2 weeks ago I had an incident with my hot water heater where it starting melting the plastic connectors and insulation and filling the house with smoke. There was a dedicated 750 Watt DC waterheating element with a built in thermostat that we had been using for about 6 months with our off grid solar system without too many issues. When I took the unit apart I could see of the 4 connectors 2 of them were soldered and had no issues, and 2 of them were just friction fit blade connectors both of which had built up resistance over time and pretty much self destructed. This event made me think it would be prudent to write an article about soldering vs using crimping or using connectors for your ebike build.
My friends Doug and Laurence built a giant Mutant Vehicle for Burning Man that was powered by 2 different 3000W cyclone motors. I built the system so that both motors were redundant and each powered one of the rear wheels. At the last Burning Man festival ‘Sparky’ the unicorn came back with both motors non-functional. Since the Playa dust is conductive and also destroys all electric connections I ended up just soldering the controller to the motor since the Anderson connectors had melted. Being out in the middle of the desert with a 1000lb art car that you have to push miles back to your camp is no fun so by soldering the motor to the controller I can prevent that connector from ever failing. I also wrapped all the connectors in a plastic ziplock bag and then use packing tape to seal it with zip ties at either end. Not pretty but it keeps out the dust and the rain.
I’ve been a big fan of soldering for a while. I’ve found that for the most part soldering works well and is more resistant to the problems you have with crimping and using connectors. The exception to this rule was my electric tractor that ran at about 10,000+ Watts continuously. I took some lugs and filled them with Solder and then heated them up with a propane torch and submerged very thick multi-stranded welding wire into them. On some of the connectors it got so hot that the solder melted and poured out causing extreme heat and melting wire insulation. Other times what would happen is that the thin copper wires would self destruct right where it went into the lug connector and as more and more of the strands of the copper would break I ended up with runaway problems since the remaining strands would have to carry more current and then they would also fail. I would say for power levels greater than 5000W using crimped lugs is a smarter move.
When Soldering I have 3 different sized guns that I use depending on the size of the wire I’m trying to connect. I have a small 60 watt gun I rarely use and then a larger 200 watt and a monstrous 350 watt gun that works well on really thick wires. If you use a gun that is too small for the work you are trying to do then you will get frustrated. There are lots of great videos on Youtube about soldering so if you are new to it, practice as much as you can.
Soldering works much better if you can secure the joint with glue lined heat shrink tubing. This also makes for a better and more waterproof connection than crimping.
When it comes to crimping I’ve found that a good crimp has more to do with the quality of the crimpers than anything else. I used to just cheap out and try to crimp connections with a pair of plyers or vise grips and many of those crimps have failed over time. I now have 3 crimpers, a small $28 hand crimper for crimping small stuff, a $27 ratcheting crimper for Andersons and other similar sized connectors and some very large lug crimpers with 2 foot long handles for crimping lugs $25 from amazon here. I also have a cheap $20 hammer crimping lug tool which I don’t really use much anymore since I feel like the very large lug crimpers with long handles does a better job.
In general I find that for higher power connections (over 5000 Watts) a good crimp with the right crimping tool will hold up better over time than a solder joint.
I have pretty much standardized on 3 different connector types. Andersons, XT60’s and XT90’s. If the total power level is less than 750 Watts then Andersons will usually work well without melting. If the power level is less than 1000 watts continuous or 1500W burst then XT60’s are generally fine. For any power level higher than that I use XT90’s. I try to keep the XT90 connectors under 50 Amps of continuous load, if it’s more than that then I will use multiple connectors in parallel and wire (just make sure the wire is the same gauge and the wire lengths are all the same). I’ve found that if the XT90s have more than 50 amps continuous that the connector can get quite hot. The Anderson’s are crimped on with special crimpers and I usually buy the XT60’s and XT90’s with pigtails on them since getting a good solder on the connector can be challenging. When you are soldering to an XT60 or XT90 it helps to plug them into their mate and solder them that way so you don’t overheat the plastic and shift the pins. If you don’t have a lot of experience soldering you should just order the XT60’s and XT90’s with pigtails.
Connectors are great for connecting and disconnecting things like batteries that you will want to remove. Often times for high power application I will solder the connections between the controller and the motor since those devices are rarely swapped out.
A good solder joint is much better than a bad crimp. Most of the bad crimps in my life have been from using the wrong tool for the job. Connectors are the way to go when you need to connect and disconnect things, but I recommend using connectors with spark arrestors if you can. Reinforcing the wire and connector with some heat shrink tubing where the wires go into the connector is really helpful. If you can use glue lined heat shrink tubing that is great, otherwise just use a squirt of silicone inside the heat shrink tubing before you shrink it and that will keep the wires from moving and possibly failing in the future.