XT60 & XT90 With Spark Arrestors : Why You Should Make The Switch

The XT90 connectors that are spark resistant have the green L on them.

The XT90 connectors that are spark resistant have a green L on them and a 5.6 Ohm resistor inside the connector

So you’ve been using whatever ebike power connector that you’ve been using for the last several years. All your chargers have it, your motors have it, and your batteries have it. You haven’t had that many problems with the setup you’ve been using, so where is the motivation to change? This article will discuss the benefits of the XT60/XT90 spark resistant connectors and show you that you don’t have to replace all your existing connectors to migrate your bikes to the new standard.

My interest in the XT60 & XT90 connectors started when I read this article on electricbike.com which was released only shortly after I had written this article on the Anderson Power Pole connectors for electric-fatbike.com . Although the Andersons work well at lower amperage and voltage levels like those you would use for the BBS02 or BBSHD, the 50 Amp Anderson Powerpole connectors were far too big and clunky to be useful. Soldering the 50 Amp connectors was a royal pain and I just decided to give up on them for higher power systems.

The best way to purchase the XT90 connectors is with pigtails so you don't have to solder the wires directly to the plug which can be tricky.

The best way to purchase the XT90 connectors is with pigtails already on them so you don’t have to solder the wires directly to the plug. It’s much easier to just solder wire to wire and cover with heat shrink tubing.

One of the problems that we’ve seen with high power packs is that when you plug-in the pack to the motor and it can generate a big spark and the BMS can go into shutdown mode. This can be a serious problem for ‘smart chargers’ like Grin Technologies’ Cycle Satiator. The Cycle Satiator wants to detect voltage on the pack before it starts giving it juice. If the BMS goes into shutdown mode you have to set the Satiator into Lead Acid mode (where it ignores the pack starting voltage) and ‘jolts’ the pack to get it to start up again. Having large sparks occur when you plug in your packs also puts a lot of strain on the connectors and often shortens their life as well and could possibly damage your controller, although that is pretty unlikely. If you have multiple connectors and they do not all have spark arrestors on them, then you should plug in the spark arrestor plug last to complete the circuit.

You can build a jumper cable quite easily to use newer batteries with old connectors hooked up to them.

You can build a XT90 jumper cable quite easily to use newer batteries with your older connectors.

When I put connectors on my wires I like to use heat shrink tubing and squirt a little bit of silicone into the end to the tubing before I heat shrink it with a paint stripping gun. The extra silicone squeezes out as the tube shrinks and is easily cleaned up with a rag or your fingers, if you like to play with goo. This makes the connector MUCH more watertight and less likely to short out. Even though I ride all the time in the rain and snow I have yet to have any connector shorting issues.

XT60 (left) and the XT90 (right)

XT60 (left) and the XT90 (right)

The XT60 is much smaller than the XT90 plug and is an excellent choice for the charging connector on your batteries. You will never need to charge any normal ebike pack at anything close to the 60amp rated capacity. For pretty much any real battery pack that can do burst or sustained power at over 40 Amps I only recommend the XT90 connectors as the main power connectors. The XT90 connectors are good to over 4000W and are not that much more expensive than the XT60. It is always better to have your build overbuilt than to just use the absolute minimum that you can get away with.

If your connector looks like this it might be time for a replacement

The 50 Amp Andersons are way bigger than the XT60, this one took too much power

Where do I buy them?

The XT60\XT90 connectors are most easily purchased through Hobby King or Lunacycle.com . Lunacycle.com has standardized on these connectors for all of their packs with an XT90 for load and a XT60 for charging. If you want XT90’s I recommend that you get this one which has BOTH the spark arrestor and the pigtails.

The best of both worlds, a pigtail and a spark arrestor $5/pair

The best of both worlds, a pigtail and a spark arrestor for $5/pair

If you chose to buy through Alibaba or ebay be aware that there are knock off XT60\XT90 connectors that will underperform at high loads. If a deal looks like it’s too good to be true, it probably is. Expect to pay about $2 a connector for anything that is not going to suck.

XT90’s on a $30-watt meter

Are you too cheap to spring for a Cycle Analyst but still want an accurate fuel gauge? About a year ago I reviewed the 130Amp Watt meter from ebay for $17 with bare wires. Recently I purchased and have been using a $30 150 Amp watt meter from Lunacycle.com located here which has XT90 connectors on both sides (one male and one female) along with one extra male & one extra female pigtail connector. I have been very pleased with the performance of this watt meter and although it looks like it may be made by the same manufacturer, the display is much higher quality and much brighter than the ebay one. Both meters max out at 60v so do not use them on any packs that are higher than 52v nominal as they could be more than 60 when fresh off the charger. If you plug this meter into a 70v Nominal pack it will stop working forever. Don’t ask us how we know that.

The newer 150Amp watt meter is awesome.

The newer 150Amp watt meter is awesome.

Having a watt meter is not only a cheap way to tell exactly how many Ah your e-bike has burned up, it also can be used for troubleshooting purposes. If your drive unit is shutting off just hang a watt meter in between the battery and the controller. If the watt meter display is still on when the motor cuts out then the problem is with the controller or the motor. If the watt meter display cuts out with the bike then the problem is with the battery. It can also be used when you are trying to charge a troublesome battery. Swap the load and source for charging so the load is on the battery side and the source is your charger and you can see exactly how much power is going into your battery. Be aware that more Ah of power will appear on the meter to go into your battery than what is actually stored in the battery due to heat and operating losses, but it will still be close.

I have found the watt meter to be an invaluable troubleshooting tool as well as being incredibly useful in finding out how much power accessories like bike lights are drawing from your battery pack. A must have for any e-bike enthusiast.

Soldering onto an e-bike pack

If you decide to replace the connectors on your battery and want to solder directly to your battery I recommend the following precautions.

  • Make sure you put the Female end of the connector on the battery side to help reduce the chances of unintentional shorts. (As opposed to the intentional shorts, right?)
  • Only do one side of the battery at a time. Strip, solder and shrink tube the negative side, then when that is done you can strip solder and shrink tube the positive side.
  • Be extremely cautious when soldering a live battery pack. Caution is not my middle name (it’s Daniel after “Daniel and the Lions Den”, because everyone around me is trying to eat me and I’m a vegetarian).

It’s much easier to make small conversion plugs pigtails with the newer connectors that will work with your existing style plugs, but some people want to have as few connectors as they can. If you want to upgrade to XT90 or XT60 plugs then that’s exactly what you should do. It doesn’t cost all that much to do it and for systems that pull more than 30 amps continuous it is highly recommended.

Ride On.


10 thoughts on “XT60 & XT90 With Spark Arrestors : Why You Should Make The Switch

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  8. Thanx for the informative blog Jon! I am also veggie for 33 years, the past 12 years vegan. I haven’t been sick since 1986.


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