ChiefPilot
Well Known Member
This past December saw the first condition inspection on my -6A. Aside from the inspection, I had decided to use this time to install some upgrades. One of the upgrades was to replace the 15.7lb PC-680 battery with a 2.7lb Shorai LFX18L1-BS12 LiFePo battery.
Much has been written here and elsewhere about the merits of Lithium-Iron-Phosphate batteries (see this thread for a great discussion). Rather than re-hash the discussion around the tech, I wanted to share how I installed this battery in my RV without making any changes to the airframe, wiring, or battery box. I hope someone finds this helpful!
Operation
Since the first question I'm sure many will ask is "How well does it work?", I'll start with that. In short, I can tell no difference in normal operation between this battery and the PC-680. I have an IO-360-B1B w/8.5:1 pistons and dual P-mags and this battery spins the Hartzell BA prop with the same gusto as the PC-680, if not more. I've had it in weather down to -1ºF and it has performed as expected. I'm continuing to watch this carefully, as I have only about five hours of running time so far but I don't expect any surprises. I do like the weight savings however!
The Installation
The first step was, of course, to obtain said battery. I ordered the battery directly from Shorai and received it a few days later.
I had previously removed the PC-680 from the aircraft and compared the two side by side. Clearly, the Shorai battery is significantly smaller - but the weight difference is even more dramatic. Not wanting to count on published specs, I measured both batteries myself. The Shorai matched the published specifications in all respects, and indeed weighed only 2.3lbs. Interestingly, the only discrepancy with published specs I found was with the PC-680 - the Odyssey site claims the PC-680 weights 15.4lbs but mine measured 14.0lbs.
One of the goals for this upgrade was to be able to preserve the ability to do a "drop-in" upgrade. This preserves the possibility of going back to the PC-680 at some point in the future, and also eliminates changes to the airframe/FWF configuration. Since the Shorai battery is significantly smaller than the PC-680, that means that an adapter is needed to secure the batter within the larger space of the PC-680 battery box.
Enter a large chunk of UHMW plastic. I love working with this stuff - it's relatively cheap, it's easy to mill, and it's reasonably lightweight. Certainly other materials could be used - aluminum, or perhaps even wood - but I had envisioned starting with UHMW and so that is the path I went down. The original chunk looked like this:
I used this material to make two "end caps" that positioned the battery in the correct location with the PC-680 box in all three axis (fore/aft, left/right, and vertically). This allows the battery to be secured in the box by the same aluminum bar and AN bolts as the PC-680. This approach also means that the battery cables reach the terminals without modifications.
The actual installation took just a couple of minutes: place the blocks into the battery box, place the Shorai battery into the blocks, install the battery straps, and then finally attach the battery cables.
The last part of the process was updating the logbook along with weight and balance information. Overall weight savings was exactly 11lbs; I'm sure this would be a bit more for folks who have a heavier PC-680. Since my RV has the training wheel up front along with a constant speed prop, saving 11lbs on the firewall was a welcome change.
Much has been written here and elsewhere about the merits of Lithium-Iron-Phosphate batteries (see this thread for a great discussion). Rather than re-hash the discussion around the tech, I wanted to share how I installed this battery in my RV without making any changes to the airframe, wiring, or battery box. I hope someone finds this helpful!
Operation
Since the first question I'm sure many will ask is "How well does it work?", I'll start with that. In short, I can tell no difference in normal operation between this battery and the PC-680. I have an IO-360-B1B w/8.5:1 pistons and dual P-mags and this battery spins the Hartzell BA prop with the same gusto as the PC-680, if not more. I've had it in weather down to -1ºF and it has performed as expected. I'm continuing to watch this carefully, as I have only about five hours of running time so far but I don't expect any surprises. I do like the weight savings however!
The Installation
The first step was, of course, to obtain said battery. I ordered the battery directly from Shorai and received it a few days later.
I had previously removed the PC-680 from the aircraft and compared the two side by side. Clearly, the Shorai battery is significantly smaller - but the weight difference is even more dramatic. Not wanting to count on published specs, I measured both batteries myself. The Shorai matched the published specifications in all respects, and indeed weighed only 2.3lbs. Interestingly, the only discrepancy with published specs I found was with the PC-680 - the Odyssey site claims the PC-680 weights 15.4lbs but mine measured 14.0lbs.
One of the goals for this upgrade was to be able to preserve the ability to do a "drop-in" upgrade. This preserves the possibility of going back to the PC-680 at some point in the future, and also eliminates changes to the airframe/FWF configuration. Since the Shorai battery is significantly smaller than the PC-680, that means that an adapter is needed to secure the batter within the larger space of the PC-680 battery box.
Enter a large chunk of UHMW plastic. I love working with this stuff - it's relatively cheap, it's easy to mill, and it's reasonably lightweight. Certainly other materials could be used - aluminum, or perhaps even wood - but I had envisioned starting with UHMW and so that is the path I went down. The original chunk looked like this:
I used this material to make two "end caps" that positioned the battery in the correct location with the PC-680 box in all three axis (fore/aft, left/right, and vertically). This allows the battery to be secured in the box by the same aluminum bar and AN bolts as the PC-680. This approach also means that the battery cables reach the terminals without modifications.
The actual installation took just a couple of minutes: place the blocks into the battery box, place the Shorai battery into the blocks, install the battery straps, and then finally attach the battery cables.
The last part of the process was updating the logbook along with weight and balance information. Overall weight savings was exactly 11lbs; I'm sure this would be a bit more for folks who have a heavier PC-680. Since my RV has the training wheel up front along with a constant speed prop, saving 11lbs on the firewall was a welcome change.
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