EarthX battery for Experimental Aircraft

[Neal]

I spoke with the EarthX folks at Oshkosh (2023) about the venting requirement for an EarthX battery. CubCrafters runs a vent tube from the battery box to the actual vent(s) on the battery to outside. For someone like me that has the "upgraded" SBS-J16 starter battery we don't have a vent line and I wanted to understand the requirement for it. The reason for the vent is the rare case of a thermal runaway in the battery which produces a lot of smoke which for some cockpits/cabins they don't have the option of opening a window, canopy, etc. The vent line requirement is for certified aircraft or if you so choose to have this. You can buy an EarthX battery for experimental aircraft that does not have the vents. It also has a monitor that you can wire into the GEA24 to show a CAS alert on the G3X if the voltage is exceeding the threshold to alert you as needed.

I then asked about a battery tender for this type of battery (LifePO4). While typically not needed I told him I go on motorhome trips and my plane does have a parasitic drain. You can either use a tender (below) or disconnect the battery altogether.

ETX900 Lithium Battery for experimental aircraft | EarthX

The ETX900 is an outstanding lithium battery that will deliver 840 cranking amps, 15.6 amp hours, and weighs under 5 pounds! Order yours today.

earthxbatteries.com

Amazon product ASIN B07NSKTNKX

 

[Cubonaut875]

I have the above mentioned optimal charger hooked up with a pigtail to theEarth X battery. It is okay to keep it plugged in to the battery for long periods correct? I do like to keep it fully charged during the winter months. Lithium batteries are outside the scope of my experience.

 

[Neal]

I don't know the answer to maintaining an Earth X battery but if I had one I'd want to see how it worked off the charger. On my non Earth X battery I seem to be able to go about two weeks before I noticed weakness. The EarthX can run at a much lower charge level and you don't risk damaging the battery either. My understanding long term storage on Lithium batteries is ideal at around 80% and not fully charged. So I'd be curious how long you can go without a charge and still crank. Worse comes to worse you either then put it on charge or use a jump device for that start if needed but I'd want to know the limits of my battery and look forward to learning what you find out. I'll likely stay with my SBS-J16 until it needs replacing then go to the EarthX for the replacement.

 

[Neal]

While my SBS-J16 is new and no issues, I think I'm going to pick up a ETX-900 (experimental) and install in my new FX-3. I have LiFePO4 batteries in my motorhome and have learned a lot about them during the recent upgrade of those. Knowing that this battery is crucial for backcountry reliability but also with electronic ignition it is the final failover after the ignition backup battery (replaced annually, and is small) is depleted. It seems like this battery is a great choice for many reasons and I'm planning to install one of these.

 

[Neal]

Here is a reason why I think switching to EarthX is a must for my Carbon Cub FX-3 with glass panel (IFR). When turning on Master right after coming off the charger, so I should be fully charged, I'm seeing a starter battery voltage of approximately 12.0 (+/-). It is showing about a -5 amp draw. AV is NOT on so the GNC 355 is not powered on yet.

12.0V is 45% power on the AGM battery. This is NOT a good place to be cold cranking your airplane! While it works, it seems the battery size is not proper for this panel setup. In the land of motorhomes we're taught never to let our lead batteries to go below 11.9V (continuous).

 

[Neal]

I ordered the ETX-900 during a slight sale Aircraft Spruce had and also the light indicator for battery status and the optimate charger. Not a cheap setup but having just converted my motorhome to LiFePO4 batteries I've become quite educated and impressed with them. Talking specifically about my CubCrafters Carbon Cub FX-3 which has a SBS-J16 battery in it, my concern is it's an undersized battery for the amount of avionics in a plane like mine with electronic ignition on top of that. It may be fine for a VFR panel type setup but as noted above at the time of engine start hot off the charger seeing 50% state of charge is concerning. We'll see how the EarthX compares.

The ETX-900 is amazingly light at 5 lbs compared to 15 for the SBS-J16. So if you're one of those trying to shed every pound, and unable to manage the one on the pilot seat, this will drop you 10 lbs!

There is an interesting omission on the EarthX spec sheet and I have an email into them asking for the data. I learned with my motorhome that the LiFePO4 battery cannot be charged when the temps are below 32F. The operating range for use is one thing, but the ability to CHARGE it is another. I find it concerning that EarthX does not show this information such as the attached spec sheet. For someone sitting in a hangar such as me in VA with OAT such as this morning of 20F you could have a problem. However, if the battery is charged at end of prior use and being a LiFePO4 battery it likely will not need to be charged and that's the major change between the EarthX (LiFePO4) and SBS-J16 (AGM lead battery). It would be smart if CubCrafters actually put in a master on/off switch such as on the side of the seat base to disconnect the battery when not in use to remove parasitic drains. The SBS-J16 essentially needs to remain tied to a charger. I'm hoping to see different with the EarthX.

One final point. I'm surprised CubCrafters does not install any vibration dampening in the battery box. Not smart IMHO. While both batteries have to meet an FAA spec for vibration, common sense says to use a dampener. EarthX includes two strips but I bought some of the material below I'll be lining my battery box with.

I bought both 1/4" and 1/8" - I'll see which will work best.

Amazon product ASIN B08P1W9QQD

 

[Neal]

There appears to be an issue with amazon links - checking into it...

 

[Neal]

For those with the ETX-900 and a G3X, I'd appreciate it if you could go to the CONFIG side and tell me what the params are for your battery voltages for green, yellow, red bands. Thank you.

 

[Neal]

I got a few replies from EarthX that they basically say it's a starter battery, starting the plane generates heat, that will then allow you to charge. I'm still trying to get my point across to them that we cannot have a charger connected to a LiFePO4 battery in the hangar when not in use and the temps (of the battery) are below 32F. Doing so may (will) damage your battery. Users of LiFePO4, as I understand it, have to know this limitation. Again, as stated above, the hope is it doesn't need to be on a charger.

From the FAQ (as they quoted to me)

EarthX batteries are engine start batteries, so the expectation is that you crank the engine prior to charging. As such, the battery temperature is increased (~ -10DegC) so it can accept charge without harming the battery (reducing its usefull life).

I'm going to put a thermal wrap on my battery which should also double as a vibration dampener.

Amazon product ASIN B01DWJ5PFU

 

[Neal]

EarthX came back with something very interesting which is the Optimate charger is temperature aware and will manage charging by its temp.

Page 5 of the attached document, bottom paragraph.