Yep, probably the Multistars not being able to cope.
Am I correct that I could counteract this by limiting the battery current in the VESC ?
Yep, probably the Multistars not being able to cope.
Yes, adjusting your max current settings will help. You may not need to once you adjust your low voltage cutoff.
@trbt555 Thanks for these updates; I appreciate the testing and the feedback. When you say that you tripped your VESC what did that feel like? What was the result? I’m thinking back to a few times I thought that I lost controller signal with a nunchunk, and I think that they were all during hard acceleration and before I fully configured VESC for my setup. If you were accelerating hard and the VESC reboots, did you get tossed?
I think @chaka could be right, because my low voltage cutoff was set so high, I was probably tripping it by demanding too much from the batteries.
I don’t think it was the nunchuck.
What did it feel like ? I hit the stick to overtake a cyclist and all of a sudden I’m no longer on the board but running. It just cut off all power.
I’m actually very happy with how the nunchuck/VESC control feels. Very precise, braking is just right. @onloop made it very easy by putting default r-spec settings in the VESC.
On the mechanical side, My board seems to have a few rattles that are bothering me, I’ll need to straighten those out too.
I’ve owned Flywheels before, but these ones tend to “creak” like a new shoe when rolling. I hope this is only part of the run-in process.
OK, now this is getting seriously fun !
Third test today on flat terrain with these modified settings: Batt max: 30A Battery cutoff start: 39,6V Battery cutoff end: 38,4V Max ERPM: 40000
Stats: Distance: 21,38km Avg speed: 20,35kph Top speed: 37,5kph Charge used: 4850mAh
No more cut-offs when accelerating. No nunchuck dropouts either. Me happy
I tried hitting 40kph but got speed wobble because I had my trucks way too loose so I backed off. I’m pretty sure that within a few rides 40kph will not feel fast at all.
Towards the end of my ride the VESC unexpectedly cut off the power twice but my wattmeter was still showing 44V by the time I turned the board over to look. The wattmeter was also reading a peak power of 4125W, which is impossible. I think it can’t cope well with the regenerative braking. It may fail soon. I was probably hitting the lower cutoff voltage so I kept off the stick and rode the last few hundred meters at snail pace. Because you know, pushing sucks
So, the batteries ain’t as bad as I first thought. I’d say acceptable for the price. Anyways, my Zippy’s arrived today so if the weather keeps up I’ll give those a try later this week to see how they compare.
I hit a few rough patches with some loose gravel, the Flywheels just ate that gravel up. The R-SPEC’s on the other hand, got pummeled: But hey, a good tool wears signs of use well
I removed the unused motor though. No use dragging it around for nothing. I hope my VESCs from @chaka come soon, dual drive will be insane.
I also started an offensive against rattle. I found one of these dampening mats at the local hardware store and put some in my control box, to prevent wires rattling. I also added some thin dampening material to keep the wattmeter from rattling against the lid:
My Zippy Flightmax Lipo’s arrived but the weather was bad and I was bored so I decided to see if I could take an objective approach to setting the low voltage cutoff and whether or not I would need different settings for different Lipo packs. So I had some good clean geeky fun with my Arduino and did a discharge test. I set up the Arduino to measure the pack voltage over the balance plug while I discharged the Lipo over a 35W halogen bulb. I had the Arduino send a timestamp and the measured value over the serial port to my PC, from where I could import data into Excel. I had a cell voltage monitor/alarm set up at 3,6V so I could leave the setup alone until stuff started to get interesting. The 35W bulb drew a current of approx 2,8A. Unfortunately I didn’t have anything more powerful, it would have been fun to see the effect of a larger discharge current, especially a current close to the max discharge rating.
My setup: The results:
- 3,6V per cell will be a good cutoff limit for both packs. Under 3,6V the voltage drops VERY fast. It took both Lipo’s about 15 min. to reach 3,0V coming from 3,6V at approx 2,5A, imagine how fast the voltage drops when you’re drawing 10 times that current.
- Both curves show a small dent at 4,0V, I don’t know what is going on there, it could have been someting in my setup.
- The Multistar takes 13% longer to discharge to 3,6V while it only has 4% more capacity, while the current in both tests was identical. I don’t know how accurate my test was but one thing for sure, range with the Zippy’s will be shorter.
If I ever decide to repeat this kind of test, I’ll put my wattmeter in the circuit as well and maybe even have Arduino monitor and log individual cell voltages, and have it shut off automatically at 3,0V
Now I’m waiting for the weather to clear so I can go out and do a real-life test. I’m also brooding on the idea of having my Arduino log values from the VESC’s over CANbus and store them on an SD card, while also logging accelerometer data, which would give me useful data to analyse after a ride.
I had a quick ride after work on the Zippy’s, on flat terrain.
Distance 17km / 10,5miles
Avg speed 24kph / 15mph
End voltage: 3,6V per cell
They definitely don’t get me as far as the Multistars, so contrary to my earlier conclusions, for a mellow riding style on flat terrain the Multistars really give bang for buck.
I hope the weather stays OK so I can try the Zippy’s on some hills.
Temperature plays a huge role in how much range you get out of your pack. As the temps drop you not get as much range. Something to keep in mind whilst comparing different brands.
Yeah I know from my RC days. Temperatures were similar to my other rides.
But what I really would need to do is run the Multistars empty and switch to the Zippy’s on the same ride.
Only, I can’t find a route long enough
I think I can top you! Bought stuff for around 2600 SEK and 826 SEK import duties, that’s almost 32%…
25% sales tax + 2.6% customs and always 100 SEK in processing costs :’(
Build looks really good, gonna build a quite flexy one quite soon too. I feel like the board flex will be my greatest challenge. Backup plan is to just get a stiff board lol.
Due to the bad weather and no daylight after hours I’ve been working on a Lipo display/alarm. It’s a small 128x64 pixel OLED display which will be visible on the top of my deck so I can keep an eye on things. Got the code running and the hardware sorted on the test bench. I’ll be able to display live data from the vesc as soon as I’ve sorted getting it back over CANbus. Don’t hold your breath though. I have a day job
I am using the same box as well. It’s from Rosti Mepal! I was doubting about the thickness, but apparently its really the perfect size.
This is a Rosti Mepal Flat Bread Lunch Box made in the Netherlands.
Materials is ABS.
My build comes closer and I also want to use these boxes. Should one buy them over the internet or can one buy them in some shops located in the Netherlands?
Did you buy them from your link or in a local store?
I have bought them both in local stores and online. Sometimes it’s slightly cheaper in the local stores, but normally they didn’t have the same colors for two pieces or more. So last time I decided to get them online from the link I’ve posted.
And I have it black on my build by spray painting it.
I got mine in a local store around the corner. They’re literally eveywhere.
Ok, thank you both. Will have a look then next time.
@trbt555 Could you tell me what local shop it was? Vaals doesn’t have that many.
I bought two of these as well. Perfect fit for 2 4s 5000MAH batteries, a VESC, and receiver. My winter project is to to paint it and get it installed. It’s very slim, and appears very durable.
Thats great! Btw I used t fit 2 3s 5000mah battery, 100A ESC, 2 Rocker switch, RX receiver & telemetry, 1 10000 micro farad capacitor, a fan and a SBEC lol. Thats like mega tight fit!
This is my version 3 build before, but somehow 5000mah just seems to be too short of a distance.
@laurnts Yes that is a snug fit, but I like it! I prefer to have everything enclosed in a small unit with minimal wasted space. Have to keep an eye out for shorts though