Hi!
I am unsure about the right KV value for my application (custom eBike/Pedelec) and I started to wonder, how important it really is.
My understanding is that I need to align the KV value together with the battery voltage so that I can reach my maximum desired speed. (If the motor runs to slow, it wouldn't support the cyclist anymore of course.)
For simplicity and focus, let's keep gear/pulley ratio out of the way and assume direct drive.
Let's assume these values:
- d_wheel=70cm
- V_max=30km/h
- U_bat_min=30V (10S battery)
That would mean:
- RPM_Vmax = 30 km/h * 1000 / (0.7m * 3.14) / 60 = 228 RPM
- KV = 228 RPM / 30V = 7.6 -> roughly 8
Until now, I thought in this hypothetic scenario would have to be roughly 8, but then I started to wonder if that is really true when using current (torque) but not RPM/duty control? Is that calculated KV value only the minimum in this case and any other value > 8 would work?
Reading a bit more on that topic I found out about motor characteristic curves and got some for different KV values (same motor) from two manufacturers (Flipsky, Maytech).
They seem to confirm that lower KV motors provide higher torque at lower current but higher voltage (due to more windings).
So for the hypothetic case described earlier, does that mean, while I could use any motor with KV > 8 in general, it makes most sense to use roughly 8 due to higher torque?
Just use the motor setup and Vesc tool Wizard. It'll figure all that out for you, or at least give you a baseline. To play with.
V E S C T O O L P R O J E C T F O R
E V E R Y O N E®
(known as Pandora's box...)
Dear Mr. Vedder...(or somebody else)
I am "happy" owner of 100A vesc controller, one kilogram weight ,3.5kW outrunner and 66 pcs. of Li-Ion cells. I highly praise and admire Your masterwork called: VESC TOOL PROJECT...but...possession is not enough to be a Lucky guy. Goddess of Fortune won't smile on you .....until you get educated. And this is a core of my problem. I am standard electrician - electrician bu trade -maintenance guy .. with some Electronic experiences.. but... FOR PROPERLY SET/ADJUSTED VESC-(tool) it's NOT ENOUGH... THIS IS A TASK FOR NARROWLY SPECIALISED - UNIVERSITY EDUCATED EXPERT(S)-! engineers... How Can a guy/girl with medium education fully enjoy their devices which costs several hundreds $or€or£...? Problems which are fixed on vesc forum are not for ordinary folk... plenty of requirements...real QUANTUM of values...Questions seems endless.... So ... what is a solution - (for everyone) ? ...
My proposal is:
pleas ...
# Create (some possible) database (list) of verified-recomended-well estabilished settings of "vesc+mot"-pairs, which's "behavior" -based on (some) requirements will be (briefly) described in attached description. (batt.type too) if it's possible, "pack of settings" could be easy sent by email . Contrive and trump up the way how to transfer "pack of settings" get into vesctool and drop it in vesc.
# Make (affordable payed) service which will Create "custom settings" based on individual "unit behavior" requirements. (May offer limited list of settings of pairs - which's behavior and properties are REALLY and SERIOUSLY tried and approved)
# Make an "homepage post" - place, where satisfied users will publish (in prescribed way) their own settings-experiencies with their pairs (vesc+mot) with behavior-properties of used drive units...(boards, scooters, bikes,vehicles...) (those people could be called DIAMOND CONTRIBUTORS )
or
# Send me some website where I Can buy some cyanide or any venom....
truly Yours...
Hopeless Holder™
... Sent From my sister's Huawei