Where to cut the motor phase wires for connectors?

[markz]

I am debating whether to cut the phase wires close to exit of the motor at about 6-8", then have an intermediate cable going to the controller connection, on the top of the rear rack.

I am 50/50, what comes to mind is that there would be higher resistance with the more connectors I use, so I am tempted to leave the wires long and have no intermediate cable.

Is it worthwhile to locate the controller closer to the motor for shorter wire lengths?

I am using ptfe teflon 10awg, mxus 3000w v2, lyen 18fet, 60V maybe 72V.

 

[slowhands]

You have to think about maintenance of the tires. You will need to remove the wheel to fix a flat or whatever. Then you must have a connector conveniently located. It should be water resistant ideally, but none of the ones I like are. For your high currents, use maybe XT60 connectors (overkill) and don't worry about losses. I'd have connectors near the controller too, again for convenience. This is a case where planning for maintenance overrides the minor loss caused by extra electrical resistance.

 

[fechter]

Like always, there's a trade-off. Having the controller closer will reduce the resistance losses in the wires. Less resistance in the phase wires will also allow higher peak currents which could possibly blow the FETs. If your wire gauge is reasonable, a few feet isn't going to be a real significant loss. Heating/melting of the external wires is rarely an issue.

I don't like making the wires coming out of the motor too short in case they need to get re-terminated later on.

If you solder the connections between the wires, the joint will not add any resistance (you have two wires in parallel where they overlap in the joint = lower resistance than just the wire).

 

[docw009]

10 AWG wire is about .001 ohms per foot. So 2 feet will be a .12 volt drop.

2 feet x .001 ohm/foot x 30 amps x 2 wires = .12 volts

 

[John in CR]

6-8" sounds good. I locate mine in the drip loop, but no connectors for me. I hard wire everything. Less cost, failure proof, no extra resistance, it's quicker to do and still easy to re-terminate later if necessary (which I've only had to do once out of 7 that I've hard wired so far. Screw over-priced unnecessary connectors.

 

[fechter]

6-8" sounds good. I locate mine in the drip loop, but no connectors for me. I hard wire everything. Less cost, failure proof, no extra resistance, it's quicker to do and still easy to re-terminate later if necessary (which I've only had to do once out of 7 that I've hard wired so far. Screw over-priced unnecessary connectors.

What happens when you need to fix a flat tire?

 

[999zip999]

John 10pairs for 3.00usd of 4mm golden bullets. Then I don't have 7 bikes some 6 phase. I guess just for phase wires 21 4mm or 9.00 usd and that's just for 3 phase systems. I guess a 80watt soldering iron takes little space.
I ride on the beach so I keep the connectors top of triangle. 4 mm gold bullet. Pure gold.

 

[markz]

So its best to have the wires coming out of the axle downward and making a drip loop?
Currently mine are facing upward.

 

[John in CR]

6-8" sounds good. I locate mine in the drip loop, but no connectors for me. I hard wire everything. Less cost, failure proof, no extra resistance, it's quicker to do and still easy to re-terminate later if necessary (which I've only had to do once out of 7 that I've hard wired so far. Screw over-priced unnecessary connectors.

What happens when you need to fix a flat tire?

The tire comes off and back on the non-wire side. The drip loop, which I consider mandatory of all ebikes, give you enough extra wire to remove the wheel. Of course you need to take that into consideration for your wire routing so the motor wheel can be separated from the bike a sufficient distance. I've gone mostly to tubeless moto tires, so flats are extremely rare, and are most commonly screws and nails, so plugging the hole can usually be done without removing anything.

 

[John in CR]

So its best to have the wires coming out of the axle downward and making a drip loop?
Currently mine are facing upward.

Downward or rearward depending on the mount. Water follows wiring like the channel of a river, so right now you have a funnel to send water into the motor. Also, assuming your motor is properly made, wire entry from the top puts your halls at the bottom and just a little water inside will put them in a hall killing bath. Hubbies breathe and cooling off in the rain sucks water in, and it's virtually impossible to prevent water ingress...see Justin's ebike seminar from a few years ago. In his testing, he discovered that they will even suck water even inside the wiring itself when sealed up very well otherwise.

Drip loops are common practice with all wiring entering something. Look at phone, cable and electric wires entering any house from a light pole. Gravity is you best defense if used properly.

John

 

[999zip999]

Good point where are the halls on a muxus 3,000 ? Wire up, halls down ? Wire down, halls up ? Unsure. Oh the halls don't spin . Looking at the inside from the outside. Thanks John.

 

[dogman dan]

Though I haven't done this yet myself, I like the idea of lengthening, and usually making thicker, the wires coming out of the controller.

Then about half way to the motor, beefy bullet connectors, then perhaps 16" of wire to the motor.

Gets the connector just a bit farther from the axle, yet not as many ties to remove to change a tire. Possibly two plugs on the halls, but more likely do the same plug location for the halls plug.

On the other hand, I've done lots of tire changes with the wire connected. Just remove 2-3 ties, then you can get the wheel off the bike. I like to use the Velcro ties for most of the ties that would be removed to change a tire.

For sure, max reliability is no plugs at all.

 

[John in CR]

I like Dogman's approach of using velcro instead of zip ties as long as it ends up tight and well secured. That eliminates my one issue with zip ties, which is somewhat sharp edges that deform the wire insulation. I've yet to have them break the insulation, but it's always a concern which I reduce by wrapping the wire with 2-3 turns of electrical tape first at the locations where there will be zip ties.

I've also used electrical tape of a color to match the bike to hold the harness in place unobtrusively. As long as you don't stretch it near the end or have the end exposed in a direction that the air flow pulls it loose, it is surprisingly durable, and always in my carry aboard tools.