One of our favourites… Only 30mins from our house. We had it to ourselves this time as well!
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That’ll happen if you don’t tell people you’re going. 
I’m only kidding. I’ve had a frantic weekend - didn’t get any time for building so I’m still down to one working quad.
Weather’s looking up though. Hopefully get out more soon. 
Sorry it was almost last minute and we didn’t have long…
Brendan being in the middle of exams doesnt help.
If you’re up for going there one evening, I’d be up for it.
Drone Circle this Sunday. Saturday I’m at a wargames tournament… it’s been a long time since I was at one of those.
Er 7 working large quads, 3 working tinywhoops and a plane in this house. We’ve not been to a bando for a while, lol.
Don’t worry. I don’t expect you to keep me updated on your every move. 
At the minute I’m struggling to make time for fleet repairs, never mind getting out flying. I’ll be trying, though.
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Well time to change that soon? haha. After the big meet maybe!
Good luck to Brendan in his exams too.
See you Sunday, we should coordinate BBQ food this time I reckon at least less breaks at Drone Circle, and you have lovely burgers
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Those venison burgers I had were delicious… though actually the two in the packet were just enough for me…
We do need some sort of burger sauce though. James had brought cheese which helped.
I’m looking forward to exploring more amongst those trees and maybe seeing properly how long I can keep the new build in the air.
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So… the main reason for the slow flying at Harborough was to get a real handle on how long this flies. Well the result is that it’s not as long as I’d hoped.
Total flight time fully loaded with GoPro on 1550mAh 4S battery was just under 5 minutes. Not bad, but hardly long range.
What had confused me was my current calibration. This is all handled by a dividing scale factor in the Betaflight config. By default it was set to 400 and it was clear after using the current sensor on my bench power supply that this was just plain wrong. After bench tests I found it needed to be around 160.
Anyway, after flying last night I did some checks to see what Betaflight reported the used mAh to be in the OSD and what the batteries needed when charging back up. I did this with all 4 packs I flew. This I then plugged into the spreadsheet in the video below along with the existing scale factor and found it actually needed a scale factor of 83.
Quite a bit different from what I had and a LOT different from the default value.
Anyway, I guess this means it was taking about twice as much current as I’d measured at Drone Circle and last time at Harborough… so probably between 15A and 21A *.This being at low throttle. The jury is out as to whether I should risk putting the 2500mAH 12C 4S LioN battery I have… 12C means a max current of 30A on that… hmmm…
Here’s the video I used to help me…
* this matches up with my battery capacity and flight time
It’s difficult with the charging method because it balances, so the mah put back is incorrect. Not sure by how much though. I’ve charged lipos up and the mah put back in has been more than the capacity on the label.
I guess if you put the li-ions on, if it maxes out, you just wont get the punch. No biggie though?
I thought it was supposed to knacker the Lions if you went with too high a current?
I’m not sure. I always take off at full throttle on my plane at 50a. Seems ok. Think they are 60a though (4s2p) @Steviegeek will know
It matches the capacity of the pack a lot closer than the OSD did… eg. the values from last night
Pack capacity: 1550mAH, charger report: 1386mAH, 1312mAH
Pack capacity: 1350mAH, charger report: 1150mAH, 1082mAH
OSD was reporting approx half that with scale factor of 160… I’ve set it now to 83.
I guess if you hover with a battery until it dies, you know the capacity exactly 
I’ve just bought some P26A’s that have maximum discharge current of 35A, they will be in 2P configuration so I can take off at up to 70A 
Fortunately I won’t need to pull that much power for too long 
You need to check the data sheet for the cells you are using as they differ widely
I have one of these…
25A, good for a plane 
Yeah I wouldn’t put that on a quad
Hmmm I can get a 4S1P config on this quad, but not a 4S2P pack. My available space is just short by a couple of cm.
Do you think a 4S1P pack (35A) would work for me?
Edit: Those cells are quoted as 25A everywhere I can find…
2nd Edit: Ah, the datasheets say 35A
I wonder about these…
I don’t have to use 18650, 21700 will fit.
Datasheet looks to say 45A… nice.
70g x 4 = 280g. The 1550mAH lipo pack I’m using is 182g hmmm…
Found a place that will do 4 for £31.50 shipped.
Looks pricey. Steve has a cheaper supplier
I tried there… worked out more expensive by a couple of quid.
Buying in bulk might work out better. But I only want a test pack to start with.
BTW, I reckon I’d get about 10mins flight time with these.
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