What's new
Van's Air Force

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

The truth about EarthX and other LiFePO4 batteries.

Dozer

Member
First, you need to watch this
https://www.youtube.com/watch?v=ShtGB07fCSs

I don't think EarthX's batteries have a charge controller to limit the current.
So, I have BIG concerns about LiFePo4 batteries

1) Let's say you didn't start a plane for several months or you played with avionics too much after previous landing, and you drained a battery.... So your battery is 20% before you start the engine next time. After right after you start the engine, the alternator goes full amps trying to charge your battery. You may burn your alternator during preflight tests, especially on idle rpm.

2) YOU NEVER try to charge a LiFePo4 battery when ambient temperature is below 0 deg Celsius. It will damage the battery. ErathX says - no worries, first you will crank the engine!, and this will warm up a battery. But what if not? not enough. Regular LiFepo4 BMS controllers just disconnect the charger if the temperature is below 0C. But in the plane, we cannot do the same. Electric cars have a cells heater, and they don't have alternators.

It looks like I better build my own battery pack with LTO (lithium–titanate battery)
 
Maybe not all EarthX batteries have a charge controller but I think this one does ..

https://earthxbatteries.com/product/etx104-back-up-battery/

On point #1, After some of my "extra" cranking, I have had my 60A alternator supply 60+ A for a short period of time to the EarthX battery. Alternator and battery all seem to be fine. (I crank with the "ALT" switch "ON".

On point #2, might I suggest using their charger to get the battery to a better state before cranking. Also, although I do not know how effective it may be, I have read that turning on items that consume a bit of current (Lights, Pitot heat, Navigators) will bring up the battery temperature a bit before cranking and thus help.

Disclosure: I have done some testing with EarthX batteries to explore the limits. I intentionally created some problems for early models like the predecessor to the one listed above (which they replaced) and have since purchased product for two RVs.
 
Backup battery complexity.

I am an Earthx user for primary battery. I will use a backup battery to assure power for electronic ignition ( not emags ). Why would I use an expensive/ more complex design than AGM to provide 7 volts to get to the nearest runway ?
 
Thanks for these good reminders - as they say, TNSTAAFL - LiFePo4 batteries are light and powerful, but they require a bit of knowledge about how to use them correctly and safely.

I have not found anything on the PlanePower alternator website to see if they have a rating for max power output time to see if there is a risk. I usually see less than a minute at "max" output after starting, which tops up the battery. Some math would tell us how many minutes max we could theoretically see for a particular battery/alternator combo, then a question to PP - "can the alternator run at max output for x minutes without damage?"

One data point from my most recent flight - my earthx 680c takes about 47 amps of power from the 60 amp PP alternator for about 30 seconds at idle RPM before filling up. My previous flight was a week before, and I didn't use the battery during that week, so the battery was quite full.

Also, on temperature, it's clearly good practice to get the engine and the engine compartment up to something reasonable before starting. If I understand correctly, LiFePo4 does not like to be charged when it's cold, but is ok to discharge. Earthx recommends using the battery before charging, which of course can be done by powering things on, and starting the aircraft. No idea if this would be enough if you are at -20 with no engine pre-heat, but I doubt you'd want to start any engine at -20 without warming it up first.

These are good considerations for us to keep in mind if we use this battery technology - thanks again for kicking off this discussion.
 
Not disputing the general points he is making in the video, but without knowing the size of the battery he is charging we can't make a valid comparison. We typically use a 60 amp alt to change a 12.4 AH EarthX (ETX680) which even in the worst case, doesn't take very long at full amperage. In a similar online video (Victron Energy) they disclose the battery in their demonstration as a 300AH battery being charged by a 90 amp alt, which naturally has to run flat out max for a long time to charge that battery and will overheat because no car alternator is made to run flat out at max for a long period. The fact that lithium will accept charging current much faster than an AGM battery is not in dispute and perhaps more robust alternators (heavier) would be appropriate for larger lithium battery use but again our typical setups don't need to run at full output very long. The temperature considerations are valid for sure as there is a trade off in weight savings vs ability to be abused vs lead acid.
 
Few alternators will produce their max amperage rating at idle unless they they have a very high belt drive ratio.

My ND requires 5000 rotor rpm to produce 74 amps. 57 amps at 2500 rotor rpm.

In any case, it should only take a few seconds to replenish a fully charged battery after 10 seconds of cranking at 200 amps. That's only .56 AH.

Not sure why anyone would roll out of their hangar and attempt a start with a battery at less than 75% charge state (and certainly not 20%) to go flying.
 
Last edited:
EarthX documentation (operating manual) shows an operating temperature range of -30C to +60C and a storage range from -40 to +70. Where are you guys getting this information about not charging it below 0C?

My own experience says otherwise - I've had mine operating since Dec of 2017 in my airplane, and do annual capacity checks which it still passes just fine. Just a few days ago I had a 2-hour flight with the battery cold soaked at +9F or -13C (my battery is aft of the baggage compartment, not FWF) without issues. 59 months and 980 hours so far.

When this one finally dies, it will be replaced with another just like it. I'm running the ETX900VNT.
 
Last edited:
I have some PlanePower data that shows that (some of??) the alternators were tested to a level that shows that they can in fact deliver a LOT more than the rated power. Don't have it before me but when I looked at it, it gave me confidence that they would work as long as I ever needed them to for the batteries that I have in my planes (EarthX).

In working with them (PP- [Hartzell]), I got the impression that the alternators (as currently shipped) are quite robust.

While I don't live in sub-zero area (South Carolina), I have not had any problems that were temperature rated with my EarthX/PP setup nor EarthX/B&C.
 
If my plane sits for longer than a few weeks, I put a charger on it for a while before flying (battery tender, approved by EarthX).
Did the same when I had an Odyssey.
And the same with my car.
No big whoop.
 
Not sure why anyone would roll out of their hangar and attempt a start with a battery at less than 75% charge state (and certainly not 20%) to go flying.

Exactly how do you determine charge state?
 
Last edited:
EarthX documentation (operating manual) shows an operating temperature range of -30C to +60C and a storage range from -40 to +70. Where are you guys getting this information about not charging it below 0C?

My own experience says otherwise - I've had mine operating since Dec of 2017 in my airplane, and do annual capacity checks which it still passes just fine. Just a few days ago I had a 2-hour flight with the battery cold soaked at +9F or -13C (my battery is aft of the baggage compartment, not FWF) without issues. 59 months and 980 hours so far.

When this one finally dies, it will be replaced with another just like it. I'm running the ETX900VNT.

Operating temperature range is different with the rule for LiFePO4 batteries "absolutely no charge below 0degC". It will damage the battery. Just google for that. But you can discharge it at any temperature.
 
State of charge

There are at least 2 ways. I've found the better one is to make sure your Optimate trickle charger is connected if you leave for more than a week. Green lights when you come back is a good sign. I have a simple 3.5 mm plug that I insert that's capable of 5 amps from the trickle charger. The other is looking at the voltage and although you need to ensure your system is properly calibrated, so you know at least the offset. At condition I discharge through a meter that totalizes the amps to ensure the battery has at least 90% amperage left. These types of batteries you need to take care of with respect. I've been working with this chemistry for over 20 years and to date never let me down.
 

Attachments

  • EarthXBatteryDis.jpg
    EarthXBatteryDis.jpg
    31.9 KB · Views: 85
Operating temperature range is different with the rule for LiFePO4 batteries "absolutely no charge below 0degC". It will damage the battery. Just google for that. But you can discharge it at any temperature.

Show me a credible link from a battery manufacturer. Google is not a credible source.

EarthX says -30C, and they make the battery.

What you are saying has some truth for Li-Ion batteries - those are completely different chemistry. Since you specifically called out the LiFePO4 batteries by type, I assumed you knew the difference. Apparently I was incorrect.
 
Last edited:
So looks like you need a good Fluke to determine charge, very small voltage change between 30-90%.
 
There are at least 2 ways. I've found the better one is to make sure your Optimate trickle charger is connected if you leave for more than a week. Green lights when you come back is a good sign. I have a simple 3.5 mm plug that I insert that's capable of 5 amps from the trickle charger. The other is looking at the voltage and although you need to ensure your system is properly calibrated, so you know at least the offset. At condition I discharge through a meter that totalizes the amps to ensure the battery has at least 90% amperage left. These types of batteries you need to take care of with respect. I've been working with this chemistry for over 20 years and to date never let me down.

I trust the chemistry but don't trust the scrap electronics (BMS..etc)
 
Show me a credible link from a battery manufacturer. Google is not a credible source.

EarthX says -30C, and they make the battery.

What you are saying has some truth for Li-Ion batteries - those are completely different chemistry. Since you specifically called out the LiFePO4 batteries by type, I assumed you knew the difference. Apparently I was incorrect.

LiFePo4 is LiFePo4 chemistry, no matters who packed the cells in a case and what is the shape of the case. In my hands I have a spec sheets of Panasonic's cells and EVE's cells. Again. You absolutely cannot charge the cell which has internal temperature below 0degC

ectrical Characteristics Nominal Voltage 3.2V
Nominal Capacity 330DmAh @0.2°C discharge, room temperature
Internal Resistance < 20mO (1 kHz AC/fully charged)
Cycle Life :c: 3000 cycles@ 0.5C charge / discharge, room temperature
Charge End of Charge Voltage 3.60V
Max. Continuous Charge 660mA (0~10°C ), 1650mA (10~20°C ), 4950mA (20~45°C )
Max. Charge Current 3300mA
Discharge Max. Continuous Current 9900mA (Burst 12000mA < 3 sec)
Discharge Cut off Voltage 2.0V (2.5V Recommended)
Environmental Charge Temperature 0
°c to 45°C (32°F to 113° F)
Discharge Temperature -20°C to 60°C (-4°F to 140°F)
Storage Temperature 6 months: -10°C ~ 25°C 3 month: -20°C ~450c (Recommended 25 ±
5
°C @ 50% SOC)
Mechanical Diameter 26.2 ± 0.3mm
Height 65.3 ± 0.2mm
Weight Approx. 87g
 
Last edited:
My own experience says otherwise - I've had mine operating since Dec of 2017 in my airplane, and do annual capacity checks which it still passes just fine.

When this one finally dies, it will be replaced with another just like it. I'm running the ETX900VNT.

I've leared about the value of capacity checks....the easy way.

A 15 Amp hour battery (I think of Ah as Gallons) has 15 Ah of capacity when its new. After that we loose capacity and probably dont really know its volume and dont care as long as the engine starts. Well, we do if our alternator fails in flight.

So when your battery is new turn on your master, look at the Voltage and start your watch. Let the voltge run down to a certain level and document the time. Do it again Next year or in 6 months. Compare the two numbers and calculate your batteyr capacity. When its down to about 75% install the old battery in your lawn mower and buy a new one.
 
These are very cheap

I use these to measure ampacity. Attached a 5-amp load (any 12-volt load) or an inverter and plug in a 60-watt light bulb. I do this every second oil change to one of the batteries to measure its health. If I find an old incandescent 100-watt bulb, I can speed up the process. Measuring the health of your LiPo battery is important.
 

Attachments

  • Screenshot 2022-12-15 221213.jpg
    Screenshot 2022-12-15 221213.jpg
    43.6 KB · Views: 89
Just a data point...

I've been blissfully unaware of not charging a LiFePO4 battery bellows 0 deg.C and live in the rather sub-Artic Southern Ontario. I pre-heat in the winter but my battery lives in the cabin (Yet another sin) so is assuredly being charged while below zero degrees all winter. I'm on my second EarthX and the first one lasted a respectable four and a bit years. I probably inadvertently have been running equipment prior to startup that may warm up the battery but my anecdotal experience appears to be they are pretty robust in low temperature use without special care. I am open to changing my practice but unconvinced at the moment.

Cheers, Sean
 
I'm with Funguy and other vocal EarthX supporters. My ETX900 is over 4.5 years into its life powering KELLI GIRL's highly electrically dependent systems. It's a STRONG battery, and I keep it happy with blast air.

A few weeks back, on an unusually freezing cold morning at KGTU having overnighted two nights on the transient ramp, I went to start the engine. First attempt, the prop only turned slightly...but that appeared to give my EarthX the preload warmup it needed. I waited 10 seconds and reattempted: It spun up all strong and normal-like and the 360 roared to life.

If I understand your original concern, it seems to boil down to this: For an OLDER battery, on a cold day, the EarthX may have a problem with initial cold cranking amperage.

Wow, really? Shocking.

Isn't that an accurate description of every battery of every chemistry out there? "The Truth About EarthX" is that EarthX is a rock-solid battery. Stop knocking it just because it's simply different than that age-old warm and comfy inferior lead-based technology.

My battery now is over 4.5 years old. I'm contemplating its replacement...

...but not yet. Not yet. :cool: (Quick, name the movie!)
 
Last edited:
First, you need to watch this
https://www.youtube.com/watch?v=ShtGB07fCSs

I don't think EarthX's batteries have a charge controller to limit the current.

Standard wiring is with a fuse or CB on the alternator output (mine does anyway), so we should already have that protection.
According to EarthX: A lithium battery can and will accept a much higher charging current than an equal size lead acid battery. If your battery is not fully charged, your alternator can potentially output a current equal to or slightly above the alternator’s rating for a few minutes to top the battery off. Your fuse, breaker, or current limiting device should be sized approximately 20% above the alternator rating. Example, if you have a 40 amp alternator, use a fuse, breaker, current limiter set to 48 amps (or 50amps).

So, I have BIG concerns about LiFePo4 batteries

I think this boils down to, wire as recommended including the a correctly sized fuse or CB, and there shouldn't be a concern.
 
the past week i have talked to earthx about this exact charging issue. their response is that the faa certifies that the battery can be left on the approved battery maintainer indefinately down to -30 deg. didn't say c or f but that is way colder than we are talking about here. the optimate charger however says don't use below -4 f.
there! that should make everything clear as mud.
 
The battery management systems built into LiFePo batteries will prevent charging when below about 0C. So, even if you have a charger/maintainer on it, it won't allow a current to go into the cells below this temperature. Fortunately, the internal resistance of these batteries is low enough where only a few % of the charge is lost per month, so no maintainer should be necessary unless parasitic loads are present. The maintainer will supply these parasitic loads, depending on its duty cycle/algorithm, preventing or minimizing the battery discharge.

EarthX relies on internal battery heating during cranking to get the temperature above the minimum charging point.

Some manufacturers of LiFePo specify a minimum storage temperature also. The batteries I put into a travel trailer specify a minimum storage temperature of -25C/-13F. I do not know the reason for this lower limit, but, given the cost of them, I removed them for the winter and am keeping them in a heated area.
 
My battery now is over 4.5 years old. I'm contemplating its replacement...

...but not yet. Not yet. :cool: (Quick, name the movie!)

Scroll - just for a datapoint - my ETX900 was purchased exactly 5 years ago this week, and put into service 2 weeks after purchase. I've left the master on and run it flat twice, and ran it pretty deep into discharge 3 or 4 times since then. Just this week it finally gave me the first indication of "weak start attempt" during a 20F cranking morning. I had an engine heater on, but my battery is aft of the baggage compartment and was cold-soaked.

It made it 5 years and 998 flight hours. I'll order a new one and replace during my condition(al) inspection this February.
 
Last edited:
Scroll - just for a datapoint - my ETX900 was purchased exactly 5 years ago this week, and put into service 2 weeks after purchase. I've left the master on and run it flat twice, and ran it pretty deep into discharge 3 or 4 times since then. Just this week it finally gave me the first indication of "weak start attempt" during a 20F cranking morning. I had an engine heater on, but my battery is aft of the baggage compartment and was cold-soaked.

It made it 5 years and 998 flight hours. I'll order a new one and replace during my condition(al) inspection this February.

That's pretty darned good service. I love these batteries.
 
One data point regarding the overheating mentioned in the video-
I have dual ETX900s on a dual 12v bus with Kelly 70a and B&C 20a altenators (IO550N- brand X... Lancair Legacy).

I have a custom cooling setup (carbon baffling and plenum) and heat damaged the Kelly 70a alternator. The switch to lithium MAY have hastened what was a (my) alternator cooling design issue.

After installing the rebuilt alternator, I epoxied a quick response thermocouple to the stator windings with thermally (non electrical) conductive epoxy. I went for a flight and on climb out the stator temps shot up to 300F.

I quickly landed and made a design change to the alternator cooling. Now, temps are much cooler, and well below the Kelly limits. No overheating issues as in the video (on my installation)

See before and after graphs. (note- I'm not an engineer, so FWIW).
 

Attachments

  • image (16).png
    image (16).png
    231.6 KB · Views: 93
  • image (15).png
    image (15).png
    211.2 KB · Views: 61
Great data !

Do you have any photos of what you did to cool the alternator?
Was it more than just a blast tube ?
 
Do you have any photos of what you did to cool the alternator?
Was it more than just a blast tube ?

It’s an IO550N, so different setup than the Vans Lycomings.
Basically I just added a small scoop to the plenum area inlet (was flush) for the alternator cooling tube.
 

Attachments

  • 183EC5CD-48A9-42E9-A998-A667C6C36023.jpg
    183EC5CD-48A9-42E9-A998-A667C6C36023.jpg
    251 KB · Views: 115
  • FA009144-9805-4045-B121-9999593F526A.jpg
    FA009144-9805-4045-B121-9999593F526A.jpg
    214.7 KB · Views: 107
  • 173835FA-B32B-41F0-912C-AED16623A7D0.jpg
    173835FA-B32B-41F0-912C-AED16623A7D0.jpg
    441.4 KB · Views: 155
  • BDC663C0-3246-4AB5-B7D5-30084904DA1B.jpg
    BDC663C0-3246-4AB5-B7D5-30084904DA1B.jpg
    387.5 KB · Views: 127
Back
Top