Needing custom Gt Control box
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As the title says. I am looking for a custom front control box. The goal is to fit the maximum space available within a rear bang bumper moved to the front.
I know what you're thinking. Why in the hell is this guy adding so much room to where the controller goes.
Well, another 18-20 batteries is why.
There's a guy on the YouTube who has figured out how to fit another set of 18s 21700 batteries, a BMS, and controller into the front of an XR, using a badgerbox torque box in the front... Why on earth hasn't anyone done that to a GT with the added room it has.
I know there are connector details that need to be addressed, configuration considerations, deletion of the front handle and a lot that goes into this design. That's all fine with me.
I can cut and shape sheet aluminum for the heat sink, I can solder and build a battery pack. I understand the wiring configurations. I just cannot design and print a box.
Anyone have any know how and want to do something crazy. Anyone who can work on this project with me can keep the design files after to use at their disposal. Sell prints, etc. id like to just fund my own adventure.
Details people will want, I'm sure.
This board is for downhill street. I've found that even on a vesc, the braking capacity reaches it's upper limits on the hills I have. This means turns and slowing down becomes dangerous. I mean, safety third, am I right? But still.I'd like to see if I can fit a 30s2p 21700 split battery in a GT, with something like an x12 or any other controllers that can handle the 130v.
I've had more then enough experience at 25-30mph on street and am just looking for a bit more control. Not necessarily mileage.
I'm absolutely open to other ideas of what to do with my extra, dead GT. I've heard the GTV is nice but again, braking power has been a limit. I can't just tail slide the bumper away, all the time.
Thanks in advance, and again, if this seems crazy, trust me, I know.
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@highspeeddirt Have you found a VESC which will support that kind of voltage? I didn't think there were any that went that high. Also, have you thought about a 20s3p configuration instead? The 20s3p would also give you hella torque from the extra current it would support.
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@biell that's true. I haven't really considered the exact battery configuration beyond wanting to do something like a 60cell combination.
There is a tonic x12 that handles 130V. It should be able to handle the voltage in and out without much issues on the 12 mosfets.
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@biell said in Needing custom Gt Control box:
@highspeeddirt Have you found a VESC which will support that kind of voltage? I didn't think there were any that went that high. Also, have you thought about a 20s3p configuration instead? The 20s3p would also give you hella torque from the extra current it would support.
After looking at how torque and motor braking works, I think you're right with the idea of 20s3p. Plus, I would up my total miles by a third, at least.
Granted on this slope, I gain 2% Regen every .4 miles easily. So with a 7mile circuit, I can't start this track with more then a 50% charge on my battery.
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@highspeeddirt 20s3p also would give you a lot of options on which controller to use, most of the popular ones right now support a 20s voltage.
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@biell true. I did some research last night on the superflux motor. Based on 80 nm+ and 20mph on a 6" rim. It can handle 9800watts. Unless I'm doing this wrong. Info like nm+ without speed and wheel size doesn't tell you everything you need to know for watt input.
I'd like to see a data sheet on the motor that tells me how much I can put into it before I start cooking things. I'll have to upgrade the motor wires to 8 gauge at least, just for the extra amperage.
Having a 3p bank is like having a very wide river of current that can all travel at once. It definitely would be able to send that motor current skyhigh with overcoming the braking system.
I think the Thor or the x12 are the only ones that can handle that 135A potential from the batteries.
My math
Discharge current: 45A x 3p = 135ACouple that with the Regen braking going on at the time. Any motor is going to get angry.
What is the max motor current anyone puts into their vesc software? I've seen 120A.
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Okay, to further look at the potential of a 20s3p vs a 30s2p battery addition to a GT. I went looking for the weakest link in the setup.
The ideal would be a superflux motor, Thor 300 or x12 controller and enough room for this big dumb battery idea.
Looking at either controller. Neither would have trouble with the voltage below 100v and neither would have trouble seeing 300amps across the mosfets.
I've been having trouble finding the peak power of the superflux motor. They give a peak torque of 80nm.
I decided to use some information from another spec sheet I could find and try to cross reference the info to fill in some blanks.
The GT motor, hypercore, produces 26.6nm at roughly 980 rpms. This produces a total wattage output of 2726watts.
If we expect the NM of the superflux HT to be 80nm then at 980rpms it should produce 8210watts with the same voltage and enough current to draw from.
That would be 109amps at 75V. So far, I have seen higher then that on a lot of videos. So, either my rpm estimate for their peak power is off, or my math is just dumb.
Regardless, changing the amount of current available for the motor has its limits, but there is still room above 20s2p. If we work with my numbers.
A Samsung 50s 20s2p battery produces 50-90A of continuous to burst discharge. This leaves at least 19A on the table of current draw from the superflux. Granted we're getting into territory of overheating the motor with the stress, but it is room.
That means a Samsung 50s 20s3p battery, putting out 75-135A of discharge fully utilizes the superflux motor. And should still fall within the controller capabilities based on the typical motor current values I've seen adjusted for the 33% potential increase of current.
But we may just see a Thor overheat if I build this thing. I'll add a copper heatsink to the underside of the controller, flush with the bumper. This isn't a trick board, just downhill. so, obviously no nose slides.
