Thinking of upgrading to Lithium EarthX battery to go with my UL350i engine. Any suggestions as to model (battery size) and suggestions of what to avoid?

Reason for upgrade is weight savings and because it sounds interesting.



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Installed a Etx900 in my Stol 750 afew years ago and performed great. It is alittle expensive with that battery and the charger, but its worth the cost.


I have an ETX900 in my 601XLB and also in my 701. It does a great job starting the motors. They spin much faster and start quicker then with led-acid. This is true even if the charge level is low. That is because of the voltage-discharge curve. The voltage and available current stay relatively high even when the battery is significantly discharged. The ETX900 is about 10 pounds lighter then the Odyssey battery I had been using.

My only issue has been that the built-management electronics in the battery are not well protected from over-voltage. Some older chargers will pulse the battery when in battery-tender mode. The pulse will fry the electronics in the battery. When that happened to one of my ETX900 batteries, it was covered under warrantee but I was warned that one time is the limit so if it happens a second time it’s on the owner.  I asked the support desk why they designed the electronics such that they can be damaged by ordinarily available charging equipment and did not get a good explanation. Perhaps this has been corrected now.


I use a Scorpion on my 3100cc Corvair, with excellent results.  Though, I've had to replace it because I baked the first one by putting it too close to an exhaust pipe.

Funny story. When I was first replacing the lead-acid with the LiFePo, my airport buddy walked up.  I waited till he got close, and pull the LiFePo out, acting as if it were heavy.  Asked him if he could hold it for just a second while I arranged some wires.  As I handed it off, he just about smacked himself in the face with it, because it was so light.  We're both still laughing at that.  :-)


WWflycorvair considers lithium batterys with Corvair engines unairworthy.  Please see his video.  The battery's internal circuitry can be fooled into shutting off - leaving no back-up (and no mags).

Oh, geez.

As is typical from that quarter, one example is mixed with bad logic, ignorance and a lack of understanding to create a lot of FUD and an old wive's tale in an authoritative voice.

The LiFePo batteries have circuitry to shut the battery down, because total discharge will destroy them.  The battery wasn't "fooled" into shutting down.  What nonsense.  The shutdown is a totally predictable result of draining the battery to uselessness. The threshold is around 10V for the Scorpion I have.  Fair enough, but it doesn't really matter, because the energy available between 10V and 6V is negligible, anyhow.  The pilot that went down may have gotten a few more minutes out of the battery without that circuit.  Maybe.  More likely, he would have gotten only seconds.

But, run time after the battery has drained to 10V is not an interesting test.  Why did the pilot let the battery get that low?  In an electrically dependent airplane, why wasn't there an active alert that the generator had stopped generating so that the countdown started when the battery was at 13.4V?  With a properly designed alarm system, the interesting test becomes, "How long will the plane run after the generator dies?"  There is at least one video online doing this comparison in which the LiFePo runs MUCH longer than the lead acid.  By this criteria, the LiFePo is much safer.

In short, I don't care to base my aircraft's airworthiness on unsubstantiated and counter-indicated FUD.

BTW, I learned from Bob Knockulls that everyone, not just those with electrically dependent engines, should perform this test, regardless of the battery chemistry.  Crank her up, switch off the generator, and let her run until enough things die to make flight uncomfortable.  A perfect situation would be that you run out of gas first.  But, us Corvair guys know our engine will go quiet way too soon.  However, what other equipment are you relying on, and how long will they last should be a known quantity.  Different appliances will have a different voltage threshold where they quit.

check out for sale area, weve got a member selling required charger for $55 , in case you are going this way. I use the same charger myself

Hey Ralph......I switched to the ETX680 battery in the CruZer with a Lycoming 0-320 engine, and added a warning light on my panel.  I saved about 20 lbs and it cranks the 0-320 as well as the lead/acid battery I previously had.  Good luck.  Think you will like it.

Back in 2015 I installed two ETX24C(old designation) batteries in my Viking 110 powered 750.  At the time, the ETX36D was the recommended type - more CCA's but slightly heavier with a bigger case size.  My 24's do not have the warning light due to their age but electrically tied together there is no problem cranking the V-110 to start.  It amazes me that for a total weight of just over 5 lbs. there is that much capacity available.  Initially I suspected a problem with one of the batteries(it was something else) and called Kathy at EarthX.  She indicated they would send a new replacement with prepaid shipping label to return the suspect battery which they did.  Turned out the returned battery was AOK.  Yes, they are a little pricey but if the average life span is 8-10 years, not a problem as I'll hang up my headset for good prior to that!

Ray from UL recommended the ETX900 which I purchased along with the relatively new insulated battery box since it will be installed on the engine side of the firewall.  If your running a UL engine you may want to talk to Rob or Ray about the wires used to connect the battery to the engine since the installation manual recommends larger gauge wire than comes with the Zenith firewall forward kit.  UL also recently posted an article addressing starting problems related to smaller gauge wire.

Where was the UL article posted?

UL Power News on Facebook  There is a lot of extra stuff on ULPower here ..... and also remember to download the latest (interactive guides) for maintenance and troubleshooting  from the ULPower website (under maintenance and troubleshooting in manuals for your engine) 


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