@Jopj die you end up with that cheap charge only BMS from AliExpress? Can you show me how you wired it up. I feel like a dork when reading those manufacturer schematics.
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Sure but it needs to be pasted into something thermally conductive in the first place, pasting it into the plastic holder would do no good. Paste between the focbox and the (future) metal mount, as well as that mount and the footpad plate is a must.
It’s not optimal since there’s a lot of solid metal between the heat source (vesc) and sink (footplate) but it should be enough.
Yeah, that’s in my battery while I figure out my own BMS design.
Beware: it does not balance the cells so you need to periodically check & balance them yourself if you use it
This is how it’s wired, except “load -” goes directly to battery - and not to the bms to bypass it in discharge. The balance connector starts from the negative side of battery, and any extra pins (for less than 13s battery) are connected together to the highest cell positive. So in my 12s case, pins “12” and “B+” both go to the top cell positive. For a 10s battery, it would be 10, 11, 12 and b+ that go to top cell positive.
This is how it looks like in the battery, although I doubt that’s much help to you as it’s so cramped in there. The extra connector is for those cells going to the second half of the battery so that the halves can be separated from eachother
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I don’t think this is the correct way to wire this BMS. If a BMS has both C- and P-, then P- is for the load and C- is for the charger. If it doesn’t have C-, then both connect to P-.
Maybe this is closer to what you described
This is mostly for folks reading this later
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Yes, that’s the “load - goes directly to the battery -” bit, I should have updated the image rather than just explaining it. Of note is that the manufacturer specifically says to avoid using P- for an unknown reason, maybe the PCB has some error regarding it. The discharge current is too low for our uses anyway.
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That’s a good question. @Jopj do your lights change based on direction, or are they hardwired red on one side, and white on the other?
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I don’t have anything in the rear, the front lightbar turns off while riding and only the power and orientation debug light stay on. It is very easy to program light changes based on direction with an external controller, and for those using the balance app it would just be an Arduino or similar which reads motor velocity over serial and blinks some leds based on that.
I was thinking of using ws2812 strips, but I don’t have a 5v source powerful enough to drive those, I don’t want to put any more load on the VESC 5V source.
One could have all kinds of patterns and pulses, or just “if(vesc.data.rpm > 0) {f=w; r=r;} else {f=r; r=w;}” 
The way I would do it: Get this library on an Arduino, test it by having it light up it’s led based on motor direction, then add whichever type of lights you want (with their power supply), and have the arduino control those instead.
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Just briefly touched 29 kph! That’s when pushback kicks in with my current settings with nearly full 12s pack and the delta-modified Phub. I’m still pretty antsy about this speed, but pretty comfortable cruising at ~20-25 along some gravel roads around where I live.
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To tackle the newfound VESC overheating issue I’m planning on an aluminum block which is screwed and thermalpasted to the Focbox’s heatsink and comes through the mounting plate as well as the cover…
And is itself screwed and thermalpasted to the bottom aluminum plate with some added ribs for good measure.
There’s going to be 15.5mm of solid aluminum between where the heat is generated and dissipated so not exactly optimal, but bound to be better than how it is now. It’s gonna be less waterproof also, but it’s a compromise I’ll take. 
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One reason why this overheating problem really raises its head only now is that I have been riding faster and harder than before due to getting better and more confident at it. And I must say I’m quite impressed with the power and torque of the modified 600W Phub. It just seems to say “c’mon you can push a bit more” when I get scared that the nose is going to drop but glance down at the screen and it’s at 60% effort 
Today while riding with some friends, I was able to get up the incline in the pic below without any problems whatsoever (until thermal pushback kicked in).
On the negative side one (or more) of the three gyros isn’t playing nice, couple of times while riding the voting-consensus logic kicked in and started ignoring one due to too much difference wrt the others. I feel the little twitch that causes, which is a bit scary at speed… I’ll need to sort that out, make the transition smoother and figure out if there’s actually something wrong with one of them. 
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Really like all the pictures 
Looking great!
You should add a loud beeper for when you’re using e.g. 80% effort. That would help you A LOT to prevent nose dives.
I’m sorry if this has already been discussed, but I just look at the pictures 
Example of a beeper. You could possibly find a louder one.
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that’s actually brilliant.
Maybe this could also be done with some kind of rumble pack placed just under your foot. (gotta give it a distinctive pattern to not mistake it with natural viabrations)
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I am considering the exact same thing 
Question is just if there is any PNP solution for it. My hooverboard esc got this feature and its really helpful same goes for when the voltage drops under a set limit
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I already have a beepers in there, 3 in fact
They beep out status and error codes, f.ex duty overspeed, low battery voltage, overtemp, as well as a “ready” beep when powering on, “footpads pressed” beep when stepping on it so you know those work and it’s ready to be driven, and a final “go” beep when it’s tilted level and the motor engages. It also beeps when I run through the UI menus and when bluetooth connects. I sure like my beeps 
Only issue is that when riding outside with lots of noise, they are not very easy to make out. I can’t push them louder since they are powered from the VESC 5v line and the power I can pull out of that is pretty limited.
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I believe those beepers I’ve linked to are PRETTY loud. Im pretty sure it’s the same I have in my EUC and It’s loud.
Just thinking out loud.
If you could possibly make the beeper get 12V from the battery and then have a switch connected that would be trigged by the 80% effort mark. Would probably take up too much space though…
Hope what I’m saying makes somewhat sense
Yes that’s the external power supply I’ve been thinking for the LED’s as well. In retrospect I should have put one in, but I didn’t.
The ones I have are also rated 95 db each, they were from battery alarms for RC planes which are loud enough to hear over the motor when said planes are cruising somewhere up high. The issue is them being in an insulated box within another box, and lack of power to drive them really hard 
They are PWM’d by the same processor that’s doing the balancing, so I can play melodies and not just beeps. Although I only have some very simple tunes to tell the events apart.
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So the DIY BMS I’m planning for this is coming along, being almost ready for manufacturing. It still needs a cleanup of the mask text + labels, some final sanity checks and of course a logo of some sort.
To fit in the Redstar it’s quite small at 3.2cm x 5.5cm which did cause me some grief when designing it.
I’m going for a pretty full set of features, so that it’d be usable in many other applications than just this onewheel.
What it’s got:
- The usual balancing + overcharge protection for 9-13S batteries
- Telemetry over CAN, Serial or USB for detailed info about battery status
- High side switching to make using telemetry easy
- 3-channel thermal monitoring, one external for cells
- Optional in/out current measurement
- Optional output switch (so not just a bypass BMS)
- Optional e-switch function
- Potentially high current capacity 60A+ (thermally limited)
- Precharge function to limit inrush current for highly capacitive loads
- Low cost to make since I’m cheap, I’m thinking ~30€ or so
It is based on the cheaper BQ76940 cell monitor chip, which brings down the BOM cost a lot. The chip has its quirks though, such as the need to configure cell count by jumpers (the things marked JP on the board) and slow internal balancing at only 5 mA. This means it’ll keep a pack balanced well enough, but a seriously unbalanced pack takes ages to sort out.
I’ll likely use it in bypass mode for the Redstar, but it’s got provisions for output switches as well. Those 2 xbox hueg power MOSFETs are rated for 300A continuous each as long as they are kept cool. This small board won’t reach anywhere near that much due to the heat. At a continuous 90A load, there should be around 2.7W combined to dissipate across both of the MOSFETs and I’m relying on the thick power cables soldered right next to them to wick the heat away. Anyone who has soldered some AWG8 cables knows how good they are at it
Another question mark is the current measurement shunt, which is the same type some VESC’s use for the phase wires. It seems like such a small component to carry the current, but the calculated heat generation in there doesn’t seem too unmanageable. Like the MOSFETs, there’s provision for 2 in case one gets too hot. For most reasonable purposes, populating only one output MOSFET and shunt should be enough.
It’s an interesting project and I hope it’ll work out
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Am I reading the data sheet right when it says 25µA operating current and 5µA standby? If that’s the case, you could seemingly leave it /on/ forever? Or is there a trigger for turning off after dropping below a maximum cell voltage deviation?
Looks like a clever solution. I especially like that it has options for thermal measurement!
A new affordable/smart/small BMS challenger enters the arena!
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Supply current when the cell measurements are active is higher than 25µA, what I’m planning on doing is that in bypass mode, plugging in the charger will wake the microcontroller, which will start cell measurements and stay awake until charger disconnects and any balancing is done. Connecting any communication interface (serial, USB or CAN) will also wake the microcontroller and it’ll keep the BQ awake for the telemetry. In bypass mode, keeping ADC alive while not charging doesn’t help much since the BMS can’t stop discharge even if it wanted to.
In non-bypass mode, it’ll also stay fully awake whenever something is talking to it, else it’ll check the cell voltages every couple of minutes and if there is any change or they are close to limits, wake up completely to see what’s going on.
If the voltages go below a critical level, it will put the BQ into the super low power “shipping” mode and go completely dark, only pluggin in the charger will wake it from this (it’s rigged to the BQ boot pin, which will power the regulator, waking the microcontroller and so on). Of course, this will only happen if there’s been no activity for a while so it won’t cut the battery while riding - better to save the rider than the battery
Currently the chosen CAN tranciever has a high sleep mode current, more than 300µA. There is a pin-compatible version with much less, but I’ll use this one for testing since it’s more easily available.
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This man rides
That’s why I don’t put big fuses on the battery main leads either…
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