skidafunk said:
Please feel free to mock my efforts
No mocking. Just a couple of thoughts:
1. What is the 1000ohm 5W resistor in series with the contactor coil for ? Is it to drop the voltage from full pack voltage to the operating voltage of the contactor ? Assuming the contactor has a 24V coil, and assuming your 72V (nominal) battery is 20S (84V full charge), that 5W resistor is burning 5W, so it'll get hot (and waste power).
2. Even after you switch off the ignition, the contactor will stay on, since you have it wired to latch. So to turn off the bike, you need to turn off the ignition
and then press the kill switch. You added a system to reduce one risk, but introduced another risk in its place.
3. Is the kill switch a momentary button, or an actual switch ? Assuming it is momentary: if you just tap the kill switch (in an emergency, you might only get the opportunity to tap it quickly...), it probably won't cut power. Two reasons:
a) Since the ignition switch would still be on, it is still applying power to the contactor (via the kill switch). So when you release the kill switch button, the contactor will re-energise (once the capacitors reach the required voltage for the contactor to activate);
b) If the capacitors in the controller don't fully discharge in the duration that you are applying the killswitch, they will still be applying a voltage to the contactor (assuming there is no diode blocking their voltage coming back out of the controller), so the capacitor voltage will just re-energise the contactor.
4. An alternate solution would be to wire a kill switch (an actual motorbike style kill switch) in series with your ignition switch, to the coil of the contactor (not latching). So when you switch either one off, it'll cut power to the coil, and cut power to the controller. Note that using a contactor to cut power will still have a delay - there will still be charge in the controller capacitors, so power will not instantly be cut. Depending on power draw, it may take a moment to fully shut down. As mentioned by e-beach, the controller might have an option for wiring a kill switch directly to it. In that case, I believe that action would signal the controller to cut throttle immediately. But then you're relying on the controller perform that function, and maybe you don't like that risk. Understood.
5. Have you thought about using mosfets instead of a contactor ? Just another option.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=105110
6. Your 100ohm 5W precharge resistor will
initially be flowing ~840mA (@64 Watts). Assuming the controller has about 2000uF of capacitors, you'll reach full charge in ~1 second. A 5W resistor can probably deal with it, but just be aware that it'll get hot. Don't use the shittiest one you can find.
7. 72V 30Ah is ok for an enduro type bike. Probably about 10kg of cells (200 x 3Ah 18650). But pulling 10kW (~150A battery) from that pack will have a bit of sag. Even something like Sony VTC6 will sag up to 10V for a 20S10P pack. I'd suggest LiPo if you can afford it. Just my opinion.
8. I'd drop the 250A fuse. Just another thing to go wrong. If everything else is fused, then it's superfluous.
