EarthX Battery Cautions

[Pat Horgan]

Cub Crafters Engineering has been in contact with EarthX and is reviewing the possibility of future use and applicability of EarthX batteries on Carbon Cubs. While the lower battery weight and starting performance is very attractive, it is important that the owner/operator understand that this is not a certified battery and there are specific interface concerns that need to be considered and addressed. Simply swapping the current lead-acid battery with an EarthX on a Carbon Cub could result in loss of engine ignition (if the battery goes into a self protect disconnect) and other significant problems. CubCrafters' Engineering does not recommend the installation of EarthX batteries at this time, unless system design and installation concerns have been addressed including:

• From the EarthX website: “A common question is can you wire the batteries in series or parallel with a lead acid battery? NO, you cannot do this. The voltage of the lead acid is lower than the lithium so it will drain the lithium battery." The Carbon Cub ignition backup battery is a lead acid battery. Interaction between main battery and backup battery of differing chemistries has not been analyzed.
• According to the EarthX downloadable manual: The battery will disconnect from the system to save the cells when the battery reaches 11.5V discharge or if a low impedance load (starter) instantaneously draws the battery to dip below 6V.
• EarthX operational voltage is 13.4V if fully charged and 12.8V fully discharged, versus a lead-acid battery that is fully charged (resting) at 12V and discharged at 10V. This means the Carbon Cub voltage indication color ranges are not applicable to the EarthX and would need to be re-evaluated and programmed.
• Fault monitoring must be incorporated into either the Engine Monitoring System or an added discrete LED on the instrument panel. This way if voltage is above 15.2V and the light is flashing continuously the pilot can know to shut down the charging system before smoke and fire. Other situations may require pilot action or attention if signaled.
• Installation warning directly from the EarthX manual: “Installation of the battery in the cockpit is not recommended, unless the battery is properly vented over-board.” The current lead acid main battery (mounted under the pilot seat) is sealed and therefore not vented overboard. Engineering and fabrication would need to be incorporated to seal off the cabin and vent the main battery overboard.

[DRL]

We were earlier adopters of the EarthX battery and have not had any issues with it, but Pat raises some valid issues. The first is the interaction with the standby ignition battery. We have not seen a discharge of the lithium battery by the standby lead acid battery. In any case, with the alternator operating normally this should not happen and the diode should prevent the opposite, the lithium discharging the lead acid. While the engine is not running and the field breaker disconnected, we see minus 3 amps on the Dynon. When the engine has not been run, over a month, we have not seen a noticeable discharge. So it is certainly possible, but so far, it has not been a problem.

The 11.5 volt disconnect may seem high but EarthX claims it is 95% discharged at that point, so it would be time to switch to the standby ignition system anyway. We lost the alternator once and it took about 35 minutes to reach the shut off protection with all the electrical items on. Monitoring the volts and amps with an EFIS is worth while. After we saw how it operates, we set the Dynon ranges to give us both caution and warning messages . It is probably not a good idea to use just the LED that comes with the battery to see what's happening. As far as an over voltage causing smoke and fire, well that should be prevented by the crow bar system and the internal battery protections if it wasn't already caught on the EMS alerting system.

When we bought it, EarthX was not recommending a sealed box and vent system, so that is a new development. If sitting on a potential safety concern is a problem then maybe it is not a good choice for some, but the trade off for the performance, weight and not having to modify the airplane's old battery box, it seemed reasonable in our view.

We have an EX so certification is not a factor as is the case with the LSA's. Time will tell, it is still an experiment.

[Pat Horgan]

We were earlier adopters of the EarthX battery and have not had any issues with it, but Pat raises some valid issues...We have an EX so certification is not a factor as is the case with the LSA's. Time will tell, it is still an experiment.

DRL, thanks very much for the great feedback. We appreciate hearing about the technical pro-con lessons learned from those using these batteries. We understand how popular EarthX is becoming with E-SLA & E-AB aircraft and fully recognize some of the great advantages. We hope to be able to implement these and other technology advancements. Our caution post serves to compare EarthX's own installation requirements with the current electrical system architecture, so folks understand compatibility. It sounds like you are having good success with your LSA. Thanks again.

[peterb]

DRL, thanks very much for the great feedback. We appreciate hearing about the technical pro-con lessons learned from those using these batteries. We understand how popular EarthX is becoming with E-SLA & E-AB aircraft and fully recognize some of the great advantages. We hope to be able to implement these and other technology advancements. Our caution post serves to compare EarthX's own installation requirements with the current electrical system architecture, so folks understand compatibility. It sounds like you are having good success with your LSA. Thanks again.

Hi Pat,
Great to have you guys looking out for us pilots. I'm currently running the EarthX with great success so far and very interested in making the EarthX work for the long term. There's so many benefits for this battery to not have you factory guys look into a good solution. Sure adds value to the whole Cub Crafters family when you guys solve these details.
We look forward to the details. I'm hoping it'll be simple like programing my Dynon FlightDek D180 for the proper limits and maybe a modification to the starting check list to make sure the system is working before each takeoff.
After seeing your first post I watch the voltages much closer.

Thanks!

Peter

[DRL]

Does the EarthX BMS depend on the limited capacity of the alternator to control maximum charging current, or does the BMS control the charge current? If the latter, why the discussion (and limits) to alternator amp ratings?

The EarthX does not control the charge current. The BMS simply protects the battery from damage due to a battery undervoltage or overvoltage. On the CarbonCub, the crow-bar will also protect it from an overvoltage by the alternator as it does on the other type batteries.

My comments on amps were related to the limits to set on a Dynon EMS to warn if the alternator was not producing enough or no current. The battery accepts whatever it needs on the high end, but recharging from a minimum charge, I have not seen it take more than 28 amps with the standard 40 amp alternator. EarthX has some limits on their website for larger batteries and alternators that are probably compatibility related.

We are at three years and all is well so far, at this point, it has paid for itself. We have run it down to the shutoff a few times and it has recovered with no ill effects. If we need another one, we would still choose the EarthX. It now has a redundant BMS that the FAA thought was a good idea. It has become standard on some RV's, they may have better information.

[peterb]

Hi All,
One more data point on the battery situation for early Carbon Cub EX.

For our 2011 EX I switched to the Braille Battery B14115 after our EarthX slowed down and this treads warning from the factory. After leaving the key on a couple of times and recharge it would stop on compression and shut off the battery. Had to reboot with master after waiting a minute or so and even jump start a few times with the micro start battery I carry at all times to get the plane to start.
Sorry the factory isn't getting back to us on a solution for the EarthX so I jumped to the Braille.

So after reading this post;

10-27-2017, 02:50 PM
jim plaster

Re: Best Battery for our Carbon Cubs?

Finally installed the Braille battery in my bird after trying the Antigravity battery for almost 3 years. Bought mine from Jegs for $169 and they shipped it FedEx next day...free shipping over $100! Currently out of service for a week now with horizontal stab issues...hopefully be flying again soon. The Braille fits nicely in the smaller battery box without any modifications. It's also a AGM style battery. If you go the Odyssey route you'll need to do the bigger battery box modification if you own an earlier airplane....the kit cost north of $600 I believe....so check your serial number to determine which size yours is..The older airplanes use a smaller battery....

Last edited by jim plaster; 10-27-2017 at 02:57 PM.

I didn't need to change the battery box size with the Braille and after a couple of months now and a new shut down procedure for the key the Braille has been working good. At this point even if the Braille quits with a few years use I feel I'm in a better/safer situation for the electronic ignition on our planes.

Best,
Peter

[Dan L]

Hi All,
One more data point on the battery situation for early Carbon Cub EX.

For our 2011 EX I switched to the Braille Battery B14115 after our EarthX slowed down and this treads warning from the factory. After leaving the key on a couple of times and recharge it would stop on compression and shut off the battery. Had to reboot with master after waiting a minute or so and even jump start a few times with the micro start battery I carry at all times to get the plane to start.
Best,
Peter

Your comment about the key caught my eye. So you must have the master contactor wired into the key switch and that turns the master on and off?

As I’ve mentioned before, my experience with the lithium batteries has been poor. I went back to the Odyessey and never have a problem. Or a worry.

[Pete D]

Your comment about the key caught my eye. So you must have the master contactor wired into the key switch and that turns the master on and off?

Leaving the key in the on position drains the battery as the Lightspeed ignition boxes are powered up, regardless of what position the master is in. It's not much draw (compared to having the master on) but it is enough to drain the battery slowly. Plus the engine is "hot" and could fire if the prop is moved.

[stede52]

DRL,
Thx for the info.

[Cubdriver2]

I thought the ignition just needed juice to energize it at startup and once running made its own current to keep operating?

Glenn