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Whether you are into drones, radio control helicopters, cars, boats or planes – there is one commonality between every aspect of radio control flight: battery connectors. Discussing battery connectors is a funny thing… if you really want to see people go at it, just go into an online forum and say “I don’t like X connector”, get some popcorn and just wait for the replies to come pouring in. People have seemed to gravitate to one connector or another and seem to take extreme pride in whatever type of connector they run in their system. Whether it be a Deans plug, XT60, JST, RC Pro Plus, or just a plain ol’ bullet connector- there are so many choices to be made… but where do I even begin?

As trivial as it may seem, having a proper connector is a big deal. Like… a really big deal! If you choose a poor connector for your application, it can potentially result in catastrophic consequences. Having been a competitive Radio Controlled 3D Heli pilot for close to 10 years and a pilot who flies drones that cost the same as my college tuition, I have come to appreciate why it is imperative for a system to have a proper connector for its intended purpose. Different applications and different load requirements will require different connectors. With all of this being said, what do I personally look for in a battery connector? What makes a good connector and what makes a bad connector? These are just my personal thoughts on the subject. Some of these may seem a bit odd or even controversial, but in my 15 years flying and working with radio control aircraft, I have arrived to these key points that help me choose the right connector for the job.

First and foremost: What is the battery connector’s intended purpose and how big is the battery?

We use LiPo’s for everything. We use them to power our aircraft/vehicles, radio control transmitters, fuel pumps, engine starters – you name it. The search for a proper LiPo connector can begin based on its size and intended purpose. Super obvious- but if you have a smaller battery, you are going to want a smaller connector. If you have a large battery, you’re going to want a larger connector. Also included in this is wire size. If you have a tiny 20AWG wire being soldered into a 6mm bullet, the solder joint has a greater chance of cracking simply due to the weight of the connector itself. Similarly, if you have a large 6s 10,000mah battery with 10AWG wiring, a small 3mm bullet connector is going to be too small for the pack. By simply realizing this, you can begin to narrow your search in choosing the proper connector for your application.

How much of a load will this connector experience?

Now that we have narrowed down the right “size” connector, here is where the real decision comes into play. Let’s say you have three small connectors that you can choose from. Finding the right connector very much depends on how much of a load it will handle in its use. For example, a small 2s LiPo that is only operating 2 servos is going to experience much less of a current draw than a small 2s LiPo that is powering the brushless motor of a small ducted fan jet. Without getting too technical- simply do your homework, run the numbers, and make sure that your connector can handle the amount of amperage that you expect it to see. I have attached some resources at the bottom with links to some connector information, showing maximum recommended & tested data.

This one is a BIG one for me… How safe is the connector? Is there ever a possibility that the battery can be plugged into itself?

I almost put this first because I think that battery safety should be of utmost importance…But the question is simple – how safe is the connector?  Can it be plugged in backwards? Does your battery connector allow the user to plug the battery into itself? If so, the connector is a poorly designed connector and I would never ever allow it even step foot in my garage. Seriously – keep it away… like really far away.

The most common example of this is a pair of bullet connectors – where you will have a female bullet connector on the negative end and a male bullet connector on the positive end of the battery. The ESC has the reverse of this. It looks like an elegant solution at first, but this means that one could *theoretically* plug the battery into itself. What happens when that occurs with a big 12S (50V) system? Well in my experience after watching a very skilled and knowledgeable pilot do this very stupid thing, it results in a loud bang, a big spark and molten solder to the cornea with a trip to the ER. Luckily, a fire extinguisher was on hand so the Fire Department didn’t have to be called. Really? Yep- really.

The biggest argument I hear from the operators who use this type of battery setup is “Why would I ever do that? Duh, that’s so stupid how can anyone ever plug a battery into itself?”. There’s a multitude of reasons I can come up with of how that could potentially happen: Maybe you are flying at night and can’t see the connector well, maybe you have many batteries in series/parallel and get confused as to which connector belongs to the battery and which connector belongs to the ESC, or maybe you want to catch the last bit of daylight before the sun goes down and you hurry while powering on your setup. I just can’t get on board with any sort of connector that can even allow this.

Personal tip: While we are on the subject of series parallel connections: I am a huge fan of creating a custom wire harness that takes care of the series/parallel in the first place. This means that if you wire it properly, you can plug in any battery to any connector in your configuration without the risk of blowing up a component or plugging in anything wrong. Just how I prefer to do it…

How universal is your connector? Can it be installed in multiple configurations?

This one seems a bit odd… but it has saved me time and time again when I really needed it. How many times have you been out at a flying field, or a job site, and for whatever reason- you really needed a battery that you just didn’t have? Maybe your pack met its end or maybe you simply forgot it? If you use a battery that is popular, this can really come in handy when you need it. Does everyone at your flying field use XT90’s at your flying field? Then I think you should consider it. Does your commercial drone operation use nothing but EC5’s? Maybe it’s a good idea to stick with them. As simple as this seems, I really believe in running what’s easy to come by if you are in a pinch. I couldn’t tell you how many times I have borrowed someone’s 2s LiPo receiver pack with a deans connector, or 6S 5000mAh flight pack with an EC5- even if it’s just for a quick test flight, a quick boot-up to upgrade a firmware, or a simple bench test.

At the same time, I am a bit hesitant to switch to any type of battery connectors that allow the user to set them up in multiple configurations. For example, there is a well known battery connector in the RC Heli world that has really gained popularity called RC Pro Plus. They are incredible connectors that are super nice bullet connectors with plastic housings, but my biggest downside is the fact that they can be soldered or arranged in many different configurations. This means that if you give a pair of these connectors to one pilot and tell him to solder them up, and another pair to another pilot to solder them up – there are so many different ways of configuring these connectors that they will most likely do it differently. Now is this really a big deal? Not really – I’m nitpicking here… but for me it’s the fact of the matter. If I ever needed to borrow someone else’s battery for a multitude of reasons, the chance of their connectors/setup being the same as mine is not so great.

How hard is it to solder the connector? Do I need Heat Shrink tubing? Is it removable?

This one makes it to number 5 for me because in my experience, the difficulty in properly soldering a connector is more on the soldering iron not the connector itself. For example, if you are trying to solder a big 10AWG wire into a bullet connector with a 15W soldering iron, you’re gonna have a bad time. But, the argument is still valid. I haven’t mentioned it yet, but I think it goes without saying that I think that every proper LiPo battery connector should only be installed via soldering – not screw in terminals. But for installing the connector- how hard is it to solder? Will the connector ever melt while installing? For some connectors, it can happen. Look at a Deans T plug for example. It’s a solid connector that has stood the test of time (and just about everyone in the world copying it), but if you get the plug a bit too hot while soldering, it will melt the housing and the pins will be stuck in a skewed position. This makes plugging in the battery to the ESC quite tricky. Not good.

At the same time, is the connector removable? Meaning, if you need to remove the connector, can you do it without cutting it off and throwing it away? Look at an EC3 or EC5 for example. The EC5 is near and dear to my heart, but if you want to remove it- good luck. Just cut it off and get a new one. Also, do you need heat shrink? If you look at a Deans T Plug once again, you must use heat shrink with this type of plug or else you risk possibility of shorting out the battery.

Does your plug have anti-spark properties?

This one is only for the high voltage setups (10s and up), but is definitely a worthwhile subject to cover. For some of the large drones, helis, and airplanes that require 10s – 14s LiPo setups that range from 42-60V, a large spark can occur when plugging the battery into the ESC. This spark is often a bit startling and can often lead to prematurely wearing on the tip of the connector causing less usable surface area, which results in poor performance over time. To combat this many of the electronics manufacturers are designing in “anti spark” technology into the Speed Controllers (ESC’s) and others which ensures that there will be no spark when booting up. For example, in my radio controlled helicopters and large drones that use 12S (50V), I can simply get away with a connector that doesn’t have anti-spark technology because both the Scorpion Tribunus (Helicopter ESC) and the DJI E5000 (Drone ESC) ESC’s have built in anti spark features. If your ESC/device does not have this feature than it would be in  your best interest to look into a connector that offers this.

Very lastly: Does it have any major turn offs? Is there something goofy about the connector that really stands out? Do you have previous history with it?

Plain and simple- there are just some connectors that I just can’t stand. After trying them, I just don’t like ‘em. Period. For example, many years ago I tried Anderson Power Poles on my RC Helicopter nitro engine starter, but found that in 20 degree weather during Baltimore winter, they would crack and leave the battery terminal exposed. No bueno. I have also used EC3’s on 2s LiPo receiver packs, but I found them so hard to pull apart that I would sometimes pull the wire out of the connector. Also, no bueno.

With that being said, I am sure that everyone has a story as to what connector works best for them and why… and usually for good reason. Everyone has a favorite… and they should! At the end of the day, if you have been using the same connectors for years without any hassle, why switch? No need to keep up with the Joneses in this area. It’s something that we come in contact with every time we want to fly, it might as well suit your needs and your personal taste.

To summarize, when I choose a connector for an application, I run down the list. I believe that a great connector can only be installed one way. There should be some sort of indication showing which connector is intended for the battery and which connector should be intended for the ESC/device. The connector should only be able to be plugged in one way, without the possibility of EVER shorting the battery out. It should be easy to solder and capable of handling the current that I need it to. I want it to be common enough so there is a possibility of one person at my flying field or work organization having a similar battery with the same connector at my disposal in case of emergencies. It should hold up under any weather conditions and allow the wire / solder joint to remain intact after hundreds of connections & disconnections. It’s not rocket science but having a proper connector can really mean all the difference in the world, especially when you are relying on these connectors to safely power your beloved aircraft.

For me personally- I tend to use JST plugs on small 2s/3s micro helis (230 size and below), Deans T plug or XT60’s on 3s-4s micro helis, 2s Receiver packs, and FPV racing drones, and EC5’s on RC Helicopter batteries and large drone batteries. I do catch a lot of flack on the EC5 connectors, but after reading through my 7 points, I think some can now have an idea of why I have chosen to keep using that connector for 8 years now. With any hope, manufacturers will continue to innovate in this area and continue to provide us with high quality products that allow us to keep on flying without hassle.

At the end of the day, there are dozens of great connectors on the market- all with their strengths and weaknesses. Simply find the one that works best for you and your application and stick with it.

Happy flying!

Bobby Watts

 

Additional Resources

Great article by TJin Tech about connectors

Great Progressive RC video detailing connectors & recommended amperage

A German page that shows some good data (Make sure to translate)