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newbie electronics question

#1
Evening guys,

I am new to the hobby and can't thank flite test enough for getting me into it and the forums for all the advice on first planes etc.

Having flown dlg's and a 3 channel powered glider I wanted to try my hand at the swappables. I can't get my head around the electronics through and have managed to puff up two lipos now (one through my own fault and the second is unknown).

I have built a ft delta and a slinger so I'm hoping to use my pod on both but I want to be sure of my electronics before I go ahead connecting it all.

I have some 3s 850mah and some 2s 500mah lipos would a 1300kv hextronik motor and a 20a esc be sufficient?? Or does any one have any other setups I should consider.


Thanks in advance

Neil 'one confused newbie'
 

Craftydan

Hostage Taker of Quads
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#2
Neil,

Delta, yes. Slinger, no.

Skipping the other failure modes (I started to write them out, but it won't help you at the moment), I'd ask what C rating are you using and, how do you know when the battery is empty? Batteries puff in one of two ways: Too much current (amps) all at once, or drawing the battery past empty.

The 24g 2370 motors (AKA blue wonders, CD motors) will max draw about 7.5A continuous, before burning out -- might take a minute or two, but it'll happen. To puff a battery from current you'd need to pull over that, but a 25C 500maH, that's ~13A. The motor would be burning hot at that sustained current, as well as having a puffy lipo.

You could prop it to pull 7.5A at WOT and *still* puff the lipo, but that would be because you ran the pack too low. below ~20% remaining, (3.7v unloaded) the chemical reactions start going in the wrong directions (the non-reversable directions!) and produce heat, gas and puffy deceased lipos. There's a good chance this is what's happening to you.

How do you deal with this? measure the voltage! Either land and check periodically:)p), or get an onboard battery checker. There are plenty versions around, but the two features I recommend are loud alarm and adjustable alarm voltage. set the voltage, fly it around until it alarms at cruise speed, then land and check -- if it's got more than 20-30% left, move the voltage down a notch. Less, bump it up a notch. I can usually dial in a meter to a power system within a flight or two, then it should remain the same.

Now for your original question -- why not the slinger? IMO, you'll want a bigger motor for that one. you might be able to get away with it, but it'll fly slow and high on throttle. If you do go for it anyways, make sure you haven't over-propped it. too much more than an 8" slowfly prop (8x4ish) and you'll likely be over the 7.5A at WOT, and on your way to burning out that motor.

On the positive side the 20A ESC is fine. Oversized, but fine. A 10-12A ESC would likely be better sized, but but if you can tolerate the extra weight and cost, a higher rated ESC is just fine.
 
#6
Wow, thank you so much for the reply.
I have been doing some reading on the case and its all quite confusing. I have managed to assemble a mini swappable using a micro motor, 12a ESC and 2s 500mah lipo which is coming along nicely in the tests. But it seems I can't get the setup correct with the bigger motors.

Your advice is very appreciated and my research is now a lot more focused. I have gotten myself a battery alarm so that I can monitor the voltage. Hopefully this will allow me a little more insight into how the lipo is coping.

So I have a 20a ESC and lots of 2s 500mah 20c lipos and a couple of 3s 850mah - what motor should I get to go with this setup? I'm mainly going to be flying the ft delta While I get used to the ailerons. and then will move up to flying the slinger!

Thanks for all the help!
 

Craftydan

Hostage Taker of Quads
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#7
Those two airframes really need diffrent motors.

The batteries you have, coupled with a 2370 "blue wonder" style motor (~85W max) will work wonderfully with the delta and most other swappables, but I think you'll find it underpowered for the blender, duster, racer (slinger), FT3D and spit.

You could step up to a larger motor on the lighter airframes (200-300W motors), but you'll likely find your flight times drop dramatically for those packs -- almost to an unusable point. You'll likely want to step up to a 3s 1300-2200 lipos when you're ready for one of the bigger airframes. For bigger motors, I've personally used the aerodrive L2215J-900 and the NTM 28-26 1200kv on airframes with good results. There are plenty of other motors, those are just the ones I've had good experiences with.

Again, that ESC should be good to run most motors in that range -- double check before you commit, though. Some may need a 25-30A ESC the closer you get to a rated 300W motor. (300w at 3S, means ~24A, however most motors in that size are rated 3-4S, so the max current for 300W at 4S is ~18A)
 
#8
brilliant, thanks again Dan,
I'm just making the transition from 3channel DLG's so I am taking it easy and following the flitetest intro to flying - I'm not about to throw a plane that I can't handle until I master the basics! And to keep it as cheap as possible I can start with the 2s 500mah and then move up to a 3s 850mah when ready!

I shall go for the blue wonder style motor and post my results on my blog - I'm hoping it won't be a picture of my first destroyed scratch build.

cheers again!
 
Last edited:

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#9
brilliant, thanks again Dan,
I'm just making the transition from 3channel DLG's so I am taking it easy and following the flitetest intro to flying - I'm not about to throw a plane that I can't handle until I master the basics! And to keep it as cheap as possible I can start with the 2s 500mah and then move up to a 3s 850mah when ready!

I shall go for the blue wonder style motor and post my results on my blog - I'm hoping it won't be a picture of my first destroyed scratch build.

cheers again!
Never fear broken foam, but once you've got the power system behaving you shouldn't have any worries after your glider expeience.

Looking forward to seeing the posts!