Best RC LiPo battery connector types: Choosing and Soldering

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Battery connectors are a common subject here and we get a lot of questions like"what battery connector is the best?" or "how to solder battery a connector?" and others. Hopefully this thread can serve as a central place to find answers to many of the questions we see when it comes to picking the best LiPo battery connector and how to use them.

Similar to what Recommend me a battery charger and What's your "budget" LiPo of choice? threads have done.

Popular LiPo Battery Connectors

There are dozen of different battery connectors one could use, but I'm only going to focus on the most popular and most recommended battery connectors that most people use in the R/C hobby on their car/truck Electronic Speed Controller (ESC), motors, and LiPo batteries.

Deans Ultra Plugs

Deans Ultra Plugs have been part of the RC hobby for years and Arrma used to use a Deans connector on many of their earlier models. Deans Ultra Plugs are designed so that it's impossible to plug them in the wrong way. The down side of Deans battery connectors is they can be a challenge to solder due to their flat ends. Due to their small size and tight fit they can also be harder to connect or disconnect.

These make great plugs for 3s or smaller LiPo batteries.

Amperage rating: 60 amps
Buy: Deans

XT-60 and XT-90

XT-60 and XT-90 connectors are very popular connectors across all areas of the RC hobby. These connectors where also found on Arrma RC models in the past. They are very similar to a bullet style plug but designed so they only connect one way. These connectors are also easier to solder thanks to how they cup the wire.

If you are running 4s or larger LiPo batteries, you would be best to use the XT-90 plug.

XT-60 Amp rating: 60 amps
XT-90 Amp rating: 120 amps
Buy: XT-60 / XT-90

EC3 and EC5

The EC3/5 connectors are popular connectors used a lot in the Losi and ECX brands. Now that Horizon has acquired Arrma RC, you will find any new Arrma RC models also ship with the EC plugs. These have been a personal favorite for a long while now. They are VERY easy to solder, thanks to them essentially being a bullet connector in a unique housing that prevents you from plugging them incorrectly. They also allow for a large amount of current to be passed through them.

EC3 Amp rating: 60 amps
EC5 Amp rating: 120 amps
Buy: EC3 / EC5

Bullet Connectors

These are common connectors typically used to connect ESC's to motors. These are NOT recommended to use for connecting batteries as there is no protection against plugging them in wrong. The advantage of bullet connectors is their ease to solder and ability to pass high current. They can also be found in a wide range of sizes: 2mm - 8mm!

3.5mm Amp rating: 35 amps
4.0mm Amp rating: 100 amps
5.0mm Amp rating: 120 Amps
5.5mm Amp rating: 130 Amps
6.0mm Amp rating: 140 Amps
6.5mm Amp rating: 150 Amps
7.0mm Amp rating: 160 Amps
7.5mm Amp rating: 175 Amps
8.0mm Amp rating: 200 Amps
Buy: Bullet connectors

Traxxas Battery Connectors

If you have a Traxxas RC then you're probably familiar with the Traxxas battery connectors as they have shipped with these connectors for several years now. The newer TRX connectors, which you can not buy, include a chip in them which communicates with the Traxxas charger to tell it exactly what kind of battery it is so that the Traxxas charger knows how to charge it.

The older TRX connector also have a flat surface similar to the Deans plug which can be tricky to solder. I've never been a big fan of these connectors as I never felt they offered anything new or a lot better than other connectors. It seems I'm not the only one either, Traxxas' Connector Crisis.

Traxxas does not sell their new TRX connectors to users. You must by a Traxxas branded or licensed battery.

Note: Even though the focus is on LiPo batteries, all of the connectors mentioned above will also work on NiMH packs as well.

Soldering RC Battery Connectors

Soldering is a just as important if not more important than the type of connector you use. Because if your soldering job is no good, than it doesn't matter if you're using an 8mm bullet plug, you won't be getting anywhere near its rated amperage usage. Instead you'll likely damage or burn something up.

How to Solder Correctly is a great resource that goes into great detail on how to and how NOT to solder. Below are several videos on the subject of soldering as well.

How to solder EC5 connectors:

How to solder to large wires together:

Recommended Soldering Tools

Soldering Iron Station or Soldering Iron - I use the Trakpower TK950 soldering station and am very happy with it's performance. The Hakko FX888D is another fine soldering station.

Solder - As already mentioned in the How to Solder Correctly article, good solder is very important. I follow what that article suggests and also use 63/37 solder:
Soldering Jig - This is an awesome little jig that will hold nearly any time of battery connector you might be soldering. From Deans, XT, EC, and bullet connectors.

You can get this soldering jig here. Another common solution is to make a jig from a scrape piece of wood or using a 3rd hand.

So these are the more common and most suggested LiPo battery connectors. I've also touched on how to solder and some very useful tools to make your soldering projects that much easier.

Now lets hear from you, what tools do you use and like? Any tips or tricks? What's your favorite battery connector?
I really should switch from traxxas connectors... should have done it earlier as now it will be a somewhat costly and time consuming endeavor. Around 20 lipo packs, 8-10 charge leads, 8-10 connectors on esc's... ugh.

I think if I was to change, I'd go with the XT90's. I've soldered a few of those for a buddy of mine and they are a lot easier to do than the trx plugs.

What does the jig do for you? Do you just clamp the connector into it and lay it down on the bench with the ends sticking up?

I use two pairs of vice grips, one normal pair and one needle nose pair and an alligator clip thingy. The knurled adjustment of the needle nose ones in the jaws of the normal ones and I put the connector in the needle nose. The heavy pair of grips keep things from moving around. I use the alligator clip holder to hold the wire in the connector.

So... odds are, a jig or something proper would make changing over all my connectors less laborious.
I use a combination of a 3 alligator clip jig and a bench vise.

I use the alligator clip to hold the wire in proximity to the bench vise. I have also recently switched to XT90s from TRX connectors. It has been a giant pain in the neck to switch everything over.

Huge props to Woodie, I read through his soldering thread and picked up some 63/37 solder.
Game. Changer.

I had been using silver electrical solder and it was making it impossible. I'm using a cheap $40 weller gun style 100 watt gun and it works perfectly.
I really should switch from traxxas connectors... should have done it earlier as now it will be a somewhat costly and time consuming endeavor. Around 20 lipo packs, 8-10 charge leads, 8-10 connectors on esc's... ugh.

Feels I have 22 lipos and all of them have traxxas plus, I have 4 traxxas chargers now lol Moving away from those plugs Is just more hassle then its worth.
I suck at soldering XT90’s lol, but the Traxxas ones aren’t too hard. They get pretty toasty when ran on 8s and pull 160-200 amps (burst) but they never have welded themselves together on me.
I suck at soldering XT90’s lol, but the Traxxas ones aren’t too hard. They get pretty toasty when ran on 8s and pull 160-200 amps (burst) but they never have welded themselves together on me.
They pop apart frequently on me on mild lawn dart landings.
No mention of the Castle connectors?? :)

Castle connectors are fine connectors, as I mentioned above there are far to many connectors to try to list them all. I was only mentioning the more popular options.

But this thread is a perfect time for someone to tell us all about a new or unmentioned connector. ;)

What does the jig do for you? Do you just clamp the connector into it and lay it down on the bench with the ends sticking up?
Yes sir, it holds the connectors in place making it easy to solder.

I too have used (still have) the alligator clamps helping hand and really don't care for it. It moves around when I'm trying to solder and I find myself wanting to throw it across the shop.
I use and love my XT150 connectors. They handle 8s with ease and are super simple to solder without worrying about melting anything. I also have mine set up so that the positive and negative can plug into each other, which is what I wanted so that I can run packs in series without any adapters or extra wiring.
I have used XT60's my entire RC career. That was till I got into Arrma, and now I use XT90's and XT60's...... almost the same thing. Never had a failure due to any connectors thus far...
I use both the deans and the xt90s. I find the deans really easy to solder, the xt90s are my preferred although I find them harder to solder as they seem to need a powerful iron.
I currently use a high powered gun instead of a wand. Seems that the larger gauge wires are easier to solder. One of these days I’ll move to a station when I’m more comfortable with the technique
I like the ec5 in terms of it's ability to stay together while bashing, but I like the deans plug better just because there's a much bigger variety with deans plugs than ec5. not too familiar with other plugs
In my own experience Deans are garbage, I would much rather use wire nuts than Deans. For the first 2 years I was in this hobby I used Deans, and in that time I went through almost 2 dozen connectors, the tabs would either wear out inside the battery plug or the tabs would bend on the esc plug causing them to not make contact inside the connector. I replaced everything with XT connectors a little over a year ago and I have not had to replace a single one. Even the one I sorta melted still works just fine, the little cap on the back side that hides the terminals doesn't like to stay on all the way though. It was my first time soldering an XT90 and I wasn't paying attention. ?

Also just a heads up on those soldering jigs, be careful when ordering them as you want one that uses a heat resistant plastic for the bullet connectors instead of one made entirely out of aluminum, otherwise the aluminum just acts like a big heatsink and it takes forever to heat up your bullet connectors.
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