EarthX Battery Bracket

Why EarthX?

For main-ship power I chose to go with an EarthX ETX900 battery.  This lithium based battery has built-in battery management to prevent among over things... battery runaway that have caused laptops and hover-boards alike to catch on fire.  Having your battery catch on fire in flight (Or in the hangar) would be a very bad situation.  Not the first to go this route, others have been flying successfully with these batteries for years and have had very few problems, and the problems I've heard of have been non-critical issues that the company has taken care of.  I'll also have a fault detection light on my panel so I will be able to see any issue prior to cranking up the plane.

The benefits going lithium are obvious to anyone who has messed with lead acid vehicle batteries.  The typical single engine plane battery weights 22+ lbs, this weights 4.9 lbs.  Given all the other stuff I'm shoving into the plane a close to 20 lbs weight savings will be great.  Especially since it's in the same area of the air conditioning evaporator, it should offset enough to bring the plane into normal W&B limits. When I opened the box and pulled the battery out two things became immediately obvious. One was how light it is, you could seriously play catch with it if you wanted.  Two the form factor is a lot smaller than a car/boat/airplane battery.

Solution

The RV-10 typical battery pad area in the tailcone is sized to fit a typical plane battery.  I searched around to see what others have done and really couldn't find many pictures, which drove my decision to do this write up.  I did find this picture which shows a dual battery setup and a ADAHRS shelve.  Looks great but I'm doing the dual battery/dual alternator system a bit different so didn't need two full size batteries.

The problem with the size of the battery and it not fitting is that the stock system relies on the sides of the battery platform to keep it from shifting and a bar that gets screwed down to keep it from falling out.  Outside of the issue of having this thing slide around, I'm not to keen on having a strip of conductive metal crossing the top of the battery which then is sitting directly over the terminals.  Even pushing it to one of the sides you still have the bar not really securing it very well. So I decided just to make one from my pile of scrap.

The solution I came up with is very easy and just took a few hours to put together.  I took a piece of angle and match drilled the original bolt pattern towards the outward edge.  It doesn't really follow rule of thumb on hole diameters to the edge, however this isn't structural and if it's exerting that much force on the battery bracket I have other issues. Setting the piece in the box on top of the battery, with the bolts through gives you some reference points for taking a chunk out so it clears the top of the battery.

With the clearance made I spaced out a few rivet holes and simply took another piece of angle flipped upside down to hold the back of the battery.  This was a little tricky because you want the battery in the holder, bracket on top to match drill, but not break through the other side and end up drilling into the battery.  I just drilled enough that I could take it all off and finish the holes on the workbench.  I did one final test fit with some AN426AD-4-5 rivets just pushed through from the bottom up to ensure everything was going to work out. Had no fit issues so just cleaned up the edges of the pieces to make sure nothing was sharp then countersunk and drove the rivets from the bottom up.  Went ahead and tossed some primer on the part and got working with the bolts.

The stock bolts are too long to be used with this smaller form battery.  I decided to just cut off the existing thread and retread about an inch back.  Using just a standard pipecutter works well for these types of things.  After I took the threads off, cleaned it up a bit with the grinder and used a 1/4 28 die to retread.  Larger bolts are harder to get started and get cut, takes a lot of WD40 and some back and forth.  In the end I had cut bolts and a primed battery bracket, took a quick snapshot of the fit.

Gave the primer a bit of time to cure and then hit it with some top coat to match the rest of the tailcone area.  After a night of curing I finished up the installation by applying some self-adhesive gasket material to the part that will connect the battery as well as on the battery pad itself.  This is the same material I used for the baggage door and has some non-skid qualities to it.

I couldn't be more happy with the results.  The bracket is clear of the terminals, and is solidly held in place. The gasket material on the bracket and the bottom prevent it from moving at all. There shouldn't be any chaffing either since there's a bit of clearance around the entire bracket top area.  All in all I call this a success!