Jump to content

Electricity problems, SE5a: and advice please.


Recommended Posts

Converted a Flair SE5a to the dark side, electric.But I can'to get more than 5/6 minutes flying time. Motor is a Tornado Thumper 36548/05, batteries are 4s 3350 at 35 c. .ESC is overlander 60amp. I've propped about as low as I can at 11.5 by 7, but I'm still getting 700 watts at full power. Model weighs a shade over 6 pound.

The batteries are getting very warm and starting to puff, which they never did in other models. I've set the ESC at low cut off but I still lose power and have to land after 5 minutes, when my battery checker says 38 per cent and 3.8 per cell.

 

The question is this: do I buy 4s batteries at 5000 capacity or downsize to 3s and prop for about 500 watts, helping extra flight time or have I got that wrong ??

IMG-20210616-WA0001.jpg

Link to comment
Share on other sites

Strange, mine flies for a comfortable 7-8 minutes on a 3s 4000 pack. I can't remember the exact spec of the motor, but I think it's around 900kV and pulls around 500W with an 11x7, which gives plenty of performance, and scale flying on about half throttle.

 

It would be worth trying a 3s pack with your existing setup. I can't understand how your model appears to be pulling so much current that the batteries puff and discharge so quickly - they barely get warm with my setup.

Link to comment
Share on other sites

What current are you drawing?  I feel a 900kv motor on 4S is a bit too much. My Flair SE5a flies (and balances perfectly) with a 4AH 4S LiPo and is good for 10 minutes (though I usually land after 8/9).  It has an old XYH 5055 700 rpm/v motor I bought from Giant Shark some years ago and draws about 40 amps on a 12x6.

 

Geoff

Link to comment
Share on other sites

1 hour ago, Maurice Dyer said:

Converted a Flair SE5a to the dark side, electric.But I can'to get more than 5/6 minutes flying time. Motor is a Tornado Thumper 36548/05, batteries are 4s 3350 at 35 c. .ESC is overlander 60amp. I've propped about as low as I can at 11.5 by 7, but I'm still getting 700 watts at full power. Model weighs a shade over 6 pound.

The batteries are getting very warm and starting to puff, which they never did in other models. I've set the ESC at low cut off but I still lose power and have to land after 5 minutes, when my battery checker says 38 per cent and 3.8 per cell.

.....................................................

 

Given the motor, prop, and battery you have, 5 mins at full power looks reasonable. Smaller prop, lower kV motor, or 3s battery are the options to increase full power duration.

 

BUT

 

41 minutes ago, Maurice Dyer said:

And yes I know it's got a throttle, just use less power etc. But that doesn't solve the problem.

Can I ask why throttling back doesn't help?

I have a 6lb biplane with 1000+ watts at full power, but I only use that for continuous vertical manoeuvres and it flies happily on 300watts or less for most of the flight.

 

Dick

Link to comment
Share on other sites

Just remember adding battery capacity follows the laws of diminishing return. The plane is heavier so it need more power to fly eating into some of that extra battery capacity. 

As with any plane flying on reduced power (either using the throttle or installing less power) is the surest way to extend duration. 

 

Link to comment
Share on other sites

One thing to try is putting a wattmeter in the system, and using an accurate luggage balance hooked over the tail and experiment. Look at the sort of power curve you get and the current used. It is normal for the current to rise significantly in the last third of throttle increase, with the static thrust rising far more slowly.  Try different props with that system.

 

That is a common battery/ESC/motor combination I use, and with an all-up weight 0f 2.7kg it should be absolutely fine. Actually I think your second posting does indeed solve the problem. Most of my planes with a similar combination fly brilliantly on just half throttle, with power in reserve for when its needed. Its a very draggy plane, and flying faster will have very limited impact in terms of speed in the ait, but will burn through your batteries faster.

Link to comment
Share on other sites

It could also be that the batteries are a bit tired and the internal resistance has increased which results in a bigger voltage drop across the battery under load, hence your ESC starts to cut back on the power before the battery is fully discharged, but after you land you measure the volts with no load.

 

Batteries getting warm is an indication of an increased internal resistance.

 

I had an E-Flite Beaver a few years back, on new batteries I could get 11 mins flight time, but that gradually reduced to less than 8 mins on the same batteries.

Link to comment
Share on other sites

Thanks all. I think it's a motor problem somewhere. I have a tingly using the following: Ask 2820/12 990kv. Swinging a 12 by 6, drawing 500 watts. Flies for 9 minutes on the 4s batteries I put in the SE. No heat or puffing. I will try 

a. 3s battery, with the same tornado motor.

b. The Axi motor in the SE with the 4s.

 

Cheers guys.

 

Link to comment
Share on other sites

1 hour ago, Simon Chaddock said:

Just remember adding battery capacity follows the laws of diminishing return. The plane is heavier so it need more power to fly eating into some of that extra battery capacity. 

As with any plane flying on reduced power (either using the throttle or installing less power) is the surest way to extend duration. 

 

 

In general, that's true, Simon, but in the case of the Flair SE5a it needs the weight to achieve balance so a bigger battery is better than lead.  Mine needed loads of lead to achieve the correct CoG when it was powered with an OS52 Surpass but none with the 4S 4AH and the all up weight is identical (6.84 lbs). 

 

1501745240_motormount3.thumb.JPG.d5e7f613a870ff099523a9fabe92131d.JPG

 

The motor sits neatly under the battery tray.  The model is over 20 years old, hence its tatty appearance 🙂

 

Geoff

 

PS, just a thought.  I had a motor that drew a lot more current than I thought it should. In the end, it turned out that the supplied cuneiform mount was fouling the colette that held the motor shaft and loading the motor.  It wasn't immediately obvious, so it might be worth checking.

Edited by Geoff S
Link to comment
Share on other sites

My Flair SE5A is a bit chubby because it has a sound sytem in it, but it uses 440 watts from a 5S A123 battery pack with a 12x6 prop.  Plenty of power for scale flight.  As others have mentioned, lead is needed in the nose for balance, so a larger capacity battery will be used if/when I convert it to 4S LiPo.

Link to comment
Share on other sites

17 minutes ago, Andy48 said:

Having had a second look, I think you have been going the wrong way with props. Overlander recommend a minimum prop size of 11x8 for that motor on 4S. Have you tried the recommended prop size?

It's fitted with a 11.5 by 7. I will try 11 by 8, but it's a dog kennel fronted se, lots of drag.

Link to comment
Share on other sites

Well took the motor out, nothing wrong. Checked with watt meter. 4s on an 11.5 by 7 prop: 700 watts and 50 amps. 

3s battery, same prop. 400 watts at 35 amps.

The decision is change the battery to 3s ( I have a 4000 mah) which is as heavy as the 4s ). New prop at 12 by 6 and see what happens. 

It's a swine this electrics, isn't it ??

Maury

Link to comment
Share on other sites

Same motor here on an 11x8 on 4S5000, showing 750W. But, a slippery airframe, sleek aerobatic type. Your power readings are what I would expect for the prop.

 

For your SE5a I would have started - on the 4S - at 12x4. Low pitch. See what that draws (power). Expected rpm would be around 10k or 11k. High pitch won't help a lot as the thing is like a brick in terms of drag.

 

For 3S your 12x6 might be closer to the mark. You may even find a 13x6 necessary to get the right power. The drop to 3S will mean less RPM, down to 7k or 8k.

 

Electric is flexible.

Link to comment
Share on other sites

Geoff

I agree there is nothing wrong with installing a bigger battery than is strictly necessary to achieve a required CofG. It is a win/win situation however I have in the past upset some by saying that if you have to put lead in a plane it is down to poor design and/or the choice of materials. 😉 

Link to comment
Share on other sites

1 hour ago, Maurice Dyer said:

Well took the motor out, nothing wrong. Checked with watt meter. 4s on an 11.5 by 7 prop: 700 watts and 50 amps. 

3s battery, same prop. 400 watts at 35 amps.

The decision is change the battery to 3s ( I have a 4000 mah) which is as heavy as the 4s ). New prop at 12 by 6 and see what happens. 

It's a swine this electrics, isn't it ??

Maury

700 watts at 50 amps means you were only getting 14 volts from the battery under load - i.e. 3.5 volts per cell - which is not exactly wonderful at that load so perhaps Frank was right with his earlier post suggesting the batteries are getting a bit "high resistance".

 

Dick

Link to comment
Share on other sites

1 hour ago, Nigel R said:

Same motor here on an 11x8 on 4S5000, showing 750W. But, a slippery airframe, sleek aerobatic type. Your power readings are what I would expect for the prop.

 

For your SE5a I would have started - on the 4S - at 12x4. Low pitch. See what that draws (power). Expected rpm would be around 10k or 11k. High pitch won't help a lot as the thing is like a brick in terms of drag.

 

For 3S your 12x6 might be closer to the mark. You may even find a 13x6 necessary to get the right power. The drop to 3S will mean less RPM, down to 7k or 8k.

 

Electric is flexible.

Guys.

I (hope) I have the answer. Tried different combos, but in my heart, I wanted to stick with 4s. Now, 4s, 12 x 6 prop: 500 watts at 35 amps full power. So it's full power for take off and then half throttle for normal scale flying. What a jigsaw that was. I flew it Tuesday evening in a strong wind..........learn a lesson maurice. Full power most of the time. Which isn't a problem for IC, but it was for leccy.

 

Thanks

Maurice

Link to comment
Share on other sites

6 minutes ago, Dickw said:

700 watts at 50 amps means you were only getting 14 volts from the battery under load - i.e. 3.5 volts per cell - which is not exactly wonderful at that load so perhaps Frank was right with his earlier post suggesting the batteries are getting a bit "high resistance".

 

Dick

Dick, batteries are not that old. A couple of dozen flights and I charge at the 80 percent rule. But they have been used in a fun fly, Overlander 35c.

  • Like 1
Link to comment
Share on other sites

1 hour ago, Maurice Dyer said:

Dick, batteries are not that old. A couple of dozen flights and I charge at the 80 percent rule. But they have been used in a fun fly, Overlander 35c.

I have just checked the data log of a flight last week and my 4s 1000mAh battery shows 13.5 volts at 47 amps. I would have expected a 3300mAh battery to give higher volts at that sort of load than a 1000 mAh one - BUT if you are now getting decent flights it is not a major issue.

 

Dick

Link to comment
Share on other sites

Maurice, it looks like you've found the answer. The 7-8 minute duration that I get is in relatively calm conditions- I get no pleasure from fighting a strong wind with a slow flying biplane, if it's windy I take something else.

 

The duration thing is quite subjective. Even when I used to fly i.c. I used to land after 7 or 8 minutes, just get bored I suppose! These days I typically take 3 models to a flying session for variety/backup.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...