I had seen that in the past, but I want to avoid having anything under the bottom of the deck, where it could get ripped or damaged from curbs or debris.
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Seems like youâve painted yourself into a corner a bit with this requirement. Enough Velcro / dual lock to be secure is too much to remove easily. Straps are the only solution that might be strong and quick to swap - you could permanently mount a bracket to the top of your deck to avoid threading it underneath.
As far as the battery goes, youâd be better off solving the spontaneous fire concern with a high quality battery and good, supportive padding. If the battery has already burned through / smoked through the enclosure, youâre not going to want your hands anywhere near it. People tend to overestimate the amount of time they have to respond to a fire.
Hereâs another crazy thought. How about Snowboard quick release bindings? Like some low profile plate type with some old boots. Carefully remove latching component or hacksaw bottom of boot off and attach to battery box?
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More charging adventures. After blowing up my first BMS due to likely plugging the batteries into the balance leads in the wrong order, I got a second BMS. Iâm a little worried about plugging everything in correctly when charging on the go, so Iâm now thinking about leaving the BMS in the battery box rather than being attached to the charger. Problem is thereâs not really any space for it, as the middle is where the wiring goes, and the batteries reach to almost the top of the box, and the foam squishes it down pretty tightly. If I remove the egg foam in the lid, it can barely clear, but then nothing holds the batteries in place. Would there be any issues with stacking the BMS on top like this? Maybe I can stick it under the foam in the lid?
Either way balance wires are going to be a bit of a rats nest, which isnât ideal but is hard to control when everything is designed to be removable (For context I would normally still use a 1A balance charger because I donât need quick charging all the time, and Iâd like to extend battery life). An additional slow 12S charger would solve this problem, but thatâs currently not budgeted. Can the LLT BMS limit charge amps through the app? I donât believe it can but that would solve this problem too.
Overall I do like having the box removable, makes it super easy to just pull it off the board and charge it wherever, and not be limited by having to drag the board to an outlet, especially indoors.
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Another minor update time. Took advantage of the Black Friday sale to upgrade the plastic Matrix baseplates to the metal ones. The footprint is way larger which is good, and they also happen to be exactly twice as heavy, which was more than I had anticipated. All in all it added an extra half pound to the board, which is probably worth it for the extra durability. I wasnât sure whether the shock pad was necessary, but I put it on anyways since it came with the baseplate and protects the deck I guess.
Another small update was to the phone holder on the front. The flush mount was angled too far downwards, which made it somewhat difficult to see the screen. I made another insert that angled it up 10 degrees, which helps quite a bit. It still feels a little low, but it works well without the phone hitting the deck. Another issue that popped up during a ride is that over longer durations, the phone would wiggle out slightly due to it being placed off center since the volume buttonâs in the way of the clamp. This lead to moments like below where itâs barely hanging on.
Easy solution to that was to design and print a retaining arm that prevents the phone from going out that direction. Pretty simple, yet effective and doesnât interfere with phone removal or charging.
Final change was to the phone display itself. I found the original design still a bit too small to read while standing, so I made everything larger. I removed the title bar to gain some vertical space, and simplified the right hand side by moving stats I donât need to under the display so I was left with 4 large numbers instead of 8 smaller numbers. Itâs a little easier to see now, and less cluttered for easier glancing.
Finally, it turns out that shaking the phone would trigger the debug log, which ended up happening a lot when the phone was mounted to the deck. Shoutout to @skate420 for identifying the root cause! I fixed that, and now it works perfectly. Iâm still running into voltage discrepancies as the battery drains compared to my voltage alarm (4.2V is 4.2V, but it shows 3.9V when itâs 3.8V, and 3.7V when itâs 3.6V?), but itâs not too difficult to account for that. Iâll need to run more testing to figure out whether thatâs an early uBox thing or a rounding/measurement thing.
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Did you ever work out an answer on this one? I always wondered the same
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Nah, I never wired up the BMS, and itâs been sitting there unused. Since I only rarely use the quick charger, I just plug it straight in and donât worry about balancing since the balance charger usually keeps it within check, and I donât fill it up all the way to run into issues either. Simpler and more foolproof than confusing balance lead ordering in the field, which is how I fried the first one. Iâll use it eventually, so if you figure it out let me know!
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Board had its first major service today. The motors didnât seem like they lined up for whatever reason for the past couple of months so I decided to completely disassemble the left side drivetrain. Itâs odd too because the left one is the quiet one, the right one tends to get vibrations.
For some reason one half of the BN clamp was stuck on the hangar pretty good. Took a few whacks to get it off.
Once that was off, it was clear there was quite a bit of wear from the clamping, and for whatever reason it was definitely off kilter. I genuinely have no idea how it happened, or how long itâs been this way. I didnât see any obvious reasons, but one potential factor could be the relatively loose tolerances of the Matrix II profile, as there wasnât too much contact to begin with.
I filed down any tall spots and reassembled it, and itâs fine now? I still have no idea what caused it originally or why it worked for so long, but I guess thatâs the advantage of chains. No need to have precise backlash or perfectly parallel shafts to still work.
I also revisited my original port on the battery enclosure. It had worked its way loose from various shenanigans with the rear binding, so I need to figure out a better adhesive.
Lastly I decided to revisit the ESC configuration and change some settings up, as I hadnât touched them since I first built the board over a year ago. Huge shoutout for Freesk8 making this super simple! The first change was upping motor amps from 75 to 80. I wasnât breaking 60C on the motors in short track racing, so I felt it was fine to raise it a bit. I also dropped the battery amps from 150 to 75, as I had originally thought it was shared between the ESCs instead of per ESC. It wouldnât have made a difference regardless. Deadzone was reduced from the default 15% to 10%, which really helped tighten up control, especially during the acceleration to brake transition. Lastly, I raised the soft voltage cutoff to 3.65V, which is safer than the original.
Other than that itâs still kicking, and surprisingly reliable. No missing or loose screws (although I had a close call with a shockblock retainer), and no broken components since the original build.
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Lots of minor updates to the board. Here is the board in its current state:
The biggest change is changing from MBS T3 tires to CST 8" road tires since I mostly take it on the road, and as expected they feel completely different. Installation was a bit of a chore because of the rear wheels, but aside from that it wasnât a terrible experience and gave me some time to completely degrease and clean the chains. The CST tubes contain two nuts on the valve which happen to fit the valve hole in the Rockstar perfectly, so I can now push into the valve and it stays put, unlike before where I had to support it from the back. The tire in general felt thicker than the MBS tires, and were significantly harder to push down, something that made tightening the inner motor mount screws tough (picture for reference).
Ride quality was similarly different. These felt so smooth and plush compared to the knobblies, almost like the difference from thane to pneumatics. The max pressure of these tires are considerably lower at 36PSI, so I ran them at 25PSI vs the 45 I usually run the MBSs. They grip a lot better in hard carving, although part of that could be the smooth profile and lower pressure. One downside that I didnât expect was that efficiency went down about 20% from the MBS tires, it might be due to pressure or something.
All four wheels have aero covers now. I like to think they help with efficiency, but at the very least they keep dirt and debris from entering. Pictured on the old tires because I donât feel like taking another pic.
I also switched the front bushings to the yellow soft ones (thanks @bboybowzer!). They definitely turn sharper, but Iâm not sure if I like it yet. It feels a bit unstable under a higher speed turn, and it doesnât feel like I can dig into the board and lean into the turn like I did with the mediums. General handling is excellent however, but I may switch it back to oranges on the track.
I also made a couple of minor updates on my Freesk8 dashboard. I removed the smoothing function on the voltage readout in an effort to make it more accurate, and it is to a point. I still seems to be overestimating voltage under 3.7V, so I need to look more into it. The other thing is I flipped duty cycle and speed. Since my top speed is fairly low, it was more important for me to know how much I have left than my actual speed, and it has been way more useful as a proxy.
Final change is I finally have a BMS on my 8A charger now. Now I can safely plug in my 8A charger without worrying about overcharging. I use the Carplounge BMS app, which seems to work pretty well. The Chinese Android app also is pretty full featured compared to the standard one, however the downside is everything is in Chinese.
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