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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Hey Ralph, I have the ETX680 in mine ((350iS).  There are two form factors for the battery and I can't recall which ones I got.  Main consideration in my mind was the Amp-Hr capacity in the event of PMA failure.  Based on the EarthX discharge rate plots you can plan on about 30-40 minutes of battery power to keep the engine running with the ETX680.  I would also urge you to put in the wiring necessary to monitor battery faults via panel lights or through your EFIS.  I had a bad battery which was promptly replaced for free by EarthX after their evaluation. Would have taken a lot longer to troubleshoot without the battery fault monitor indication which I could watch during test flights.  Lots of good info on the EarthX website regarding the topic.  Good luck, hopefully you are getting close to flying again?


Our GRT EIS monitors the online battery, but the fault lights let you know if there's a problem with the offline battery.  We installed fault lights above each battery switch.


I will review the EarthX site for info on fault monitoring. My panel is still open and now is the best time to install new wiring. My big question on battery selection is that EarthX offers two series of batteries in the same style of case, the 680 and 900 series. The 900 has a lot more juice and of course a larger price tag. I admit to having a thing about having good tires, good brakes, and good batteries in my toys. As such I am tempted to go with the 900 if it would work. The 900 hundred weighs a pound or two more than the 680, but I have dropped 35 pounds of excess fat this year so a couple pounds less of weight savings on battery is not the big deal it used to be.

My Dynon D120 offers some monitoring, but contacting Kathy sounds like like a very useful idea. 

Getting closer to flying again. Remaining tasks are building and installing doors, windows, new style oil cooler, cowling, and installing the wings. And I have to find the time to take the wife south to get warm for a couple of months this winter. Almost done...


ETX900-VNT my suggestion, has provision for external venting. Over a year so far of trouble free service

In the past these batteries were prone to catching on fire and were susceptible to vibration causing failures of one kind or another.  I have one of these batteries sitting in my hangar and I have been reluctant to install because of these issues.

Also, this battery requires (if I have been told correctly) its own special $100 charger.

Can anyone shed any light on these issues.  I would love to save the weight over the Odyssey  battery I currently have installed but I feel I am (somewhat) irrationally worried about top two issues.

Flying CH-650


All lithium batteries are not the same and certainly not all lithium batteries use the same chemistry. Different battery chemistries are used with trade-offs being energy density/storage vs weight vs potential combustion.  Lithium polymer batteries ("LiPo") are used for RC aircraft, hoverboards, laptops, phones, and many other devices.  They are very light but have the potential to spontaneously combust and many fires have been reported in these devices.  Lithium cobalt oxide batteries have very good power density, but also have some potential for spontaneous combustion and are famous for the Boeing battery fires.

EarthX uses lithium iron phosphate (LiFePO4) chemistry.  As I understand it, it has a little less power density than some of the other lithium chemistries, but it has almost no potential for spontaneous combustion.  It will certainly burn if subjected to fire, but the fire has to be coming from an external source.  If you're already on fire, whether your battery will burn, too, is the least of your problems!  ;>)

You do have to have a lithium battery charger (like the OptiMATE already mentioned) to get an optimal charge on the EarthX, but you only really need that if the battery is depleted from leaving a master on, etc.  Otherwise, most aircraft's electrical systems will maintain the battery's charge just fine - since it has the BMS electronics on-board the battery, it'll balance charge the cells and protect the battery from over-charge or over-discharge.

I've had a good experience for hundreds of hours with EarthX batteries.



(not affiliated with EarthX, just a satisfied customer)

Thanks for this!  I think it is time for me to get past this irrational fear and install this battery.

I know this is not the 650 forum but I monitor here as well becuase there is always good info from all of the lists.

I have a Lycoming, 0235 in my CH-650.  Because the engine is kind of heavy I have my battery all the way in the back to help with W&B.  I have the Odyssey battery 15 pounds.  Anyway, that battery weight plus the long, heavy battery cables added quite a bit of weight to my plane. 

Even with a brand new 680PC battery my low voltage indicator light will start flashing almost the moment I flip on the master.  This drives me nuts.  The plane starts fine, and all electronics function as expected but that flashing yellow light drives me crazy.  I have been told the long cable run and this battery is what is causing this condition even with a fully charged (and/or new) battery.  I have been told the EarthX battery will help resolve this condition.

Based on your comments I think it is time I put this to the test!

Regarding engine starting: a couple of other side notes for those who might be interested...

In the past on COLD mornings it was hard to start my engine and unless very careful I could wear down the battery.  To resolve this I did two things...both worked but one seems to have worked better.

1.  I installed an oil pan heater.  This worked the oil warmed up and engine would start fine.  The problem is, it takes about 20 minutes for the oil to warm up enough to make a significant difference.  At my airport the management does not allow unattended electric to be connected so I could not leave the oil pan heater plugged in allowing me to preheat the engine before I showed up.  I ended up putting the heater on a timer but that had limitation and the airport doesn't even want things plugged in, even if they aren't turned on.  I even installed a plug I could access remotely via a web application but there was still the issue with the airport not wanting things plugged in while unattended.  (this is kind of BS but they can actually evict you for breaking these rules)

2.  I installed a primer system on engine.  This works great.  So far, even on the coldest morning I prime the engine she will start right up...the coldest mornings might take some babying.  If I combine the engine warmer and the primer...well, one turn of the propeller and engine will start!


BTW, Steve, I definitely would call EarthX to order and talk to Kathy (sales manager).  She can make sure you get the appropriate battery and it never hurts to see if you can get some sort of "deal," especially if you're buying a charger, too. ;>)

She provides great customer support - in their early days, I had to get a warranty replacement on one of their batteries and she had it shipped-out the same day I called!


I have two ETX680C lithium battery in my Zenith CH-750 Cruzer, never a problum,

I highly recommend a OptiMATE Lithium 4s 9.5A TM-275 Battery Charger with Select & TUNE ECU Flash, you can work on your plane with the power switch turn-on with out pulling on the battery, Also a standard battery car charger will not top-off the battery's.

(If you forget to turn off the master power switch ((pilots never forget to do that, LOL)) it will not kill the battery, it has a auto-off function to prevent from damaging the battery.

Check out Jan's battery video on the Viking Engines Youtube site. It is called "Lithium or Lead Acid Batteries for your airplane"

ETX900 is the best option.  You need to have the cranking power PLUS the amp hours to sustain operations for about 30+ mins in the event of an alternator failure.  You can even consider 2 batteries weight wise (gives you more sustainable time 'in the event of a failure' -  much as the saving on weight is there.... there is a cost in $$$$.  Do fit the witness LED to the cockpit too..... 


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