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Electrical connectors: where to use a mini, large, or Deans connector

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Old August 2nd, 2006, 02:15   #1
MadMax
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Electrical connectors: where to use a mini, large, or Deans connector

I realize in a recent upgrade discussion that many airsofters are unaware of the actual current specifications of their electrical connectors.

Having taken some introductory courses in electrical engineering and perhaps more importantly having some experience in electrical R/C helps one appreciate why a range of connectors exists to the hobby market.

There are two connectors in wide use in airsoft:

-small Tamiya
-"large" connector (basically a scaled up Tamiya type connector)

both connectors have white or yellowish/cream natural nylon bodies and are 10mm and 13.5mm wide respectively. I believe the smaller connector is actually a Tamiya properietary connector which has been adopted by airsoft because of it's wide availability and compactness. The larger connector resembling a scaled up Tamiya connector is more commonly referred to as a power connector made by Molex/Waldom in the electrical industry.

The Tamiya connector is typically rated for 9A continuous current flow. The larger Molex connector is rated for 15A of current flow. The continuous current rating specifies the maximum current flow that the connector is designed to pass on a continuous basis. I would guess that this assumes a 20C environment of unmoving air.

This means that a large connector can pass 15A continuously in still air (no forced air cooling) for hours or days without melting down. Whatever voltage drop occurs over the connector at 15A can cause the connector to warm, natural convection will remove heat fast enough that the connector will not fail.

This does not mean that the connector is working efficiently. It only means that it will not completely fail. Some voltage drop occurs over the connector (which warms it) so a reduced voltage is applied to the final load (the motor in the case of airsoft).

A relatively new connector style is becoming more popular with technical airsoft enthusiasts: Deans Ultra connector. The Deans Ultra plug is rated for around 40A of continuous current transmission. It features gold plated flat contacts which make firm large area contact between connections.

In the R/C world, the constant current rating of connectors is very important. Model electric aircraft or cars are expected to run their motors continuously for minutes at a time. In the case of planes for perhaps even tens of minutes. Because of this, it is very important that their connectors don't fail from the heating caused by sustained current flow.

In the case of airsoft, we don't have such stringent requirements. Typically airsofters fire in relatively short bursts lasting seconds. We can accept a degree of connector heating as there is often a period to allow cooling between bursts. However, a warming connector means that we are not supplying full voltage to our AEG motors. Some voltage drop occurs over switch gear and various connectors and within the battery itself.

If we are to expect optimal performance from our AEGs, series resistances between the motor and the battery should be reduced. In some cases, the series resistances are not very high. In others, they are significant.

I will address a few different situations:

-stock AEG, mini battery
-mid upgrade AEG (~330ish fps), large battery
-high upgrade AEG/LMG (~400fps), large battery

Stock AEG, mini batt

-low current requirements due to low stiffness spring
-relatively high battery internal resistance

The low current requirement for driving a stock spring don't really stress the mini plugs typical in stock AEGs. If you fire your AEG for a long burst you may note a bit of connector warming, but nothing particularly interesting.

Minipacks typically have a considerable internal resistance so removing every connector resistance is not hugely effective as the int' resistance of the battery pack is considerable compared to the resistance of the rest of the AEG components. Since the total resistances in series with the motor are added, eliminating connection resistances may not affect the total sum all that much.


Mid upgrade AEG, large battery ~1700mAh and higher

-med/high current requirements to drive upgrade springs
-lowish internal resistances in the battery pack
-AEG typically owned by someone who likes to shoot a fair bit

Usually in mid upgraded AEGs, the 15A fuse is removed or at least changed to a 20A or 25A fuse. This indicates that the current req's of a mid upgrade AEG are actually higher than the rating on the large Molex connector.

When firing short bursts this is not a particularly bad issue as the Molex connector can pass higher surge currents than the continuous current rating. However you do incurr an appreciable voltage drop over the connector. Enough to warm it up anyways.

If you've got a Tamiya connector up close to the mechbox, you've got a 9A rated connector in the series which is probably heating up a fair bit more than the Molex connector.

If you plan to use a very high capacity battery (say 3000+ mAh) the pack resistance will be quite small. The resistances of the mini plug and battery connector start to become considerable.

If you plan to use high end battery packs and upgrade springs, consider splicing around the ditzy mini connector at the rear of the mechbox. This is certainly feasible with fixed stock AEGs. It can be a bother with MP5's wired to the foregrip through a mini coming out the back of the mechbox.


High Upgrade/LMG AEGs:

-AEGs typically used for long bursts (LMGs)
-heavy upgrade springs used
-high voltage, high amperage packs with low resistance

Sustained current flow can really warm up crappy connectors. Definitely solder around the mini on your mechbox.

Consider switching all temporary connections with high amp Deans style connectors. If your aim is high ROF and you've gone through the expense of a big heavy pack, remove as many series resistances as you can.
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Old August 2nd, 2006, 02:57   #2
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Good post. I tend to just slap a deans on almost everygun and battery as I upgrade and work on them.

One thing I really like about the Deans is the small size. It has saved my butt a few times. Like in my real wood stocked m14 where I didn't have room for the large connector.

And also in my 249 I wired it all to the box mag directly from the motor and to get a large connectro thru the small hole in the box mag is impossible but Deans no problem.

Not to mention the low resistence and great connection.
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Old August 2nd, 2006, 03:38   #3
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Very excellent rundown Carl!

Like John, I've always used Dean's plug for their small size and secure connection, without thinking specifically about their resistance advantage. I'll be splicing around the tamiya connector on my M14 now as well, thanks for the tip.
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Old August 2nd, 2006, 03:48   #4
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Actually some else that I can add now that I thought of it.

I have 2 m249s a STAR and CA. Well I got the CA I thought its ROF was killer even higher then the STAR which was already excellent. Both guns firing the same FPS roughly.

Well after I swapped a Deans plug on the STAR (just this evening as matter of fact) using the same 9.6v battery on both the STAR has no surpassed the CA for ROF and its a fricken Laser beam of BB's. The box mag is sputtering trying to keep the beast fed. I think I will be going back to the 8.4v batteries again on it cause its just too insanely fast now. ;-) And its shooting about 360 FPS.

All thanks to the brillance which is Deans Ultra plugs!
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Old November 8th, 2006, 22:37   #5
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I installed them on my RC helicopter a few years ago and hadn't even thought about using them in my AEG until now.

See this video if you're new to soldering and wishing to upgrade. http://www.ezonemag.com/~awilletts/deansultra.mpg
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Old November 8th, 2006, 22:51   #6
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I've actually had the solder break once on me already, lucky it happened just before a game instead of at a game. I now pop holes in the tabs on the connectors and run the wires through em, twist em around, solder em on, and heat shrink em. Don't know if it increases resistance or not because I only know the very basics of electronics but I'll be damned if that connector breaks off again.
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Old November 8th, 2006, 23:17   #7
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Solder doesn't often pop off well wetted connections. Did you make a cold solder junction? It's important that you heat the Deans terminals so solder wets onto them.
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Old May 26th, 2007, 15:49   #8
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After reading all that 1 question comes to mind.

Whats a good gauge wire to be using? for Deans and for the large and mini conecters?
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Old May 26th, 2007, 16:12   #9
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small connector- max 18awg
large - max 14awg (though most large batts have 16 i think)

deans-??
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Old May 26th, 2007, 17:11   #10
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I just got for 100% Deans when and where I can, smaller, more reliable. I've had well used large connectors fail on me twice, both times I noticed was right before I was about to shoot someone from close range (the lucky bastards!) And since soldering is one of my expertise areas, I never had a Deans fail on me. One thing that Max mentioned, you need to use a hot iron, with a dab of solder on the tip, to heat up the metal on the contact enough that the solder will melt when it touches the contact near the iron. I always tin the contacts first, then rub the iron around in the puddle to clear off as much gold as I can (gold is crappy when it comes to solder) and guarantee a good joint.
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Old May 26th, 2007, 17:46   #11
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Quote:
Originally Posted by LUTNIT View Post
I've actually had the solder break once on me already, lucky it happened just before a game instead of at a game. I now pop holes in the tabs on the connectors and run the wires through em, twist em around, solder em on, and heat shrink em.

it's better not to twist them though, the wire actually handles tension/torsion better if it's not twisted.

my 2 cents
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Old May 26th, 2007, 18:08   #12
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Quote:
Originally Posted by roughshadow View Post
After reading all that 1 question comes to mind.

Whats a good gauge wire to be using? for Deans and for the large and mini conecters?
If you have access to the good Belden Teflon wire, #18AWG works just fine. Is actually pointless to use higher gauge wire simply because the only wires you can run through the mechbox to the motor is #18AWG.............. so all I use is #18AWG Teflon insulated wire.
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Old May 26th, 2007, 18:22   #13
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Thank you stalker
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Old May 26th, 2007, 18:44   #14
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No problem, I tell that to all people that want to go the "low resistance wire" direction, which is kinda funny because it doesn't matter if you have #0AWG running form your battery to your mechbox, because inside you can only fit #18AWG teflon, so nothing changes expect less beer money. Lol
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Old May 26th, 2007, 18:49   #15
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Quote:
Originally Posted by Jimski View Post
it's better not to twist them though, the wire actually handles tension/torsion better if it's not twisted.

my 2 cents

It'll actually cause the strands to break faster if it's not twisted. Best to have a bit of the solder creep a millimeter or two under the insulation, it will provide better strain relief than having exposed strands that aren't supported.

One thing I'll point out, when you solder stranded wire (and unstranded solid conductor) it actually changes the temper of the metal itself, but is still much more reliable than the 'butterfly' type crimp, found on the Tamiya connectors, it cuts the strands when crimped.
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