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Earthx ETX900-TSO + FAtlee Dodge Battery Box in a PA-18-95

sdischer

sdischer

ATP, CFII, A&P
MEMBER
COLLEGE STATION, TX
I already have a B&C generator and starter and I now am ready to lose 25 pounds (and several hundred $) from behind the back seat by dumping the old 30# battery.

1. Has anyone been successful getting ETX900-TSO battery approved in a certified A/C? Process, 337 or what?

2. Should I put it under the seat or is the firewall an option?

3. Should I be concerned about sitting on top of a potential fire if under the seat?

I don't know much about these batteries other than they are lightweight, powerful and expensive and potentially explosive if overcharged but hopefully the B&C generator, regulator and crowbar circuit prevents that.

PS: Any "helpful" advice like "remove the electrical system and throw it away", don't, I already know that, and if I want to prop a plane I will fly my J3 which I have owned and propped for 30 years. Been there, done that, no more T-Shirts needed. I am spoiled now and I like pushing the button!

Thanks ALL!
 
It's a good setup. I like them under the seat as it's handy for maintenance and away from engine heat. Realistically, it's light enough to put most anywhere handy. The fire thing comes up once in a while but these are NOT the 'lithium' batteries that you hear horror stories about. Different chemistry. I personally only know of one fire involving an EarthX and it took place when the system was first powered up, so I don't believe the battery was at fault. Read the instructions with the battery. EarthX usually states that a specific model battery cannot be used with an alternator above a certain size. So make sure your B&C is not larger than that limit.

I'd replace the battery cables with new 4ga copper cables and put a master relay on the battery tray. Maybe a new braided ground from the crankcase to the fuselage tubes. That will give you an electrical system just like every other aircraft out there. And I'm one of those crazy guys that installs batteries and signs them off because they meet the requirements of CAR3.

Web
 
Legally, installing the battery would be no different than installing any other battery in the stock location since it's a TSO'd battery. Just a simple logbook entry notating the battery was replaced. The relocation of the battery from the stock location however is considered a major change and would require an STC as well as a form 337 to be submitted to the FAA to notify of a change.

It would be best to relocate it to under the seat since Atlee has a nice STC'd battery relocation kit for that.

Like was already said, the EarthX batteries are not a normal lithium battery but a lithium-iron battery that isn't prone to heating up/combusting like a Li/Ion type battery. No concern for fire with these batteries.
 
Where is your CG right now? I would recommend leaving the light weight battery in the original location behind the baggage, otherwise you will likely need ballast in the baggage compartment to offset the heavy nose you created. Ask me how I know...
 
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Moving a battery doesn’t require an STC or field approval BUT 43.13-2B doesn’t include lithium batteries, so that part may need an approval. I’ll leave that for others to sort. As for the battery on the firewall? Mine’s on the cabin side of the firewall. I’ve seen installations on the cowl side, too, but I was out of room on that side. I recommend the battery status light in the panel. My first battery flashed a code and had to be replaced. I never thought I was in danger but EarthX advised me not to fly it until the battery was replaced. Other than that my battery has been perfect. And to the alternator output? I recall that being an issue with the smaller batteries. The 900 has the capacity for any alternator you’re likely to have in a Cub.
 
MZ18 said:
Where is your CG right now? I would recommend leaving the light weight battery in the original location behind the baggage, otherwise you will likely need ballast in the baggage compartment to offset the heavy nose you created. Ask me how I know...
Click to expand...

Good point!


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"Moving a battery doesn’t require an STC or field approval"

My FSDO guy said it did. CG change, and strength of mounting issues for "massive" items in the passenger space. Field approval was easy though. But that was one inspector in one FSDO.
 
This 30 second video of my test to destruction of one of my old e bike batteries was very reassuring. Note it was a quality battery, assembled in the US, with a well designed BMS, and with Samsung cells, NOT no name cells from China. The old battery: https://lunacycle.com/52v-mighty-mini-cube-samsung-ebike-battery-pack-30q-6ah-3-pounds/

The video:https://youtu.be/-1W66PeBdac

The new battery will be even better/safer, as it's fully potted in some type of silicone compound, and the connections are all done using ultrasound I believe. So having an EarthX in the plane is the least of my concerns, and it's mounted right on the floor, inside, in unused space between the rudder pedals it's so tiny.
 
MZ18 said:
Where is your CG right now? I would recommend leaving the light weight battery in the original location behind the baggage, otherwise you will likely need ballast in the baggage compartment to offset the heavy nose you created. Ask me how I know...
Click to expand...

sdischer said:
Good point!
Click to expand...
Taking out 30 lbs and replacing it with 5.4 lbs is good. Shifting the CG forward, not so good. Better do some W&B calculations, you may find moving the battery further aft is the answer.
 
Putting the battery under the front seat of a 90 hp Super Cub was a huge mistake on my part many years ago. CG is much better with it aft. Elevator effectiveness when slow was poor.
 
Steve Pierce said:
Putting the battery under the front seat of a 90 hp Super Cub was a huge mistake on my part many years ago. CG is much better with it aft. Elevator effectiveness when slow was poor.
Click to expand...
Thanks. Experiences like this are very valuable. Leaving the battery where it is is also 10x easier for me!
 
I’ve never flown a plane without 30-40# of tools and “survival” stuff pushed into the back. If I had the chance to put an improved battery up front using new, shorter cables and save weight doing it? I’d do it and adjust the tag-along ballast for CG. Or install fixed ballast way aft if necessary. You’d still save weight while improving utility.
 
skywagon8a said:
Still do a W&B. You may find it advantageous to add ballast at the tail post.
Click to expand...

That has always been my advice for any proposed alteration. Work up a W&B for the proposed configuration before you commit to it. Do a full work up, most forward and most aft to see what it does to the usability of the airplane. Keep in mind, most airplanes prefer CG towards the back end of the envelope. Tailwheel airplanes land better, cruise speed will be greater. You do sacrifice some stability, but as long as it is within the envelope you are good.


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MZ18 said:
Where is your CG right now? I would recommend leaving the light weight battery in the original location behind the baggage, otherwise you will likely need ballast in the baggage compartment to offset the heavy nose you created. Ask me how I know...
Click to expand...

6B38FE7C-FA9A-4B3F-8394-CE72AFA0EE8A.jpeg

mine isn’t super nose heavy but I machined a steel spacer for the baby bushwheel. Adds 8lbs to the tail.
 

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Use caution adding mass at the extreme end of the airplane. While bringing it into the published CG range, it can have a significant impact on spin characteristics. Think of a spinning object with all the mass on the extreme outside radius, lots of momentum. The TC for the Howard requires a placard for no intentional spins if ballast is installed on the rudder post!


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dgapilot said:
Use caution adding mass at the extreme end of the airplane. While bringing it into the published CG range, it can have a significant impact on spin characteristics. Think of a spinning object with all the mass on the extreme outside radius, lots of momentum. The TC for the Howard requires a placard for no intentional spins if ballast is installed on the rudder post!
Click to expand...
Did you ever spin the Howard? What was the nose down spinning angle?
I had to place a roll of lead flashing at the tail post in my TCOW Cub on floats to get the stall break in order for the spin to happen. Then the nose was very low in the spin with no tendency to flatten. Too much lead in the tail would make for the situation you describe in a Cub, IF the plane's spinning angle was relatively level/flat under normal conditions.
 
One characteristic of the EarthX is that they don't charge well when cold. We left mine in the original spot behind the baggage in the Maule for W&B issues. Charge issues a couple times in winter/fall.

We are moving it forward now, and dealing with how to adjust the balance later.

As an aside, It appears I will reduce weight 1.5 lbs by shortening up the cable.
 
A consideration of mine as to where to mount the Earthx has to do with ease of connecting a jump pack. Under seat in a cub is ideal in that I can control all connections, start engine, manipulate throttle, and disconnect jump pack without doing any unusual yoga poses.

I'm in the planning process of doing that my Maule too. George , if you come up with any clever ideas feel free to post them.

Jerry
 
cubflier said:
A consideration of mine as to where to mount the Earthx has to do with ease of connecting a jump pack. Under seat in a cub is ideal in that I can control all connections, start engine, manipulate throttle, and disconnect jump pack without doing any unusual yoga poses.

Jerry
Click to expand...
IF you have a jump pack concern rather than place the battery in an unfavorable location for CG purposes, just install a wire in a convenient location to connect the jump pack into the system. CG is more important than many seem to imagine.
 
wireweinie said:
8 lbs all the way back in the tail seems like a LOT. What caused the need for it?

Nice machine work and great thinking 'outside the box' by the way.

Web
Click to expand...
Tom is too cool to just gorilla tape 10lbs of lead to his tail spring like all the rest of us gentiles do before a STOL comp;-)
 
skywagon8a said:
IF you have a jump pack concern rather than place the battery in an unfavorable location for CG purposes, just install a wire in a convenient location to connect the jump pack into the system. CG is more important than many seem to imagine.
Click to expand...
If you are that concerned about CG then keep the heavy battery in it's original location. CG is such a moving target in the way I fly that it's hard for me get worked up about such a simple utilitarian mod. I'll just move that propane bottle a little further aft.

Jerry
 
cubflier said:
A consideration of mine as to where to mount the Earthx has to do with ease of connecting a jump pack. Under seat in a cub is ideal in that I can control all connections, start engine, manipulate throttle, and disconnect jump pack without doing any unusual yoga poses.

I'm in the planning process of doing that my Maule too. George , if you come up with any clever ideas feel free to post them.

Jerry
Click to expand...

I am going to be unconventional and creative in the Maule: Use the Maule placement under the right front seat where it is approved! :wink:

To access slide the seat forward and flip it back.
 
wireweinie said:
8 lbs all the way back in the tail seems like a LOT. What caused the need for it?

Nice machine work and great thinking 'outside the box' by the way.

Web
Click to expand...

Stock cub with the battery under the front seat. Front mount cooler the cg is forward. Gets worse when I take my crap out and fly in the stol contest. Brings the empty cg with low fuel a little bit further back to when the cub had the battery in the stock spot. Has an upper baggage now.


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