Flight times, temperatures and all that

[MombasaFlash]

Having inadvertently derailed a couple of other threads I thought I had better start clean here with a new and specific one.

It all started with the MK Octo as the guinea pig to see what all the MR fuss is about - coming from the single rotor world. Other than some MK quality control hiccups at the build stage I could not help but be impressed with the relaxed flying experience and the general lack of fuss. So, the next stage was to get a bigger one to carry a decent camera. The Panasonic P2 video camera is just too large and heavy for a multi-rotor so it will have to be the Canon 5D. Lo and behold 2814 motor class Octo's are aimed at 5D's. Perfect!

One lovingly assembled Droidworx AD-8 v3 HLE later and .... it is all getting a bit tedious. Without a shadow of a doubt my AD-8 does not really like carrying the Canon 5D. It lifts it up easy-peasy and scoots around no problem and delivers nice smooth video but ... it gets so HOT. The battery cable is too hot to touch immediately after a flight and the BL Ctrl temperatures are being read out as reaching 90+°. BL #1 is ALWAYS the hottest and the coolest is always BL #6.

BTW, does anyone have a good explanation for why there is always such a wide range of BL temps? A variation of 10-15° would not seem unreasonable but on my AD-8 BL #1 is consistently almost double the temperature of BL #6.

Anyway, today I tried to get a handle on it once more with some good old statistics (not sure about accuracy of the stated weights - I cannot find a better scale than this crappy fisherman's spring-thing).

Flight 1: MK Octo with 1x 5000 LiPo and Sony NEX-5N (16mm lens) and HDMI converter, total weight around 2.7kgs -- flight time 10':06"
Flight 2: DW AD-8 with 2x 5000 LiPo and Canon 5D, total weight around 5.9 kg -- flight time 09':34" -- BL temp range 42 - 84°C
Flight 3: DW AD-8 with 2x 6600 LiPo and Canon 5D, total weight around 6.2 kg -- flight time 11':58" -- Bl temp range 48 - 93°C (plus really hot battery cable)
Flight 4: DW AD-8 with 2x 5000 LiPo and Sony-5N, total weight around 5.0 kg -- flight time 13':05" -- BL temp range 40 - 80°C

Krleas reckons he gets 10-12 minutes from his AD-8 with a 1.5kg camera, AV200 360 and two 6000mah 5S packs. That lot has to be close to 6.5 kg take-off weight and he says he has no temperature problem.

I don't get it. Why is mine getting so hot?

 

[Sebas600]

I thought BL's could not take 5S?
maybe he's using DJI with other ESC's?
or to thin battery cable?
to long battery cable.
wrong battery cable?

maybe some more info on your setup?

 

[jes1111]

Cables too hot to touch is a definite problem that you should change immediately. They are obviously not heavy enough for the job - change up one or two "gauges" on the AWG scale - 6 x2814 should require at least 10AWG from pack to distribution point - make them as short as possible (and twist them together).

90º+C on a BL is way over spec - that's going to kill them sooner rather than later. Do they have airflow? heatsink?

Once again... eCalc - and if what eCalc says differs widely from your reality then look for the reasons, and don't fly again until you've found them.

90

 

[MombasaFlash]

This overheating issue is only apparent when carrying the Canon 5D. No payload at all or carrying the Sony NEX does not produce the same BL temps or hot battery connector/cable. The LiPo connector is a Deans and the cable is an MK shop item that was ordered along with the first Octo.

With the exception of the added I2C isolator board, the AD-8 build is a standard MK stack with FC, NC, GPS PDB & BL's decorated with heatsinks, with both the 'High Airflow' Dome and the PDB sitting on 20mm stand-offs. Removing the canopy altogether reduces BL temps (as displayed by MKTool) substantially. This is detailed in another thread and brings the Hi to Lo range down to 41-67°C (with the Canon 5D onboard).

Bear in mind that these high BL temperatures started with the 0.86d firmware update. That same other thread described how going back to firmware FW0.84a produced a BL range of 55-83°C - with the Canon 5D onboard and a standard 'no cooling holes' dome NOT on standoffs.

This whole FW 0.86 overheating issue has not been resolved as far as I know and I am surprised there is no chatter about it anymore. The forums were full of it with nobody knowing what the cause was and then Holger jumped in with the FW0.86e update which was supposed to address the issue by introducing an option to turn off 'Motor Smoothing'. I have no idea what that is but whether it is On or Off makes little difference to the high temperatures in my tests.

 

[Sebas600]

I think changing out the battery cable for a thicker one and tossing out the deans for something better.
And you are using a two lipo setup, give each pack it's own wire to the esc distribution.
none of the wires should ever get hot! this means danger, high resistance and so loss of power

good wire for the double lead setup: http://www.hobbyking.com/hobbyking/store/__9672__Turnigy_Pure_Silicone_Wire_10AWG_1mtr_BLACK.html

good connector for double lead setup: http://www.hobbyking.com/hobbyking/store/__9283__HXT_4mm_Gold_Connector_w_Protector_10pcs_set_.html

hope this is of help

 

[BorisS]

id even go a number bigger ! http://www.hobbyking.com/hobbyking/store/__9194__EC5_5mm_Connector_Pair_.html

93a flying with heavy loads two lipos 5d etc and having to give it emergency throttle can be easily reached.

Boris

 

[MombasaFlash]

The trouble is none of these solutions address the BL temperature issue. Lots of folks use the MK stack and, assuming most have updated to the latest firmware, I am wondering why this issue is not still being tossed around.

As to giving each LiPo a dedicated cable, yes of course it sounds logical but how on earth do these big fat cables get reliably soldered to those tiny pads on the PDB - and without getting in each other's way? I have never liked those pads anyway, sitting 1mm apart with all that current smashing through.

With hindsight I might have gone for the neat looking Hercules system but did not learn of it until Boris' CS build thread. But then again, the MK Octo did okay so there was no indication that scaling up a bit to the AD-8 would be anything but better.

Does the Hercules use an I2C bus? What happens with regard to I2C redundancy with that system? Or is it that much better integrated that it is not a potential weakness?

By the way, all these BL temperature readings are taken during extended periods of hovering. This is deliberate in order to impose the maximum stress and to ascertain maximum safe battery autonomy. A bit of movement brings the BL temperatures down by 10-20° almost immediately and of course also lengthens flight times.

What about the wide temperature discrepancies between the eight BL Ctrls? Does everybody else have this too or are the temperatures normally more equal?

 

[*****]

Deans are a nono for your octo , had many issues with them.
first of all they can't take the heavy loads , the metal parts that pushes the connector together gets warm and lets go , resulting in less contact creating heat etc etc.
best is to go to 6mm connectors they can handle it better.

your temps:

well the build looks ok to me , however what is the blue stuff you use to glue the coolers on the esc?
we use only the silver adhesive .

difference it temps:

Balance ok?

when in flight PH read temps and turn the craft 180 degrees read temps again? any changes?

your cooling looks ok to me same as we do it on our crafts.
the 5D that you use what is the real weight? i know with stock lens it should be around the 1,5 kilo range

whats your amp usage in hover? should be around 55 amps?
i do know that its best to use rather 2 4 s battery,s to deal with the higher loads.
or use a 8000 4S with 30 C they worked for us best.


or herkules works fine also.
problem with herkules is you need if you have jeti: Expander mui 150 or 200 and temp sensor.

or wait for the Aerodron power boards and you don't need to worry about temps.

 

[BorisS]

Hercules actually comes from the MK side and is designed for I2C, i was probably one of the first actually using it for PPM. Concerning redundancy i cant give you a answer but i would ask Andreas Baier directly www.andreasbaier.de. Concerning temperature with or without the a heat sink i know you will not have any issues with the hercules boards. When i fly, (check out my logs http://www.multirotorforums.com/sho...erkules-II-Build&p=15083&viewfull=1#post15083 first value left "A2 value"on the line graph), the temps are not even touching 10° when hovering. okay i most add though that the air temp was maybe 5 °.

What you also have to do if you are interested in the hercules is find a way to get the voltage reading from hercules over you given telemetry system. As far as I know the MK FC and hercules communicate and the FC pushes on the voltage reading as long as you fly 4s and 5s the MK FC cant any more provide the data. But I know that krleas (matjaz) from kopterworx.com found a work around to get all the relevant data no matter 5s or 6s.

Why your MK BLs are reading out different temperatures i cant tell you. I remember though back from my MK days that they didn't or only did if i have strong sunlight impacting only one side of the copter. 90° i never reached those values with my MK BLs on my AD 8 with 2 x 6000 mAh 4s and a canon 500D with a 10 - 22 mm lens. I would be worried to fly expensive equipment in this state at the moment.

Boris

 

[Stacky]

I had a battery cable that was too small for the current drawn on an old Hexa i built. I had been messing around at one point with trying to lift a dslr which the Hexa could do but the hover point was a bit low. Anyway a day or so later I was getting ready to fly and when I plugged in a battery there was a bang and a short circuit. The plastic insulation on my battery cables had finally given up and shorted out. Luckily I wasn't in the air at the time. The insulation on the cables had become brittle and lost their flexibility etc. I think the current loads when I had been lifting the dslr had been the straw that broke the camels back

 

[MombasaFlash]

I have never liked the Deans design. Very good for polarity but those bare tabs sticking out the back requiring heatshrink are really rubbish.

That blue stuff is the adhesive that was supplied by FlashRC when I ordered the heatsink kit. Have no idea how good it is. The only way to tell is to try and pull the heatsinks off. Then, if one comes off, I'll have a mess to clean up :nevreness:.

As for the overall balance, I cannot imagine that the centre of gravity is very far off. The only individual items that are not balanced out by an identical component opposite are the Rx and the two 6 LED strips around the rear motors - and all that is at the rear. If motor #1 is working harder it would suggest the whole thing is front heavy, but there is nothing there at the front. Otherwise the circular design ensures that every component has an identical component compensating on the other side. Batteries are under slung and central and cameras are always mounted such that their own centre of gravity is in line with the MR's. However, I have noticed that the CofG marker wanders over to the left in the window within MKTool.

Have not checked in-flight amps. I'll have to find it in MKTool and check it.

The Canon 5D mk2 weighs in at 1594g with the 24-105 zoom and 1524g with the 14mm UltraWide.

Thanks for the Hercules input Boris. I will try and sort out the current setup first since it is otherwise working OK. I will organise some heavier battery cables and connectors first off and then if the BL's insist on getting hot maybe swap the dome for a crash cage. Perhaps a future firmware update will remove the overheating BL's gremlin.

 

[jes1111]

Sorry to persist, but I'd still use eCalc as a reference point in order to establish deviation (in consumption, time, temperature, etc.) from the theoretical ideal and, subsequently, the relative success of corrective actions.

 

[Bartman]

with the camera, if the pivot points (tilt and roll) aren't directly through the camera's center of gravity then the balance will shift forward as you tilt forward. that might explain the hot #1 BL but #6 should be cooler. Also #2 should be equally hot and #5 should be equally cool. #1 is the front one left of center, right? Have you double checked the mixer table to make sure the motors are all properly assigned their jobs for control and lift?
regarding power to the distribution ring, it would be nice if MK would make a second set of solder tabs for connecting power leads. Two independent sets of leads to two independent sets of solder tabs would be ideal.
bart

 

[MombasaFlash]

Persist away Jess. That's what this is for.

I had call to test a modification to the camera mount suspension and decided to risk flying from my hedged in, well foliated tiny back yard because it is too much hassle loading up the truck to go to the field. It was also a camera comparison session.

Starting with the 5D the cable got warm as expected. As it was quite gusty in addition to the rather narrow passage to the open sky I didn't have too much time to concentrate on the computer screen but I did note that the current draw was 66.7 amps. Well above the 55amps that Krleas mentioned.

With the NEX-5N, and Panasonic HDC-SD9 camcorder on board there was nothing untoward with temperatures and the cable was not hot.

Bart ... Yes, totally agree it would be nice to have a second pair of main power lead tabs. I have ordered some 10AWG and 8AWG cable and 6mm connectors. I will probably try removing a small length of insulation in the middle of a double length cable to avoid trying to solder two separate cable ends to each pad.

I did not look at temperatures this time but from past records, including the most recent readings, BL #1 is ALWAYS the hottest, followed by #2. Next is 3 & 8, then 4 & 7 and the coolest are 5 & 6. So yes, that would all suggest a front heavy situation.

This pattern is repeated with the NEX-5N but the temperatures are all between 15-20° less.

I realised that there was in fact one other non-standard thing and that was a 3S LiPo for the downlink, mounted just behind the front gear arch. Perhaps its weight was significant enough to cause the front motors to be constantly working slightly harder. That has now been removed and the downlink is powered from the main packs. When I can get out into the open I will have another go and see whether this makes a difference to the distribution of temperature readings. I will probably not leave the downlink powered by the main packs because it invites interference with no filter and all those motors and also leads to even more demands on the main packs.

Don't you think that if the mixer table was set wrong it would be completely unflyable?

As for gimbal balance, yes, it is very important to balance the camera within the gimbal for optimum performance. It is habit I already have with the pro heli. However, the MK Highsight SLR2 is not really very good and allows the 5D to tip forwards if you use the provided slots. In contrast, the Sony NEX-5N tips backwards. So, as with the camera plate on the big heli gimbal, each camera has its own dedicated mounting hole or slot in order to get it as central as possible.

So the 5D sits as far back as it can (which then prevents it tilting a full 90° forwards but at least it is better balanced for the majority of its travel), and the NEX is mounted forwards.

The centre of gravity will of course shift when the camera is tilted if there is no provision for height adjustment - which there isn't on the SLR2.

 

[Tahoe Ed]

Deans are a nono for your octo , had many issues with them.
first of all they can't take the heavy loads , the metal parts that pushes the connector together gets warm and lets go , resulting in less contact creating heat etc etc.
best is to go to 6mm connectors they can handle it better.

I have to disagree with your assessment of Deans under high load. I have used them on a 700E single rotor with 12S with no issues. I will say that I used the "real" Deans not the Cheans that are around. I would never trust my expensive gear to them.

 

[MombasaFlash]

So, taking note of Jess' recommendation I have persisted.

My singular, solitary memory of computer class in 1968 or so is the expression GIGO. Garbage In Garbage Out. So first of all I went out and bought as accurate a digital scale as I could find and then I weighed absolutely EVERYTHING, individually and then collectively to verify totals. With this information I now felt properly equipped to try and get some meaningful theoretical numbers out of eCalc.

I find that eCalc does not calculate the total weight correctly when using the 'Without Drive' option and so opted for the full verified weight under 'With Drive'.

The result gives readings pretty close to actuality in terms of current draw and flight time BUT, eCalc says I have to stick with the SLR2 camera Mount because there is insufficient payload available for the increased weight of say, the AV200.

Indeed, adjusting the overall weight to include the AV200's 590g in place of the SLR2's 281g takes it over the edge and red numbers start to appear.

Therefore I am partially gratified to discover that my original statement that the AD-8 HLE is NOT actually man enough to carry a Canon 5D, despite the marketing claims, is borne out by eCalc. I bloody well knew it !!

That 'partial gratification' is rapidly replaced with annoyance at the realisation that the 5.5K euros spent building this Droid flat 8, which was purchased SPECIFICALLY AND SOLELY to carry the 5D, has not been well spent.

However, changing the LiPo to a 5S suddenly makes everything look comfortable. The only question is whether or not the MK electronics (BL Ctrls., FC etc.) and AXI 2814/22 motors will be comfortable with the extra voltage.

Who can give the answer to that question?

eCalc with 5000 mah 4S packs ...

eCalc with 5000 mah 5S packs ...

 

[*****]

So, taking note of Jess' recommendation I have persisted.

My singular, solitary memory of computer class in 1968 or so is the expression GIGO. Garbage In Garbage Out. So first of all I went out and bought as accurate a digital scale as I could find and then I weighed absolutely EVERYTHING, individually and then collectively to verify totals. With this information I now felt properly equipped to try and get some meaningful theoretical numbers out of eCalc.

I find that eCalc does not calculate the total weight correctly when using the 'Without Drive' option and so opted for the full verified weight under 'With Drive'.

The result gives readings pretty close to actuality in terms of current draw and flight time BUT, eCalc says I have to stick with the SLR2 camera Mount because there is insufficient payload available for the increased weight of say, the AV200.

Indeed, adjusting the overall weight to include the AV200's 590g in place of the SLR2's 281g takes it over the edge and red numbers start to appear.

Therefore I am partially gratified to discover that my original statement that the AD-8 HLE is NOT actually man enough to carry a Canon 5D, despite the marketing claims, is borne out by eCalc. I bloody well knew it !!

That 'partial gratification' is rapidly replaced with annoyance at the realisation that the 5.5K euros spent building this Droid flat 8, which was purchased SPECIFICALLY AND SOLELY to carry the 5D, has not been well spent.

However, changing the LiPo to a 5S suddenly makes everything look comfortable. The only question is whether or not the MK electronics (BL Ctrls., FC etc.) and AXI 2814/22 motors will be comfortable with the extra voltage.

Who can give the answer to that question?

eCalc with 5000 mah 4S packs ...

eCalc with 5000 mah 5S packs ...

5S is no problem the FC can take it no problem
i would however chnge the caps on the PB to 35V

we lift a 5D with no issues on a 8000 4S HLE-8 with av-200
however we do use active coolers on all fets.
and lift the dome by 15mm spacers , and use a ventilated dome with holes around
you will stay below the 80-90 degrees
typical flightime is about 10-12 minutes
props 12x3,8 apc or carbon (apcs have a bit less rpm)

 

[MombasaFlash]

5S is no problem the FC can take it no problem
i would however chnge the caps on the PB to 35V

we lift a 5D with no issues on a 8000 4S HLE-8 with av-200
however we do use active coolers on all fets.
and lift the dome by 15mm spacers , and use a ventilated dome with holes around
you will stay below the 80-90 degrees
typical flightime is about 10-12 minutes
props 12x3,8 apc or carbon (apcs have a bit less rpm)

This is weird. With an AV200/5D yours is even heavier. I am using the lighter HiSight SLR2 mount, have the heatsinks on all FETs and the ventilated Dome is raised on 20mm stand-offs. Flight times for the last session with the 5D onboard were 09:34 with 2x 5000 4S and 11:58 with 2x 6600 4S - same sort of ballpark as you.

But don't you have 465mm booms and 13" props? I have only 410 booms with 12"/3.8 APC props. I am actually happy to stay with 12" shallow pitch props if I can as they should present less load and give more docile flight characteristics.

Are you sure the BL Ctrls can handle the 5S cells? What is the other capacitor space for? The 4 labelled C1 - C4 in between the BL Ctrls?

Perhaps I will wait before changing over to 5S until the main power cables and connectors have been changed and see if the range of BL temps can be narrowed from the current 43°-95° because swapping the capacitors without cutting will be quite a pain.

***************

As an addendum to the previous post with the eCalc screenshots, I later realised that I had not entered local altitude and outside temperatures. The calculation was done using the default 500m and 25°C. Changing these to 100m and 15° provides a little more headroom with the 4S setup BUT, as this gear is supposed to go to Africa at some stage it needs to be able to cope with 1800m and 40°C - which the 5S setup will accommodate, according to eCalc.

 

[MombasaFlash]

Two more questions relating to the MK PDB board...

First, and this has been asked before elsewhere but no satisfactory explanation yet, what are these extra capacitor spaces for (labelled C1 - C4) and what value caps should be there?

Second, what is the purpose of the voltage regulator that is shown on RTF PDB's on the Kopterworx shop ...

 

[krleas]

First of all i would get rid of the heavy box that came with the hdmi to sd converter.
Second the traco power is for powering video link. (pls take notice that it is instaled wrong , the white dot needs to be on right side). On the MC board, they marked it on the wrong side so they got it wrong. We need to change picture but we forget it until someone link it and reminds us of the error.

ABout the extra caps. With high curents it is better have them instaled.

Krleas