This build focuses to use as many parts as possible from the remains of the first iteration of my raceboard - RaceBro.
Unfortunately as that originally race ready all purpose board turned more and more into a raceboard, I no longer felt like it belonged in the woods. This build makes sure that I can still have some fun in the woods.
This will also be a rolling build thread. At the moment I am still waiting for parts.
So, here’s the basics: haero bro stiff deck, pelican im2050, MakerX D100S which has a small external heatsink pointing downwards. The pelican is quite heavy and it’s going to stand quite empty but I already have the parts built out so I’ll just use them. At least the batteries between the two boards will be compatible.
For now I am going to use the BN310 precision channel trucks that also came off race bro
They are pretty nice for traditional channel trucks but are still traditional channel trucks. I am heavily considering changing these out for a set of Tito’s sometime during spring.
I recently stood on my old Matrix IIs and after riding Tito’s for what feels like an eternity (4 months), I could barely turn on them. So we will see how these go. But no money for a second set of Tito’s until spring.
Now, something exciting.
Drives you’ve never seen before. The all mighty @Boardnamics 7:1 ratio straight cut steel drives, of which only 3 sets exist. The other two sets are on @Esk8Hills 4wd monster. They are fairly large and heavy but these will definitely make sure that I won’t be lacking torque.
The motors are going to be Reachers of course, I went with 6375 for some weight savings, 170KV in the v6 version. They should arrive in approximately 3 weeks. Hopefully it will be a nice balance of power and weight. If they overheat too quickly I can grab the 6385s from the front of the raceboard and exchange them with those. I do plan to push a ton of amps and this is 2WD so will see how it goes.
Now let’s talk battery stuff!
This is going to be a high voltage build, to spin up those 7:1 drives properly. However, for weight saving reasons, only 1P. But hold up. It doesn’t mean that it has to be weak does it?
For now I plan to test out the shiny new BAK 45D cells, which offer a tabless construction and (according to it’s datasheet) 3.4 mOhms of resistance. They are supposed to be able to peak 126 amps. My plan if all goes well is to peak 100A. And that’s not the whole story. They are cheeeeaaaaaap. Less than 4€ a cell. Some might say too good to be true. But I am happy to spend 80€ to find out. If the experiment doesn’t go that well I can just a build a second pack using JP40s or EVE 40PLs.
That is however asking a lot from a single P group. I do not recommend others to follow, this is going to be a potentially quite dangerous experiment! Especially during the first few cycles of testing, I will need to constantly monitor the cell temperatures, determine voltage sag, adjust battery current accordingly.
Also, constructing a 1P battery pack with beefy enough connections that it can carry that current without the connection themselves heating up too much is no small feat!
Here’s my plan so far assuming I want to do 20S.
I plan to 3D print cell holders, fold 30x30x0.2 nickel (or if I manage to source some then nickel plated copper) onto the sides, and run an extra wire down the side for some increased current carrying capability, to reduce the current which is going straight between the cells on the nickel and spread it out a bit more. Will it work well enough for this current level? Well that’s part of the testing I suppose. I do have a 100A battery pack tester at work which I might be able to use…
Also. This is arguably not the smartest idea, but I plan to completely skip having a BMS inside the board, but have the balance harness soldered up and use it only for charging.
I am however considering installing one of my spare ESP32s and NTCs onto the pack in order to be able to get real time temperature measurements over Bluetooth. Not sure on this one just yet. But it would definitely be a good idea for gathering data during testing.
At the moment I need to decide if I want to do 20S or 21S. The reason for 20S would be to avoid crazy reverse voltage sag if I pull a lot of braking current which could get me near the limit of the 100V hardware. As these are unknown cells which I plan to push really hard, this would be the smarter call.
But I am lazy. So the reason for 21S would be that I don’t need to adjust the charger’s voltage output, as I plan to share the same adjustable charger with RaceBoi which is has a 21S4P pack, and I need a screwdriver to adjust charger voltage. I am also considering rebuilding that board’s pack to a 20S4P with these cells, but if I found out I wouldn’t have to worry about reverse voltage sag at 21S I might go 21S again on the raceboard, where after a rebuilt pack I would like to be able to push 18kW+. Also 21S is 5% more range. Decisions, decisions.
Regarding the rest, mostly there’s just tires hubs remote and bindings. Gonna be F5 bindings + heelstraps as usual, GT2E remote with a 3D printed case probably, some lightweight plastic hubs, probably plain old mbs rockstar ii, and for tires I am considering 8" trampa mudpluggers and the cheapo clever 8" offroad tires from ali.
Timeframe for completion is roughly a month.
