Just started building a new model for a 90mm fan unit.

I ve decided to go electric, and have settled on the WemoTec Midi Fan , (Ø90mm)

I have been recommended the following setup,

Mega Motor , 22/30/2
5 s Lipo 3400
Jeti Spin 66 ,

Hopefully all in she'll weigh in at about 2 -2.5 kilos , but all the above numbers are new to me, and I just wanted to "get a second opnion" .
Also how do you estimate power consumption ? , obviously V×A =W , but how do you estimate the current draw of the motor and fan ???

cheers Nick

The 22/30/2 on 5S in the midi is going to give figures like:

62A and approx 1100-1200 watts.

You might like to consider some larger LiPos, near 5000mAh?

Yes 5000 mah lipos will be better, I use Thunder Power Extreme 5000 mah. The Extremes have great power and give me about 150 watts more than my older 5S4P Prolites did, and weight about 4 oz less. Yes flight time has decreased but the older Prolites (which ran cooler than the Gen 2s but still got hot) would get hot if I ran through 7000 mahs of the 8000 that I had, especially in the summer months in the desert.

When I first started flying the 22/30/2 and midi I was getting about 850 watts on the first generation lipos from Thunderpower, around 55 amps. I puffed a couple of rows of cells from flying too long. Each generation has run cooler than the last, and finally with the Extremes I lost some weight and the packs are cheaper. I only fly 5 minutes max vs 7 before but my batteries no longer boing and I get almost 1200 watts at the start of the run.

I see what you mean, if the setup is sucking 62A , with a 3400 battery, it works out to about a 3 minute flight time, 5000 are a bit better at five minutes, I suppose that is full power all the time.

I have been eyeing up the Hextronik Lipos on the United hobbies websites, 5s 4100mah , max discharge of 15-25 C , this would give me a 4 minute max power run.

Where can I get 5000 lipos ?, but at those nice cheap prices of United Hobbies ??
somehow I think its going to be those 4100's


Nick

I read a report on 2000 mah class batteries recently, the ones from Hextronic (I don't know if that's what United Hobbies sells for sure but I possibly) came out consitantly in the 10 and 15C tests on the bottom. They had the lowest per cell voltage and the highest heat gain. At 15C they were the lowest voltage and the test was terminated prior to the end due to the temperature getting too high (cells would puff if they got too hot, up near 170 to 180 degrees). They didn't even test them at 20C. Other cells brands were in the middle of the pack, and the two top of the pack brands were ThunderPower and maybe Polyquest or Evo or Vampower in the middle.

I've ran three different generations of cells on the Mega 22/20/2 setup and puffed cells several times from flying too long, that was with the 8000mah 4P packs. With these 5000 packs I can't fly as long, but they don't get as hot (less resistance in the bigger cells) and the power is higher than the old cells. You may save some money buying the cheaper cells but I can't tell you how they'll run as I've not tested them, but if they're built from the smaller hextronic cells I wouldn't waste my money. EDFs demand a lot from batteries, high amp draws to match the performance of prop airplanes. The 5S 5000 Thunder Power extreme pack is about 275 bucks I think, that's cheaper than the old 8000 5S4P packs, which were 400 bucks (and I couldn't use the full capacity anyway due to heat buildup). You could buy a 150 dollar pack and have to watch the throttle the whole time because you're worried about heat and maybe it will last but if you puff it you end up having to buy the good pack anyway. Buy cheap, buy twice. I have a hard time throttling back with a jet.

ok cheers for that, you get what you pay for at the end of the day...

could you point me in the direction of that report, Ed ?? is it online ?

cheers,


Nick

No the review was in Steve Neu's "Power On" column in a recent issue of Flying Models magazine, published here in the US. I didn't buy it, just browsing. My place is full of old magazines, I don't buy them anymore, I figure I've learned all I can from them.