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.