Aircraft

Are lithium iron phosphate batteries suitable for Jabiru engines?

Safety, Batteries, Jabiru

Tuesday 18 October, 2016

RAAus is aware that LiFePO4 chemistry batteries are being advertised that they are suitable for use in light aircraft powered such as Rotax and Jabiru engines.

ATTENTION: Rotax and Jabiru state they do not support the use of this type of battery with their products.

Members should consider that in some circumstances and design that the charge controllers associated with the permanent magnet alternators used on some engine types offer no form of voltage control. They function by allowing sections of each half wave to pass to the battery at full output current and unlimited voltage at a frequency of up to 1200 Hz.

The time interval of each charge pulse is varied by the regulator in order to regulate the charge condition. LiFePO4 batteries cannot safely be exposed to charging voltages in excess of 14.8 volts. Independent tests conducted by some of our members on these charging systems show that the voltage output exceeds 30 volts at full power. Lead acid batteries can be safely charged using systems where the current amplitude can be time limited on each half cycle and are immune to the applied voltage peaks. 

A secondary risk is that LiFePO4 cells have an inbuilt safety switch which will open circuit the cells if the voltage reaches a critical danger level.  While this will prevent the cell becoming unstable it results in the high voltage spikes passing from the regulator directly to the instrument panel without the battery moderating the voltage spikes and will quickly destroy components such as radios, transponders, glass panels etc. Schicke Electronics GMBH, have developed a safety switch system which disconnects the alternator from the regulator when this occurs in order to protect the panel instrumentation.

RAAus owner-maintainers and L2’s are reminded to seek the appropriate supporting documentation from light sport aircraft manufacturer prior to the use and fitment of a lithium iron Phosphate battery. Owner-maintainers and L2’s of other RAAus aircraft are reminded to review battery documentation and seek appropriate guidance and information prior to utilising this new battery technology.
 

Response from Jabiru Aircraft Pty Ltd

We have not tested any Lithium Iron Phosphate batteries in Jabiru aircraft or with Jabiru engines and do not recommend them.

From the J230 flight manual:

Document No: JP-FM-07

8.4.9 BATTERY SERVICE

The J230 must be fitted with a "no maintenance" 12 volt, PC625 Odyssey Sealed Lead Acid Battery (Jabiru P/No. PM0095N).
 

Response from Australian Agent for Rotax

In regards to the use of these batteries in current 912 iS manuals see attached documentation to this fact sheet.

Other 912 - 914 range of Rotax engines please find following reply from Rotax:

The aircraft manufacturer has to ensure that the permitted limits of the used battery (for example the maximum permissible charging voltage) may not be exceeded in any case.

It must be ensured that the operating limitations of the battery are strictly adhered to also in case of a defect of the charging system.

This may be ensured by using a proper battery management system.

A similar statement will be added in the next revision of our installation manuals for carburetted engines.