I’d like to get the discussion started on this.
From what i’ve read, we need some sort of dynamic braking module that power flows through that talks to a VESC to know when to divert power to the braking resistors.
After 10 minutes looking around, pack of 50 of these would take up way less space than 50 18650 cells, and wired up in series (right?) could dissipate up to 750W of power.
For those of us with lower charge ratings, those of us who want to save their batteries from the stress of higher charge currents, or those of us who just want double the breaking power or more for emergency situations, I feel like a small box of braking resistors as an add-on can make a lot of sense. I realize now it’s not just as easy as wiring up some resistors in parallel, since we need a way to divert the power intelligently.
Have any of you experimented with braking resistors for esk8 yet?
Just gonna go ahead and be that guy…
It’s spelled braking.
Thanks, I won’t edit the original post. My mistakes are written in stone. Braking.
edit: I take that back, that’s in the title. Thanks! Fuck it, edited everything.
Those resisstors are probably overkill,
Any heatsink with a resistance roughly a few ohms will do. Might be worth just using the heatsink itself
I admire your honesty all around. You could theoretically wire in a rheostatic break to split breaking regen amps between your battery and the rbreak That would allow you to double breaking current.
Just an idea I had a while back, not sure how motors battery and vesc would handle it real world.
So, these maytech rheostatic brakes, take four together and that’s 20A @ 10S capable.
The only thing I don’t like about these modules is that it says that they kick in when your BMS cuts out from over charging, meaning they wouldn’t work with a BMS bypassed for discharge only? It’d be great if you could just wire them up and they would just suck their fair share up to 5A per module of charge into the resistor: Wire four up, set a brake current of -50A, up to -30A goes to the battery and up to -20A to the brake modules.
a 200lb rider at 30mph has about 2.27 watt hours (8157 joules) of kinetic energy…
KE = (1/2)MV^2
M = 90.72kg
V = 13.41m/s
KE = (1/2) * 90.72kg * 13.41m/s^2 = 8157 joules
@Venom121212 wait you did it too! What is this…
You don’t necessarily need resistors to dissipate the power.
Properly heatsinked BJTs configured as a clamping circuit will function the same.
I might miss something, but I check my ride logs and the max bat min value I got is -25A on a big mtb for a spike of maybe 2sec when I brake hard with 6384 motors. That’s on a 7p pack so i‘m still far off what the cells can handle. I checked the rides of my smaller hub build with a 3p config and there i‘m at max -10A which again is still fine. My personal conclusion out of it is, that something like the maytech resistor bank makes only sense if you have a discharge bms and want to brake at full charge without your bms to cut off (or bms cut off and you non the less have braking force due to the resistors. Not sure what kicks in first as I don’t have any of this units).
The more I think about it, the more I want mechanical brakes. Anything esk8 that relies primarily on electronics to brake, and then mostly on the rear wheels, just isn’t good and reliable enough.
@flasher and @Skatardude10,
Click that little edit pencil next to my post and you’ll find the evil joker that did this
Maybe your values were per ESC? I have -20A total on my build, and I still would like much more. Ideally I’d like to brake as much as I can accelerate on any given build, and with current battery cell technology that’s just not doable
It is very much doable. Braking is only for a few seconds, even Liion can take much more than their rated charging current which applies to a full charging cycle.
I run -40A regen per VESC for a total of -80A on my Trampa with a 12S7P 30Q
I’m jealous; my setup is (was) a 12s2p
You can always go LiPo if you need crazy charge / discharge currents from a small battery
It’s metr values of two vescs. -25A max with batt min set ti -20A on the vesc. That’s enough to fully lock my chain drive on gravel and slide. Or stop in front of a traffic light from 35km/h without to get the wheels locked up. So for me it’s more than enough.