E640 flight times

[hANDYman]

Saw a new Radikal E640 at the LHS the other day, and the owner of the shop was saying that it would fit 2 - 6S 5000mAh batteries. Just wondering if anyone has tried 5000's in a 12S setup, and if so, what kind of flight times are you getting? Might be tempted to get something like this over a Trex 700E, etc if the flight times are significantly longer...

[Dennis P]

I am not running 12s I run 10's on my current E640.I run 1850 head speed which is going to make the largest change to flight time (faster uses lot's more).With 4000mah 10s I am getting 8.5 minutes with 70% capacity used.I usually play around some at 1700 at the beginning of my flights.I am running the Century 565kv 650A motor. I plan on putting a demo 6s unit together also in the near future. Update I am back down to 7.5 minutes as I am getting comfortable and pushing the heli harder I guess.Still flying at 1850 but burning more fuel (heavy foot)

[ngin]

Everything else being equal, the biggest factor in the consumption of battery power, is the headspeed you set to turn any set of blades, on any helicopter.

For example, if you turn a particular set of blades at 1900 rpm, that requires an average of 1000 watts over any particular flight, then at 2100 rpm (about a 10% increase) it would reguire about 35% more - 1300 watts.

That means you would get that much less flight time on the same set of batteries at the higher head speed.

This is why nobody can honestly give you a definite answer to your question, unless you can give more info relative to the head speed you want to turn your rotor at.

Dennis's answer is a good one, because he gives you a lot of important particulars - e.g. battery pack stats, rotor speed & flight times after using 70% of their 4000mah capacity.

Looking at his info, you can figure out that 70% of 4000 mah is 2800 mah, and 8.5 minutes is 0.14 of an hour. From this we can calculate the average wattage over that 8.5 minutes.

In 0.14 hours, we consumed 2.8 (2800 mah) amp hours. This means that the avarage amperage demanded would be 2.8/0.14 = 20 amps. As he is using a 10 cell pack, we will use the mean voltage (37V) of such a pack to calculate the average wattage (V x A) which is 37 X 20 = 740 watts. So now we know that at 1850, the average wattage required for his flight is 740 watts.

Of course, with a set up that uses 12S/5000 amp packs, at that rotor speed, we can now do some calculating. A 12S pack's mean voltage is 44.4V. That means that the average amperage needed to generate the required 740 watts, is only (740/44.4) 16.7 amps!

So obviously, your 12S/5000 packs will give you a lot more flight time at an 1850 rotor speed, even considering the slight extra overall weight with them. Now 70% of 5 AH (5000mah) is 3.5 AH. That means that with a consumption of only 16.7 amps, you would get flight times of about (3.5/16.7) 0.21 hours (a hair over 12 minutes)!!

Of course, in a set up for a higher head speed of about 10% (2100) that flight time would decrease to about 8 minutes, due to the increase in amps required. On the other hand, decreasing the head speed by 10% to 1650 would increase the flight time to about 18 minutes.

Of note also, is that the larger the heli, the higher will be the battery consumption at the same rotor speeds. Consequently, on the same set of 12S packs, you will get longer flights on the E640 then you would on the T700.

[MotorRotor]

Originally Posted by hANDYman

Saw a new Radikal E640 at the LHS the other day, and the owner of the shop was saying that it would fit 2 - 6S 5000mAh batteries. Just wondering if anyone has tried 5000's in a 12S setup, and if so, what kind of flight times are you getting? Might be tempted to get something like this over a Trex 700E, etc if the flight times are significantly longer...

Check the good read from ngin relative to your flight times.

What flight times where you looking for?

[hANDYman]

Thanks for the replies guys...

I wasn't really looking for info on a particular setup (ie headspeed = xxx), I was simply looking for general info. My thought was that if I could get x number of minutes on a 700E, then I would expect to get >x minutes on an E640 setup using the same (5000mAh) batteries.

Also wanted to confirm what the guy at the LHS said, in that 5000mAh batteries will fit in the E640...

[Dennis P]

No problem with fitting the 5000mah 6s packs.I have Voltz 5100 and Spyders 5300's here and no problems with fit

[codfish124]

Wow the 5000mah fit I tried 2 4200mah volts they fit it was tight can't tell u flight times as one of the cells blew up 2min into the flight

[MotorRotor]

Not all 6S/5000 packs have the same dimensions. They may have different cubic volumes but some may be taller and shorter, while others may be shorter and longer or wider.

But most of those I have seen will fit. A good thing to do with any heli is to check the dimensions of any packs that you plan to buy or use.

As for flight times, in conclusion of ngin's post above, you will find that on any particular set of batteries, you will get a longer flight time with the 640 compared to a 700 at the same rotor speeds.

[Dennis P]

I just measured the battery slot and it is 53mm wide x 55mm high.It is actually higher but the landing gear lugs make it's dimension narrow up at the bottom so I excluded that part from the height. The Voltz 5100 6s is 52mm high and 44mm wide.So it will fit either way but straps would become a issue if put in on it's side.I was going to run these originally so I had them all slide in and strapped down. I am very happy with the flight times at 7.5 minutes ,weight and power from my 10s 4000mah packs. Take care.

[hANDYman]

Thanks again for the info guys... looks like it's not a bad heli.