LiFePo for turbine engine starting DIY

[Flyeyes]

Cool project!
To get 800a output you must have some massive battery cables running to the starter. How frequent are crank/no start or cranking a second time in attempt to start? IE how often does this get put to use more than once per day?

Normally, I'd be yelling and screaming about needing a BMS. But, your engine costs much more than any BMS.
I'd run the charge and the 70a discharge through the BMS and have some visible indicator of "ok to start" and a visible SOC to know if you've got enough juice to try again.

That's exactly what I'm thinking. To get power from the battery pack to the airplane I typically build a jumper with #2 welding cable and a standard GPU plug (picture attached). I've built battery packs from lead acid in the past, and am currently using a commercial 8s LiFePo battery to run the radios on the ground for training and maintenance.

Most of the time there is one start per any given day day, and the amp draw drops to almost nothing once fuel is introduced and the engine starts to turn itself (about 15 seconds). Once a month or so, we'll do a "desalinization wash" which involves running the starter for 30 seconds while spraying water into the engine to rinse salt deposits (caused by landings next to salt water). Each time we wash it will be twice in about five minutes. That would be the most severe use of the battery.

For radio maintenance/training/updating databases I'll plug in and draw probably 15-20 amps at 28 volts for up to an hour.

Once a year or so, we'll test systems like the flaps (electric motor) and landing gear (electric/hydraulic power pack) but these are trivial compared to the starter.

Eventually, I'd like to add inverter(s) to run incidental AC loads in the hangar in the case of a power outage, or needing power on the airport away from the hangar.

 

[bgflyguy]

I must have missed something, but have you considered LTO cells? 800amps is easy with a small set up. I have a 2p6s with 40ah yinlong cells I'm using as a starter pack.

 

[Flyeyes]

I must have missed something, but have you considered LTO cells? 800amps is easy with a small set up. I have a 2p6s with 40ah yinlong cells I'm using as a starter pack.View attachment 102714

Those aren't on my radar. I know I could google, but do you have a quick link handy?

 

[Flyeyes]

I have been googling, obviously I need to do some more research. At first pass those look ideal. The different cell voltage will take some different planning.

 

[Maitake]

I'm thinking maybe bypass the BMS during starting to avoid hot starts? Last thing you want is for the BMS to trash your turbine to save a weak cell. Def need a BMS for charging and monitoring though.
Maybe use a BMS with a contactor that can be wired parallel to the start switch. Or better yet battery, fuse, cable to starter plug. No way for bms to disconnect during start. Just use it for maintenance and charging.

 

[BoloMKXXVIII]

I would vote for the headway cells, but in a 5s configuration. Then you have to figure out charging.

 

[FLD]

Not a jet, but small SETP (Single Engine Turboprop). It has a single Pratt & Whitney PT-6 engine which has astonishing reliability. It can climb from sea level to its normal cruise altitude of 23-27,000 feet in about 17 minutes, and then cruises about 280 mph (240 Knots) while burning 28 gallons per hour of Jet fuel. Ours is the smaller red and white one View attachment 102707

Nice aircraft! I'm betting yours is considerably more comfortable than the T-38 and has much longer range. A friend flew the T-38 during his USAF Academy years and said it's amazing but definitely not a long range aircraft.
It's been close to 20 years since I stepped away from the general aviation world but I still have fond memories of the people I met and the aircraft I was fortunate enough to work on and fly. A few that I worked on were powered by the Wright R-1820, the RR/Packard V-1650 and the T-53 turboshaft.
I built a few lead-acid ground-start battery banks for both 14-volt and 28-volt systems back in the day (waaaay before lithium).
If I recall correctly (again, it's been almost 20 years), your PT6 can in certain instances pull more than 800 amps briefly at starter engagement. I can't remember the T-53 starter amp draw but it's voltage drop is similar to yours.
I'd encourage you to "over-build" your ground power supply in case you were to encounter a startup amp draw in excess of 800 amps.

 

[bgflyguy]

Anyone Use LTO for a Starting Battery?

It looks like Yinlong does better in 6s configurations. Has anyone actually reported trying Yinlong in a 5S config? At this point we can only say Yinglong works well with 6S, but we don’t know if that’s the best. I have completely oversized the batteries and have an lfp bank for "house"...

diysolarforum.com

Here are some spec sheets for the cells I used. I'm still not entirely sure on the max c discharge rate, but I suspect it's more about cell life than delivery.

For 28v you could probably do 11s and as many in parallel as you want for capacity and amperage.

How are you going to charge this? Jim has been testing a pack he leaves completely discharged for over a year now. He charges it back and tests periodically, but hasn't seen any degradation. So lvd isn't a big concern, it's mainly watching the top. I'm currently only using active balancers and no bms, but I'm only charging to 14-14.5v max for a 6s configuration. If you did 11s for 28v you would get better charging, but would be a lot closer to over charging a single cell if they go out of balance.

 

[Maintenance guy]

These are the beasts These cells are in two in parallel and can push 400 amps continuous with 800 amp peak per 16 ah cell. these are better then headways, are cheaper and put out more amps. just add the proper buss bars to very thick cables and you are home free. use a BMS to charge only running the start cables direct off the buss bars.

 

[Flyeyes]

These are the beasts These cells are in two in parallel and can push 400 amps continuous with 800 amp peak per 16 ah cell. these are better then headways, are cheaper and put out more amps. just add the proper buss bars to very thick cables and you are home free. use a BMS to charge only running the start cables direct off the buss bars.

That’s a great find. I missed those on the website, was about to buy two of the headway packs and parallel them. These look better for my use case

 

[Maintenance guy]

They sell the rods to compress them and sell the buss bars but not 800 amp though. They already have the holders on them and the rod holes to compress them.
Awesome and good luck.! Now go build the beast!.
PS. I am so glad I caught you in time. That is what humans are supposed to do, help one another.

 

[Flyeyes]

I’m trying to keep it simple ( my understanding of these batteries is pretty basic, hence my questions). I think I can make bus bars myself though, I do have a mill with a 5 foot bed in the back of the hangar.

my personality is such that I always have 5 projects going at the same time, but I just ordered 16 of these cells and a BMS, so I’m thinking it’s a couple of weekends and I’ll have it functiona.

 

[sunshine_eggo]

PA-46-350P with a PT6A-34?

 

[Maintenance guy]

You sound just like me as I always am doing something. Yes make the buss bars yourself and I am assuming you are going 8s2p. i would think you need more in parallel like at least 4 but hey rock on Flyeyes.
CONGRATS!

 

[Flyeyes]

You sound just like me as I always am doing something. Yes make the buss bars yourself and I am assuming you are going 8s2p. i would think you need more in parallel like at least 4 but hey rock on Flyeyes.
CONGRATS!

Adding more should be pretty simple. I have a big pile of 1” square mild steel tube at the hangar for projects like this, so expanding a frame is trivial. A few weeks ago I made my more or less annual pilgrimage to the Oshkosh air show, and got to talk to a bunch of vendors.

The Pratt & Whitney guys had no answers, said the starters were an airframe part and I needed to talk to the airframe guy. I talked to Raisbeck and Blackhawk as well as Rocket Engineering, and got numbers from 200-600 as peak amp. Everybody agreed that designing to 800 was plenty of overkill.

Our airplane is one of the 20% or so of PA46 JetProps with the smaller PT6-21 engine instead of the -34 or -35. It’s the same engine as a billion 90 series Kingairs, so spares are plentiful and relatively cheap. Down low it’s equivalent to the bigger engines, but temps out in the high teens so a bit slower climb and less power (and fuel burn) in the flight levels. For our typical 350-500 NM legs it is cheaper to run.

 

[sunshine_eggo]

The Pratt & Whitney guys had no answers, said the starters were an airframe part and I needed to talk to the airframe guy. I talked to Raisbeck and Blackhawk as well as Rocket Engineering, and got numbers from 200-600 as peak amp. Everybody agreed that designing to 800 was plenty of overkill.

You try putting a clamp DC ammeter on one of the leads to measure it?

 

[Flyeyes]

You try putting a clamp DC ammeter on one of the leads to measure it?

I literally just ordered a new clamp ammeter for that reason. Arrived two days ago.

 

[FLD]

Not that this has any bearing on the thread's subject;
My wife and I had hoped to attend this year's Airventure, camping in Camp Scholler for the week. Unfortunately, my health issues prevented us from going. Same thing happened last year. Darn. Next year for sure!
Are you still planning on building a 28-volt battery? Or will it be a 24-volt battery?

 

[Flyeyes]

Not that this has any bearing on the thread's subject;
My wife and I had hoped to attend this year's Airventure, camping in Camp Scholler for the week. Unfortunately, my health issues prevented us from going. Same thing happened last year. Darn. Next year for sure!
Are you still planning on building a 28-volt battery? Or will it be a 24-volt battery?

It should be close to 29-30 volts fully charged at 8s. There will be a little voltage loss through the welding cable but not much.

I have attended Oshkosh almost every possible way, camping some years in Scholler, and a few times under the wing of an airplane. Once I camped with the plane in Find du Lac.

This year I flew into Madison, WI and rented a car on Turo to drive into camp Scholler. It was easy, and I was able to share a site with old friends who go every year and set up a week in advance.

As long as the weather is decent, it’s great to tent camp, and wake up to the sound of warbirds overhead doing dawn patrol. This year, I was very close to the TBM and Cirrus hospitality tents, and they had coffee stations set up within about 50 yards of my campsite.

 

[Maintenance guy]

Flyeyes;​

You are going to knock them for a loop with your new starter pack. I am grinning right now hehe!. I have a 48 volt pack I am building and used the 60280's from batteryhookup. I know my bus buss bars are over kill but hey, I always go overboard hehehe!. The pack is for a four wheel two person buggy using 29 inch white three spoke rims. 100 amp BMS with a 48 volt 57 ahr 16S in a 8S2P config bat. Here is the pic of the buss bars. Been so busy I haven't finished them yet. 1 1/2 x 1/8 inch thick with a top amperage of like 385.




I figured you might need this third pic, is a DC Buss ampere chart.
I want to build a starter pack for Auto's from the one I showed and you bought. They are unmatched and a step above almost anything out there. Would love to build a huge bank for a home with those you bought, talk about headroom hehe.