First Eagle Tree data - man this is gonna be fun

[fishboy77]

Alright folks my Eagle Tree data logger showed up at my doorstep today. The weather was disgusting so I only managed to do a little hovering indoors. I used one of my tiny new Mystery 1500 mAh 25C packs starting with a voltage of 3.9/cell. The graph shows amp draw, battery voltage (check out that sag), and headspeed (this is measured by the brushless motor RPM sensor coupled with the knowledge that the gear ratio is 15.556 with the 9T pinion I am running). At the beginning of the flight I'm in normal mode with a throttle curve of 0-25-70-70-70. It's only pulling around 9.3 amps at a headspeed of 2,300 rpm. At around 1.4 minutes I switch to idle up (100 all the way across), increasing the amp draw to around 10.5 and the headspeed to 2500.

Can't wait for the weather to improve so I can get outside for some full flights with more demanding maneuvers and different battery packs.

[BennyTRD]

This is very neat info. I too was thinking about an Eagle Tree system. Which one did you go with? The eLogger V3 with with Wire Leads, 70 Volts, 100 Amps (MPRV3-LEADS-100)?

[azheliguy]

fishboy77, Now that is cool, who did you get it from? Is it pricey?
Thanks

[fishboy77]

Originally Posted by BennyTRD

This is very neat info. I too was thinking about an Eagle Tree system. Which one did you go with? The eLogger V3 with with Wire Leads, 70 Volts, 100 Amps (MPRV3-LEADS-100)?

Hey Benny. It's the eLogger V3 with integrated Deans connectors, 70 volts, 100 amps. Now I wish I had gotten the one with wire leads - connecting both the battery and the ESC is a PITA. I wish it had a connector on each side rather than both connectors on the same side.

[fishboy77]

Originally Posted by azheliguy

fishboy77, Now that is cool, who did you get it from? Is it pricey?
Thanks

Yo AZheliguy. I got it from Advantage Hobbies - best deal I could find by far. It's $66 but you get 10% off on for orders over $100 for the holiday season. Or, if you order is below $100 you can get 5% off if it's your first order there. Orders over $50 ship for free. I ordered mine on Sunday and got it yesterday!! BTW the brushless motor rpm sensor is an accessory - costs around $14.

[Slyster]

That's amazing! Can't wait to see your data... give me the scoop on my fave 2400mah batteries

[fishboy77]

Originally Posted by Slyster

That's amazing! Can't wait to see your data... give me the scoop on my fave 2400mah batteries

Hell yeah. I'm going to try to test all of my batteries today even though it's supposed to be pretty cold. BTW I had my first Mystery mishap last night - one of the balancing wires broke off a 2400 pack. Shouldn't be TOO hard to solder it back on, but kinda annoying.

[Tail boom]

This IS amazing. Especially the head speed.

I just checked it against the online head speed calculator at ReadyHeli (http://www.readyheli.com/Online_Head...lator_s/81.htm), and they match (if you apply the actual pack voltage at a given time, rather than the 11.1V).

Example:

In the beginning of your test, you spooled her up briefly. You were at approx. 11.6 V at that time. Taking into account your 9T pinion and a drag coefficient of 0.9:

11.6V x 3800kV / 140/9 * 0.9 = 2550 rpm.

Nice!

Keep it coming!

Best,
Frank

[BennyTRD]

Originally Posted by fishboy77

Hey Benny. It's the eLogger V3 with integrated Deans connectors, 70 volts, 100 amps. Now I wish I had gotten the one with wire leads - connecting both the battery and the ESC is a PITA. I wish it had a connector on each side rather than both connectors on the same side.

I was thinking the same thing. Thw leads would allow to mount it in alot of other places. I think I have found me a stocking stuffer!!

[fishboy77]

Originally Posted by Tail boom

In the beginning of your test, you spooled her up briefly. You were at approx. 11.6 V at that time. Taking into account your 9T pinion and a drag coefficient of 0.9:

11.6V x 3800kV / 140/9 * 0.9 = 2550 rpm.

Frank, are you talking about that quick blip at the beginning? I've been reading the manual and apparently that's what the recorder reads when the ESC initializes and the motor does its song and dance. Once the motor spins up under load the voltage drops a lot more than at the very beginning. The headspeed calculation holds up well without the drag coefficient: in idle up the voltage was about 10.5, which would predict a headspeed of 2565 with no drag coefficient. With the drag coefficient it would be 2308. Actual headspeed was just over 2500. So it seems that either the drag coefficient is negligible here, the motor kv is higher than 3800, or the data logger is not calibrated exactly.

[Tail boom]

Originally Posted by fishboy77

Frank, are you talking about that quick blip at the beginning? I've been reading the manual and apparently that's what the recorder reads when the ESC initializes and the motor does its song and dance. Once the motor spins up under load the voltage drops a lot more than at the very beginning. The headspeed calculation holds up well without the drag coefficient: in idle up the voltage was about 10.5, which would predict a headspeed of 2565 with no drag coefficient. With the drag coefficient it would be 2308. Actual headspeed was just over 2500. So it seems that either the drag coefficient is negligible here, the motor kv is higher than 3800, or the data logger is not calibrated exactly.

You are right, that IS odd. Maybe it is because you were hovering only, so the main blade pitch was just around 4-6 deg, thus the higher head speed. If you were to do punch outs, the drag co might come into play. Or your rpm probe needs calibration ?

[joediamond]

Under the "Advanced" menu in the EagleTree software you can set logging triggers. I have mine set to start logging when the current reaches 1 amp. This way I don't get the annoying spikes when the ESC pluses the motor during initialization.

[BennyTRD]

You could probably move the main unit from heli to heli right? It would be cool to use it on multiple heli's without having to purchase multiple units. All you would need is to have what ever sensors you wanted on each heli, then move the logger over.

[fishboy77]

Originally Posted by BennyTRD

You could probably move the main unit from heli to heli right? It would be cool to use it on multiple heli's without having to purchase multiple units. All you would need is to have what ever sensors you wanted on each heli, then move the logger over.

Oh yeah. You can use the same unit on as many models as you like. The only external sensor I have is for rpm, and it isn't that hard to move around.

[fishboy77]

OK here's the latest data. Flew four packs today in the following order:

Mystery 1500 mAh 25C (4 minute flight)
G-Force 1300 mAh 20C (4 minute flight)
Mystery 2400 mAh 15C (7 minute flight)
Win Force 2800 mAh 30C (6:40 flight, had to land early due to frickin' motor bearing failure )

I flew the Mystery 1500 pack in normal mode, 70% throttle. The other three are in idle up, 100% across.

Mystery 1500: 674 mAh expended in 4.4 min., 153 mAh/minute = 9.2 amp average
G-Force 1300: 807 mAh expended in 4.2 min., 192 mAh/minute = 11.5 amp average
Mystery 2400: 1464 mAh expended in 7.5 min., 195 mAh/minute = 11.7 amp average
Win Force 2800: 1372 mAh expended in 6.6 min., 208 mAh/minute = 12.5 amp average

Assuming that my old G-Force and 2400 mAh Mystery packs are not overrated, then clearly I can get longer flight times out of them as I only used about 60% capacity in these flights. In the past I have based my flight times on cell voltage at the end of the flight, where I was shooting for 3.75-3.8V/cell (resting) to keep the packs happy. A while back somebody (Redfire I think) posted data on the Zippy 2200 mAh 25C packs. After being drawn down to 3.8V/cell they required about 1300 mAh (60%) to be fully recharged. So there's some consistency here.

One last point is that based on this data I'd say that a 25 amp ESC is plenty for the B400, at least with a 9T pinion. Only with the 2800 pack did I ever exceed 25 amps and that was just barely, for an instant. Perhaps when I change my motor bearings I'll put the 10T back on to see how much more current it pulls.

[Tail boom]

Great, thanks for sharing.

I am still wondering about the rpm numbers though. Can it be that you would have to set up a drag co in your software?

Thanks,
Frank

[josh mcormick]

Hey fishboy how do you like them 2800's. Did you notice the weight diff? Feel notice any more punch with the 30c or does the weight make it about the same? Have you tested the max flight time yet? If you happy with yours, I might not send mine back. Thanks Fishboy

[fishboy77]

Originally Posted by Tail boom

Great, thanks for sharing.

I am still wondering about the rpm numbers though. Can it be that you would have to set up a drag co in your software?

Thanks,
Frank

Hey Frank. I didn't see anything about drag coefficients in the software. The only things I had to program for the headspeed/prop parameter were the number of poles in the motor (6) and the gear ratio (15.556:1).

[fishboy77]

Originally Posted by josh mcormick

Hey fishboy how do you like them 2800's. Did you notice the weight diff? Feel notice any more punch with the 30c or does the weight make it about the same? Have you tested the max flight time yet? If you happy with yours, I might not send mine back. Thanks Fishboy

Yo Josh. I thought you ordered the 2450s? Those should be about 20 g ligher. Anyway these 2800 packs feel quite hefty but honestly I didn't notice any difference in performance. As shown in the graph, this pack holds voltage better than the other three I tested today. The max amp draw was 25.66, whereas with the 2400 15C pack it was 21.62 (and significantly lower for the smaller packs as you would expect). So if the weight is an issue then the increased power output seems to compensate for it. That was the first flight on this pack so I can't tell you how long it will fly. If it's really 2800 mAh then it should go for at least 10 minutes without going below 20% - my 6:40 flight used less than half the pack (1372 mAh).

[josh mcormick]

Yes I did order the 2450's but received 2800's. But mine were accually mystery's but I think (like you said) your win-somthing brand is the same. I think they said the weight was 208 grams, but took it to the post office and weighed out at 201.2. Accurate within .01 oz they said. Cool, I was mad at first about not gett'in the right batts and was goin to ship back,but if yo digg'em I might give a try.