First Electric Motorcycle Conversion Advice (1974 Honda CB360)

[harrisonpatm]

Electrically, that all looks like it will work as intended, to me at least.

One thing I am still confused on is where the "Trig -" wire from the contactor should go. Is where I have it in the diagram correct, or should I have it spliced into the "B+" wire.

You have it draw correctly, Trig - goes to B-, not B+.

What's the difference between the two rockers? Just color?

If you're going with 1kohm precharge, keep in mind that depending on the controller's capacitors, it could take anywhere from 5-20 seconds for a decent precharge. Which is fine.

Also, if you're going with 1kohm, you can basically use "any" 1kohm resistor, not sure you need a $10 item. You already ordered, but here's 10 suitable resistors for $6.

 

[RealPolarBear]

What's the difference between the two rockers? Just color?

Yup, literally just color. In my mind this will help me differentiate between the two different functions: one enabling the precharge circuit, the other operating the contactor.

Also, if you're going with 1kohm, you can basically use "any" 1kohm resistor, not sure you need a $10 item. You already ordered, but here's 10 suitable resistors for $6.

Ha, that is fair. I figured I mind as well order it all from one place for simplicity.

 

[Dui ni shuo de dui]

Alright so I've been working on incorporating everyone's feedback and I believe I have come up with a pre-charge contactor circuit that will work for me. Parts have been ordered.

For those curious about the components, they are as follows:
72V Coil Contactor
72V SPST Switch
72V SPST Switch
250A Fuse
1k Precharge Resistor
400V 3A Suppression Diodes

View attachment 351606

One thing I am still confused on is where the "Trig -" wire from the contactor should go. Is where I have it in the diagram correct, or should I have it spliced into the "B+" wire?

For me there's a mistake at the flyback diode system.
If you really want to use two diodes, in my opinion one should be a zener diode. I don't think it makes sense to use two regular diodes as you will be blocking the current in both direction, which essentially seems to me like an open circuit. Basically it's like having nothing at all.

I wouldn't bother with overcomplicating this thing and simply go with the traditional single diode system, as it's working absolutely fine.
But I'm not an electrical engineer, it's just my opinion.

So basically you plan on having 3 switches just to turn on the bike (not mentioning another physical or virtual switch to turn on the BMS so that's 4 in total). That sounds rather complicated to me but it's not my machine so if that's what you like then no problem. Otherwise you could simplify a bit by merging the precharge switch and the coil switch into one single switch. For example you could wire it to a three position switch, so that the right position if off, the middle position activates the precharge and left position activates the coil. Since you have to pass through the middle to go from OFF to ON then it would precharge just before switching ON no matter what.

Ah, also I would add a fuse before the coil, to protect the wiring system in case there's anything wrong with the coil.