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Anyone want to help modify a Radio Flyer Model S?

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We are on the same page as I have tinkered for many decades in my workshop and now I am training grandkids (teens) in the safe use of mill, lathe, welder, band saw so that they too can tinker. I bought them an Arduino starter kit to get them programming robotics so I know the value of letting creative minds expand when they have the skills and tools to make things. Together we tackle any broken item as a project and hopefully that self-confidence will stick with them along with the tool collection that each have started.

My concern was young children being given a souped up EV toy car that might be beyond their ability to control. The quality of the parts being used also could be a safety risk so my advice was to leave the toy car as is. It suits smaller children best given the plastic body panels and crude steering. Building an EV car for them that is Go Kart sized makes more sense to me and our neighbour's boy has done that with my help and his Dad's experience. We welded a frame and steering and they run it on Li-ion drill batteries.

Our grandkids are now big enough to drive a car so I take them to an empty school parking lot on weekends to learn the controls and to practise parking. It's the next step in the journey that started with a plastic 12V toy Jeep.

I know adults who enjoy RC model car racing and that's the world where the sky is the limit for go fast mods. That hobby seems more suited to the list that you have presented, in my opinion, except for counter steering which is a motorcycle attribute to induce lean. The grandkids ride with me on my bike. They wear the right gear and know the feeling but they are not strong enough yet to control it. That can wait until they express an interest as the danger is real.

Enough said on this topic. You are aware of safety for your kids and that's what is most important. I trust that you will always do the right thing in that regard and not make them test pilots where things can break.

Take care and thanks for taking the time to respond to my concern.
 
I was testing the circuit ahead of changing out the switch and discovered a pair of wires that don't make much sense to me, and likely explain the other problems described above. The drive switch is a VS80B. This is much more than a dumb switch. It has a microcontroller in it, it has low-voltage protection, over-current protection, and the website says it can be configured for stepless variable speed, and has three selectable speed modes (variable? low? high? - getting variable speed might be easy). A brief explanation is here:

VS80B series Variable Speed switch with Microcontroller for t-Welcome to Shandong weida machinery co.,ltd.

I have emailed them (in English) asking for a detailed datasheet. I don't know if I will get them. If someone is fluent in Chinese would like to try, please reach out to them.

There are red and black into the switch from the battery. There are smaller green and blue soldered to the same battery input terminals. Green and white are outputs to the motor - they are labelled M1 and M2. There are two smaller red and white wires that go into the switch case on terminals labelled 1 2 3 4. Photos show the details.

I desoldered the small red and white wire thinking they were the headlight power connections, but the car won't run without them. It is clearly something important - battery monitor? I tried flipping the forward/reverse switch and the 1-2 speed switch and see no change on these red and white wires, so think it isn't that. White seems to be labelled "com". Red "DP".
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Hi Don,

It's hard not to respond or not to respond sarcastically since the tone could be interpreted as questioning parenting abilities. I know you meant well and I share your concerns. Once while riding bikes my 7 year old at the time went ahead and turned a corner while I was stuck with my slower 4 year old. We had already established the rules so privileges were lost for a week! Never did that happen again. My biggest concern modifying Power Wheels was not catching my garage or kids on fire. Both of my kids have also had "time out" from the Jeep for running into a curb or driving unsafely (too close to people/things, not paying attention, etc.).

Since you don't see any advantages to such a project I would like to share some because it has been very rewarding experience (and we aren't done, we always have more ideas and not enough time). I would be hard pressed to find another project with such wide educational and applicable experience. My kids range in age so each got different value out of it and they definitely grew more engaged as the Jeep became "better" or "different" and asked deeper and more interesting questions. I realize many of these come from a different mindset of tinkering and making which I would love to see more parents do.
  • "It's not a toy" -> Yes I say that
  • Safety First (Helmet, Flag, Visibility, Seat-belt, "Slow Children Sign" [chuckle])
  • Fixing things (Jeep was used and original battery dead)
  • Value (saved money using low cost Pb back batteries first)
  • Braking as a separate function (installed second break petal)
  • Alignment
  • Shocks (well, bungie cords)
  • Emergency kits (make shift variable pedal broke @ the park and I had to "tow" it home ... we now keep a toolset in the Jeep).
  • Fabrication (we used aluminum and dremels ... we talked about 3D printers ... almost had an excuse to buy one!)
  • Curcuitry
  • Voltage, Amps
  • Power and Capacity
  • Chemistry (Lithium battery came only in 18V ... making for a higher speed and need to run in parallel instead of serial)
  • Charging and low voltage performance
  • Resistance, Variable Resistance
  • Wire resistance
  • Gauge, wire stripping, crimping, wire nuts, etc.
  • Various tools and parts (no, bolts are not "screw nuts")
  • Serial/Parallel sources and motors
  • Fuses
  • Three way switches and connecting in parallel
  • "Gears" (although we changed that form low/high to sport/insane)
  • Shorting vs. Disconnecting motors
  • Cooling
  • Listening
  • Understeering, Oversteering, Countersteering
  • Lingo ("donuts")
  • Traction
  • Responsibility
  • Consequences
  • Team Work
  • Success & Failure
Those are all topics that came up in the process and I would say most are because of or resulting in differing speed. The goal was never racing but if I did want to introduce my kids to driving skills (under/over/counter steering,etc) I would not want their first experiences to be at any tracks that I've seen. It was also our first "EV" in the family which facilitated Tesla related discussions for me ;)

Now that the EV is complete, time to build yourself a nuclear plant to power the charger (and maybe the house while at it). Think of all the things the kids can learn from it, physics, thermodynamics, electricity generation, hazmat safety, the patriot act, law, bureaucracy, etc. This one project alone can give them an education well beyond what they can get from many college degrees ;) Oh, and definitely a good excuse to buy a 3d printer, maybe two (plastics, metals). :p
 
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I've completely stripped mine, since I'm doing a RC/autonomous rover conversion.

The red wire coming off the pedal switch is a simple 5v switched power supply for the lights/sound system. It goes high when the pedal is pressed and times out after a while.

P_20180329_001609.jpg

The white wire has some kind of serial protocol on it, and the battery won't output any meaningful amount of current unless it receives this signal. Permanently holding the "gas pedal" switch down doesn't work either, it needs to be pushed after the battery is connected, hopefully I can just put a zip tie on it after I change batteries and it'll stay on, but if not I might have to decode the data and program a microcontroller to fake it.

P_20180329_001506.jpg

I need to dig up my logic analyzer and spend some time trying to decode this, hopefully it's just an "on" command and not bi-directional...
 
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Reactions: hoang51
So had anyone successfully modded one of these?

Wouldn’t it be easier to rewire the entire thing? I mean at what point of modding is it worth ditching the entire factory harness and going from PB battery to new ESC to new pedal to motor just directly?
 
I've already stripped the entire factory harness, the only part I really want to use is the factory battery, which needs a serial command from the gas pedal switch to activate. Hopefully just holding it in the on position after changing the battery will keep everything on until the battery is low.

I'm waiting on a few other parts for the project.

Navio2 Autopilot
Reach RTK module
Sabertooth 2x32 motor driver
HS-7954SH high torque servo

The goal is for the car to fully autonomously drive around a pre-programmed route, with centimeter accurate GPS. Later on I want to add sonar and computer vision for obstacle avoidance.
 
Hey,

I am also planning on modifying the Model S for kids. I've ordered a Neato XV LIDAR unit along with a brushed motor controllers. I plan to control the steering column with a belt drive and some 3d printed gears. I also have some ultrasonic parking sensors I might attach to the car as well.

I haven't made any detailed plans or investigations on this yet, but I hope to be able to run a simple SLAM algorithm on a Teensy 3.6 or at least some rudimentary obstacle avoidance. The idea is that the car should follow me to the store and then I use it to carry my groceries back (it's not very far by foot).

Does anyone have any idea how much power can be drawn from the battery? I'm not at home at the moment, but if I am not mistaken the battery only lists voltage and capacity.
 
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I've already stripped the entire factory harness, the only part I really want to use is the factory battery, which needs a serial command from the gas pedal switch to activate. Hopefully just holding it in the on position after changing the battery will keep everything on until the battery is low.

I'm waiting on a few other parts for the project.

Navio2 Autopilot
Reach RTK module
Sabertooth 2x32 motor driver
HS-7954SH high torque servo

The goal is for the car to fully autonomously drive around a pre-programmed route, with centimeter accurate GPS. Later on I want to add sonar and computer vision for obstacle avoidance.

lol omg this is amazing. I seriously can't wait for the video of this.
 
Ordered a 3D printer for some other projects, but I'm working on something for this too. Replacement wheels with TPU (phone case rubber) tires that will take proper bearings and the original hubcaps...

upload_2018-3-30_21-36-42.png


Hey,

I am also planning on modifying the Model S for kids. I've ordered a Neato XV LIDAR unit along with a brushed motor controllers. I plan to control the steering column with a belt drive and some 3d printed gears. I also have some ultrasonic parking sensors I might attach to the car as well.

I haven't made any detailed plans or investigations on this yet, but I hope to be able to run a simple SLAM algorithm on a Teensy 3.6 or at least some rudimentary obstacle avoidance. The idea is that the car should follow me to the store and then I use it to carry my groceries back (it's not very far by foot).

Does anyone have any idea how much power can be drawn from the battery? I'm not at home at the moment, but if I am not mistaken the battery only lists voltage and capacity.

I'm mounting a servo under the car for steering, seems quite a bit easier than your approach, have a look underneath at the steering rack.

The battery contains standard 18650 cells inside, I believe it was either 4S4P or 4S5P, I'd have to open it up again to check. The standard battery has a bunch of extra slots for cells that I assume are filled in the extended battery.

I might actually gut the PCBs inside and use the 2 smaller connections on it for cell balancing connections, maybe even order some genuine Tesla 18650s to fill it up :D. Or I could always drill a small hole for a balance lead and go 6S
 
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May or may not fit, but I just grabbed 2 of these.. 960W continuous, 1680W burst PER MOTOR

Turnigy TrackStar Waterproof 1/8 Brushless Power System 2300KV/120A

If it doesn't fot, I can certainly think of a couple other projects for it. Probably finish my build with the stock motors first, because I feel like I'm going to be machining a new gearbox in short order with these. Stock battery definitely won't handle these. Might have to fill the entire frunk with 18650 modules.
 
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Ordered a 3D printer for some other projects, but I'm working on something for this too. Replacement wheels with TPU (phone case rubber) tires that will take proper bearings and the original hubcaps...

View attachment 290582



I'm mounting a servo under the car for steering, seems quite a bit easier than your approach, have a look underneath at the steering rack.

The battery contains standard 18650 cells inside, I believe it was either 4S4P or 4S5P, I'd have to open it up again to check. The standard battery has a bunch of extra slots for cells that I assume are filled in the extended battery.

I might actually gut the PCBs inside and use the 2 smaller connections on it for cell balancing connections, maybe even order some genuine Tesla 18650s to fill it up :D. Or I could always drill a small hole for a balance lead and go 6S

I considered the servo approach, but I was concerned about the torque and the speed of the steering response. It might be that the servo you've found does the job though. My plan is to attach a pot to a gear on the belt and experiment with different gear ratios to get the optimal steering.

Did you do any kind of investigations into the maximum discharge rate of the stock cells? I also suspect the ESC/motor combination you have there is gonna outdraw the battery by quite a bit, but it might be interesting to know how much power can be drawn from the battery for other on-board consumers other than the drivetrain.
 
Hey guys!

I looked a bit closer into the stock battery on this thing. As mb300sd said, it is a 4S4P setup with 2200mAh LGGAMF11865 cells. According to this AliExpress listing, the cells are rated for 10A. I didn't find a dataset, so I'll take it on face value although I don't know if the cells on AliExpress are genuine.

That means that it should be possible to draw 40A from the stock battery (depending on the stock BMS which I don't know anything about). If anyone swaps the motors or adds other consumables, this 40A (peak) limit should be considered.

It's probably not a good idea to buy extra batteries from the link above to expand your battery capacity. In general you shouldn't mix and match batteries in battery packs unless you really know what you're doing. For battery modifications I would rather do what was mentioned earlier, swap out the BMS and fill up the entire compartment with genuine brand cells from the same batch.
 
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THIs is great! I am following this thread as since I’ve gotten my mini S, I have been wanting to mod it to autonomously pull my paddle boards up the two blocks from the beach somehow with a tow hitch.... I was thinking rc servos for steering and prob program route somehow. Dammit Jim, I’m a doctor not an engineer! But I would look forward to the challenge, and come from a long line of tinkerers...
 
Still waiting for more parts for my steering linkage.. They were cheap enough and I ordered extras so if one servo doesn't cut it, I can go to a dual approach.

I decided to ditch the stock battery, as much as I like to keep it clean, the BMS board has been a pain to hack. I'll probably end up gutting it and filling it up with cells.

In the mean time, I 3D printed these... They're 4S5P packs made with genuine Tesla cells.
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I got the motor controller hooked up and working with a basic RC receiver. Just need steering now and I can get to programming all the autonomous functions.

P_20180410_191644.jpg

I'm going to have to find another approach for the tires. Unfortunately my 3D print of the TPU tire failed after 30 hours and going though 1/3 of the spool. The 95A hardness doesn't have enough grip IMO anyway. Softer filaments are available, but they're significantly more expensive.