Alternate Battery Brands

[Shadrach]

2 hours ago, A64Pilot said:

Now I’m a huge fan of Lithium batteries and in particular LifePo4, AKA LFP...

If I flew IFR there is no way I’d consider a battery with less AH available, I can’t imagine being in the clouds without a functioning electrical system, that’s often a death sentence, and I can’t imagine the FAA let that slide, it has to be a mistake, surely the battery has at least as much reserve capacity of the lead acid it replaces?

I just replaced four 85 lbs each Trojan 150 AH batteries in my golf cart with four 25 lb 100 AH LifePo4 batteries and so far couldn’t be happier, even though I lost 50 AH in theory I didn’t lose any based on you can cycle a LFP battery deeper with less detrimental effect than lead. I lost 240 lbs though and you can really tell the weight in performance, the LFP charges to much higher voltage and less voltage sag under load really makes a huge difference in the cart...

You need to rebadged that golf cart with  “Superleggera” nomenclature…

You clearly have a deeper knowledge than many of us regarding batteries. 
Have you analyzed the specs? It seems to me that 29Ah vs. 15.6Ah is a pretty straight forward comparison. Is it possible that original batteries spec’d in the TCDS were much lower capacity? For instance a Gil G35 is a 23Ah battery.

EarthX ETX 900

Concord RG-35A

Specifications

Voltage 12 Volt Capacity 29 Ah Weight 29.5 lb / 13.4 kg  IPP 23° C  1000 -18° C  675 -30° C  475 IPR 23° C  800 -18° C  575 -30° C  350 Heated No Engine Starting Yes Cold Cranking Amps 390

[Shadrach]

7 minutes ago, Fly Boomer said:

Concorde has PMA, so that's the legal end.  I guess eligibility hinges on the word "identical".  We tend to focus on amp-hours and such, but weight should be part of that determination too.

I believe it is (+/- a percentage of original spec). That is likely why the EarthX is STC’d rather than PMA’d.  I’m sure it could be STC’d for the long bodies with the addition of Charlie weights, but there would be no market for it.

[philiplane]

35 minutes ago, Shadrach said:

You need to rebadged that golf cart with  “Superleggera” nomenclature…

You clearly have a deeper knowledge than many of us regarding batteries. 
Have you analyzed the specs? It seems to me that 29Ah vs. 15.6Ah is a pretty straight forward comparison. Is it possible that original batteries spec’d in the TCDS were much lower capacity? For instance a Gil G35 is a 23Ah battery.

EarthX ETX 900

Concord RG-35A

Specifications

Voltage 12 Volt Capacity 29 Ah Weight 29.5 lb / 13.4 kg  IPP 23° C  1000 -18° C  675 -30° C  475 IPR 23° C  800 -18° C  575 -30° C  350 Heated No Engine Starting Yes Cold Cranking Amps 390

The Gill 35 has a 40 amp discharge rate for 30 minutes, whereas the ETX is 31 amps to 100 percent discharged. That's a 25 percent loss of capacity in an alternator-out situation. The Gill has a 23 amp hour rating, versus the 15.6 amp hour for the ETX, which is 30 percent lower than the Gill. I don't know why anyone would choose to give up any capacity, especially at twice the price. 

Edited December 18, 2023 by philiplane

[A64Pilot]

We lived aboard a sailboat for three years cruising, not it a Marina except hurricane season.

Most everything that makes it cruising and not camping relies on your battery bank, as they cost a LOT of money and improper care will kill a bank every year you get smart on their care and feeding. I had 1,000W of solar panels and that wasn’t enough to keep the bank full so I had a 165 amp alternator on a serpentine belt because you can’t pull that kind of amperage from a V belt, it will slip, two generators and a 125 amp inverter / charger and a standalone 60 amp charger, anytime an engine was running  I was harvesting as much energy as I could to charge that bank and keep it healthy, as well as of course what I could get from Solar.

Wind generators are mostly a waste of time, it takes a LOT of wind to make significant power and if the wind is that strong your in a protected anchorage hiding from it.

So full time cruisers become battery smart out of necessity.

Lithium is the Holy Grail for off grid, lightweight, doesn’t suffer from partial SOC cycling in fact you really never want to fully charge, lasts a LOT longer as in years longer and it can take just about as much charge you can throw at it, you can charge in an hour or two or less where AGM takes 5 hours no matter how big the charger is and you don’t have 5 hours of good Solar so no matter how many panels unless grossly oversized you can’t fully recharge a lead battery by Solar alone and if you don’t fully recharge the bank begins to die from sulphation.

If your curious as to how fast is it possible to charge an AGM battery this article explains it, and the test battery is a Lifeline which is essentially identical to our aircraft Concorde batteries, both made by Concorde.

https://marinehowto.com/how-fast-can-an-agm-battery-be-charged/

Anyway if we were still on the boat I’d certainly have a LifePo4 bank now and be much happier, but the Pandemic and my knees needing replacements, plus 2% Mortgage rates made ending cruising and buying a house make more sense.

[Shadrach]

22 minutes ago, philiplane said:

The Gill 35 has a 40 amp discharge rate for 30 minutes, whereas the ETX is 31 amps to 100 percent discharged. That's a 25 percent loss of capacity in an alternator-out situation. The Gill has a 23 amp hour rating, versus the 15.6 amp hour for the ETX, which is 30 percent lower than the Gill. I don't know why anyone would choose to give up any capacity, especially at twice the price. 

There is no reason other than weight savings. 25 pounds of weight loss represents as much as a 3% increase in UL for some of the more portly birds. For me it represents a substantial step towards configuring my plane to meet or exceed the factory marketed UL of 1100lbs.

[EricJ]

1 hour ago, Shadrach said:

It’s an interesting question. After researching the subject a bit, it appears that any company can apply for PMA under 21.303 and receive installation eligibility provided the component is identical to (or better than) the component it replaces. Most of our aircraft are flying with parts (by STC or PMA eligibility) that not specifically listed in the TCDS.

Some of the processes are not nearly as difficult or rigorous as we tend to imagine.   When I was developing avionics for airliners we used "qual by similarity" a lot.   If something remotely similar had been done and qualified before, we referenced the crap out of it so that we didn't have to do it again.   The FAA seemed to like that, too, since it saved them a lot of evaluation time.  

[A64Pilot]

27 minutes ago, EricJ said:

Some of the processes are not nearly as difficult or rigorous as we tend to imagine.   When I was developing avionics for airliners we used "qual by similarity" a lot.   If something remotely similar had been done and qualified before, we referenced the crap out of it so that we didn't have to do it again.   The FAA seemed to like that, too, since it saved them a lot of evaluation time.  

It really depends greatly on who you get, FSDO wise some years ago the FAA let all the inspectors know they they can individually be held liable for their actions that they personally could be sued.

I have no idea how realistic that is but I don’t believe it was coincidental that was when the No more field approval policies came into effect. There are still field approvals, but 99% of them come from an inspector that you have known for years and have a history with.

Basically an inspector has nothing to gain by granting a field approval, and nothing to lose by not, excepting lessening their work load.

Most often to get what you want means hiring a DER as they accept liability and it lets the FAA inspector off of the hook/

 I don’t know who issues STC’s but I have seen ATL FSDO rescind one, I would think ACO would issue them as they are the keepers of the TCDS etc.

The Who’s on first has always been sort of vague with the FAA