As I understand it, the amount of braking current often isn’t the big issue. These cells have quite high max charging current level ratings. Though, I do understand what you’re saying.
We can’t control how the current is divided between the caps and pack very well so the caps can’t be counted on to divert enough current without very careful consideration of pack/cap voltages and impedances.
There’s a real safety issue though.
If the pack is fully charged then the caps need to absorb 100% of the braking current as you don’t want any going to the pack. Up until that point the caps aren’t really even needed unless you’re above the max charging current ratings.
Good point about the current dropping as speed drops but for downhill or already charged packs there are concerns. The numbers would have to be run to see how large a cap pack would be needed for the expected use of the battery pack.
Could one not rig up a system where regen goes into a separate, small pack/large cap, that discharges slowly(or even quickly, as long as it is in a controlled manner) into the main pack? I understand the use cases are few and far between, but as a safety feature, if you happen to live in a situation where regen-popping has any effect on your real life rides, it’d be pretty cool.
And as a non-safety feature, it could probably get the maximum real world results out of regenerative braking.
Costs to results, again, probably make this a solution for a problem that sits somewhere between never and very rarely being a good move.
Yeah I figured.
Space constraints quickly turn esk8’s into cars when too much innovation.
Cool concept tho. Any of the flux guys have space for an extra p group or two and some other junk to science out if maximizing regen is remotely worth pursuing? /S
Hey el mucho, one last question for ya: in an impossibly ideal situation, do you know off hand what one could really expect out of max regen?
Like how much of our spent energy goes to forward push of mass vs what could theoretically be reharvested, in an impossibly ideal situation, where it is purely electrons going back to where they started? Just curious.
Sorry, I don’t know.
My guess is not much due to power losses in the cells, connections, electronics and wiring added on to the frictional losses of the drive train. We need to add on the losses for getting the charge back into the regen pack and then back into the main pack too.
Seems like that would be a question someone, somewhere has really dived down into though. Someone out there must have a decent estimate.
Yeah… it’s expensive science.
And we have serious space constraints.
It would make more sense for like, the electric self driving 18 wheeler GE is working on(while I bring them snacks and occasionally ride with the one dude with a onewheel 5 times a year), to pursue such things.
And as long as its built to order, thats still a great product, problem is good old low demand.
What about a tiny low power vesc (20a or something max) that since on top of your standard vesc and it communicates with your vesc testing for cutouts
If something goes wrong with your main vesc during a ride (short or something) then this mini vesc takes over and gives ability to brake / accelerate lightly to stop you from dying
I could be missing something but I think a decent amount of the inefficiency of 4wd is the extra weight, inertia and drag of 4 drivetrains. Cutting out the electrical losses would likely help a bit, but I think the gained efficiency would be similar to running a “low power mode” that’s just a throttle curve. Riders just don’t accelerate as hard if they have to more consciously floor it to get that power output
One of the prebuilt 4WD boards, I think it’s the Atlas 4WD, can switch between 2 and 4 (not intelligently) but I need to check what impact it has on performance/efficiency. I do love the idea of programming your way out of a problem instead of throwing hardware at it though, I assume there is still some efficiency or performance to be gained from running a 4WD like that Vs just 4 all the time
I feel that sentiment but empirically, I’m approaching it from a point where I don’t want to sacrifice any top speed for torque but I wish my board would take off a smidge faster.
Too many HV escs be poppin these days for me to buy a new expensive battery and HV time bomb esc and motors to match so I’ve been considering going 4wd just for take offs but am worried it will change the feel of my drive too much. That’s when I though “it’s be cool if they only kicked in when I really needed them” and well here we are.
Yeah makes sense, I think it’s a really cool idea. Given the spirit of the thread my mind immediately goes to mechanically switchable motors, like they’re not involved with the wheel until they’re needed to reduce drag. Leave the motor pulley and belt always in contact but have a clutch between the motor side pulley and the drive shaft? It’d be bulkier but I’m picturing 2x6374 or 84 in the rear, and 2x(servo-driven clutch + 6354) in the front. Also if you know you’re only going to use them for launch or something you could use high reduction gearing on those motors and a smaller ESC. Two mini 4.12s with a nice safe 15-20A battery limit and as much motor current as you can hammer into them
Alternatively if you want to be “sensible” (read: boring), gear low and use field weakening for top speed if you’re not regularly going to be cruising above the non-FW speed limit
I was talking to someone a while back about that. Probably even in this thread. The general consensus was that it’s not a bad plan, as long as it’s not too much extra work and your free roll doesn’t suck too bad. Good use for direct drives or hubs.
I’ve seen people mention putting weak motors up front and having that esc set to only give power up to a certain speed but that seems like it might jolt me if I don’t get the throttle curve and duty cycle current limit start setup perfectly.
Yeah, it’d obvi require a lot more fine tuning…
What if you had, say, 2 motors w high kv ratings and 2 w low?
The low get you that starting torque, the high kick on at the top end for that top speed boost.
Now I wanna know how that would act in a realistic case… would the slower tires speed up, due to being rolled by the faster ones? Would the faster ones do a little rolling burnout?
I don’t really mess round with throttle curves, but wouldn’t this be possible by using a different throttle curve / deadband and maybe diff current settings for the front esc?
