What do you think about "e-soaring"?

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danmoser

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You know fire triangle, Fuel, Heat, Oxygen. Deny one no fire. So plenty of fuel is available, and heat is the problem so deny Oxygen.
Not quite correct.
Yes, once the electrolyte catches fire, Oxygen in the air is consumed, but Oxygen in a Lithium ion battery fire also comes from within the battery cells, specifically in the Nickel-oxide layers in the cathode (at least in NMC and NCA chemistries).
These cathode crystals exothermically decompose in a fire, releasing more heat & oxygen.
In fact, that's usually where the battery fires get started .. inside the cell.
In contrast, LFP cells (Lithium Iron Phosphate) have much more stable Iron Phosphate cathode crystals that release much less heat & oxygen when subjected to a fire.
That's a big reason why LFP cells are MUCH safer than NMC and NCA.
"The Limiting Factor" YouTube channel has a series of very informative videos with excellent explanations.
 
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John.Roo

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Not quite correct.
Yes, once the electrolyte catches fire, Oxygen in the air is consumed, but Oxygen in a Lithium ion battery fire also comes from within the battery cells, specifically in the Nickel-oxide layers in the cathode (at least in NMC and NCA chemistries).
These cathode crystals exothermically decompose in a fire, releasing more heat & oxygen.
In fact, that's usually where the battery fires get started .. inside the cell.
In contrast, LFP cells (Lithium Iron Phosphate) have much more stable Iron Phosphate cathode crystals that release much less heat & oxygen when subjected to a fire.
That's a big reason why LFP cells are MUCH safer than NMC and NCA.
"The Limiting Factor" YouTube channel has a series of very informative videos with excellent explanations.

I definitelly agree that Li-Po and Li-Ion cells are not ideal from safety point of view.
However actual weight difference is really signifficant.
For small battery pack (as mentionned - capacity 5-6 kWh) is not important only weight, but also reasonable "C" rate. Unfortunatelly we need at least 15 kW for safe takeoff (ideally with possibility to get a bit more for short time). For me is acceptable compromise 3C for takeoff and 1C for cruise.
And here is point where we need to make compromise.
LiPo - highest C rate. low weight, low safety.
LiFePO - low C rate, high weight, high safety.
LiIon- acceptable compromise between safety (known characteristics becouse of massive use in automotive industry) vs acceptable discharge rate.

It is still necessary to make battery box (boxes) with detailed temperature monitoring.

I found one interesting info.
Tesla has been using active cooling with space between cells, however now they changed cooling system to "cooling plate".
Due to complexity (and weight) I don´t expect to make active fluid cooling in small homebuild airplane.
However maybe could be helpfull to try to allow some airflow to battery box and cover top (or top and bottom) with Aluminium profiles like on passive PC coolers.
1643267202505.png
 

John.Roo

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I was a bit looking for reasonable priced cells....
I use like reference Sony VTC6 (3,7 V, 3 000 mAh, type 18650).
1643355098406.png
Seems that price is 2,80 USD - 3,80 USD.
Lets assume higher range - 3,80 USD.

Capacity:
6 kWh battery pack = 5 kWh of energy we can use (keeping 20% as reserve).

Weight:
6 kWh = 540 cells
540 cells = 540 x 50 g (range of weight is 48-50 g) = 27 kg

Price:
Cells - 540 x 3,8 = 2 052 USD only per cells.
3D printed holders - 3,74 USD for 100 pces = 41,14 USD for 1 100 pces (2 pces / cell)
1643355265349.png

Solding machine (investment only for fist time) = 160 USD.
Nickel solding strip (5 m is 11,54 USD....) = approx. 20 USD?

Balancers... later, afer discussion with e-bike producer.

Actually we are on approx. 30 kg battery pack with 6 kWh (5 kWh really useable) capacity.
Price 2 273,14 USD. With shipping... 2 500 USD?
6 kWh for 2 500 USD = 416 USD per kWh

No surprise :cool:
As expected... majority of price are cells. Every cent saved on cells will affect final price a lot.
In reality would be better to buy a bit more cells (you never know...).
Lets say +-5 % more = 560-570 cells. Better is to calculate with 570 cells.
Price 2,80 USD / cell = 1 596 USD.
Price 3,80 USD / cell = 2 166 USD.
Etc...

Rest of material...
Owners of 3D printer can print their own cell holders, however this is only a very small saving.

Case...
I found some Alu cases like this... with different sizes.

1643357138731.png

E-bike battery cases are very nice, only they seems to be a bit too small for or use...
1643358244088.png
Of course I will keep searching and asking for recommendations, however maybe this could be a way.
Close cells into Alu case and lead airstream from NACA intake arround box and out...

This ventilation can have two effects.
1) cooling down whole batt pack.
2) in case of fire leading gases out
...and one negative effect = feeding possible fire with a lot of air... 🤔

Reality and physical laws are tough opponents ;)
 
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John.Roo

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Range extender.....?
I am very glad that some teams are working on range extenders.
55 kW of cont. output power with 55 kg weight sounds promissing for small (2-4 seat) GA airplanes.
As usually - question is price and real performance, but at least we can see some progress 👍
 

John.Roo

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Seems that on Banggood (and for sure also on many other websites) are available interesting BMS systems 👍 I have to search more info about this affordable BMS.
For example this one is for LiFePO cells, but they are existing many types...
1643378527161.png
1643378543137.png
1643378789053.png
 

John.Roo

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For better impression how is done by professionalls in automotive industry - this is whole battery system of Audi e-Tron.
1643439973316.png
I already mentionned here before that would be very interesting to get one module to test it ;)
1643440740526.png
However seems that this would be not really optimal solution,
Reason is simple...
Capacity is OK (2,6 kWh), but voltage is very low.
Cells are solded in
3S 4P = 3 x 3,7 V = 11,1 V or
4S 3P = 4 x 3,7 V = 14.8 V
Info is from here...
It means you need min. 4 x 14.8 V packs for reasonable voltage.
4 x 14,8 V = 59,2 V and this means TakeOff current of 253 Amps (15 000 W / 59,2 V)
I would prefer lower Amps using at least 72 V (ideally arround 100 V) systems.
So lets go back to DiY systerms ;)
 
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John.Roo

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I will also try to visit this Czech company...
They are not really nearby from my house, however they seems to be really experienced and may they could give me some advices ;)
 

John.Roo

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Very interesting page 👍
A lot of usefull informations, advices and sources where to buy parts.
 

blane.c

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For better impression how is done by professionalls in automotive industry - this is whole battery system of Audi e-Tron.
View attachment 121318
I already mentionned here before that would be very interesting to get one module to test it ;)
View attachment 121319
However seems that this would be not really optimal solution,
Reason is simple...
Capacity is OK (2,6 kWh), but voltage is very low.
Cells are solded in
3S 4P = 3 x 3,7 V = 11,1 V or
4S 3P = 4 x 3,7 V = 14.8 V
Info is from here...
It means you need min. 4 x 14.8 V packs for reasonable voltage.
4 x 14,8 V = 59,2 V and this means TakeOff current of 253 Amps (15 000 W / 59,2 V)
I would prefer lower Amps using at least 72 V (ideally arround 100 V) systems.
So lets go back to DiY systerms ;)

I am curious that after reaching a voltage easily capable of shocking a person which 100v will do, why stop at a 100v? Why wouldn't it be better to go to higher voltage like 200v or maybe higher? Stopping of course before you get to a voltage that will arc over substantial distance like 600v will.
 

John.Roo

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I am curious that after reaching a voltage easily capable of shocking a person which 100v will do, why stop at a 100v? Why wouldn't it be better to go to higher voltage like 200v or maybe higher? Stopping of course before you get to a voltage that will arc over substantial distance like 600v will.
You are absolutelly right 👍
For bigger project I would definitelly go to higher voltage.
However in our case we are discussing (so far theoretically) about affordable system.
Controller or motor for voltage above 120 V is expensive.
If we try to keep voltage arround 100 V we can think about motors like MP 15470 (30 kW)
I suppose that run it at 15 kW or less could be reasonably safe....
1643479550587.png
For this motor would be max. voltage 100 V = 24S batery pack fully charged (24 x 4,2 V).
Above mentionned motor is actually for 650 USD.

Controller FRC 500A 28S could be OK for this motor and it is for 440 USD.
1643479865882.png
6 kWh battery was arround 2 500 USD (+ costs of box and BMS system) so without charger we are on...
3590 USD (650 USD + 440 USD + 2 500 USD)

Seems that woud be possible to make DIY propulsion system for 1 seat "glider like" type under 5 000 USD (I nstill eed to get more info about chargers and BMS systems).

For basic comparizon....
Small 2 stroke ICE motor like Polini Thor 303 (28 kW) is arround 4 460 USD (without VAT).

It is still a lot of DIY work, endurance and performance of electric propulsion with 6 kWh battery will be on lower border of realistic use, however I really like that we are discussing here above use of existing (and available) components and technical challenges.
Really thanks for that dear friends 👍

P.S.
I'm also watching a thread about "why a battery-powered plane will never have a significant range."
Honestly - I would be careful with the desire to have an electric aircraft with the same power as ICE-powered aircraft.

Why?
Because God has a really good sense of humor ;)

The same range does not automatically mean better batteries. It can also mean a significant deterioration of the range and use of aircraft with internal combustion engines. Due to environmental restrictions, price of fuel, high taxes aplied on airplanes with ICE propulsion or restricted airspaces (protected areas etc.). We can´t see inside heads of politicians and not all politicians are technically educated pilots ;)
So far, we are lucky to have the freedom to choose propulsion system that meets our individual requirements.
I hope and wish that we will have that freedom for as long as possible...
 

blane.c

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You are absolutelly right 👍
For bigger project I would definitelly go to higher voltage.
However in our case we are discussing (so far theoretically) about affordable system.
Controller or motor for voltage above 120 V is expensive.
If we try to keep voltage arround 100 V we can think about motors like MP 15470 (30 kW)
I suppose that run it at 15 kW or less could be reasonably safe....
View attachment 121336
For this motor would be max. voltage 100 V = 24S batery pack fully charged (24 x 4,2 V).
Above mentionned motor is actually for 650 USD.

Controller FRC 500A 28S could be OK for this motor and it is for 440 USD.
View attachment 121337
6 kWh battery was arround 2 500 USD (+ costs of box and BMS system) so without charger we are on...
3590 USD (650 USD + 440 USD + 2 500 USD)

Seems that woud be possible to make DIY propulsion system for 1 seat "glider like" type under 5 000 USD (I nstill eed to get more info about chargers and BMS systems).

For basic comparizon....
Small 2 stroke ICE motor like Polini Thor 303 (28 kW) is arround 4 460 USD (without VAT).

It is still a lot of DIY work, endurance and performance of electric propulsion with 6 kWh battery will be on lower border of realistic use, however I really like that we are discussing here above use of existing (and available) components and technical challenges.
Really thanks for that dear friends 👍

P.S.
I'm also watching a thread about "why a battery-powered plane will never have a significant range."
Honestly - I would be careful with the desire to have an electric aircraft with the same power as ICE-powered aircraft.

Why?
Because God has a really good sense of humor ;)

The same range does not automatically mean better batteries. It can also mean a significant deterioration of the range and use of aircraft with internal combustion engines. Due to environmental restrictions, price of fuel, high taxes aplied on airplanes with ICE propulsion or restricted airspaces (protected areas etc.). We can´t see inside heads of politicians and not all politicians are technically educated pilots ;)
So far, we are lucky to have the freedom to choose propulsion system that meets our individual requirements.
I hope and wish that we will have that freedom for as long as possible...

I have heard that if you want to humor God, tell him your plans.
 

blane.c

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Weight and time under power.

It is difficult to compare weight as it doesn't translate straight across, the weight of an ICE engine cowling is likely to be more than the weight of an electric motor cowling because the motor is more compact than an engine also other particulars of a motor mounting are likely to be lighter than an ICE for the same reason. I mention this because it would be nice to know apples to apples where you are starting from weight wise a clean sheet ICE powered compared to a clean sheet electric motor powered before and after you add gas to the tank of the ICE. Then you would know how much battery you can have "free" in regards to weight vs a ICE empty and then a typical fuel tank with fuel could be added and except for the fact that you lose weight as you progress through time with and ICE engine you would again have some "free" battery weight for the electric motor at least initially. Then the compromise for time aloft and additional battery weight and rules and regulations kick in.

I don't see how a clean sheet ICE craft can look the same as a clean sheet electric motor craft because to take advantage of the compactness of the electric motor would require different decision making. It depends on any number of factors after that would decide which clean sheet design would weigh more or less sans the powerplants and necessary accouterments such as landing weight and expected time powered aloft for examples.
 

John.Roo

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They're for jumbo-sized drones, but this is example of battery series that look pretty good for Part103/FLPHG drop in e-power -> Tattu Plus 1.0 16000mAh 44.4V 15C 12S1P Lipo Smart Battery Pack with AS150U Plug. Smart-packs with BMS, Panasonic 18650 cells, good packaging, and useable 140wh/kg 12s out of the box.
Interesting - thanks for link 👍
1643559190767.png
16 Ah and 44.4 V (12S) = 0,710 kWh
Weight is 4,7 kg.
With 8 packs you have 5,68 kWh capacity, weight will be 37,6 kg and it will cost 5 400 USD.
So it is +- 1 000 USD / kWh for Ready To Use solution.
 

John.Roo

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Weight and time under power.

It is difficult to compare weight as it doesn't translate straight across, the weight of an ICE engine cowling is likely to be more than the weight of an electric motor cowling because the motor is more compact than an engine also other particulars of a motor mounting are likely to be lighter than an ICE for the same reason. I mention this because it would be nice to know apples to apples where you are starting from weight wise a clean sheet ICE powered compared to a clean sheet electric motor powered before and after you add gas to the tank of the ICE. Then you would know how much battery you can have "free" in regards to weight vs a ICE empty and then a typical fuel tank with fuel could be added and except for the fact that you lose weight as you progress through time with and ICE engine you would again have some "free" battery weight for the electric motor at least initially. Then the compromise for time aloft and additional battery weight and rules and regulations kick in.

I don't see how a clean sheet ICE craft can look the same as a clean sheet electric motor craft because to take advantage of the compactness of the electric motor would require different decision making. It depends on any number of factors after that would decide which clean sheet design would weigh more or less sans the powerplants and necessary accouterments such as landing weight and expected time powered aloft for examples.
I agree that "ideal" electric airplane should be designed from beginning using all advantages (and many limitations) caused by characteristics of electric propulsion.
With actual battery limitations I see only one way how to make homebuild electric airplane - use TMG or self launch glider design. Seems to me the only way how to decrease power required for safe TakeOff and how to achieve lowest possible power required for horizontal flight.
Key is to find compromise between reasonable L/D and low weight.
I have some experience with composite materials so I am looking for types suitable for this mission with composite airframe.
Idea is not only to TakeOff, but also to use electric propulsion to "sponsor" L/D etc. (as mentionned in this thread before). Therefore I am not comparing for example range or weight with ICE propulsion.
Because limitations of electric propulsion (especially actual generation of batteries) are well known I just try to find way how could be possible to make it for price comparable with ICE propulsion.

You probably noticed I am conservative about design.
Well... reason is that pilots like to dream about special designs, however they want to fly with airplanes with predictible flight characteristics. "V" tails, flying wings, many motors on different places of airframe... why not - lets design it. However finally I have enough stress from new propulsion and I don´t need to be extra stressed by non standard spin or stall characteristics.

Numbers I am using (6 kWh battery, 15 kW motor, voltage arround 100 V....) are comming from experience from real flights. I have been flying with 400 V system used on two seat TMG and also with 60 V system used one one seater. The difference between complexity and prices is.... really huge.
For example only 400 V controller price was 5 000 EUR.

The ideas I am posting here are something like my "note book". Looking for solutions and trying to collect enough info about available systems. I can see large progress in the offer and performance of various components.
My idea is to make one whole DIY propulsion system and test it.
Normally I would definitelly prefer (and recommend) to buy whole system from known supplier, but actual prices are killing idea of simple and "cheap" e-glider so I would like to try this "challenge".

Lets see where this technical discussion will follow ;)
 

blane.c

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I have no interest in 400 volts, it'll arc across to great a distance and with the amperages involved it is another complication in safety. Low 300's like 330 max but preferably around 240v or 250v for max voltage something in there. Others can do as they wish.

But maybe for cost the 100v system may be better with a two seater, just use two motors. If a 100v system costs as little as a high voltage controller?
 

raumzeit

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I have no interest in 400 volts, it'll arc across to great a distance and with the amperages involved it is another complication in safety. Low 300's like 330 max but preferably around 240v or 250v for max voltage something in there. Others can do as they wish.

But maybe for cost the 100v system may be better with a two seater, just use two motors. If a 100v system costs as little as a high voltage controller?


Prices get expensive on the controllers with upping voltage with corresponding parts count, especially MOSFETs. The BOM on controllers before its even assembled is significant.

12-16s is well-suited voltage to power and physical setups in really small aircrafts. Higher voltage rapidly becomes desirable in bigger applications. Moving 100kw of mechanical power from battery in fuselage to a motor ten feet out on a wing - at 50v that wire is a heater even with giant heavy copper wire. Teslas run 440v internally to minimize those kinds of losses over much smaller component distances in their cars, but look at the power levels (500kw burst outputs and up) and it makes sense. An aero example is Lange gliders running a 40kw e-power setup on their big 21 meter self-launcher and I think that's 24s system and that makes perfect sense for the application.
 
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