What do you think about "e-soaring"?

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danmoser

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Thanks for detailed info 👍
Seems that best way is to follow your recommendation ;)
"Honestly probably less work to build your own BMS than test someone else’s undocumented one enough to trust it."
After a frustrating search for a BMS that matches a good battery pack, the "build your own BMS" option is something I'd like to explore.
Does anyone know of a good source for BMS design recommendations, guidelines, best fabrication practices, things to watch out for?
I've got a basic knowledge of electronics, but would need more detailed knowledge about BMSs before tackling such a project.
Thanks! ;)
 

John.Roo

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Start by reading and understanding the data sheet for the TI BQ79656-Q1 — there are other options, but that’s a really good start. From there, so a fault tree for the charging, passive, and operating states and decide what faults you really have to deal with. Then let’s chat in detail.
If is not classified information.... on what electric airplanes projects you have been working?
And what is your opinion about electric propulsion in sport aviation?
 

addaon

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I worked at Wisk.aero for three years, which is by far the most directly relevant. Also built a personal electric powered paraglided. Worked adjacent to electric in automotive as well — previously at Zoox, currently Rivian.

I think that we have a good while to wait yet before automotive battery investments get us to the point that batteries are useful for more than niche sport aviation purposes — but I think that those niches are pretty fun, and I also know that developing these platforms (especially to certification) can easily take a decade or more, so it’s not a bad time to start and wait for the tech to catch up.

Personally working on a gas design because I have a range requirement electric just can’t even come close to, but hope that sometime in my life I can swap in an electric power pack.
 

Bille Floyd

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... I also know that developing these platforms (especially to certification) can easily take a decade or more, so it’s not a bad time to start and wait for the tech to catch up.

...

I'm getting kinda Old ; I'm hoping the time-line becomes :
Shorter !!!

Bille
 

addaon

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Well, that’s what home building is for! Certification takes time for pretty good reasons (in my opinion) — building a homebuilt to near-part-23 standards can be much quicker, and building to your own standards…. As quick as you dare.
 

proppastie

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horizontal flight max. 1C or below.
I am very ignorant about this but sort of skimming because the e-power probably should be better than the "giant scale model airplane engine" I currently have and plan to initially fly with.
Does 1C discharge in your bird mean you only have 1 hour endurance......... with the long flights you have posted seems like you might be mostly soaring if this is the case.
 

addaon

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1C means that your maximum power draw corresponds to a one hour discharge time — in practice you generally cruise anywhere between 75% of peak power (most “fast” small planes), to 50% (slow STOL-style craft) down to 25% (motorgliders), all of which would mean that a 1C max has more than a one-hour zero reserve endurance. But factor in your 30 or 45 minute reserve…

Also, as the previous numbers pointed out, it’s pretty darn hard to size for a 1C battery pack with today’s tech. 2C is still darn hard, 5C (12 minutes max power endurance, -33 minutes with IFR reserve) is more likely.
 

proppastie

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Payload ratio (the weight of the maximum payload divided by the weight of the empty vehicle)
1967 Mooney M20C1996 Mooney M20J
Takeoff/Landing Weight Normal Category2,575 lbs.2,900 lbs.
Takeoff/Landing Weight Utility CategoryN/AN/A
Standard Empty Weight1,525 lbs.Data Not Available
Max. Useful Load Normal Category1,050 lbs.Data Not Available
27 more rows
?......68% Mooney C
 

addaon

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See previous numbers. If you want a two hour cruise duration on, say, a C172 that cruises at 117 hp, so 1.5 C for a 180 hp max… you’ll need about the same battery pack weight as the MTOW of the aircraft. And that’s still less than 150 mile range with reserve.
 

John.Roo

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1C means that your maximum power draw corresponds to a one hour discharge time — in practice you generally cruise anywhere between 75% of peak power (most “fast” small planes), to 50% (slow STOL-style craft) down to 25% (motorgliders), all of which would mean that a 1C max has more than a one-hour zero reserve endurance. But factor in your 30 or 45 minute reserve…

Also, as the previous numbers pointed out, it’s pretty darn hard to size for a 1C battery pack with today’s tech. 2C is still darn hard, 5C (12 minutes max power endurance, -33 minutes with IFR reserve) is more likely.
Exactly... 👍
When I flown with small Sagitta I used 15 kW takeoff power.
For horizontal flight I measured 5 kW. So it was 30% of max. power.
In this case is 1C = 5 kWh capacity.
However as mentionned - is not good idea to go below 20% so 5 kWh + 20% = 6 kWh capacity.
15 kW takeoff power is in this case 2,5C.
That seems to me achievable goal because I already test flown airplane with similar parameters.
Of course we are still in category of self launch light single seat e-gliders.

6 kWh battery capacity = approx. 30 kg weight if Li-Ion cells are used.
For manipulation would be better to split battery in two packs (2x 15 kg).
To reduce risk I would stil recommend to recharge battery slowly and outside...
"Slowl recharge" is anyway the only way available practically in all EU airports.
As mentionned before - for example in France is available on most of airfields only 220 V socket = useable power arround 2-2,5 kW.
 

henryk

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John.Roo

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France is also famous for the Maginot Line.
France is a bit "special" country.
As mentionned - they have a very high fees for 400 V 16 (32) Amps. But they have also very strong glider pilots comunity and beautifull country to fly ;)


It makes sense to design charging of e-glider "compatible" with 220 V system even is there will be charging speed limitation.
In worst case would be possible to use for re-charge small ICE generator. They are affordable with acceptable fuel consumption.
 

John.Roo

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More details about Piper electric trainer....
 
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