What do you think about "e-soaring"?

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John.Roo

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Cheap, safe, and long-lasting Lithium Iron Phosphate cells (LFP) keep improving their performance, lately achieving specific energy in excess of 200 Wh/kg at Guoxuan High-Tech in China, AKA "Gotion."
This should be plenty good enough for most e-soaring aircraft.
Gotion is now establishing a HUGE production plant in the US in a joint venture with an unnamed EV manufacturer: Large US manufacturer orders LFP cells from Gotion - electrive.com
Now we learn that Gotion's HQ in the US will be located in .. drumroll .. Fremont, California.
No prizes for guessing which EV manufacturer. :D
Look for an announcement soon.. probably Wednesday, would be my guess. ;)
LFP 210 Wh / kg? That sounds really interesting.
Safety of LiFePO calls is very good so I hope that also price will be OK ;)

GEB Battery offers Li-Po cells 10 000 mAh (3,7 V, 182 g).
It means 50 kg battery = 9,99 kWh (+ case, wiring BMS etc.... only cells capacity)

Or Li-Ion 6 000 mAh (3,7 V, 140 g).
It means 50 kg battery = 7,925 kWh.

This new LiFePO would have capacity of 50 kg battery 10,5 kWh.
Hope it has no special conditions like 100 cycles lifetime.... 🤔

This battery together with high efficiency solar cells could be very interesting (and safe) combination 👍
 

John.Roo

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I have been looking for components you need to make your own battery.

Of course you need cells ;) - that depends on type of application, availability and acceptable price/capacity ratio.

1643053750224.png

Nice help are cell holders...
They are plenty of available types for every type cell I can imagine.
1643053276989.png

Cell solding machine will be probably also "must have component".
They are many affordable types available
1643053530496.png

Than you need nickel strip tape...
1643053622192.png1643053700652.png
And than starts a bit more sophisticated work - balancers.
I will try to meet my friend producing electric bicycles to get more info about balancers for small battery packs.

It is not easy work and probably will be necessary to "sacrifice" some old cells to learn how to solder it perfectly.
It will be also a bit boring - for 5 kWh battery (reasonable minimum size for one seat ultralight) you need for example 450 pces of Sony VTC6 (typical Li-Ion 18650 cell with 3 000 mAh capacity). Imagine to solder together....

Positive is that you can decrease final price and also make repairs / modifications.
200 pces of above mentionned Sony VTC6 = 670 USD.
Total capacty = 2,22 kWh = 300 USD / kWh.
OK, price is not low like automotive industry (150 USD / kWh) but still better than 1 000 EUR / kWh (typical price for solutions available in EU).

However I will probably start with small batery for electric bicycle.
Set of electric motor + accesories has affordable price (check Bafang motors) and I can gain a lot of positive points from my wife if I modify her bicycle ;)
1643054600651.png
 

Vigilant1

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...and then starts a bit more sophisticated work - balancers.
I will try to meet my friend producing electric bicycles to get more info about balancers for small battery packs.
....
Positive is that you can decrease final price and also make repairs / modifications.
So, if you are looking into this, what attributes would be especially useful in a battery specifically intended to power an aircraft? Things that come to mind:
- Fine grain in-battery health monitoring. Perhaps our airplane battery shouldn't be a single big pile of cells wired in series and parallel, but many monitorable (and in-flight shuntable) packages of cells. Got an overheat/anomalous voltage in one sub-battery? Take that sub-battery offline and continue flying. Do diagnostics on the ground, but prevent an inflight fire with monitoring and inflight actions before things turn critical.
- Cooling to improve safe C-rate (charging and discharging). Lots easier with more cells exposed to your chosen coolant working fluid (air or otherwise).
- Sub-battery containers to contain/limit effects of a thermal runaway. Facilitate active suppression of a fire? Intumescent coatings are light and effective within limits, can they slow the spread of fire and buy an extra 30 critical seconds in a bad situation?
- Plug-and-play subbatteries of convenient size and weight? There will be use cases where it is not optimum to charge batteries in the aircraft (where safe charging rates are just too slow, and a leisurely recharging on the ground extends the expected lifetime of the batteries). Being able to swap out twelve 10 lb sub-units is a lot more convenient than a single 120 lb battery or two 60 lb units.

To me, the safety aspects are top priority. A fire in a car or scooter battery is a big deal, but still the options in those cases are likely MUCH better than a runaway inflight fire in an airplane. I'd go so far as to suggest that pilots who aren't concerned about inflight fire (regardless of power source) haven't given the issue much thought (or they fly gliders).

Oh, and we need cheap, light, powerful, and reliable.
 
Last edited:

John.Roo

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So, if you are looking into this, what attributes would be especially useful in a battery specifically intended to power an aircraft? Things that come to mind:
- Fine grain in-battery health monitoring. Perhaps our airplane battery shouldn't be a single big pile of cells wired in series and parallel, but many monitorable (and in-flight shuntable) packages of cells. Got an overheat/anomalous voltage in one sub-battery? Take that sub-battery offline and continue flying. Do diagnostics on the ground, but prevent an inflight fire with monitoring and inflight actions before things turn critical.
- Cooling to improve safe C-rate (charging and discharging). Lots easier with more cells exposed to your chosen coolant working fluid (air or otherwise).
- Sub-battery containers to contain/limit effects of a thermal runaway. Facilitate active suppression of a fire? Intumescent coatings are light and effective within limits, can they slow the spread of fire and buy an extra 30 critical seconds in a bad situation?
- Plug-and-play subbatteries of convenient size and weight? There will be use cases where it is not optimum to charge batteries in the aircraft (where safe charging rates are just too slow, and a leisurely recharging on the ground extends the expected lifetime of the batteries). Being able to swap out twelve 10 lb sub-units is a lot more convenient than a single 120 lb battery or two 60 lb units.

To me, the safety aspects are top priority. A fire in a car or scooter battery is a big deal, but still the options in those cases are likely MUCH better than a runaway inflight fire in an airplane. I'd go so far as to suggest that pilots who aren't concerned about inflight fire (regardless of power source) haven't given the issue much thought (or they fly gliders).

Oh, and we need cheap, light, powerful, and reliable.
You are right - safety should be top priority.
Monitoring, reasonable discharge "C" rate, battery case slowing down fire.

I have been flying with 5 electric types.
Pipistrel Velis and Pipistrel Alpha Electro - looking similar but definitelly not the same for flying. 2 battery packs (one in the front, one behind pilots).
Phoenix D-14. Two assymetric battery packs (16+34 kg) in the front.
Phoenix U-15E. Three battery packs. 2x 40 kg in the wings, 70 kg in the front.
Sagitta. One seater. Retractable motor. Two battery packs behind pilot (2x 15 kg).

Lets be realistic ;)
Homebuilder will not make battery like proffesionall company. We have to try to make it with maximum safety = simplicity.
I would stay with idea of small battery for one seater like Sagitta.
For easy manipulation lets assume approx. 2x 15 kg (2x 33 lb) = 30 kg total (66 lb).
That can give us 6 kWh = TakeOff power up to 15-18 kW, Power for climbing +- 10 kW.
If we use typical well approved 18650 cells VTC6 (3,7 V, 3 000 mAh) than we will need +- 540 cells.

Case...temprerature monitoring can be done simply by adding multiple temp sensors between cells.
Question is what material should be used for case.
Of course would be ideal some material able to hold fire inside for as long as possible.
It means another question - how long time is long enough...
With plane like Sagitta is expected flight under cloud base and soaring.
In EU is not typical to fly often over 2 000 m (6 500 ft.).
If you notice temp. increasing you need to go down = trying to increase descent ratio to maximum.
Lets assume 5 m/s (+- 1 000 tf/min).
That means really long descent during approx. 7 minutes + time for landing.
So it is critical to give pilot notice as soon as possible that in battery is temp changing over limits.
Metal case will be probably too heavy, so we have to look for special protections.
Available is for example KERATEM able to survive 1 100 °C.
1643095589446.png
We used this on fire wall on UL airplanes.
It is a "sticker" - glass fabric covered by Aluminium.
It is very easy to work with.

Also development of fire retardant paints is going well forward...

And here we have two conflicting requirements.
Close cells into case (no ventilation = no way to manage some cooling) or make active ventilation / cooling (but than you must be sure to lead possible fire gases out from cockpit).

From my point of view simplicity = safety.
Close cells into fireproof box, make good monitoring of temp by multiple sensors.
With "conservative" way of takeoff you use max. power (max, discharge rate) for as short as possible time. When you in the air at safe altitude (different on each airfield) decrease TO power to "continuous" climb power.
"Cruise" power should be 1C (=5-6 kW).
Going back to Sagitta I was using following settings:
- takeoff power 15 kW (possibility to go up to 20 kW).
- at 50 m (150 ft) reducing to 8-10 kW.
- cruise at 5-6 kW.
I beleive that that is "achievable" performance for homebuild airplane with acceptable electric propulsion system complexity and acceptable safety.
 
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Exian

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And than starts a bit more sophisticated work - balancers.
I will try to meet my friend producing electric bicycles to get more info about balancers for small battery packs.
About balancers, is it needed to have balancing working during flight, or only during charge?
If during charge only, then many chargers can deal with this, no need to have the system inside the battery.

In my case I will have a 28S battery separated into 4x 7S Packs. There are high performance hobby/models charger going up to 8S in balancing capacity, just connect the 9 wire connector to the charger... Even 4 of these charger are a lot cheaper than "aerospace" grade charger that deal with 28S at a time (need balancing system of the BMS also to work).

For insulation material, there is also cork! Even some high tech airplanes use it (video about airplane "Spirit of innovation" posted earlier)
 

John.Roo

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="GBRS" ? (Gravity Battery Resque System ...) =the whole Battery Pack landing with chute. (as light bomb)


=30 kg, / < 0.5 kg
About balancers, is it needed to have balancing working during flight, or only during charge?
If during charge only, then many chargers can deal with this, no need to have the system inside the battery.

In my case I will have a 28S battery separated into 4x 7S Packs. There are high performance hobby/models charger going up to 8S in balancing capacity, just connect the 9 wire connector to the charger... Even 4 of these charger are a lot cheaper than "aerospace" grade charger that deal with 28S at a time (need balancing system of the BMS also to work).

For insulation material, there is also cork! Even some high tech airplanes use it (video about airplane "Spirit of innovation" posted earlier)
Cork - good idea 👍

Balancers are most important during charging. For example on D-14 prototype we had balancers part of charger an it worked perfectly.

In my opinion is better to have balancers inside airplane (battery box). That allows you to use simple on-board charger + you can have a very detailed info about cells. However in self launch glider is not a problem to safe weight and complexity and have balancers in chargers, Depend on mission - self launch gliders are suppose to land on same place where they took off ;)

By the way - good idea with RC chargers 👍 That can really save a lot of money...
 

John.Roo

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If Lithium quits burning when it runs out of Oxygen maybe remove or limit the access to Oxygen. If there is no Oxygen to begin with then no fire?
Good question 👍
I personally don´t know the answer....
For better impression - here are tests of different cell types:

Quick research....
Important part...
"In a powerful thermal incident, the Li-ion battery may release some of the flammable electrolyte along with various flammable/toxic gases such as hydrogen (H2), methane (CH4), carbon monoxide (CO) and hydrofluoric acid (HF). This means that the Li-ion batteries have all the elements needed to self-sustain a fire."
 

proppastie

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Cell solding machine will be probably also "must have component".
They are many affordable types available
I see battery holder systems that do not require soldering or spot-weld....a little heavier with fasteners but less expensive with out the spot welder..
Any thoughts?
 

blane.c

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Good question 👍
I personally don´t know the answer....
For better impression - here are tests of different cell types:

Quick research....
Important part...
"In a powerful thermal incident, the Li-ion battery may release some of the flammable electrolyte along with various flammable/toxic gases such as hydrogen (H2), methane (CH4), carbon monoxide (CO) and hydrofluoric acid (HF). This means that the Li-ion batteries have all the elements needed to self-sustain a fire."
The only oxygen listed above is in the CO and is a byproduct of combustion, not a contributor. If oxygen was denied prior to combustion then no CO.
 

PiperCruisin

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The Sagitta looks cool. The deployment of the propulsion took a minute. One reason I don't like the turtle deck config.
Funny enough, I have a patent of a fire retardant system for I-joists.
 

EzyBuildWing

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Where Panasonic is at:

Panasonic revealed it will begin producing its new 4680 lithium battery cells as early as 2023.

The batteries, which were developed on request from Tesla, would improve the range of a Model S from ~404 to ~466 miles.
Panasonic
estimates production will cost 10% to 20% less than previous versions due to capacity efficiency.
Batteries comprise approximately 30% of the production costs of an electric vehicle.
 

John.Roo

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The Sagitta looks cool. The deployment of the propulsion took a minute. One reason I don't like the turtle deck config.
Funny enough, I have a patent of a fire retardant system for I-joists.
You are right - the deployment of the propulsion is too long.
It is home made prototype and of course could be done different way to deploy motor faster.

My favorite propulsion config was Windex / Sunseeker Duo...
I mentionned this idea before - it would look like this:
Phoebe - fin prop version.jpg

Simple folding prop, large distance of motor from ground etc....
 

John.Roo

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Where Panasonic is at:

Panasonic revealed it will begin producing its new 4680 lithium battery cells as early as 2023.

The batteries, which were developed on request from Tesla, would improve the range of a Model S from ~404 to ~466 miles.
Panasonic
estimates production will cost 10% to 20% less than previous versions due to capacity efficiency.
Batteries comprise approximately 30% of the production costs of an electric vehicle.
Li-Ion 4680 cells are improvement 👍
Not real "gamechanger", however less cells for same capacity = less solding points etc.
I hope they will not "kill it" by price.
Price for large automotive companies will be probably OK, question is price for "normal" homebuilder...
1643179737495.png
 

EzyBuildWing

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