[Dale(294engr]]

This is a contact resistance problem, (one black, one red)

caused by improper connector seating (i.e. not fully inserted / mated)

exacerbated by crud, dirt, scratches on the contact surfaces +alignment

worsened with use (insertion cycles), years of use / misuse

(so these units more likely to be relagated for use only with practice robots)

analysis:

Two considerations:

P=I^R 1st order heating /melting localized at conductors contact point

2nd order Vdrop=IR = degraded robot performance: less I due to less V

A good estimate for average competition Robot current draw is ~50A

50^2= 2500 * RohmsPerContact =.001 ohm (1 milliohm arbirtary example)

P=2.5W =no problem with heating, no time limit

now include intermittent multi motor high current start / reverse periods .1-.3 sec of currents up to ~400A ^2 = 160,000 *.001 = 160W which is only a problem if it exists too long i.e. allowing build up heat at connector contact(s) junction.

at ~1sec expect some melting!!

Realistically.. Anderson contact resistance greater than .001 ohm happens
then at .002 ohm double the above.. .003 triple, .004 quad etc.

2nd order performance problem is connector contact IR drop,
i.e. Voltage drop (V-IR)
or sag as it may be referred to

400A *.001 = .4v loss * 2 for both sides) = .8v droop or 11.8v available to all robot systems

(brief battery Vsag is ~= .1v/50A so 400A is 4v additional loss
.. 12.6 -4.8 = 7.8v available to motors (and all electronics)
(simplified, disregards that motors will draw less current as Vbatt sags)


(12.6-.8v = 11.8v for new battery, fully charged, discharging at 50A so must subtract an additional .1v for internal battery Resistance sag at 50A delivery, Batt Voltage now is 11.7v Best Case!)

.. critically, motors provide less torque as less peak current is available as more voltage is dropped across contact resistance(s)
(plus all other connections & wire, to & from all motors)

.. before the melt and fall apart.. melt progresses quickly past a certain point, the contact resistance quickly rises, hastening the melting process due to I^2R heating leading to a forced disconnect due to melting apart.

The single surface contact area used by Anderson has always concerned me.
Seems a bifruc pin into a barrel would guarantee more surface area at the cost of a slightly larger physical connector (or perhaps two, one single for each side - just need to assure logistics of improper polarity mating.. opposite sex for + & -and a way to prevent plugging Battery into itself unfused..

Perhaps ALL batteries should be fused at the battery side.

I have witnessed upset robots battery terminals short against aluminum frame, overheat and smoke. Batteries have lead internal "fuse" safety link connections between the 6 ea 2v cells.. so depends on the condition in competition of battery charge state /condition plus resistance of terminal to frame "short" to determine when & if link melts (fuses), opening the circuit, or just smokes until the stored charge is consumed... in heat!

Good luck in competition

.. and may all your connector contact reisistances << .001 ohm until after the championships...