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

Aircraft Battery for experimental aircraft. The ETX900 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.

 

[Cubonaut875]

So if we have the Optimate charger, which I do, I can leave that on charge as I have been doing. Good idea or bad idea?

 

[Neal]

So if we have the Optimate charger, which I do, I can leave that on charge as I have been doing. Good idea or bad idea?

According to EarthX the charger is temperature aware. When I install mine I'm going to monitor it off the charger and see how long it can go. I prefer not to have it on charger unless needed. The SBS-J16 has to live on a charger, not sure EarthX is the same. If there a stinking battery disconnect switch it would solve this problem too to eliminate parasitic drains.

 

[ve6yeq]

According to the Garmin documentation that I have read, there is some "keep alive" power supplied to things such as the GTX 345R (to store the last known GPS data) so there will always be a very small draw from the battery. So connecting ground power seems like a good idea to me...

 

[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.

I emailed EarthX, very responsive which is nice, and they pointed me to the manual, so I RTFM'd and found this which I'll set once I find the right sensor location in the G3X config:

 

[Cubonaut875]

Now you have to call the wonderful people at Garmin and they will tell you RTFM, you will read the 464 page manual and not find your answer, you will then call them and they will give you the hidden combination of buttons to press that will reveal the screen you need

 

[Neal]

Can’t wait to put my EarthX in. I believe the SBS-J16 is too weak for this plane. Today had failed first start and second attempt barely turned over. Just came off of weeks on the charger.

 

[Neal]

In talking with Pete from CubCrafters yesterday I inquired about the CubCrafters settings for EarthX battery installs. He sent me the chart below. I'm probably going to modify my values, for example anything above 13.0V in my opinion is in the green band. 12.9 down to around 12.5 will be my yellow band, below 12.5 will be red. I have to check what I already configured and where I set alerts. I'll take a screenshot when I sort this out.

Also in the chat Pete mentioned that simply the voltage alerts in the G3X are sufficient for warnings about the battery health which is great to hear as I bought the battery fault light and don't intend to use it. I agree that voltage values alone should be sufficient to monitor what's going on with the battery.

Here are LiFePO4 battery state of charge which is very different from AGM (lead) batteries.

 

[Cubonaut875]

In talking with Pete from CubCrafters yesterday I inquired about the CubCrafters settings for EarthX battery installs. He sent me the chart below. I'm probably going to modify my values, for example anything above 13.0V in my opinion is in the green band. 12.9 down to around 12.5 will be my yellow band, below 12.5 will be red. I have to check what I already configured and where I set alerts. I'll take a screenshot when I sort this out.

Also in the chat Pete mentioned that simply the voltage alerts in the G3X are sufficient for warnings about the battery health which is great to hear as I bought the battery fault light and don't intend to use it. I agree that voltage values alone should be sufficient to monitor what's going on with the battery.

View attachment 304​

Here are LiFePO4 battery state of charge which is very different from AGM (lead) batteries.

View attachment 305​

That's not even close to what I sent you on my panel. Very interesting indeed

 

[Neal]

That's not even close to what I sent you on my panel. Very interesting indeed

I highly recommend raising your seat and verifying what battery you have installed, make sure you have an EarthX (blue) or a AGM (orange). Based on your production order experience, I don't know what you have under your seat

 

[Neal]

I'm sure I'll be tweaking this more but this is 90% there for what I want for my settings. I wasn't sure how common values worked between two settings. For example should yellow range + alert be 12.7 to 12.9 and the yellow range below it 12.9 to 13.0? The common value of 12.9 is what I'm not sure is right to set or if the values need to be different.