Editor note: Part 1 of a 5 part series on the wiring of DIY ebikes

Choosing the right connectors for your electric bike battery can be a critical decision for a person who is new to electric bikes. If you become a real ebike enthusiast later, the connector you select now will impact your ebike experience for the next 10 years. The reason being is, you probably will opt to use the same connectors on your different battery packs so that you can use the same charger, use different battery packs on different bikes. We recommend you pick a good connector now and stick with your choice.

Inevitably many DIY ebike builders use their connectors as on/off switches (read our story on on/off switches) and in this case your connector will need to be extra robust because it will be plugged and unplugged often which is hard on connectors because they arc and spark.

When considering which connector to go with, consider convenience, reliability, durability, water resistance level, smallness (how easy is it to hide), and price. Ebike connectors for battery pack wires should be impossible to accidentally plug-in facing the wrong direction (this is called polarized)…remember, you might be fidgeting with these in dim light if you are using them for an ON/OFF switch.

For your convenience, here is a list of various ebike connectors with recommended maximum amperage and a quick run down of pros and cons.

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Anderson Connectors

I see these a lot on DIY bikes as charging connectors. That is because chargers rarely charge over 7 amps and these connectors are cheap. They are an old technology which I feel has been surpassed by better connectors. Note that this is the mini version of the Anderson connector and shouldnt be confused with its big brother which is much larger and I feel too big to be used in an ebike.

The shape of the 30A Anderson connector housings allows two (or more) of them to be connected together side-by-side. It is “possible” to mate two of them so that they can be plugged in backwards to the opposing pair. I recommend that if you buy these (or buy a product that already has them installed), attach the two side-by-side housings so that the pins inside form the shape of a “T” when you look at the end. Once they are configured for safety, put a piece of heat-shrink tubing over them to prevent them from coming apart (and then possibly re-connected in a bad orientation).

Their official name is Anderson Power Poles (APP).

Maximum Amperage 30 amps Cost Extremely cheap…less than a dollar each..as cheap as 50 cents a pair. How easy is it to install? Pretty easy if you have the right crimping tools (read our story on going solderless) How easy is it to Plug in? Not so easy…it can be a pain in the ass. also the black and the red come disconnectted a lot requiring a lot of tinkering to get it to work right. Life expectancy? Is it durable? Not very durable, both electrically and mechanically. These are easily roasted and easily smashed. If you want to go with robust go with the bigger brother. Is it small in size? yes pretty small Electricbike.com recommended? No not recommended…this is an antiquated technology Source where to buy cheap You can buy them 50 cents each here in bulk on ebay

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Deans Plugs

Deans plugs are extremely popular with DIY ebike builders and RC modelers alike. People have figured out they can handle a lot of amps, are dirt-cheap, and are a small size (their tiny size is the main reason they are popular for wires inside the body of an RC plane). However they are notoriously hard to solder, and they have very poor moisture resistance (it may not be raining when you go out, but it might start raining before you get home). We recommend if you are going to buy these buy them with pig tails (a factory pre-soldered section of wire), which will make your life so much easier. (read our story on solderless ebiking)

In the pic below, you can see that even when the pair is fully connected together, moisture getting on the plug-set could lead to a short very easily. This is what we mean for moisture resistance, and Deans do not score well.

As you also can see in this pic, when this pair is dis-connected, the male pins are fully exposed. This is the reason that electrical tradition puts the female connector on the battery side of any part of the system. If you are working on parts that are on the bench, it would be easy for the male connector to brush up against something metal, creating a short circuit, huge sparks, maybe a fire, and possibly damaging your expensive battery. Even if you use a double-shrouded connector (like the XT’s below)…if you put the male end on the battery side, it is one of the signs of an amateur.

Maximum Amperage 50 amps, and some people push them even further. Cost extremely cheap..less than a dollar per pair…50 cents in bulk. How easy is it to install? Pain in the ass to install…requires solder and good technique. The hardest connector on this list to install. We recommend you buy with pigtails. How easy is it to Plug in? Not so easy…it can be a pain in the ass. Life expectancy? Is it durable? Fairly durable. Although it can roast with continual plugging and unplugging. Is it small in size? very small and compact… Electricbike.com recommended? If you buy with pigtails it is an acceptable solution Source where to buy cheap Various sources but keep in mind there are authentic deans which are usually better than clones. Hobbykings clones however are better than original.

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XLR connectors

XLR’s have a heavy-duty metal shell with a latch that will prevent them from coming apart by accident. They also score very high for moisture resistance. They can be ordered with a variety of pin-counts, but the more pins you choose, the bigger the connector will be. There is nothing wrong with them, and I like how the male pins are enshrouded when it is apart, but…their bulk makes them a tight fit inside a battery housing, and the metal shell makes me nervous.

There should never be any loose wires inside a battery housing for the XLR connector housing to short against, but…if something does work loose, I don’t want anything metal exposed near a lot of wiring connections. Whats better? Your E-bike comes to a halt and you have to find a loose connector? or…you are riding and suddenly smell smoke?

Maximum Amperage 40amps because it is hard to squeeze thick enough wires into it. Cost Cheap $1 each How easy is it to install? Fairly difficult…requires soldering. Hard to find with pigtails How easy is it to Plug in? Super easy…the best. Life expectancy? Is it durable? Very durable Is it small in size? No…fairly large and hard to conceal Electricbike.com recommended? For lower power bikes this is a sweet solution. Source where to buy cheap Various sources

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XT60

These are our favorite connectors for E-bikes. They come in two sizes. We still recommend you buy them with pigtails attached, but they are fairly easy to solder wires to. If you do solder to them, attach a male/female pair to hold the pins in perfect alignment, until the soldering is over. The pins can rotate in the housing (with needle-nose pliers) if you want to lay them flat on their sides and have the solder/wire “cup” facing up. I use these for 14ga/12ga wire, and cover the soldered joint with 5mm heat-shrink. Ron likes to use these for the charging connector to the battery (female on the battery side!).

No connector in this article is truly water-PROOF, but…the XT connectors (and also the connector types shown below) are as moisture-resistant as you can get.

Maximum Amperage 60amps Cost Cheap $1 each How easy is it to install? Fairly hard. Requires soldering, but easier to solder than a deans. How easy is it to Plug in? Very easy Life expectancy? Is it durable? Very durable Is it small in size? small Electricbike.com recommended? awesome new generation of connector highly recommended Source where to buy cheap Hobby King

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XT90

The same as the XT60, but a little bit larger and doesn’t melt with 90 amps of power. These are pricey at 1.50 each but worth every penny if you are running high power. Highly recommended. The wire insertion cup fits very fat 10ga wire (or smaller, of course) and I use 6mm heat-shrink tubing to cover the solder joint. “Heat shrink” is dirt cheap from Hobby King. Ron uses these between the battery and the controller. Of course, your life will be easier if you order them with factory installed pigtails.

Even with this style of connector housing having a well-designed “fully enshrouded” shape on the male pins, it is still traditional to attach the female connector to the battery side of the wires. When the controller is unplugged, there may be a small amount of energy still stored in the capacitors, but…the battery on a high current E-bike can have a fiery melt-down if you set a metal tool on the workbench and the tip shorts the two male pins together.

The enshrouded male plugs on the XT90 connectors make that scenario very unlikely, but…we still use female connectors on the battery side.

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Bullet connectors

The pins inside these plastic housings range in size from 2.5mm up to 8mm in diameter, with corresponding current handling abilities. Tops in the price / current handling ratio. The 4mm size is commonly used by RC chargers & is also used in “HXT 4mm” plugs , that combine a male and female bullet connector with insulation inside a polarized housing to make one nice and easy to use connector. The moisture-resistance is as good as the XT90 connectors that we like.

LiPo battery packs are the best choice for racing, but we want to encourage E-bikers who charge batteries in their home to use the much safer packs based on the 18650 cell. That being said, the 4mm HXT connector shown is what is commonly used to connect 6S LiPo “sub packs” (we call them bricks) to a wiring harness. That kind of wiring harness (looks like an octopus) connects all the LiPo sub-packs up to one connector that goes to the controller. The main connector should be much bigger than the sub-pack connector, and we would recommend the XT90 (seen above) for that job.

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JST Balance Connectors

Most battery packs have balance wires going into a Battery Management System (BMS). These small diameter wires allow the BMS to track the state of charge of each cell. Also, when a battery pack is “bulk charged” (the common method), each cell might end up with a slightly different state of charge. Most BMS’s will trickle-drain the cells that are higher for a few minutes, so that the end result is a pack where every cell starts out at exactly the same precise voltage.

Balance plugs are why we started liking pigtails from the factory (which only require a simple “butt splice” to connect two wires). There was one project that we wanted to look professional, with as few wire connections as possible. We bought the pins and connectors for the JST balance plugs. These pins are TINY!, to fit the tiny wires. It was a nightmare, and even if we thought we had done a good job, one loose connection that “looked good” could ruin a cell in the middle of an expensive battery pack.

We’re mentioning JST balance plugs because E-bikers who are using a LiPo pack have a paralleled balance plug harness so they can “balance-charge” their pack (using an RC charger), since most DIY LiPo battery packs do not use a BMS

If you need a JST balance plug and socket set, they are very cheap and well done by the factory (don’t even try to buy and crimp the wires into the pins, then insert into the plug). Order an “extender” like the one shown in the pic above, do a continuity check with a cheap voltage meter to verify its good, then cut the wires in the middle.

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QR Connectors

QR stands for “quick release”. Like some newer smart-phones, there is a connector called an RoPD that is becoming common on factory E-bikes. The shallow plastic housing is polarized, so it can’t be plugged in backwards, and the flat-faced metal contacts are held together by a magnet. I doubt the DIY guys will ever use these, but we thought you’d like to know what these are called when you see them on expensive factory E-bikes.

The latest technology is usually the domain of commercial ebikes, and these snazzy connectors shown below are making their way slowly to the DIY scene.

Putting the connectors together:

We really recommend that if your going to order connectors, get them in bulk with pigtails installed (the shipping often costs more than the connectors, so…why not get extra?). This will make your life so much easier. Instead of soldering yourself, have some guy in China solder your pig tails on for you. Then use a crimp connection to attach the 2 wires and you’re done (bend the exposed copper wire of both ends into a “J” shape, insert them into the copper cup, crimp it, and slip heat-shrink over it). Make sure to buy heat-shrink tubing at the same time if you buy connectors from Hobby King.

Instead of investing in a 100W soldering iron…invest in a good set of crimpers and some crimp-connectors from Waytek. Using these, you can do electrical repairs even when there’s no electricity around for the soldering iron. And we can clamp-down the heat-shrink insulation over the wire joint with a simple cigarette lighter.

Here’s our article on crimping and soldering wires to connectors. It was written for mid drives, but it is useful for any ebike wiring job.

Sources for electric bike connectors:

Powererx – wide variety of connetors. A bit expensive but convenient and fast.

Hobbyking – Great cheap source of connectors and adaptors..but you are ordering out of china and shipping can be slow.

Waytek An excellent resource for various connectors especially for crimp connectors

Top Secret EV If you are an ebike manufacturer and looking for a way to soure nifty QR connectors