Balance Lead Upgrade
Before the race this weekend, I wanted to streamline my charging setup. I manufactured and installed two wire harnesses that connect to the balance leads, and expose them on an accessible DSUB15 connector.
Dustcap on, dustcap off.
I then made some additional harnesses that connect to these two DSUB15 connectors.
One connects the two DSUB15’s in parallel and has a JST-XH connector that connects to my iCharger x12. This, along with an XT60 added to the terminal blocks of the G300’s, allows me to balance charge all 6 lipo’s inside the board at 1000W, WITHOUT needing me to take off the bellypan.
The other one can connect to the port and quickly see the status of all of the cells. While this can be done with the above harness and iCharger x12, it would require external power to turn on. While not super accurate, This gizmo makes checking the state of cells as simple as plugging it in. Probably won’t use it much in the long term, but it’s useful when testing.
“Brief” AVS Riderfest Recap
For those uninitiated, AVS stands for Apple Valley Speedway, and is north of LA. Big track made for drifting cars. Lap times for esk8 usually range from 1min20s~1min40s. I was able to post a 1min30s during qualifying on Ankle Wreacher.(I believe the esk8 lap record was set by @MarioChacon today, at 1min11s. I could be incorrect about this)
There was a race event held here on Today(Sunday). Qualifying times determine heat race positions, which then determine access to the Final race. The races are 3 laps(lasting about 5 minutes)
Overall, I couldn’t have asked for a better first race with the board, and I can’t wait to get the kinks ironed out. Thanks to the whole SDESK8 ARD Team for being such incredible, supportive, talented teammates (and congrats to @HAIRYMANJACK on 2nd place!) Wish I had more pictures to share.
Unfortunately. I had considerable problems with Ankle Wreacher throughout the day.
The main issue is that it would overheat incredibly quickly, which significantly affected my race results. Halfway though the 3rd (and last) lap every race, I would loose significant power as the motors thermally throttled. I lost 3~4 positions in the final race because of this (such is the nature of racing 
).
Once I came to a stop at the end of the third lap, the board would barely be able to move under it’s own power until it took a few minutes to cool down. Thank goodness it only needed to last 3 laps.
While it was 90°F outside, and nearly every esk8 board was having cooling issues, none had them to the same degree as mine (pun intended).
Most notable was @HAIRYMANJACK’s board(160A motor amps each motor, Reacher 7490 165kv), had a similar setup, but did not have the same overheating issues. Notable difference is rider weight (I’m ~50% heavier) and 165kv vs 265kv.
The fact I overheat but he doesn’t bucks my intuition. I would think that having 4x motors would lead to distributed power, meaning each motor would only get ~half the heat then a 2x motor board setup, right?
Relevant Hardware grey box
12s2p 9500mAh 150c LiPo
Reacher 7490 265kv motors
22T / 78T = 3.55 ratio
Relevant vesc settings grey box
Motor Temp Cutoff Start 85C
Motor Temp Cutoff End 100C
I adjusted the beta value of the thermistor to match a Reacher motor(same value as used by @HAIRYMANJACK)
Motor current started at 100A/motor, but I lowered it to 85A/motor after qualifying in an attempt to reduce overheating (to little avail)
I should be able to push significantly more then 85 Motor amps through these motors without issue…They’re rated for 10kW; 145A continuous, 200A max.
My hypothesis is that the 22T doesn’t give nearly a high enough ratio for the 265kv motors, especially for the racing at AVS where I spent the turn-y bits of the track at 20~25mph.
If I change out the 22T pinions for 18T, it would increase the ratio 3.55 → 4.33, which would let the motors run at a higher, more efficient RPM. This might also help with the Wh/mi efficiency problem.
I’d love to hear alternate opinions about what’s going on here, and if you’ve got it, best way to fix it.
Here's a bonus screenshot of me breaking the silly 100Wh/mi barrier, taken after coming off the track for qualifying(and after my motors cooled a bit).
esk8 news calc for either pinion size, for your convenience.
