16 AWG wire OK for parallel XT60, 4S battery system?

Gary Seven

Gary Seven

Rocketman
Hello folks.

While picking up the usual odds and ends from HK a few weeks ago, I decided to buy their parallel adapter with XT60 connectors for the F550 build I'm working on. This build will utilize the DJI E310 system and I plan on using two 4000 mAh batteries in parallel. Anyway, to my concern my stuff arrived and I immediately noticed that the parallel adapter I ordered was built using 16 AWG wire. Does this seem way "underspec" to anyone else?

Here are the specs on the E310 system: http://www.dji.com/product/e310/spec
As per usual DJI's numbers are sparse and far and few between, but if I build a hexacopter with six ESC's rated at 20A plus the six motors, my gut feeling is the 16AWG adapter is NOT going to handle that. Seems to me the wire gauge should be around 12 AWG. Could someone please advise? Thanks!
 

Bartman

Bartman

Welcome to MultiRotorForums.com!!
what is the wire gauge of the batteries? using anything thicker than what is coming out of the batteries would be a waste, no?
 


Pumpkinguy

Pumpkinguy

Member
I would match the battery conductor size. Or one size up if you have both batteries feeding the pdb off one main lead.
 


Bartman

Bartman

Welcome to MultiRotorForums.com!!
yes, use 10 AWG but keep in mind that if one battery fails the other will be picking up the load (as well as zapping the crap out of the failed battery) so things can get funky very quickly.

just thinking out loud, maybe we should be building zero ohm diodes into our parallel adapters so the good battery can't run voltage back into the failing battery thus starting a fire and draining the good battery.

hmmmm....
 

Pumpkinguy

Pumpkinguy

Member
When I talk about wiring it's mostly based on my experience outside of rc. my position is that you can't oversize but under sizing is definitely a problem and we are talking about such short lengths that weight is not an issue.
Rc applications tend to put more current thru a conductor than I've ever seen elsewhere so I always air on the side of caution.
 

Gary Seven

Gary Seven

Rocketman
Thanks to both @Bartman and @Pumpkinguy for your replies. Bart, in all honesty it never occurred to me that one battery failure in a two-battery, parallel arrangement could take out the good battery as well thus crashing the vehicle. My whole point to building my F550 this way was supposed redundancy, and the got the idea from the folks here at Multirotorforums (think it was you, Bart)!

So my choices are, go with a one-battery setup and hope I don't have a cell failure in flight; or go with a two-battery profile and hope that a failing battery doesn't take out the remaining good one and equally crash my vehicle. Yes?

Honestly, I'm at a loss now at what to do.:(
 

Gary Seven

Gary Seven

Rocketman
Bartman said:
just thinking out loud, maybe we should be building zero ohm diodes into our parallel adapters so the good battery can't run voltage back into the failing battery thus starting a fire and draining the good battery.
hmmmm....
Click to expand...
That's a damn good idea. I assume you mean a zener diode? But how to physically wire in such a (micro) beast?
 

Bartman

Bartman

Welcome to MultiRotorForums.com!!
Gary, I'm using two in every helicopter i fly. a cell failure with a single battery is an instant crash. a cell failure with a two pack (not tupac but two pack :) ) system is still a problem but you'll have some time to react.

need to look into diodes and how to mount them....maybe a new thread? go for it Gary, no guts no glory!!
 

Gary Seven

Gary Seven

Rocketman
Bartman said:
Gary, I'm using two in every helicopter i fly. a cell failure with a single battery is an instant crash. a cell failure with a two pack (not tupac but two pack :) ) system is still a problem but you'll have some time to react.

need to look into diodes and how to mount them....maybe a new thread? go for it Gary, no guts no glory!!
Click to expand...
Bart, back in the 80's I did time in Silicon Valley as an Engineering Liaison between my company's engineering group and it's clients nationwide. We built silicon microstructures (accelerometers, pressure sensors, etc.) and I believe were the first to take micromachined devices (accelerometers) to the industrial and automotive markets in general. My expertise was materials, NOT electronics. Can you see where I'm headed with this?:D I could start the thread, but I need some people with solid electronics to join in and take me by the hand!!
 


econfly

econfly

Member
A standard diode inline for each battery in the harness would work (need to have to correct specs, of course, for the expected current load and voltage -- could be a real problem at, say, 30V 150A). The point Bart is making (a good one!) is that we don't want current flowing into a battery in flight. Now it may be in practice that a failed battery is not capable of allowing much current, but that depends on how/why it failed.
 

Gary Seven

Gary Seven

Rocketman
After doing some reading, it would appear a standard diode may not be the route to go because of the "forward voltage drop." Further investigation reveals that even a Schottky diode, although better than a standard diode, may subject the power system to an unacceptable voltage drop. However, that same article talks about P-Channel MOSFETs. Maybe that would be our starting point boys??

Edit: This video talks about reverse polarity protection, but me thinks the circuit would also do the job in the aforementioned post with @Bartman
 
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