jaustinmd
Joined: 27 Jul 2014
Posts: 1
Location: Crossville, TN
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 Posted: Sun Jul 27, 2014 1:59 pm Post subject: Lithium Battery Experience - Sept. Kitplanes Article |
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Bob requested in his recent article that those experimenting with Lithium batteries relate their experiences. I built a Zenith STOL CH750 with a Jabiru 3300 engine - a day/VFR, non-electrically dependent aircraft - perfect for experimentation!
I originally installed a PC680 and it worked flawlessly. As I accumulated hours and increased empty weight from various modifications, I looked to using a LiFePO4 battery to gain back some useful load. I had heard that the Aerovoltz 12-cell would readily crank the Jab 3300, so I purchased a Ballistic 12-cell (same battery but cheaper!). Initially, things were fine - it spun the 3300 as good or better than the PC680 (and saved about 12-13 lbs doing it!). However, I began to get erratic tach readings and looked at the alternator leads where the tach picks up and the Jabiru OEM female spade leads appeared burned! After consulting Jabiru USA, I replaced the rather flimsy leads with quality AMP female spade connectors. THEN, my 20 amp alternator breaker began to trip!
At this point, I did a lot of research and found that since the Jab 3300 doesn't output charging current 'til about 1800-1900 rpm, my theory was that the connectors were frying due to the surge of charging current after take off and low internal resistance of the battery, and once the connectors were corrected, the little Ballistic battery was getting hit with a surge of charging current in excess of 20 amps and tripping the breaker.
I did two things - I reviewed my wiring and found I was good for up to a 35 amp breaker to protect it, so I replaced the breaker with a 35A, and switched to an EarthX ETX36D which supposedly has close to the capacity of the PC680. I'm really happy so far (several months) with the ETX36D - it seems to function just as well as the PC680. It spins the prop for starts as well or better as the PC680 and although the Jab 3300 is not charging during ground operations, there is negligible voltage drop when powering-up the EFIS, transponder, radio, etc. (The PC680 found a happy home in my '82 911SC Porsche, which was a weight savings vs a conventional auto battery!) The Ballistic will be re-purposed in my UTV.
Time will tell as to durability and performance of the EarthX, but for now I'm a happy camper!
John
N750A
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