Lithium batteries Warning

[Orv Neisingh]

Our not being familiar with lithium batteries, we could see a constant 12.7-12.8 volts during that flight which was a great voltage for a standard battery but not a lithium battery. On that particular flight we had two failed start attempts before finally getting the engine started. Those failed attempts drew the battery down and when the alternator was turned on after engine start the lithium battery drew all of the available amperage to recharge, drawing more than the 30 amps the fuses were rated for so they failed. We were then running on only the power remaining in the batteries. 

After researching the proper solution we installed an external voltage regulator designed for the lithium battery, it comes with a warning light that we installed on the instrument panel. We also installed an amperage sensor that the alternator leads pass through and it's associated amp gauge that is mounted in clear view to monitor during flight to insure that the alternator is providing power to the charging system. We also installed a 30 amp breaker for the overhead panel and a 60 amp breaker with #6 wiring next to the alternator to provide the lithium battery with ample amperage when required. 

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The top photo shows the amp gauge on top of the fuel tech computer, the middle photo is how I wired my own alternator with amp coil and 30 amp breakers, the bottom photo shows the wiring we did on the lithium battery with voltage regulator, 60 amp breaker for the battery with #6 wiring to the battery.