Finally taking the time to document this build. This build is a combination of everything I’ve been working towards for the past couple of years. This board came from my last build (deck and motors), but upgraded from chaka 4.12 vesc’s to focbox’s and from 8Ah to 25Ah and a DieBieMS instead of no bms. Please excuse the dirty grip tape and deck paint imperfections, as I didn’t feel like putting another $100 and hours or work to do another fresh deck, just for a perfect look that will be dirty and banged up by rocks in a few days, lol.
First off, the full specs:
- 4wd hummie hub motors (all motors are between 80-90kv, 84mm wheels, poured by a&e)
- 12s25ah zippy lipo battery, 1110wh (2x 6s5p 5000 mAh packs, so 10 in total)
- DieBieMS for the bms
- 4x focbox’s (settings are 50 battery amps and 120 motor amps per focbox for a total of 200 battery amps, 480 motor amps)
- Modified hummie deck to create a larger pocket and decrease wheel bite
- @psychotiller enclosure (The Alter Wedge)
- Metr Pro Bluetooth Module
- 2.4ghz mini trigger
Now onto the story:
After riding with many of you in Vegas, I realized I needed more range. 4wd hubs are not exactly efficient, especially if you ride the way I ride. I was getting best case 11 miles on 8ah. so at 25ah, I can expect more than 30 miles now. And at worst case, I’ll i’m expecting 15 miles, since I was getting in the worst case 5 miles before.
This board is still young. Only about 10 miles put on it, most of which was the Barrett Junction Race. Partly because it started off with a drv issue with 1 of my 4 focbox’s, and a canbus issue with my DieBieMS. @barajabali sent me a replacement focbox, which I just received, thank you very much for that btw. And @JTAG offered to fix my bms’s. So thank you, again!
So the goal was long range, charge and forget. But lipos can be very sketchy. I figure it was time to finally bring the DieBieMS into the mix. Thanks to @rpasichnyk’s integration into the Metr pro app, I decided to pull the trigger and use one for this build. And to get the full experience, I needed the metr pro module.
I won’t bore you with too many details but if you haven’t heard of the DieBieMS, you should look it up here on the forum. It has an integrated backlit push button power switch, push to start (which is really nice), oled display for battery charge status, up to 12s, built on top of the vesc firmware (which means with canbus, it will play nice), and you can get individual cell voltages on your smart phone thanks to the metr pro app. You can also adjust a lot of settings, such as min and max voltages to protect the battery, and what voltage balance charging should kick in (very nice). Besides the other normal bms features such as balance charging. What a bms it is…
Back to the battery:
I didn’t want to waste space with the battery, so I looked at how I could maximize battery space not waste space in the enclosure. I did a lot of calculations with about a dozen or so different lipo cells. And this is the cell I came up with this cell sitting sideways as the best option:
I got a steal of a deal as I picked them up as part of the black friday deals. That with an extra 10% off for signing up with hobbykings text messages, meant I only paid $47 per pack, for a total of $470 shipped to my door. That is $0.42 per wh. Not too bad.
With assembly, the idea was to have a neg and a pos in a straight line down the pack’s length. Make 1x 6s5p pack, then flip to start putting together the next 6s5p pack in series for get to 12s. I just worked one pack a time, starting by connecting the pos and neg and then connecting the balance leads from one pack to the next.
I wanted a plate I could screw my electronics into so it would be easy to replace things easily if needed. So 3d printed a plate with inserts for small nuts that everything can be screwed into. This plate is then fixed to the board with glue.
With a full acceleration, it is incredibly difficult to stay on this board. 0-20mph in under 2 seconds, No hill is too steep for this board. And range anxiety is a thing of the past.
Thanks for checking out my build and I hope this can inspire others to build big, over powered machines of death lol.