Power connector question

[Hickbeard]

I've just been reading through the battery current vs phase current thread.

I'm still confused about all this.

I've got a 40a BMS and the leaf motor 40a controller. So I assume these are 40a cont.

Now the 3 phase wires coming out of the motor. What's the max current these wires will have to take.

I'm currently using 2 XT90 connectors and want to look at getting a 3 pole connector instead to tidy it up.

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[goatman]

you can try a mt60, its what the phaserunner uses for it phasewires. a phaserunner does 90 phase amps and it does 60amps from the battery with xt60

https://www.bing.com/images/search?view=detailV2&ccid=zCQcSel%2b&id=3145F70C63C47D655AC83A12718B0CF6DCEC5F34&thid=OIP.zCQcSel-YbZcQ5zYTBEtuwHaEo&mediaurl=https%3a%2f%2fwww.hacker-motor-shop.com%2fhacker_e%2fprodpic%2fMT60-connector-plug-socket-A85068_b_1.JPG&exph=400&expw=640&q=mt60+connector&simid=608015194157416808&ck=92A965DDEEB7DA7867FE4C91DB5125E0&selectedIndex=10&ajaxhist=0

 

[Hickbeard]

That looks good.

MT60 thanks.

Am I likely to be running that many amps?

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[Hickbeard]

Also when you say 90a phase. Is that each phase or total split across the 3 wires?

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[john61ct]

The max peak amps you actually use (and for how many seconds per burst) inside the motor

depends on your rig's total loaded weight, maximum grade and length of the slopes on your route

the speed you take those slopes

how hard you twist the throttle at starts from stopped

even head windspeeds etc etc

You can of course program your gear to set a maximum current, and limiting allowed temperature buildup inside the motor is also good idea.

 

[goatman]

Also when you say 90a phase. Is that each phase or total split across the 3 wires?

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i havent a clue :lol: :lol: :lol:

 

[fechter]

Each phase wire might see something like 3x the battery amps. I think XT90s would be fine for a 40A controller. On one of my bikes I'm using wimpy little 45A Andersons on the phase wires and I can pull over 50A on the battery when climbing a hill. They get warm and I've tortured severely and have not had any failures.

In general the peak phase current will only be a short duration so things don't melt down. Using heavy wire helps reduce heating too.

 

[Hickbeard]

Wow a lot more then.

Really don't understand all this.

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[john61ct]

W = V * A

Low speed, low volts

high torque, high amps

same watts but higher heat

 

[goatman]

i was thinking phase amps is double battery amps.

heres a link to amberwolf

https://endless-sphere.com/forums/viewtopic.php?f=30&t=107341&p=1571345&hilit=2+phase#p1571345

 

[methods]

The copper cabling is the heat sink for the contact point in the connector. To prove this you can take something like a PP45 (Anderson Power Pole rated for 45A)

Attach 22AWG to one pair
Attach 10AWG to another pair

Run 10A continuous, check
Run 20A...
Run 30A...
Run 40A...

You will find that the exact same connector tied to 10AWG will tolerate much higher current than the connector terminated in 22AWG. Good connectors are actually specified to a given current ONLY when attached to a minimum gauge wire.

...

So the point there, is that Heat is the issue you are addressing and that is I^2*R, so your current squared times your contact resistance.

The contact patch is basically constant, but the current (in the formula) is the AVERAGE running current. On an ebike (most ebikes) your average current will be quite low. Off the line you may dump gobs, but once the motor catches up the draw will fall back. If you are riding regularly (not going nuts) then ... you can pretty much run anything reasonable.

If on the other hand you are heavily over-volting, you have a soldered shunt (over-burst-currenting) you may actually get to the point where you can melt off a connector.

...

The phase wires are small, but they run a high temperature insulation (teflon) so - ... the wires will likely not melt, but they also will not pull much eat away. I run 10AWG phase wires, but most controllers come with something much smaller.

Eh...
Just run a connector rated for 40A continuous and you will likely be fine. I have never melted an Anderson on a phase lead, even wired to pinner wires. I run (or ran) a hundred volts with 40 or 80 battery amp limit.

...

Focus on Power instead of Current to simplify things.

A Kilowatt
2KW
3KW
4KW...

If you are seeing a KW or two on your battery side it will not be a big issue. Your motor will probably overheat FAR SOONER than your motor connections will. That is what I have found, but - that was dry. These days everybody runs oil in their motor or some kind of aggressive cooling.

While selecting a connector remember that you may have to sort the phases (when you change setups or controllers). This is why we originally used Anderson's

Good luck, let the smoke out of it.

-methods

 

[Hickbeard]

@methods yeah the cabling out the motor is pretty piddly. So attaching larger diameter cable to the other side of the connector will act as a heatsink and help pull heat out.



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[methods]

Your motor windings will probably overheat before your connectors.
Lets see

-methods