of charger, don't perform well below 32F), but they are generally regarded as being very safe.
     
  7. Oct 20, 2019 #7

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,649
    Likes Received:
    3,281
    Location:
    Memphis, TN
    What is great over Nicads is battery management. LiFePO4 have very low static discharge. Leave it a year and you might have lost a percent of charge. Nicads have to be treated like little children. They are benign, but you have to feed them right, exercise them right. Treat them right and they are happy campers. Treat them bad and they die. I still use Nicads in my RC transmitters but not in my planes much anymore. I only have one electric so I’m a glow traditionalist. I have two main lithium iron batteries and move them to the planes I will fly. I let a number of Nicads sit and usually they died. They like use. They like varied discharges, never drain them, and they like slow charging. Use them week to week and I have had them last ten years of trust on RC planes. In attention and they might go one year. My RC flying is intermittent at best right now and the LIFE batteries stay ready to go. They also charge fast.
     
  8. Oct 21, 2019 #8

    radfordc

    radfordc

    radfordc

    Well-Known Member

    Joined:
    Feb 5, 2008
    Messages:
    1,242
    Likes Received:
    503
    Yes, a complete discharge does often harm the battery. Many of these batteries have a built in battery management system (BMS) that prevents both over and under voltage.

    https://earthxbatteries.com/our-batteries/lithium-battery-technology
    Lithium batteries are fundamentally different than lead-acid batteries. The lithium cells inside the battery need electronics to monitor and balance the voltage/charge of the individual cells. Other companies sell a balancing charger, which you have to plugin periodically to “top off” and balance the cells. Inside every one of the ETX series batteries is a microprocessor Battery Management System (BMS) that monitors the charge level of each cell and balances the charge when needed, protecting the cells from overcharge or over-discharge. What this means for you is more starting power, longer battery life, and the safest lithium battery on the market. All types of lithium batteries (not just ours) require a “BMS” that monitors and balances the cell charge and protect from over discharge or over charge.
     
    SVSUSteve likes this.
  9. Oct 21, 2019 #9

    SVSUSteve

    SVSUSteve

    SVSUSteve

    Well-Known Member

    Joined:
    Aug 21, 2007
    Messages:
    3,889
    Likes Received:
    938
    Location:
    Evansville, Indiana
    True, but I plan to operate in cold weather because of the need to travel to Michigan frequently due to one of my volunteer engagements. Plus the LiFePO4 ones I saw (that did not have bad reviews regarding service life) would work out to be FAR heavier (especially once you factor in wiring, battery boxes, etc) since I would need several of them to get the amp hour ratings I am wanting. I think the design went from four LiFePO4 batteries to two NiCad.

    I'm not planning on letting them sit for anywhere near that long. If it's parked for anywhere near and, if it's sitting at home it will be plugged into ground power (need that for the engine heater anyhow). Plus, as someone pointed out, a battery management system will prevent that problem. I specifically asked about that when talking to the manufacturer.
     
    Last edited: Oct 21, 2019
  10. Oct 21, 2019 #10

    Terrh

    Terrh

    Terrh

    Well-Known Member

    Joined:
    Nov 12, 2016
    Messages:
    73
    Likes Received:
    10
    Location:
    Windsor, ON, Canada / Detroit, MI, USA.

    Just to be clear:

    This electronic system is INSIDE the battery. You don't need to do anything special to it. It is invisible to the user. I have killed mine dead dead twice and just jumped the car to charge it. It will not allow the user to damage the battery. You can't discharge it to the point of harming it even by shorting the terminals together. You can charge them with any lead acid charger, or the alternator in your airplane, you don't need anything special.


    These batteries cannot overheat through too rapid of charge or discharge, and they will not catch fire even if punctured. The fire risk is negligible.
     
  11. Oct 21, 2019 #11

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,649
    Likes Received:
    3,281
    Location:
    Memphis, TN
    First off wet or dry Nicads? Most of this is about dry before I thought of wet.

    You can’t just keep it topped off. It actually likes the ups and downs. There is no hands off management system I know of. Lots of good smart chargers that can do a lot to help keep the life in them. Varying discharge somewhere between 25-50% of capacity once or twice a month will keep them exercised. Don’t just keep the idling on a charger until ready to use. They will be junk in six months. Just punching discharge into a charger is not the best. You need to vary the discharge rate. The memory of the batteries will set up. Early Satellites had this problem of the exact same charge cycle, in and out of the sun, constantly going on that would reduce capacity because the same thing went on and on. Varying drain and occasional cycling will go along way to keeping the batteries good a long time.

    Wet. When cycling those you draw them down to zero volts. Clipping resistors on individual cells and leave them for a couple of days. Saft has like a 90 day cycle if I remember to keep top performance.
     
    pictsidhe likes this.
  12. Oct 21, 2019 #12

    Aerowerx

    Aerowerx

    Aerowerx

    Well-Known Member

    Joined:
    Dec 1, 2011
    Messages:
    5,009
    Likes Received:
    1,362
    Location:
    Marion, Ohio
    What type of NiCad are you talking about?

    There are the little sealed ones that like like normal AA size batteries. Then there are the wet cell vented NiCads. I think SVSUSteve is using the wet cell vented NiCads, if he is using them to start his engine.

    The vented cell NiCads will last virtually forever, IIRC, if they are treated properly with (relatively simple) periodic maintenance. (Got a book about them around here somewhere) Another interesting thing about them is that the voltage output is pretty much flat until right at the end of the charge, and then drops like a rock. More modern batteries have a higher energy per pound, but no where near a flat voltage curve.
     
  13. Oct 21, 2019 #13

    SVSUSteve

    SVSUSteve

    SVSUSteve

    Well-Known Member

    Joined:
    Aug 21, 2007
    Messages:
    3,889
    Likes Received:
    938
    Location:
    Evansville, Indiana
    No clue wet or dry. I talked to a guy who was two years behind me in high school and is an electrical engineer who specializes in aerospace systems. He pointed me to a manufacturer who has a system that handles all of the cycling etc you describe. I'm not just trying to cobble the battery management together like Tony Bingelis would.

    Even still, chances are good that I will be flying 300+ hours a year since we plan on using this aircraft to travel for casework for the nonprofit. I doubt that downtime will be an issue like it would be with the <50 hour per year VFR birds. If it turns out to be an issue, we are not so close to MTOW with our design (I think we're currently 150 or so lbs under the weight used to design the wings and structure) that we could not fall back to an alternative system.
     
  14. Oct 21, 2019 #14

    TFF

    TFF

    TFF

    Well-Known Member

    Joined:
    Apr 28, 2010
    Messages:
    11,649
    Likes Received:
    3,281
    Location:
    Memphis, TN
    My post started out as dry but then I thought about the wet. So a little disjointed.

    My experience with dry is RC since 1978. Best times and best hobby money spent. Except the pattern planes no ARFs, and my pattern planes are second hand. Lots of love has gone into Nicads over the years. I have only had two flight failures, crazy part was the same Ugly Stick. One on landing it locked up and went into the catch fence with a puzzled look on my face and another where the plane went into a gentle turn and the went dead. It circled about six times before it hit. Nothing like an Ugly Stick. It’s still going. Let’s say fifty packs over the years.

    Wet experience was at a regional airline for nine years. I never worked directly in the battery shop but would do some stand ins. Some of my best airline friends were in the battery shop so they showed me the ins and outs more than just hefting the 80 lb thing into the planes. I do know they can last a long time. I also know that there were two and a half 40 ft trailers full of dead wet Nicad Saft batteries as it was cheaper to hide them than dispose of them. $5000 a bite. As good as they are bullet proof they are not. They take some major chargers. If wet, don’t get them close to lead acid or they will neutralize themselves with each other.

    My point is love the battery you put in and don’t take it for granted. Does not matter the chemistry.
     
    SVSUSteve likes this.
  15. Oct 21, 2019 #15

    SVSUSteve

    SVSUSteve

    SVSUSteve

    Well-Known Member

    Joined:
    Aug 21, 2007
    Messages:
    3,889
    Likes Received:
    938
    Location:
    Evansville, Indiana
    No piece of an aircraft should be taken for granted.
     
    MadRocketScientist likes this.

Share This Page



arrow_white