Batteries-connectors and Amp`s for heavy Octo & Hexa

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xtakos

Member
I am in the process of building an AD-8 HLE and i will be using 2x 4S batteries in parallel for longer flying times.
I am mostly concerned about the main battery connector, the one that will power the whole octo.
First of all, let`s see the max amp`s the octo might draw.If each of the motors (MT2814/770 with 11*5) can draw 25Amp, that is
a total of 8*25 = 200Amp at WOT.I am sure that nobody needs the WOT for a long period of time, but i believe mostly for
safety reasons, we should be on the safe side.Moreover, the fall of an octo with a 2000$ dSLR mounted on it can easily lead to depression. ;)
You never know when you might need the whole power of the heli and depends on what kind of flights you perform(filming on an action scene`s might easily need all that power)
In my project i will be using 2 distro board.Each will power four motors.The max amp stress of the board will be around 100Amp which can be handled without a problem.
Now, the problem is the MAIN CONNECTOR that will power all these from the batteries in parallel.I have made a quick draw of my configuration to be more clear.
That main connector should be able to provide the 200Amp without overheating.I have seen many configurations using deans connectors.As the deans can transfer up to 50 amp,that is a
disaster waiting to happen.I am thinking to use the EC5 connector, but even that, the supported rate is 120Amp.
Droidworx site has made an alert note (a failure reported) about these connectors used on heavy amp-hungry multicopters -> http://www.droidworx.com.au/conceptx.html
What kind of main connectors do you guys use for your setup?
I have found some Anderson connectors that are for solar connections and can deal with these amp`s easily. http://www.andersonpower.com/products/multipole-sb.html


Also how can a 4S battery at 6000mAh and rated at 25/50C can deliver 150A (6*25) constant when the battery connector (HXT 4mm) is rated for up to 93Amp???

Any advice will be appreciated.

Let me know if i have calculated something wrong here...

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Macsgrafs

Macsgrafs

Active Member
I use 4s 400ma lipos x 4 per flight. I also use 4mm bullet connectors. so i have 4 connectors in parallel & they should easily take my 320A WOT current draw.

Ross
 


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xtakos

Member
Even if i join the 2 power boards the main connector amp will still remain the same....the load to the main connector will not be less.The question is whether the main connector will stand the total load?
 


J

jes1111

Active Member
I agree with homer911 - a connector for each battery. I'm using 4S x4 - each one has Anderson 45A Multipole connectors - they all feed to a single "PCB" with 0.5mm copper - the whole setup will handle 200A WOT, no problem. I hate bullet connectors, Deans, EC5, Traxxas and all those others - their current handling claims are exaggerated, I believe. Anything from Anderson is credible.

BTW - if you study the Anderson documentation carefully you'll see that many of their connectors have two versions of the contacts - "high detent" and "low detent". The default is "low detent", but the "high detent" ones have a much more positive "lock and hold". Mouser.com has both but you can't tell from their description which is which, so get the right part number from Anderson. The 45A Multipole connectors also have PCB contacts so you can mount the aircraft-side connector straight to the PCB instead of having a wire from the aircraft-side connector to the PCB. Again, be careful - there's a 25A version and 45A version - feed the right part number to Mouser's search box.
 

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xtakos

Member
That can be the one solution, one battery to each board.Although i am not quite sure if in the event of a one battery failure the one distro would handle the whole load for delivering power to the second one.I will be using these boards http://www.kkmulticopter.kr/index.h...selected=Center&sn=power_board_octo&id_no=120

Jes1111, do you have a picture of your setup?But one the other hand wouldn`t be easier and safest if i use a heavy duty connector from anderson?

Thanks for the help guys.
 

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jes1111

Active Member
xtakos said:
That can be the one solution, one battery to each board.Although i am not quite sure if in the event of a one battery failure the one distro would handle the whole load for delivering power to the second one.I will be using these boards http://www.kkmulticopter.kr/index.h...selected=Center&sn=power_board_octo&id_no=120

Jes1111, do you have a picture of your setup?But one the other hand wouldn`t be easier and safest if i use a heavy duty connector from anderson?

Thanks for the help guys.
Click to expand...

That KK board claims the copper is 1.0 µm thick. Obviously a mistake - try that number here and see how much current it would handle! See what I mean about "credbility"! ;)

Two or three problems with using the big Andersons (like the SB series) -

- you shouldn't really put more than one wire into the crimp - the rating is likely to compromised.
- to crimp the SB-size contacts properly you really need the big-*** ratcheting crimp pliers - very expensive.
- you don't really want your batteries permanently wired together - very inconvenient if one dies and you want to swap it out of the pack.
- have you seen the size of the SB series? It's HUGE.
- the cable from that connector to the board(s) would also have to be HUGE.

That's five! Oops! :)

P.S. If one battery fails catastrophically then you'll probably be falling out of the sky anyway so I wouldn't be worrying about ampacity at that point ;)

EDIT: corrected the link - brain must have been in neutral
 
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jes1111

Active Member
Did someone tell you that KK board can handle 100A? Since the board itself is only 1mm thick, I suspect the copper will be standard "1 ounce" - in which case 100A would melt the whole thing, for sure!
 

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xtakos

Member
The 'here' link doesn`t work.I have seen many hexa using it and the users reported they are drawing 120Amp without getting hot.The one that solds them also claimed ratings above 100Amp.That is why i decided to use 2 of them.
 

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jes1111

Active Member
Yeah - I should have said that I've heard people (experts, but only in the internet sense ;)) saying that such boards can handle the power because the distances are short and so on - but my view is that physics is physics and you can't really change it ;)

Certainly we get away with using 10 or 12AWG wire on batteries that can put out vastly more amperage than any published tables will tell you such a wire can handle. The run length is certainly a factor, plus domestic wiring (for example) is enclosed and therefore more subject to heat build-up. But with the possibility of third party damage or injury (let alone my own precious camera gear) I'm erring on the side of caution in such matters.

Here's my setup:
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K

Kari

Member
Can AD8 HLE really consume lot over 100 amps in any case? Don't know what estimated auw will be but hard to believe hovering amps are even close that high. Of course there are situations it needs more amps for example for recovery but don't think it tries recovery with every motor at the same time for long periods. My cinestar 6 consumes 40-50A in easy flying and fast climbing i have only managed draw 70-80A peaks for very short times. My cs auw is 5kg and props 11X5 graupners, think bigger props would even be more efficient. I use 5,5mm bullets and 1 afropower PDB, which has yet never been even slightly warm.

Kari
 

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xtakos

Member
You probably won`t be needing that power quite offen, but since each motor on bench can draw 25A, the whole setup should be build not according to what you will regularly need but even to what you might need.I really don`t know how much it will draw in fast climbing but 80A it seems quite low for a 5kg hexa.So each of your motor at WOT draws only 13Amp?What motors do you use?
 

K

Kari

Member
I have quadrocopter.com qc3328 motors in cs, i have never managed to get them even warm yet with high timing settings. Had some issues lately with maytech 30A esc:s but dont know if it has anything to do with amps, more like quality of esc:s and compatibilty with motors. Looks like one of them is damaged, and to be sure i'm replacing them with 40A:s to be sure there is enough amps though. Still dont believe any of motors will ever go over 30A peaks.

Kari
 

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Stacky

Member
I am currently testing my X8 and I have the KK power distribution board shown in an earlier posting. However i didnt trust that it would be able to handle the current draw of my X8 which weighs 5kg including gimbal and camera. I scrapped off the coating over the copper and then added a thick layer of solder to increase the current capability. Completely unscientific and I have no way of theoretically checking if it would work.
I am still unsure about the connectors side of things and have used deans connectors on the batteries which are 5000mah 4s batteries. The first time I tried a short hover I found the deans connectors got warm, the flight was less than 1 minute long. Also that was using only 1 battery to provide all the current needed. After a discussion with a very helpful and experienced RC shop owner near me he convinced me that the deans connectors I was using were cheap copies and that the deans he was using in high powered RC cars would handle 100 amps without heating up. Im still testing things so dont know if this is true.
I have 2 batteries and each battery connects to the power distribution board seperately so each battery connector is taking half the load.
I have been running short flights to test current draw and temperatures. So far to hover I am drawing 60amps peak. I have only run 2 minute flights but did one 9 minute flight and upon landing there was no problematic warming of the connectors, wiring or power distribution board. 8 motors drawing 60 amps to hover split by 2 supplies means my deans connectors for simply hovering are drawing 30amps each. I did one short flight with only 1 battery connected and the 60 amp peak current draw during hover, I didnt feel any warmth in the connector after this flight either but it was only a short hop and not a long flight where temperatures would build.
However the power distribution and current draw though the deans connectors, wiring and also the power distribution board do worry me. I checked the current drain on a simple quad using a 4s battery and when just hovering it peaked at 12amps, however when I used full power to arrest a fast descent the peak current went up to 44 amps. This was on a quad weighing about just under 2kg (not my quad btw).
I am concerned as to what my current draw will be when arresting a fast/emergency descent with my 5kg X8 so this thread is timely and very helpful. Over the next few weeks (time and weather permitting)I have a series of test flights planned where i will be measuring the current draw and checking the temperatures as I slowly increase the loads either via fast ascent or descent or adding weights.
What I am doing with this test machine hasnt been done with any proper number crunching or intelligent number crunching but via a rudimentary knowledge and from advice from people I believe know what they are talking about. However i wouldnt advise anyone to do it this way, it wont surprise me if I encounter problems. Im not convinced that the deans connectors or the power distribution board will handle the required current loads over long series of flights or period of time.
 

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xtakos

Member
What do you use to measure the current Amp?The first test i will do when i finish my octo (after a hover) i will stick it to the ground and apply gradually throttle and measure the current at each point of the throttle curve and i will also check the temps of everything.I won`t mount my dSLR under it unless it survive`s a 15-20sec burn test at WOT!!:tennis:
 


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