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I lost 17 lbs: Battery!

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MNForrest

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A few weeks ago there was some discussion on the Acro exploder - and maybe on here - about the new "less volatile"Lithium chemestry batteries on the market for RV's and such - and weather they were acceptable for use on experimental aircraft. As it happened, that discussion took place just as the B&C battery in my Pitt's S1 crapped out.
My S1 with the B&C is relatively heavy, but built exceptionally strong and sleek. 920# with unusable fuel and oil. AEIO-360A1A. Battery behind seat. The previous owner (Phil) did a lot of work on the aircraft, and flew it successfully in Advanced for many years. He was 160# after a big meal. I'm 213#. Needless to say, I push the aft CG limit just by sitting in the thing, and it has always flown "tail heavy" to my experience. The idea of shedding some weight in the rear was appealing.
I did some research, and ordered a Shorai battery with slightly fewer CCA than the B&C, but nearly as much capacity.... and 19 pounds less weight. Yes, four pounds versus 23.
Removed the B&C. Picked up some 3.5x2" 14ga. channel from the local steel supplier: painted, drilled, bolted in place to adapt the battery tray to the new power source. Improvised some rubber fuel line, steel tubing and AN bolts to hold the battery centered in the new tray.
Since the Shorai is made in Japan, it's has all metric terminal fittings. I had some SAE M6 bolts drilled for safety wire and installed the battery as I would have the B&C, using the original hold down - which fit perfectly.
The primary concern with these LiFe batteries is overheating. The Shorai has a maximum charge rate of 24 amps at 15 volts. My alternator never exceeds 14 volts, 8 amps. Adding a level of confidence, I procured a small digital remote-probe thermometer, and installed it temporarily as a "battery temp" gauge - just to keep an eye on the thing. The probe is wedged between a layer of insulating foam and the battery case.
I charged the battery overnight with a tender (1A). Initial output was 13.6 volts.
With everything tightened up, it was time to test-crank. OAT 52 degrees and too windy to fly. Cranking was exactly as advertised given the conditions: Fuel full lean... First crank of 8 seconds was stiff, but I think would have got her running. As per Shorai, I let it rest for about 15 seconds to "warm up". Seconds crank, much better. Easily as effective as the fully charged B&C would have been. Third crank - wow. I might have taxied down to self serve on just the starter.
Today: First flight with the new battery. OAT 55 degrees and she started right up first try. Tail came right up. Stall speed about the same, but less "float". Hammer's much improved. The thing just seems to track more where I want it to. Still plenty snappy, but stops snapping quicker. On landing, much less float than expected. Even with a gusty wind right down the runway, I was able to sink her right on to all three with no long-lasting float (something I had come to expect from my tail-heavy Pitt's). Battery temp stayed low and steady (55-60 degrees).I get the feeling she flies more like she did with Phil in the seat now, and I am very happy with the upgrade.
Battery $285. Parts and pieces: $60.
Your results may vary.
Forrest
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Edited by: MNForrest
 

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