Ah, there we go. I understand now. That sounds like a pretty good way to load test. The only other thing I could think of was getting the motor I want and having it spin with some resistance. I do have the good fortune to have access to a dynamometer, so I could probably hook that up to the e-motor at some point and load it down with a couple nm. It's not a big dyno, thankfully. But, otherwise I will look into the heaters. Definitely simpler
I mean as long as I get it near it's max torque, that should be near max current, right? The dyno should be able to load 250Nm which is what a lot of the hub motors I'm look at claim.
One thing to remember is that phase amps are equal to the torque of the motor and the voltage at the output of the controller is equal to its rpm. So if your motor is spinning at lets say 200rpm, and while doing so it is outputting its max torque, the battery current will not be at his max at all, because the voltage going to the motor will be small and the phase amps will be high the power draw on the battery will be relatively small (in this exemple). So, to get more load on the battery side, it will be necessary to increase the rpm of the motor. If your dyno can handle enough rpm it should not be a problem.
My thoughts exactly. We'll see what I end up having to do.
Yeah, I do remember that voltage is proportional to rpm and current to torque, but max torque at low RPM should still be max current out of the controller at any rate. It should just be lower power like you said. This is fine with me. But, I would like to do thorough testing for torque speed curve and power use and all that. We shall see what happens.
I think 0.5mm copper buss bars will be enough. If you really want to be on the safe side and maybe push your battery a bit more in the future you could go for 0.75mm (if available). For the spacing of your cells, in my opinion, it is fine because some ready made cell holder (from what I can see) have the cells closer together than your design. I think the clearance of the cells in your design is better than these holders.
That was more or less what I was thinking, but at the same time I am trying to pull a lot of current. I just wanted to make sure before I melt things in testing. I'll check what pricing differences are between 0.5 and 0.75mm, though.
I was hyperbolizing a bit, for sure, but I also don't have a thermal cam yet. I guess I should probably get that before building the battery, huh. Thank you for the good advice, yet again.
Great question. I was wondering where to add it and then got side tracked. It'd be one of those shorter bus bars, but I'm not sure which direction or top/bottom.
I do want them to be the wider ones, but I'm not 100% sure how to make that happen.
Yes, one of the end bars of each half has to be connected to the one other end bar of the other half. You can do that however you want, but the easiest way is probably just to make bars that overhangs the pack and then screw it together like I initially suggested. or if you want to weld them, make bent bars that you can then weld from the tops of each pack.
God, thank you. I keep working on this in between other things and making myself more confused. I appreciate the input more than you know. I somehow convinced myself parallel was series. What's that saying again? Measure 14 times, cut once? I swear I have a degree.
Yeah, I was wondering if it should just basically double the width of the narrow bars and have them jut out on both sides. On the side that isn't bridging between the two halves (which I do want to do internally like you suggested), I was thinking I'd get them to bend the bars so they sit flush with the bottom of the battery and bend away from each other. I'd like a lot of surface area to put any wires on for the bms and the controller. Does this sound reasonable? Like below but for both sides.
I was thinking one side would probably just jut out like 2 inches or so for screwing/soldering/welding together somehow. Just parallel plates, nothing fancy going over the top. Unfortunately, copper is expensive lol. Otherwise, yeah the main issue will be keeping the end terminals apart and insulated. Gonna need something fairly thick in between I feel like. Like 1-2mm.
I haven't picked a BMS yet. I'd like more than two if possible. It all depends on what's available at this voltage it seems.
