Plan is to put an extended baggage compartment, and put a lightweight battery behind it.
Also put the ELT behind the lid of the extended baggage compartment.

With this, the calculations are that instead of 70 pounds of ballast in the cargo area , I would only need about 20 (which is survival gear) in the extended baggage compartment.

Which lightweight batteries are available for the C170?

The only "Approved" lightweight battery is the SJS-J-16 battery, commonly referred to as the "Odyssey". It is a sealed lead acid battery, so can be installed on its side, which is the way I'd mount it, UNDER the extended baggage compartment, with a simple hinged door for access to the battery. The certification regulations specify an "Approved" lead acid battery.....and that Odyssey battery is TSO'd, so "approved".

I'd also mount the ELT the same way, UNDER the extended baggage floor. Picture below of ELT. Could easily do the same with battery laid on its side.

Mounting those things BEHIND the extended baggage will make access to them a BITCH! Unless, of course, you install a small access door in the side of the fuselage....meaning cutting into that recently painted surface....and, structure.....the skin is structure.

The other "lightweight" battery is the Earth X ETX 900. I don't believe there's an STC for that battery, and Earth X is quite clear that NONE of their batteries are "approved" for use in "Certificated" airplanes, such as the 170. They are being used in a number of Experimental aircraft, and the ETX 900 was specifically designed for that application, with various protection, etc.

I'd be reluctant to mount a lithium battery inside a fuselage, though the ETX 900 has overboard vents in case of venting. And, in any case, that far aft....

That said, the ETX 900 is ten pounds lighter than the Odyssey.




MTV

Thanks Mike, like the idea of mounting the battery and ELT under the extended baggage compartment.
I see Earth X makes a TSO battery, wouldn't that one work?

https://www.aircraftspruce.com/catalog/ ... -18242.php

motoadve wrote:Thanks Mike, like the idea of mounting the battery and ELT under the extended baggage compartment.
I see Earth X makes a TSO battery, wouldn't that one work?

https://www.aircraftspruce.com/catalog/ ... -18242.php

That battery is TSOd, but there is no STC. To be legal in a certificated airplane, it would also require either a STC or field approval.

While the “Odyssey” batteries are also not STCd in most airplanes, the FAA’s Instructions for continued airworthiness state that a battery in a certificated aircraft may be replaced with any approved LEAD ACID battery…..or words to that effect.

So, on that basis, my large 12 volt battery was replaced with a smaller “Odyssey” battery via a logbook entry.

Unfortunately, there is no such route to approve a lithium battery. And there is a not so good history of lithium batteries in aircraft. They have been used successfully in some applications (turbines, for example), but there have been issues in others.

I believe that Earth X has developed answers for those issues in their ETX 900 battery, which has overboard vents, overcharge/over discharge limit circuits, etc.

BUT….there is no valid approval in a 170 at present, short of a field approval. I’d print off the description of the ETX 900 from Earth X website, take it to your mechanic and see if he or she thinks they can get a field approval. Really depends on the FSDO. I understand some have been field approved, mostly in AK.

If you do elect to mount a battery aft, the location I noted is a good one. In my opinion.

Good luck.

MTV

mtv wrote: The only "Approved" lightweight battery is the SJS-J-16 battery, commonly referred to as the "Odyssey". It is a sealed lead acid battery, so can be installed on its side, which is the way I'd mount it, UNDER the extended baggage compartment, with a simple hinged door for access to the battery. .....I'd also mount the ELT the same way, UNDER the extended baggage floor. Picture below of ELT. Could easily do the same with battery laid on its side.
Mounting those things BEHIND the extended baggage will make access to them a BITCH! Unless, of course, you install a small access door in the side of the fuselage....meaning cutting into that recently painted surface....and, structure.....the skin is structure......

IMHO mounting those items aft of the extended baggage should create an access problem.
Just put an access door(s) in the panel closing in the aft end of the ext baggage,
or make that panel easily removable. Or both.
A stock early 180 has the battery & usually the ELT behind the standard baggage area, accessed as I described,
as did my old C150/150TD. No problems with access.

hotrod180 wrote:

mtv wrote: The only "Approved" lightweight battery is the SJS-J-16 battery, commonly referred to as the "Odyssey". It is a sealed lead acid battery, so can be installed on its side, which is the way I'd mount it, UNDER the extended baggage compartment, with a simple hinged door for access to the battery. .....I'd also mount the ELT the same way, UNDER the extended baggage floor. Picture below of ELT. Could easily do the same with battery laid on its side.
Mounting those things BEHIND the extended baggage will make access to them a BITCH! Unless, of course, you install a small access door in the side of the fuselage....meaning cutting into that recently painted surface....and, structure.....the skin is structure......

IMHO mounting those items aft of the extended baggage should create an access problem.
Just put an access door(s) in the panel closing in the aft end of the ext baggage,
or make that panel easily removable. Or both.
A stock early 180 has the battery & usually the ELT behind the standard baggage area, accessed as I described,
as did my old C150/150TD. No problems with access.

Yes, but there's a world of difference in just reaching through the baggage door, or sitting in the standard baggage compartment and reaching a battery that's just aft of the main baggage aft bulkhead, compared to having to literally crawl back into an extended baggage compartment, lay on your belly, and try to work on things....

My 175 came with a battery access door on the left side of the fuselage. IF I were going to mount this stuff ALL the way aft, that's the ONLY way I'd provide access.

BUT, the other issue with moving the battery waaaaay back behind the extended baggage AND using a small battery is that there is already significant line loss in the very long battery cables to the stock location. Moving them aft a ways isn't going to make a huge difference, but adding another three or four feet of cable probably isn't a great idea with these small batteries.

Me, when I switched to an Odyssey battery in my 175, I moved the battery to the firewall. I'd do that again, CG be damned. Short cables in cold weather are a good thing. And, those big cables aren't exactly light either.

MTV

What is the best option for extended baggage compartment?
I see
Airglass 5.5 pounds $1,500
Slikirk 11 pounds $820
Any other option out there?

hotrod180 wrote:

mtv wrote: The only "Approved" lightweight battery is the SJS-J-16 battery, commonly referred to as the "Odyssey". It is a sealed lead acid battery, so can be installed on its side, which is the way I'd mount it, UNDER the extended baggage compartment, with a simple hinged door for access to the battery. .....I'd also mount the ELT the same way, UNDER the extended baggage floor. Picture below of ELT. Could easily do the same with battery laid on its side.
Mounting those things BEHIND the extended baggage will make access to them a BITCH! Unless, of course, you install a small access door in the side of the fuselage....meaning cutting into that recently painted surface....and, structure.....the skin is structure......

IMHO mounting those items aft of the extended baggage should create an access problem.
Just put an access door(s) in the panel closing in the aft end of the ext baggage,
or make that panel easily removable. Or both.
A stock early 180 has the battery & usually the ELT behind the standard baggage area, accessed as I described,
as did my old C150/150TD. No problems with access.

I was thinking just that, will Velcro be legal to close the panel?

I have the airglass, I like it. I'd use riveted in nut plates instead of rivnuts. In fact the next time it comes out at annual I intend to replace the rivnuts with nut plates.
My ELT is behind the extended baggage, my battery is on the firewall.

I’m installing Airglas right now. I am using nut plates instead of the rivnuts - they just look automotive to me.

The glasswork (carbon) is superb, and the floor has a core and two deep stiffening ribs. Totally class product

As you can see I have an issue with my ELT, not sure where that will end up.

FWIW
https://www.aircraftspruce.com/catalog/ ... -18242.php

I'm considering an extended baggage for my 175 now. Unfortunately, Airglass doesn't have an STC for the 175, so if I go, it'll be Selkirk.

Airglas makes great stuff, and so does Selkirk. The one I had in my 170 was Selkirk...was long before Airglas got into baggage compartments.

I wouldn't hesitate to go with either one.

One thing I forgot to mention in my earlier message is bear in mind that these things all have a very low weight limit, like 50 pounds or less. Meaning, if you have to crawl back in there to service a battery or ELT.....you may be doing some damage. With the access doors to under the baggage floor, you can service things without having to actually put much weight on the extended baggage.

MTV

This thread may be helpful to the Odyssey vs. EarthX decision

https://backcountrypilot.org/forum/eart ... hx#p352715

If you don’t want to read the whole thread, my conclusion below. And possibly the heavier Odyssey would seem to further your CG goals.

“OP here. After some research, the switch simply wasn’t worth the 10ish pounds.

-Mounting a new box(or perhaps modifying the existing box),
-Installing a warning light in the panel
-Field approval hassle
-$700 for the battery

Or, order a new Odyssey for $185, and install it in 10 minutes.
Cranks our Pponk just fine”

When ya see what some will spend for titanium gear, the Earth X looks like a bargain for money spent vs weight saved.

I looked into the requirements for field approvals for the Li Iron batteries, and found that it's not even a possible route. STC only, so moving on. Odyssey is the way to go.

EarthX has their first STC for a 182, I think other models are coming soon. Did you call EarthX to see when 170s will be added?

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