Electric paramotor endurance builds

I am will soon be building a paramotor with endurance capabilities in mind. I am open to suggestions, comments, questions. This would also be a great place to hear from everyone on their longer endurance builds and paramotors.

As for the basics this is what I am planning on:

  • MAD M40 43kv motor
  • e-prop 125cm 4 blade or 2 blade. I will test both
  • not sure on esc (square wave or sine wave esc?)
  • for the battery I will likely use a 22s15p Samsung 30Q pack

I would expect roughly one hour flight time on an XL wing. The Paracell paramotor claims to get up to 70 minutes with 6 more 30Q cells than what I will likely use. (their battery pack will hold an extra 60wh of power under load). This number is also par with the flight time to battery kw ratios of Exomo, Skyjam, Black hawk AMP, And sp140. Because most of the time wont be flying an XL wing and I wont push the battery to being completely dead on every flight I do expect to get closer to 45 minutes on the average flight.

I would later like to try and use a 22s20p battery to get theoretical flight times over 80 minutes with a large wing.

One thing is I want it to be able to do with this paramotor is hold 130+ lb constant thrust at 5000’ for climbing up mountain sides with medium or small sized wings when flying with gasoline powered buddies. I know it will kill the flight time, but I would like to have that much power when I want it.

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The best way to do this is to find the prop/RPM combination that will give you both the thrust and efficiency you want, then work backwards from there to determine how much motor power is required and what motor KV/battery voltage you want to use. Then source the motor and controller.

As a general rule, for a given amount of thrust, a larger diameter prop spinning at a slower RPM is going to give you higher efficiency. E-props has a useful calculation tool on their website that might help you nail down the prop diameter you need.

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Thanks, Not sure how I forgot about the E- prop calculator. The problem I have is it doesn’t calculate how rpm effects thrust, it just assumes you have the best prop pitch for the rpm the motor runs at.

I do a lot with drones as I fly race drones, camera drones, collective pitch stunt helicopters, and basically everything in between I also have competitively flown rubber powered free flight models. So I do know that if you want to go fast you use a small Diameter, high pitch, high rpm prop like a race drone and if you want lots of thrust for the power used and to fly slow you want a large diameter, lower pitch, low rpm propeller like all human powered aircraft or long endurance rubber powered models like what I have built.

So for the propeller I want to use a 125cm because that is the biggest size the frame can use without risking a broken prop when I learn to fly. I also like the 4 bladed props because they tend to be more efficient than the 2 bladed props. I know that in general 2 bladed props are more efficient but for some reason in the paramotor world the 4 blade props tend to be the most efficient.

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Full throttle motor RPM is mostly a function of the motor KV and battery voltage, so you can select the motor and battery pack configuration once you know what RPM and mechanical power is required for your prop to produce the thrust that you want. As a rough guideline look for a motor/battery configuration that has a no-load RPM that is 125% of your target full-throttle RPM. You can use that to build a list of motor/battery combinations that should be close, and then compare them all in eCalc to see which is closest to what you want.

This is what I WISH I did on my project. Instead, I did what you’re doing, which was pick a motor and work it all out from there. Unfortunately the motor that I have becomes very inefficient below 4000 RPM, so I am limited to a 40" prop before the prop tips go transonic. I’m still trying to make it work, as there are some benefits for me to use a smaller prop, but if I was just trying to make a gas-equivalent ePPG there is no way the motor would work without a reduction drive.

If you don’t already have a subscription to eCalc you should get one. It will save you a lot of time and money in the long run.

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it is also easier … use material that was designed for it.

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Ok thanks, I had previously come up with the loaded rpm being roughly 80-83% that of the no load rpm. Which was actually a more accurate than I previously thought.

I probably should run the 24s14p battery configuration that I was originally planning on as at 3.6v per cell that would give me the 3000 rpm or 130-135 lb thrust at my altitude with a 43kv motor.

I will definitely look into an eCalc subscription

It won’t have data for the big motors we are using, but you can get all the data you need to enter it as a custom motor (KV, Io, Rm, weight, pole count, case length) from the motor manufacturer. The most important factors to watch are the waste energy and motor heat parameters. It seems like eCalc is very optimistic with the heat calculations and if you want to run your motor WFO for more than a minute or two to “climb mountains” you probably want that number around 40-50c with “very poor” cooling selected. I have found that on my project I’m hitting that heat number with “very poor” cooling after around 4 minutes of full throttle. Unfortunately for me that is taking me to the temperature limit of my motor. Don’t make the same mistake that I did; make sure you select a motor that looks like it should run VERY cool. In reality, it’ll probably run hot, but acceptably hot.

Almost any >2 kg brushless motor will make the kind of thrust you are looking for. The real question is how long it will run at that power level and RPM before it overheats. Depending on the motor weight, efficiency, and cooling, it might be anywhere from a few seconds to indefinitely.

The M40 that I’m looking to use can handle 15kw constant and at 130lb thrust it shouldn’t uses more power than that. If I where to take it down to sea level that could cause some problems as the thrust would go from 130lb to around 155lb and it could exceed the constant power capabilities.

Does anyone have any suggestions on a good BMS for a 24s li-ion battery pack. I would like the BMS to be rated for at least 250a. I have seen many cheap Chines BMS for $100 that will theoretically fulfill my needs, but I want this to be a paramotor not a pile of ash in a year.

Any suggestions on ESC? I have checked both hacker and MGM for a good esc but none of them handle the 24s battery that I will be running. I can always use a MAD esc, but It costs $1300usd and it still doesn’t have telemetry. A cheaper option would be the $900 HEFI fulcrum ESC but it weighs almost 5lb.

mgm and hacker naturally also have esc for up to 120 volts. but only for professional applications. the 60 V regulation applies to diy e-bikes, e-karts, rc models, etc. Imagine building a 24 S battery. as soon as you touch both + / - once you are definitely dead with a battery that can deliver the impulse regardless of whether 12 S or up to 24 s up to 6000 amps. the body can cope with up to 60 V. from 18 S you get muscle cramps. from 22 S it becomes fatal at dc. take a look at a welding machine that produces the arc at full power at mostly 20 volts and 250 amps. imagine 20 times that going through your body through the heart. the heart is a sensitive muscle …

unfortunately there are people who have been blinded by a short circuit at over 100 volts dc through the arc. or deaf from the extreme bang. be careful! e-motor systems with a continuous output of more than 5 kilowatts dc are not toys or with rc. model comparable.

hacker and mgm have their own pages for industry and aviation. there is of course only a little information there because the companies do not want to buy something for beginners without specialist knowledge. then possibly have an accident and thereby make the brand bad. the companies also have a responsibility and duties to perform. security is the biggest issue. I know in China and other countries it doesn’t matter. but one should ask the question, what is a human life worth? to have a fatal accident because of saving little dollar? it is free for everyone to think about it.

True, I know they make the m40 in higher KVs so I will ask them about it. If I can get it in a 70kv I could run a 15s battery which ago be a lot safer.

if you want to fly quietly, powerfully use a motor with 50 -60 kv. then you can work with speeds in the range of 1600 rpm in level travel flight and with about 2100-2300 at the start. quiet, powerful and highly efficient. if you only have 125 cm available, use a 3-blade propeller that has been optimized for maximum performance from 2100 to 2200. as an example of the e-props for the hdp 10 motor. no theory. I measured everything exactly years ago.

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Ok, thanks. Could that setup get me the 130lb thrust at my altitude(5000’) or roughly 150lb thrust at sea level? I do want to be able to fly with small-medium sized wings. Would the rpm be too low to efficiently fly would those wings?

it’s all very easy to solve. you make a setup that achieves the desired thrust at 5000 ft, for example at 2300 rpm / 130 lbs. If you then want to start at 0 ft on vacation, simply change the setup to a maximum of 2150 rpm / 130 lbs in the software. it takes 15 seconds. it is done using the rpm limmit function. this is generally used to compensate for the voltage drop a little. example with me: that means the drive could make 2340 rpm with a full battery. if the battery is half full, it can be 2210 rpm. but I set a general limmit of 2200 rpm that is well matched to the propeller in my takeoff and flight altitude and the desired thrust. so I have the same maximum output of 2200 rpm available regardless of whether the battery is full or half empty.

Ok, that should also help increase the number of cycle the battery can go through because it would limit how much power is used.

@bratwurst
I know you really like using 21700 cells. I what do you like so much about them? As for an energy stand point the 18650 cells often have a better gravimetric energy density 250+ w/kg.

there are values from cell manufacturers, sellers, etc. These mostly apply to 1 cell that was measured. the cells give each other the heat in a battery pack. I therefore do hundreds of cycle tests under real-life conditions. simulate a flight with a lot of take-off power, or level. or full gas etc. I isolate the test cells with eg. foam. the best cell types win the match and I use them. has proven itself 100% for me. I don’t care what salespeople or theorists say, it’s worth nothing. The power density is extremely dependent on whether the cells can meet the requirement at all. that means a cell that is overloaded may only bring 70% of watt hours what is printed …

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Ok, I understand. That if I were to do that I could run a custom wound 55kv M40 motor with 55.5v/ 15s battery pack which would be a lot safer. I do have family and neighbors that are electrical engineers that could help me build the battery if I need it. Then I could also run the MGM 400a esc and the Chargery 300a BMS which is better than the cheap Chinese BMSs that I was afraid I may need to use.

As for the battery cells I am currently thinking about building the battery with the Samsung 30q cells as they are cheaper to get at roughly $3.50usd per cell and they are one of the more popular cells used in professional electric paramotors.

yes you can certainly use the samsung 30. however, the most used is the Sony VTC series. if you are using a mgm the HBC series TMM 25063-3T with active fan for standard E-PPG is best. yes i also fly 54 kv motors with standard e-ppg and thermik-e-ppg.

I have seen them and if they where the same price I would use them. For me I chose the 30Q because it would save me about $300 over the Sony vtc cells.

you can compare things from the price, yes that is possible. but if the quality, performance, is different. it is impossible that 2 different things have the same price. the best way to see it is with e-ppg motors and esc. even a child can see the difference here and understand why the motor and esc from the pilot who flies much longer and more efficiently also costs more in terms of price. however, it is not “more expensive” but you always pay for the usable performance of a product. a simple beginner wing costs 2000.- a high performance that is built much more complex costs 4000.- but it also flies with much more power and performance. you could list thousands of examples. But of course there are also compromises like in the rc area, something simple and cheap is enough for a hobby pilot. Anyone who flies competitions or wants performance will also use the branded product here. there is definitely no such thing as top performance and cheap.