Lightning Rods big block WYE/DELTA project

[ElectricGod]

For anyone who has seen Michaels kits, they are top notch. The motors he uses are solid too. They are somewhat large compared to a 3220, but considering they cost half as much, it's worth the lesser cost. Also they are solidly built and strong motors. I own 2 of them. The first one I purchased about a year ago and other than a hall failure which was 100% my fault, the motor has given me no trouble at all. I run it at about 3500 watts and my scooter tops out at about 50mph. I can easily out accelerate most cars despite my scooter weighing 120 pounds while carrying my lard butt 240 pounds. I've wanted to play with WYE/DELTA switching for a good while now and haven't had the time until now to do it. with the purchase of my second big block, I prepared in advance to be ready to convert it to WYE/DELTA switching before it ever got it installed in anything.

Eventually it will go in this moped. It needs some work still, but is pretty close to rideable.

Initially I will be running at 82 volts since I already have the battery pack built for that voltage, but eventually it will be running at 130 volts. On to the motor rebuild...

The big block is capable of running at well over 3000 watts. Some people report that they run them at 5000 watts. I'm going to use that 5000 watts as my starting point and see how far I can push it. The first thing I did was get the end plates opened up so I can push air through the motor to keep it running cool. I'm expecting that with a fan or blower, I can run the motor at 5000 watts with no overheating issues and probably a lot more.

Some pictures of the motor as a I received it from LR. He normally cuts off the fan shaft and paints it black, so this is going to look a bit different than what most people are used to seeing. Some of you will notice the ratings lazered into the front of the motor. The Chinese to get around our import laws under rate the motors by quite a lot. Ignore the information on the motor...it's waaaaay wrong.

This is the opened up end plates.

Once I had tested the motor and it was obviously in good shape, then it was time to start taking it apart. Once I got at the windings, this is how I found all the phase wires were connected to the windings. This is the WYE connection. Somehow they melted the copper wire ends together. There's no way that connection is ever going to fail. Obviously I had to cut that blob of copper off of there to separate the phase wires.

This is the phase ends after I tinned them. I then figured out which end was the other end of each phase and temporarily labeled them with some masking tape.

I then reconnected all the phase ends to colored 10awg wires with wire crimps and then soldered everything together. The connections should easily handle the maximum capabilities of the phase wires.

The original phase ends, I labeled as B1, Y1 and G1 and the secondary ends I labeled as B2, Y2 and G2. This is the 6 phase ends with 2 layers of heat shrink on each connection.

The wires needed to be secured and bound down inside the motor so several zip ties made quick work of that. I'll get some cotton thread later to tie it all together to make it all permanent. Zip ties tend to melt when they get too warm.

I've looked at several peoples schematics for how to set up a relay for WYE/DELTA switching, but none of them made clear sense to me so I drew my own. It was obvious what needed to be done so I just figured it out for myself. In the relaxed state the relay needed to connect the B2, Y2 and G2 wires together and in the activated state, they need to be connected in Delta. This schematic is the final result.

I guess I should have taken a few more pictures along the way, but you get the idea. The cable that comes on these motors is about 3 feet long. I used sections of that cable to make all the connections you see here. Once I had everything bound together and brought out of the motor case, I then added 2 more layers of heat shrink around all the wires where they come out of the motor case so that they couldn't get scuffed or worn through by vibration or motion. I zip tied all the wires together where they exit the motor so that nothing can move separate from anything else and become fatigued or break. Every phase end terminates in a male 5.5mm bullet which are good for 100 amps or so...plenty for this motor. This allows me to disconnect the relay from the motor and manual connect the motor in WYE or delta if needed. This is the completed motor and relay set up.

A side note about Grinfineon controllers...

The grinfineon controller I was using for testing is the older version (7240-NC) and not the best thing there is. Its eRPM is quite low and only really effective for hub motors. They are very basic controllers, but better than your Chinese trapezoidal controllers. At least it can be sinusoidal. IMHO, the most redeeming value it has is that it uses IRF4110 mosfets. Otherwise, they are not that great. They can run sensorless or sensored which sounds great. Since the controller has to "sense" the halls, if there is any kind of an issue, it defaults to sensorless mode. When you are trying to figure out the correct hall to phase pairing, this controller is more of a hindrance than a help. You can't be totally sure you have the correct pairing since if the controller finds anything wrong, it just defaults to sensorless. When I first got everything wired up for WYE/DELTA switching, I made no mistakes. Everything was wired correctly and the controller would not see the halls. As a result I fiddled around for probably an hour trying to "find" the correct pairing and eventually ended up back at the original combination. I prefer a controller that simply doesn't work when the phase and hall pairing is incorrect. This controller really needs a switch that hard wires it into sensored or sensorless modes. There's two versions of the Grinfineon. The older 7240-NC and the newer 7240-GR. All the videos are made with the older version which has a lower eRPM than the newer version. Anyway, the older version is really only effective for hub motors. In the videos you will see that the controller loses sync at different times. With halls at 48 volts the controller could spin up the big block motor most of the time to full RPMs. Without halls, it can get maybe 40% throttle in WYE. In delta, the controller can deal with 40% throttle with halls before losing sync. I just purchased one of the more expensive versions so I have nothing to say about it...yet, but the older/cheaper version is inadequate for anything not a hub motor. Supposedly the newer version is good for 28,000 eRPM. For anyone looking for a basic and cheap controller, don't buy the older/cheaper version (7240-NC). You will be disappointed. I have received the newer version and took it apart. The battery and phase wires on the old and new versions are 14 awg nylon insulated. In fact all the wiring is nylon insulated. The insulation is not low temperature, but it can melt. I have a couple of cheap Chinese controllers of similar ratings and they have teflon coated wiring. IMHO, all major wiring ought to be teflon or silicon. Even though 14 awg is probably enough for a 40 amp controller, I would still make it thicker. As a result I replaced all the battery and phase wires with 12 awg silicon in the new controller. I wanted to use 10 awg, but the solder holes in the board were too small and 12 awg was all the larger I could go. For anyone looking for a cheap sinusoidal controller, don't get the cheaper version. It's just not worth it. I'll add another post about the 7240-GR once I have tried it out.

Here's several videos on the project.

This one is running sensorless at 48 volts.

https://www.youtube.com/watch?v=m3rZCvAX37k&index=1&list=PLP5ztAvpP73YOFCiuzRm1DAUWoxep2mrR

This is running sensored at 48 volts.

https://www.youtube.com/watch?v=hB-Pt67wDdA&index=14&list=PLP5ztAvpP73YOFCiuzRm1DAUWoxep2mrR

Since I had an 82 volt pack I built for the moped, I hooked it up too. This video was made without ever trying out the controller in advance. I started up the camera and tried it out. The Grinfineon is rated to 88 volts so it wasn't going to be an issue.

https://www.youtube.com/watch?v=B0bx7uYJg38&list=PLP5ztAvpP73YOFCiuzRm1DAUWoxep2mrR&index=13

 

[ElectricGod]

Saved for further posts...

I have received and tested out the C7240-GR grinfineon controller on my bench. I was running at 82 volts and pulling 3 amps. I was just running the motor up and down the throttle and suddenly things just stopped working. I took apart the controller and that's when I noticed they had used a single layer of kapton tape as an insulator between the heat sink and the mosfets. Kapton is brilliant stuff, but it's also very fragile and tears easily. I found that the kapton they had used as an insulator was a single layer thick and had several tears and nicks in it. I found that 3 mosfets had a dead short to the heat sink to their drains. I pulled all the IRF4110 mosfets and found only one had blown...so I lucked out in that regard. I really wanted to replace the kapton with mica insulators, but I didn't have enough of them so I used 4 layers of kapton instead. Hopefully that wont hurt heat conduction too much, but one layer of kapton was obviously inadequate. The controller also uses 14 awg nylon insulated power and phase wires which is pretty lame. I replaced them with 12 awg silicon wires since I had the controller open. Replacing the blown 4110 mosfet was easy to do...I have 40 of them. It wouldn't have failed if the insulator had not failed.

Once I had the controller running again, I was able to test it out and it is much better than the older NC version. It detects halls way more reliably than the older version did on it's best day. Also, it handled the big block with or with out the halls quite well in WYE, but in delta, with out halls, I was not able to reach full RPMs. I don't really care too much since I will use halls every chance I can get. Anyone looking for a cheap sinusoidal controller, the C7240-GR is far better than the older version, but the kapton insulator for the mosfets may be a total crap shoot. It worked fine for a while and then failed. The controller had less than 30 minutes of use on it. That's pretty bad reliability IMHO! Replace the insulator or add to it before trusting these controllers.

This is the crap insulator that failed.

 

[LightningRods]

I'm really excited to see how the Big Block runs at high voltage with delta/wye. You're going to be able to make way more speed than I would ever want to see on a scooter!

 

[ElectricGod]

I'm really excited to see how the Big Block runs at high voltage with delta/wye. You're going to be able to make way more speed than I would ever want to see on a scooter!

That's the goal...way too fast for the platform.

 

[ElectricGod]

More videos coming soon...

I've blown up the new controller twice now, just bench testing it under no load. There's probably another blown mosfet inside. While making the 82 volt video, the motor stopped suddenly and then the controller was flashing 3 fast blinks on the LED. Previously when I was just running up and down the throttle, the same thing happened. I'm guessing another mosfet was weakened by the shorts in the kapton and died while making the third video. Fortunately replacing mosfets is fairly easy to do...just a pain to do. This controller isn't working out so well!!! I'll double up the mosfets in it so that it can handle 80 battery amps before I use it for real riding. My Kelly controllers been running for a year now and never given me any trouble. I guess you get what you pay for! $300 vs $180...hmmmmm. LOL!

I'll post the videos later.

 

[ElectricGod]

Some more videos on the new Grinfineon controller. In the third one I was switching between WYE and delta and the controller blew another mosfet. I haven't taken the controller apart yet, but I suspect the 4 layers of kapton didn't fail. Probably a mosfet from the previous blow up was just weak and died.

Grinfineon C7240-GR wye-delta switching at 48 volts and no halls
https://youtu.be/t0J4w2LgN-s

Grinfineon C7240-GR wye-delta switching at 48 volts with halls
https://youtu.be/YvZEfhBk1xA

Grinfineon C7240-GR wye-delta switching at 82 volts with halls and blown mosfet
https://youtu.be/al9Y5z1NHY4

 

[Rube]

Epic series of very informative posts especially the inclusion of the switching diagram. Thanks.
Unfortunate problems with the controller. I look forward hearing about your experience on the road.

 

[ElectricGod]

Epic series of very informative posts especially the inclusion of the switching diagram. Thanks.
Unfortunate problems with the controller. I look forward hearing about your experience on the road.

Thanks

 

[nutnspecial]

Ditto man, awesome job and write-up that makes understanding of termination switching easier.
Am I correct in assuming this allows you to trade some efficiency for 'overdrive'?

 

[ElectricGod]

Ditto man, awesome job and write-up that makes understanding of termination switching easier.
Am I correct in assuming this allows you to trade some efficiency for 'overdrive'?

More or less...that's true. Delta for the same amount of torque draws a lot more curent.

 

[macribs]

What was the outcome of Recumpence wye/delta project? Seems to remember he did not keep it for some reason but I can't remember why not?

Are you looking for higher top speed as the outcome here? Flipping the switch will let your motor rev higher? So is dalta/wye anything similar to OVS, where more current increases top speed at the costs of efficiencies? If so, maybe you should look at the Mobipus controller from Samd ?

Haven't really had the time nor motivation to read up and grasp the full concept of wye/delta switch and the pros and cons of such a setup so pardon if my questions seems stupid, that is because I don't know

 

[ElectricGod]

What was the outcome of Recumpence wye/delta project? Seems to remember he did not keep it for some reason but I can't remember why not?

Are you looking for higher top speed as the outcome here? Flipping the switch will let your motor rev higher? So is dalta/wye anything similar to OVS, where more current increases top speed at the costs of efficiencies? If so, maybe you should look at the Mobipus controller from Samd ?

Haven't really had the time nor motivation to read up and grasp the full concept of wye/delta switch and the pros and cons of such a setup so pardon if my questions seems stupid, that is because I don't know

I didn't know about recompence doing a wye/delta build out, but he builds bikes and then sells them off so that's likely why it's sold. Very likely he used a nitrogen filled relay for switching. I will too for the final build. They don't arc across the contacts.

Increasing a motors KV will make it spin faster for the same voltage so yes...it's like a 2 speed transmission. OVS is just addapto trying to make it sound like they have something cool that no one else has. It's just feild weakening. Just about any controller that does FOC, can do field weakening to get more RPMs out of the motor. If that is what you are referring to, then the Modipus isn't special in that regard. Lots of controllers do it now days. I think you will find that as the older MCU chips become more and more obsolete, that MCU's with FOC will become the norm for all midrange or better controllers. It's been around for a few years now.

Pros:
1. Typically more motor RPM's means higher battery voltage since KV is a fixed motor spec. Bumping the Kv by 1.7 by switching the motor from WYE to delta gets the same effect without rewinding the motor or increasing battery voltage.
2. It's pretty simple. There's no added mechanics or gears or other mechanical losses.
3. If you build it right. it doesn't create any reliability issues. Use a top quality sealed relay that can handle the current loads you are running at.

Cons:
1. More current draw in delta than in wye for the same amount of torque
2. Added relay to do the phase wire switching...more complex motor wiring.
3. Possibility of blowing the mosfets in your controller if you switch under load.

 

[notger]

i'll stalk you, sounds interesing.

did you actually try it under load in your moped already?

greets

Notger

 

[ElectricGod]

i'll stalk you, sounds interesing.

did you actually try it under load in your moped already?

greets

Notger

Not yet...The controller was shipped today. So I'm waiting for that.

 

[macribs]

Cons:
1. More current draw in delta than in wye for the same amount of torque
2. Added relay to do the phase wire switching...more complex motor wiring.
3. Possibility of blowing the mosfets in your controller if you switch under load.

2: I guess each to his own, if the pro outweigh the cons of added complexity in wiring then sweet.
3: Should be possible to prevent that with clever wiring? If you got say a push button to switch between delta/wye couldn't there also be a "numb nut" setting that automatically disengage the throttle before the switch is turned? Controlled by say ardunio or similar?

 

[ElectricGod]

Cons:
1. More current draw in delta than in wye for the same amount of torque
2. Added relay to do the phase wire switching...more complex motor wiring.
3. Possibility of blowing the mosfets in your controller if you switch under load.

2: I guess each to his own, if the pro outweigh the cons of added complexity in wiring then sweet.
3: Should be possible to prevent that with clever wiring? If you got say a push button to switch between delta/wye couldn't there also be a "numb nut" setting that automatically disengage the throttle before the switch is turned? Controlled by say ardunio or similar?

Quite a few people have done this. So it's not new or theoretical by any means. Large industrial motors use wye/delta switching to get them running all the time. The motor would burn out just getting it's own mass turning from a dead stop if it started from delta. So the motor is switched to wye to get it started and then after it gets spinning pretty good switches to delta. I just need to plan ahead for the implications of what I'm doing. I have 3 50 amps relays. I'll probably put 2 of them in parallel or just find one of those nitrogen filled relays that are really expensive. The complication in wiring is only initially more complicated, but you already have all of that in any EV set up. It's just hidden from you since you cant change from wye to delta. You're hard wired for one or the other. Most inrunners are wired for WYE and most outrunners are wired for delta. This is not anything more than being able to switch from one to the other.

I'm working on a numb nuts circuit right now. It will do several things. The easy part is not allowing wye to delta switching or back while under throttle. It's just a simple comparitor circuit that measures throttle voltage and a memory cell that remembers what the last switch state was. If X throttle threshold is exceeded, then don't switch. The actual wye/delta switch will just be a signal that is acted on or not based on whether there is throttle present or not. The other thing that possibly blows controllers is switching from delta down to wye under high motor RPM. The back EMF is pretty strong for about 1-2 seconds when you switch down. A simple frequency counter that has a settable trigger frequency will make an effective RPM detector. The counter reads one of the halls and when it detects the threshold is crossed it enables or disables its settable output. I'll use that signal to enable or disable the switching process. The whole circuit requires 4 op-amps, some resistors and pots, caps and a few other minor components and a frequency counter to implement. I'm a marginally intelligent guy so even with out the numb nuts circuit, I'll be able to switch without issue. With the circuit in place, I can switch and not pay attention that I did everything right or hand my ride to anyone else without concern. I could go really crazy and automatically null out the throttle signal easily enough with a small mosfet, but that's not necessary. The selector switch will be accessible by my right thumb which is also where the thumb throttle is. To hit the button, I'll have to let off the throttle. Physical location alone will make it difficult to switch under power. The actual relay will be turned on and off by a mosfet. I'll probably implement a manual switch over or bypass too. What happens when the detector circuit doesn't work? I could easily bypass the whole thing by disconnecting a jumper or closing another switch. Then it's totally manual switching. I was thinking a small rotary key switch would do the trick. You couldn't do the bypass without the key...which of course I will have on my key chain. Of course just unplugging the relay will keep me in wye. I can easily get home and then deal with the problem later.

I had another idea, but I probably wont do it. I've already found a cheap frequency counter ($27...gotta love the Chinese!) that has the functionality I need. I could use that trigger to switch from wye to delta and back down again based on motor RPM. There's a place in every motor where torque starts dropping off in wye and switching to delta is like giving it an adrenaline shot. All I have to do is determine that RPM and set the frequency counter to the equivalent hall signal frequency. When the signal changes, it triggers the wye to delta or delta to wye switch over. There would be no point to having a physical button to hit. I really hate automatic transmissions in cars so why would I want one on my moped? I'll probably not do this. The other stuff is to protect the controller from numb nuts or an accidental switch over...that part is valuable. This little option...not so much.

 

[Punx0r]

Large industrial motors use wye/delta switching to get them running all the time. The motor would burn out just getting it's own mass turning from a dead stop if it started from delta.

This isn't true. Starting in wye reduces the inrush current, which eases the load on the supply (bear in mind mains supply is not current limited). The motor itself would take it. Running in wye for the same line voltage reduces motor output power, so there might be some scenario where a heavily over-loaded motor might survive in wye but would cook in delta, but then it's really a case of an undersized motor.

It might be worth considering that AC induction motors increasingly use a Variable Frequency Drive, which provides soft-start through current limiting and makes wye-delta switching redundant. They're pretty similar to a BLDC speed controller in what they achieve...

 

[ElectricGod]

Large industrial motors use wye/delta switching to get them running all the time. The motor would burn out just getting it's own mass turning from a dead stop if it started from delta.

This isn't true. Starting in wye reduces the inrush current, which eases the load on the supply (bear in mind mains supply is not current limited). The motor itself would take it. Running in wye for the same line voltage reduces motor output power, so there might be some scenario where a heavily over-loaded motor might survive in wye but would cook in delta, but then it's really a case of an undersized motor.

It might be worth considering that AC induction motors increasingly use a Variable Frequency Drive, which provides soft-start through current limiting and makes wye-delta switching redundant. They're pretty similar to a BLDC speed controller in what they achieve...

Ever work on a large industrial motor? I have. They used a centrifugal weight to switch over once the motor was up to speed. A lot of induction motors use a similar mechanism to switch out starter caps/coils. I know lots of motors use controllers now days, but that's not always the case. Besides...this is a mute point. This thread is about switching wye to delta on a BLDC big block motor so lets focus shall we?

 

[Punx0r]

Yes, but not my full-time job and only up to 100kW. We use Direct-on-Line (start in delta) for smaller motors and wye-delta for the larger ones otherwise it causes a local brown-out as the supply voltage dips. I'm not aware of a motor that will melt-down from spinning up in delta - the total power capacity of the motor is identical in wye and delta.

It's fairly well established that wye-delta does not provide the equivalent of two "electrical" gear ratios.

Start/run capacitors are for single phase motors - nothing like a BLDC motor.

If it's impossible or impractical for a BLDC controller to source sufficient phase current to provide the start-up torque you need then I see why you would consider the hassle (size, complexity, cost, reliability) of wye-delta switching. I know you don't want to discuss the rationale behind your decision to use it, but I feel obligated to point out possible errors in your reasoning, if only to provide balance to other people who read this thread. That aside, I wish you luck in your project and applaud your hands-on, practical approach.

 

[ElectricGod]

The real question are three...
Did you READ what I wrote? If you did then you wouldn't be stating the things you did. Where are you getting your information? Have you done a wye/delta build yourself or just going on what others have said and have no actual personal experience?

I have met several people on ES that have gigawatt ratings and all they do is spread FUD and attempt to diminish the work and effort of others. I was told the same thing about my used laptop battery build and 18650 battery holder project. Never the less it has been working since March 2016. I got told things like laptop cells can't hold up to the discharge rates and that battery holders are unreliable among other things. Anyway, I ignored all the FUD and built them anyway. I ride to work every day on my scooter assuming the weather is good...summer and winter and I have found that despite the FUD, that I have had a a lot of successes with my used laptop battery builds. Do I get the range of brand new EV grade cells? Of course not...never expected to. Do I get the discharge rates of EV grade cells? Never expected to, but I'm running on FREE used laptop cells that cost me NOTHING. I've even had a few laptop cells die on me (less than 10 out of 240), but they were soooo easy to replace. Pop out the bad cell and pop in a good one and I'm good to go. BTW...my experience is that laptop cells can handle 2 or 3C discharge just fine. Just a load of FUD IMHO. Those doom and gloom experts were all wrong.

OK...so back to WYE/delta switching...
I'm an experimenter. I LIKE trying things out for myself. I went to school for electrical engineering. I don't really care if people say I should do X rather than Y. Let's say that switching is a dead end street. Well great...I just found that out for myself. However a BLDC motor will get only so many RPMs at X volts. To get more RPMs out of the same motor, you need field weakening or more voltage or add Kv to the motor. How about all 3 of them? How about making a comparison of all three on the same machine? We all know how to get more out of motor. I'm doing all of them at the same time. I'm going to throw it out there that wye/delta switching by itself will get me some performance improvements...just like FOC and more battery voltage will. I'm willing to risk it wont suck completely.

WYE vs Delta...and a two speed transmission analogy
If my motor has a Kv of 64 and I have tested that it does, then at X volts it will produce Y RPM's. At some point it stops developing as much torque as it did at lower RPM's. This is the nature of BLDC motors. So if my 64kv motor can now have a 1.7X boost in Kv, then it will continue to develop torque at higher RPMs than it was capable of at the lower Kv. That equates to a 2 speed electronic transmission. Any ICE powered machine has a power band. Run that engine at too high of an RPM and it will get less and less efficient and develop less torque. A BLDC motor will also do something similar towards it upper end. With an ICE you simply change gears and get engine RPMs back down where the engine runs best and you keep on going. With a BLDC motor 1st gear is WYE and second gear is delta. It's an analogy...not an exactly duplicated process.

Anyway, thanks for the input/feedback, but I'm going to do this regardless of what anyone says. Worst case, I pull out the relay and run the motor directly. It all connects up via 5.5mm bullets so it's very easy to connect/disconnect things if needed. Besides, I've already built it and it works. Next up is to mount the motor on the moped and give it a ride. I'm going to wager that it will be a great ride!

 

[Punx0r]

Did you READ what I wrote? If you did then you wouldn't be stating the things you did.

Yes. I read:

Large industrial motors use wye/delta switching to get them running all the time. The motor would burn out just getting it's own mass turning from a dead stop if it started from delta.

I know this isn't true, so I simply pointed it out.

If my motor has a Kv of 64 and I have tested that it does, then at X volts it will produce Y RPM's. At some point it stops developing as much torque as it did at lower RPM's. This is the nature of BLDC motors. So if my 64kv motor can now have a 1.7X boost in Kv, then it will continue to develop torque at higher RPMs than it was capable of at the lower Kv. That equates to a 2 speed electronic transmission.

Only if you are working with a limited voltage or current supply. The motor itself doesn't care if it's in wye or delta - just hit it with the appropriate voltage and current and it will be capable of exactly the same speed & torque & efficiency. Which is why, as I said, before unless you can't use a controller capable of enough current, you might as well permanently leave the motor in delta . Same top speed, same starting torque, just need to hit it with more phase current.

 

[Rube]

Hi, the Wye/ Delta debate is good but maybe it could be a thread?

EG's experiments are fundamental to the test and learn method that makes ES great. I'm interested in the outcome and having a go myself.

I learn from the debate between Punx and EG's testing, and I'm keen to see EG progress and hear from Punx, but there comes a time when the discussion is off topic.

Anybody for Delat/ Wye debate topic (even better with tests!)?

 

[Punx0r]

I was mindful of the thread going OT, but EG's replies aimed to simultaneously draw a response while having the last word. I decided to respond to avoid giving the impression that I couldn't respond, which might be seen as an admission of me be being wrong.

FWIW there are already a number of threads (mostly debunking) wye-delta switching. They seem to take a similar path to the single speed Vs. multiple gear ratios threads. All can be found using the search feature

 

[nutnspecial]

I'd just ignore him EG, where you need to. Dude brings some obvious knowledge to a discussion, but in my experience he also has an attitude, and seems subjective sometimes to a 'me over you' type of mentality behind posting/discussion.

This is a nice job and write-up so far. Keep in mind you don't see many jaded assholes do the same, or often even a simple single build on es.

Imo it's as simple as stated at core w/ no real debatable aspect: a fairly simple/cheap avenue to retain original performance while gaining an additional taller gear at the cost of amperage. Yes one could achieve similar by running a higher voltage, but that comes with it's own drawbacks, as does running a true dual voltage setup, or a physically larger drive. Right?

Also, on the switching part, letting off the throttle to switch shouldn't need to be idiot-proofed imo. We don't have that with actions like shifting a manual transmission, or cutting a steak without taking off your finger lol. Shouldn't be a problem imo.

 

[spinningmagnets]

I remember a few years ago, there was some experimentation on delta/wye here at ES. IIRC, the concern was the poor availability of high current batteries. Delta provides a faster Kv at the top end, and starting in Wye reduces the max current drawn.

There are several members using packs made from low-current laptop cells that are very cheap, and sometimes free. I certainly understand the appeal. DrkAngel has written expensively about harvesting, testing, and assembling laptop cells into a pack. It seems the previous way to achieve higher currents with such cells is to build a very large pack, which obviously would work, although it would also be bulky for some frames. How high of currents? high enough for some builders, not enough for others...

That being said, I can see how Delta / Wye switching could reduce the minimum size of a laptop cell pack to achieve "X" amount of wheel-torque. Discussion of theory is always interesting, and I want to hear all sides of such a discussion, however...when any member wants to actually build a test prototype? I say we should all encourage real-world testing.