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LIPO Battery Duration Query

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Keith Berriman28/10/2019 20:20:15
747 forum posts
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One for the Electric Flyers. I have an Easy Street with recommended Quantum motor and fly on three new 3S 2200 batteries, but seem to be low on duration ( 5 mins ) and looking at two options

Do I upgrade to a 3 cell 2900 or 4 cell 2200 ?? both around the same price

Appreciate the 4 cell will increase speed but then I can throttle back

Former Member28/10/2019 20:33:54
3577 forum posts

[This posting has been removed]

Andy4828/10/2019 20:50:39
1549 forum posts
10 photos

You will get a significantly longer flight if you fly at less than full throttle, yet you will barely notice a speed difference. Above 2/3 throttle, the current consumption rises substantially, yet with much less improvement in thrust.

Ben B28/10/2019 22:05:53
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1435 forum posts
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Go for the bigger capacity 3s. If you go 4s you'll produce more peak power but your esc and motor might find it too much unless you prop down. Unless you're looking for more power just up the capacity. You could work out the total kwH of the two packs and theoretically there's an advantage in terms of less pack sag to using a higher cell count but on a reduced throttle curve to maintain the old wattage pulled but it feels like overkill for a simple plane.

extra slim28/10/2019 22:50:47
495 forum posts
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Personally, I’d experiment with props and a watt meter before I look at batteries. Big differences between sizes and different make of same size on amps drawn, which equals time in the air

gangster29/10/2019 09:17:59
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Unless you have a meter that will show power and current draw I would not advocate playing with cell count or prop size. Such a meter is dirt cheap and a must have for levy flyers who wish to experiment. If however you have room no problem increasing to 2800 or3300. What I did discover when I started flying electric was what the throttle stick was for and use it for economy. The knock on effect is that I use the throttle much more when flying if as well now

extra slim29/10/2019 10:40:37
495 forum posts
49 photos

just reading again, and your comment makes me think that it is an easy street 2??.. if so, plenty of room to increase capacity, but gangster's and my comment of getting a watt meter still stands..

Keith Berriman29/10/2019 12:34:07
747 forum posts
11 photos

Thanks for replys Wattmeter was used when first set up and all as should be. Will get watt meter out again and go for different props

Frank Skilbeck29/10/2019 13:05:49
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4751 forum posts
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Looking at it from watt hours in the battery the 3s 2900 mah has 32.19 wh and the 4s 2200 mah 32.56 wh, just over 1% more stored energy..................

Other factors like battery internal resistance will have a bigger impact on duration.

Edited By Frank Skilbeck on 29/10/2019 13:07:04

Bob Cotsford29/10/2019 16:41:11
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8636 forum posts
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Looking at the log files, I get around 7 1/2 minutes flying on a 3S 3000 pack but the alarm is set at 66%. It flies nose heavy as I recall and the pack needs moving back a bit so I was thinking of trying it with a 2200 pack.

Former Member29/10/2019 20:22:24
3577 forum posts

[This posting has been removed]

Keith Berriman29/10/2019 20:36:13
747 forum posts
11 photos

I am a predominantly an IC flyer and can have long stint in the sky as our patch is usually quiet when I can get there in mid week but busy on weekends, I have a Sarik Tracer E on a 1700mAh and easily get 8 mins which is enough.

Appreciate the Easy Street 2 is a heavier model but I can see at 4.5 mins it time to get it down and was only looking to see what others may get on 2200 or 2900 capacity batteries

Andy4829/10/2019 21:24:25
1549 forum posts
10 photos
Posted by RC Plane Flyer on 29/10/2019 20:36:13:

I am a predominantly an IC flyer and can have long stint in the sky as our patch is usually quiet when I can get there in mid week but busy on weekends, I have a Sarik Tracer E on a 1700mAh and easily get 8 mins which is enough.

Appreciate the Easy Street 2 is a heavier model but I can see at 4.5 mins it time to get it down and was only looking to see what others may get on 2200 or 2900 capacity batteries

I guessed so. Before you buy anything try out my suggestion above at the field. Most IC flyers who start to go electric almost always fly on full throttle most of the time. However, the characteristics of an electric setup are quite different. There is a lot of power at lower throttle settings. I rarely need more than half throttle to take off.

Also remember that adding a larger battery adds more weight, which may well affect the handling characteristics, and almost certainly will require more power, so somewhat counter productive.

Keith Berriman30/10/2019 18:36:57
747 forum posts
11 photos

Just done a quick check tonight before I start with watt meter tomorrow

The motor is a Ripmax Quantum 25 S ( 1200kV rated ) which advise a 10 x 7 and equivalant to a `25 ic on 3 s

it advise a 9 x 7.5 on 4 S. Maybe the 10 x 7 is a little course and have to see what props I have in the hanger

Keith Berriman31/10/2019 19:08:41
747 forum posts
11 photos

Bit of an update from this morning fitted various props and noted the following results

Measured 310 watts on an 11 x 5.5

295 watts on the recommended 10 x 7 Noticed on the box in mentions a 2700 MaH not on data sheet

275 watts on an 10 x 5 I had in the hanger

Took the Easy Street with 10 x 5 on to strip this afternoon ( Along with an IC ) and did some more testing

I found take off different in that it needed a longer run to get lift, once in the sky all was okay but was a little docile, timer buzzing at 4.5 mins and it was still flying with power and so round for a landing. This time I had to ensure I had low throttle on to keep the nose up. Capacity check when taking out a very cool battery showed 45%. Second similar battery fitted and away we go, take off a little better and flight okay and full power again for 4.5 mins, landing was same as above. Battery capacity still another 45% and cool. Passing model shop tomorrow so will pick up a 10 x 6 and see how we go. May put a 2700 battery on the Xmas wanted list

Happy Flying to all

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