8mm connectors vs. 6.5mm connectors

**Mike Caruso** · 12-22-2013, 03:52 PM

I like the hard solder motor to esc.

**Fluid** · 12-22-2013, 04:07 PM

Why is it that I see many people using such bulky connectors on motors and esc's when 6.5mm connectors from Castle, HK etc will hold the current fine?

"Hold the current just fine" - you know this how? It's all about contact area and connector mass. The more contact area, the lower the reisitance of the connector and the more amps the connector can handle. Some 6mms have less contact area than good 5.5s so the latter are preferred. The 8mms have more contact area and more mass than others, and will have minimal voltage drop at high current loads than will smaller connectors.

These: XT150 will handle 250 amps just fine.

Really? You know this how? Maker's connector ratings are as easy to manipulate as are battery "C" ratings, and given HK's rep I would take their claims with a grain of salt. What does "handle" mean? Does it have a low voltage drop, or will it just not weld itself together at under 250 amps?

Why do some folks de-solder connectors when running? Other than a poor solder job, it is because the connectors have too much resistance and get hot. I have used 5.5s on most of my builds, except those with voltage above 4S or current draw above 200 amps. But I might get slightly better performance if I switched to 8mms.

...Furthermore once you have your boat setup, why not hard solder the motor wires and forget about those connectors?

Some folks do this, but then the problem is how to best solder the wire ends together. A good bullet connector may have lower resistance than the same length of wire and be far easier to get a good solder job than trying to join two bare wires together.

Use what you want of course, but lower resistance is always a good thing.

.

**ray schrauwen** · 12-22-2013, 06:41 PM

I've used the XT150's and they never get hot in the 40" mono TFL 5682 1200kv on 6S SF240. I haven't pushed the envelope on them yet but, so far so good. Actually I've had a hard time heating the whole system up. I just find it hard to deal with 8mm connectors because of their size I guess. Very hard to get them on and off for batts.

I appreciate the extra information I've missed, thank you!

HK actually has some very nice quality connectors if you've tried them you'd know.

Some folks do this, but then the problem is how to best solder the wire ends together. A good bullet connector may have lower resistance than the same length of wire and be far easier to get a good solder job than trying to join two bare wires together.

As long as it is not a cold solder joint joining wires together for hard wiring is very simple. Once the solder has permeated the fine stranded wire the advantage of the muti-strand wire is gone is it not? Since the current will travel on the outside of what is now a solid conductor.

**Mike Caruso** · 12-22-2013, 06:54 PM

Originally posted by Fluid

"Hold the current just fine" - you know this how? It's all about contact area and connector mass. The more contact area, the lower the reisitance of the connector and the more amps the connector can handle. Some 6mms have less contact area than good 5.5s so the latter are preferred. The 8mms have more contact area and more mass than others, and will have minimal voltage drop at high current loads than will smaller connectors.

Really? You know this how? Maker's connector ratings are as easy to manipulate as are battery "C" ratings, and given HK's rep I would take their claims with a grain of salt. What does "handle" mean? Does it have a low voltage drop, or will it just not weld itself together at under 250 amps?

Why do some folks de-solder connectors when running? Other than a poor solder job, it is because the connectors have too much resistance and get hot. I have used 5.5s on most of my builds, except those with voltage above 4S or current draw above 200 amps. But I might get slightly better performance if I switched to 8mms.

Some folks do this, but then the problem is how to best solder the wire ends together. A good bullet connector may have lower resistance than the same length of wire and be far easier to get a good solder job than trying to join two bare wires together.

Use what you want of course, but lower resistance is always a good thing.

.

Thanks Jay,
As always I count on your expertise sir you have been then done that and see it before.
Regards,
Mike

**keithbradley** · 12-22-2013, 08:15 PM

There is an application for everything Ray. I personally believe that 99% of "hot bullets" and desoldering issues are caused by poor soldering and/or improper setup. I've pulled over 300A at 30v through 5.5mm connectors, so they are capable of moving a lot of energy, but that doesn't mean they are the best option. I've also had a 5.5mm connector unknowingly come loose from the back of a motor. The result was an $800 loss between motor and ESC (yes, they both failed). 8mm bullets are harder to disconnect, which can either be a positive thing or a negative thing, depending on your needs. If you have feeble lady hands, you may want to go with easy to disconnect. If you want to make sure your equipment stays plugged in, you probably want a firmer connection.

I use 5.5, 6, 6.5, and 8mm plugs. They all have their place and each one has it's own advantage.

**Mike Caruso** · 12-22-2013, 08:51 PM

All valid points thanks for replying Keith

**Jeff Wohlt** · 12-22-2013, 11:21 PM

You certainly want to make sure the wire is in direct contact with bullet bottom and/or side. I always make sure the wire is making good contact into the bullet before soldering. If not you are running the current thru solder and not the connector. The right electrical solder is also key...not plumbing solder...LOL.

**jcald2000** · 12-23-2013, 07:19 AM

Ray, remember Jorge tested bullet connector's years ago for resistance and bigger was better so I run 8mm on every thing.

**ray schrauwen** · 12-23-2013, 11:29 AM

Except in the case of 3.5mm bullets vs 4mm bullets. The 4mm bullets were as good as Sermos 45 amp connectors at best where the 3.5mm ones were far better.

Originally posted by jcald2000

Ray, remember Jorge tested bullet connector's years ago for resistance and bigger was better so I run 8mm on every thing.

I just don't really get it if the wire, say 10G or 8G is soldered into any connector larger than the wires outer diameter how it makes the connection any better than a connector with as much surface area but, smaller diameter (same diameter as wire, no less).

Like I said before once you add solder to any Gauge of multi-strand wire it becomes a SOLID conductor and to go to a larger connector to connect the 2 wires together and finally back down to the original diameter seems pointless at best.

It's like water flow. If you have water flowing through a 6mm tube and then you open the flow to 8mm for approx. an inch and then shrink it back to 6mm afterward what have you achieved?

**Doby** · 12-23-2013, 11:59 AM

Ray: you've seen my boats...5.5mm's on everything from 4S to 10S setups. You even commented that you were surprised they held up. I am using 8mms on my Blade between the motor and the controller as the Proteus motor has 8mm females installed already.

With the right flux and soldering iron things went easy. Is bigger better? One thing's for sure, the 8mm's are easier to grab on to!

**flraptor07** · 12-24-2013, 12:04 AM

I use 6mm on motor connectors and 8mm on batteries, I think the key thing to keeping bullet connectors working optimal is tension adjustment and keeping all the blades contacting uniformly. I'll spend a hour adjusting connectors in a boat, and knock on wood I've never had a connector issue.

**iridebikes247** · 12-24-2013, 09:34 AM

I too make small adjustments to connectors when needed the 8mm ones are sometimes impossible to seperate. My 8mm connectors separate easily just make sure they're all equal if making adjustments.

when it comes to connectors each has its own advantage. If the connector looks silly on the wire chances are it is. When I started buying batteries with 8 gauge wires I just soldered up 8mm connectors, they fit right. I pull 340 amps and never have had an 8mm connector go on me. Good soldering + good solder is the key imo. I have seen 6.5mm connectors handle more current than my setup never an issue.

**NativePaul** · 12-24-2013, 02:27 PM

Originally posted by ray schrauwen

Except in the case of 3.5mm bullets vs 4mm bullets. The 4mm bullets were as good as Sermos 45 amp connectors at best where the 3.5mm ones were far better.

I just don't really get it if the wire, say 10G or 8G is soldered into any connector larger than the wires outer diameter how it makes the connection any better than a connector with as much surface area but, smaller diameter (same diameter as wire, no less).

Like I said before once you add solder to any Gauge of multi-strand wire it becomes a SOLID conductor and to go to a larger connector to connect the 2 wires together and finally back down to the original diameter seems pointless at best.

It's like water flow. If you have water flowing through a 6mm tube and then you open the flow to 8mm for approx. an inch and then shrink it back to 6mm afterward what have you achieved?

The good 3.5mm connectors Joerg tested were the inside out ones with a solid 3.5mm OD male and split 3.5mm ID female like these

Nearly all connectors are made from plated brass (the only exception that I know of are the hollow aluminium 4mm Kontronic connectors) and brass despite having a decent copper content is a p!$s poor conductor at just 28% of copper's conductivity, so if your brass bullet connector was the same size as the wire it would be a huge bottleneck, and it needs to be far bigger than the copper wire to flow the same amount of electricity without heating up more than the wire.

Image taken from this article if you want more information.

**Doug Smock** · 12-24-2013, 03:00 PM

Originally posted by jcald2000

Ray, remember Jorge tested bullet connector's years ago for resistance and bigger was better so I run 8mm on every thing.

Neue 6mm Ultrahochstromstecker von LMT

http://www.eco-idc.de/eco-news/6mm-stecker.html

I like those 8mm connectors that sound like a tuning fork when you disconnect them.

8mm connectors vs. 6.5mm connectors

8mm connectors vs. 6.5mm connectors

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