Schwinn S750 wanting to go Brushless outrunner. Help wanted.

[tropmonky]

Hello everyone!

I'm not a 100% newbie but I know there are a bunch of smart people here and I'm not afraid to ask for your ideas and help. I checked all over the place and I haven't found any info regarding one of these style scooters being converted over to a brushless ourtrunner so I thought I'd get everyone's opinions and as much info as possible before going at it.

What I'm starting with:
Schwinn S750 as pictured below (not my actual scooter, just for reference).. I'll be taking many pics when the build starts though.

I got this used off craigslist for $100 with dead batts.... The next day I got a couple 8AH SLA's ($30 brand new, again off craigslist) that matched one I already had and slapped them in the scooter to just get it running. It's in pretty good condition for the price I paid, the tires still have plenty of life left on them. This thing is a BLAST and it's everything I thought it would be. However as everyone knows here SLA's are lame, and I want more speed and distance.

My wants:
Speed:30mph cruise speed so I'm guessing 35mph or so max speed
Distance: 15 hard miles
Brushless outrunner.

Hardware I think will get me there (off the top of my head without much thought put into it):
-Motor: Turnigy TR80-100-a http://hobbyking.com/hobbyking/stor...0-100-A_180Kv_Brushless_Outrunner_(eq:_70-55)
-Speed Control: Turnigy Monster 2000 http://hobbyking.com/hobbyking/stor...Turnigy_Monster-2000_200A_4-12S_Brushless_ESC
-Throttle: Would love opinions on this! Wouldn't mind making a thumb throttle.
BEC: Turnigy http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6320 (I already have one)
-Battery: I don't know, but I'm guessing hoping 20Ah will get me the spces I'm looking for.

Other MISC stuff to think about:
-motor sprocket (it'd be nice but not needing a freewheel sprocket) (I'd like to keep the stock chain size)
-Have a watts up meter to mount and use
-mounting the motor to the existing motor plate looks easy enough

Uses: I'll be using the scooter around town mainly to grab meals, going to the beach in the summer (don't have to fight to get a parking spot here in Southern CA, Los Angeles), and possibly visiting a couple of my clients that are close to where I live (I'm a computer consultant).

That's about it! I'm looking forward to hearing from anyone that is willing to give their input! Oh, and of course the info I provided above is just off the top of my head and I'm totally open to everyone's suggestions. That's the reason I've started this post!

Thanks in advance!

 

[tropmonky]

Wow, not even one post yet.

Additional info: I'd love to get info regarding good website to purchase items from. Obviously I already have Hobbyking.com, but other locations that may have good sources for hardware I may need are welcome to.

 

[spinningmagnets]

Welcome tropmonky! I've found there is some confusion over calling a vehicle a scooter. It can mean the typically 50-cc Vespa-style of street vehicle, it can mean the style of vehicle you show, and a Google search also shows up lots of senior-citizen mobility powered wheelchairs that are often called scooters.

No one will mind if you copy/paste these posts over at the non-hub bicycle section. Even though these don't have pedals, that is where the majority of the RC-activity is, and I'm sure you'll get lots of suggestions. Fechter is one of the site gurus and this is the type of vehicle he rides to work very often, he was even on TV riding it. Best of luck.

 

[tropmonky]

Thanks, yeah I was thinking about doing that... it seems mostly licensed bikes are in this forum, with the exception of the other kick scooters.

I'll give it a try.

Cheers!

 

[tropmonky]

Hello everyone!

I'm not a 100% newbie but I know there are a bunch of smart people here and I'm not afraid to ask for your ideas and help. I checked all over the place and I haven't found any info regarding one of these style scooters being converted over to a brushless ourtrunner so I thought I'd get everyone's opinions and as much info as possible before going at it.

What I'm starting with:
Schwinn S750 as pictured below (not my actual scooter, just for reference).. I'll be taking many pics when the build starts though.

I got this used off craigslist for $100 with dead batts.... The next day I got a couple 8AH SLA's ($30 brand new, again off craigslist) that matched one I already had and slapped them in the scooter to just get it running. It's in pretty good condition for the price I paid, the tires still have plenty of life left on them. This thing is a BLAST and it's everything I thought it would be. However as everyone knows here SLA's are lame, and I want more speed and distance.

My wants:
Speed:30mph cruise speed so I'm guessing 35mph or so max speed
Distance: 15 hard miles
Brushless outrunner.

Hardware I think will get me there (off the top of my head without much thought put into it):
-Motor: Turnigy TR80-100-a http://hobbyking.com/hobbyking/stor...0-100-A_180Kv_Brushless_Outrunner_(eq:_70-55)
-Speed Control: Turnigy Monster 2000 http://hobbyking.com/hobbyking/stor...Turnigy_Monster-2000_200A_4-12S_Brushless_ESC
-Throttle: Would love opinions on this! Wouldn't mind making a thumb throttle.
BEC: Turnigy http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6320 (I already have one)
-Battery: I don't know, but I'm guessing hoping 20Ah will get me the spces I'm looking for.

Other MISC stuff to think about:
-motor sprocket (it'd be nice but not needing a freewheel sprocket) (I'd like to keep the stock chain size)
-Have a watts up meter to mount and use
-mounting the motor to the existing motor plate looks easy enough

Uses: I'll be using the scooter around town mainly to grab meals, going to the beach in the summer (don't have to fight to get a parking spot here in Southern CA, Los Angeles), and possibly visiting a couple of my clients that are close to where I live (I'm a computer consultant).

Additional info: I'd love to get info regarding good website to purchase items from. Obviously I already have Hobbyking.com, but other locations that may have good sources for hardware I may need are welcome to.

That's about it! I'm looking forward to hearing from anyone that is willing to give their input! Oh, and of course the info I provided above is just off the top of my head and I'm totally open to everyone's suggestions. That's the reason I've started this post!

Thanks in advance!

 

[mwkeefer]

Do you want to have to kick start this scooter?

If the answer is no then may I suggest the following - look at outfitting an RC motor with hall sensors and think 6 fet infineon (plenty of room under the deck) for a reliable sensored controller in a good price range (they run about 30-50.00 avg).

Next look into how that motor you specified is terminated (check the rc forums or google) my guess is delta based on the kV and currents - I would personally convert that motor to wye which would increase the torque by 1.73:1 and decrease the kV of 180 RPM per volt by the same factor resulting in a new kV = 104.04 RPM per volt.

(honestly that motor is far too big for this scooter, you would be better off looking into the 3hp range like the tower pro 5330)

Now for 35mph on a 10" wheel (I think the S750 is a 10" wheel) we can do the following quick math:

35 (mph) * 336 = 11,760 RPM / 10 (" wheels) = 1176 RPM Required to sustain 35mph on a 10" wheel.

Now I am usually wrong but I have a scooter very similar so I will assume the onboard (default) reduction is somthing like 13t to 76t (I think that's my goPed ESR 750 gearing)... or 5.846:1 ratio reduction...

This means we need that motor to spin up to 1176 * 5.846 RPM or 6875 RPM minimum at pack LVC and under load.

Since you have the motor RPM you will need for 35mph travel - you can factor the rest of the build up:

Assuming the motor in stock delta termination is about 80% efficient (doubtful, maybe) we would need to take that into account to ensure proper RPM is available under load with losses so 6875 * 1.20 = 8250 RPM is actually the minimum no load RPM we are trying to acheive.

8250 / 180 = 45.83v

Since 48v is the max you are supposed to spin this motor up with... changes to your drive line will be required (more than just a simple swap up build).

Again I think that motor is way too much for the scooter... even with 4kw peaks and minor (5:1) reduction you would be hard pressed to keep the front wheel on the ground at anything below the maximum speed.

If your stuck on that motor for a specific reason, then the reduction needs to change...

if 48v is the maximum voltage it's calling for a 12S pack of Lipo (12 * 4.15v = 49.8v)... I'm assuming (it's specified as MAX afterall - not nominal)... so LVC for a 12S pack (conservative so the lipos last) would be 3.3v per cell or 39.6v at pack level.

Now reverse calculate the reduction required using the known kV (stock termination):
Motor Minimum RPM (no load): 7128 RPM
Motor Minimum RPM (assuming 80% efficient): 5702.4

So 5702.4 RPM under load for 35mph on a 10" tire is: 5702.4 / 1176 = 4.8489:1

Basically you need to count the large teeth on your 10" drive sprocket and see if you can acheive the 4.8489:1 or how close you can get - you could look at belt drive if you wanted to quiet things up, the hxt belts that recumpence uses in his drive systems are quiet.... you could also just source an appropriate motor sprocket and rig a bolt up frame mount.

The reason I recommended adding halls to the RC and using the infineon - now you don't care about freewheeling so much because you can regen brake (built in) and they are small enough for your purposes... they also have some advanced features for ev use that normal RC controllers just dont and finally the only area where I know of issues with these controllers on RC motors is in high RPM situations > 8 or 9K which are a non-issue for you.

Range is another thing all together... what peak currents do you expect or want to run, nominal?

-Mike

 

[tropmonky]

Awesome info Mike and thanks!

I'm not totally stuck on that motor, but from my past it's nice to run a larger than needed motor to help dissipate heat... I see hills around 7-8% grade and have no idea what the peak currents I'd run into yet. Plus the torque curve on the larger diameter motors is typically better to.

I don't mind needing to kick start the scooter, however it sounds like the controllers that I could use if I install some hall sensors are cheaper and more reliable? What does it take to install hall sensors on these outrunner motors, is it difficult? Plus, being able to take off from a stand still is a nice thing if you have to stop on an incline.

I think I would like to keep it chain driven to keep things simpler. Also if I can get away with a motor with a higher kV then I could get away with running a lower Voltage battery thus saving space and hopefully allowing it to fit inside the deck without mods. The current depth of the deck is about 3.25in (82mm) deep.

Like I said in my first post, I'm not a total newbie, but I really only know enough to get myself in trouble LOL. Trying to keep costs down is a factor for me as well. I figure I'm willing to splurge on a really good battery pack that I know is capable of handling the pretty high amps this is going to pull on the hills.

I think you're about right on the sprocket size/teeth. I measured the large sprocket at around 7.25in and the motor gear at about 1in (very very sloppy measurements)... it'd be nice to find the stock info on this and I'll have to do some fact checking online to see if I can find that, but the info you provided sounds and looks spot on. The rubber on the tire measures 12in, does this constitute a 10in or 12in rim/tire?

Summer is fast approaching and I'd like to get his done in the next two months!

Thanks again for the help, it's much appreciated!

 

[mwkeefer]

I think it's a 12" tire then...

Is this the model you have?

http://urbanscooters.com/P/Electric-Scooters/Schwinn/Schwinn-S-750-Scooter.html

Higher voltage is always better than higher current for the same power, that said... your scoot holds 3 SLAs in series for 36v right? That should provide plenty of space for a 12S/10S at 2-3P weighing about 9-12lbs total but able to deliver 200a or bursts of 300a.

That said... with proper gearing and an fairly efficient outrunner (I think Jermey Harris posted he gets upwards of 88% efficiency from a Tower pro 5330) the numbers need to be refactored for 12" diameter tires but otherwise... I see ZERO issue with going from your current setup to a whopper with 3x the power - doing a delta to wye conversion would add torque and reduce kv and no load current accordingly (and sometimes much more than 1.73 with regards to idle currents).

With regard to the controllers i suggested... doing hall mods is covered all over this forum so I will leave that for you to seek out, also converting many motor types from delta to wye and vice versa is also covered so I won't expand on that now but in your situation there would be very signifigant advantages.

One other issue those turnigy controllers, the general concensus (as far as I have been able to surmise) is they are not quite dependable with the types of loads we (and you) apply to them.

But the infineon specifically would be well suited as it has 3 programmable speed (current) limits... now stock I think they are configured for about 22 amps but can be programmed up to 35a or so without mod, with a second shunt in parallel - and you double the possible current... or just beef it up with solderwick.

In either case... S%2 is the default selection on power up so... Perhaps if you have 3hp on tap (at minimums) then I would say use 1hp for the normal mode (on 12S and 3.3v cutout you need to allow for 19 Amps - 18.93 a) and set Speed %2 for 33%, Speed %1 could be extra power mode at 66% and about 2hp and from 100-125% for 3hp.

There are other tricks you can use but... in terms of range, assume in 1hp mode (equal to your current motor) with average riding I would assume you will see between 18-20wh a mile consumption with pulse and go - this is a guesstimate not a calculated fact.... just somthing to think on... now a 12S2P pack (4 6S 5AH packs) would be 49.8v fully charged and 10AH of capacity in about 8lbs (or the weight of a single SLA) with a power density of 498wh and a range of 24mi at 20wh per mile and the physical space of about 1.5 of your SLAs but in 3 seperate sections... you could break this up any way you want... pull the deck off, hold up a yard stick and snap a shot... I don't know how your SLAs are laid out or their own dimensions - that will explain alot more in terms of internal clearances than anything else...

Given your estimated 30mph cruising but 35mph guaranteed minimum (passing and manuevers and such) I think avg wh per mi on such small tires will be pretty low... maybe even less than 30wh per mile and that's without accounting for eBraking (if it even works worth squat on 12" tires) - at 30wh per mi (I get this with a hub motor, geared running at 27mph) your pack would have about 16.6 miles - it would likely be more and you should be able to double the parallel packs up for a 12s 20AH pack and greater than 33.2 mi range.

Do some searches on CCCV bulk charging... for more info about cheaply charging LiPo like this.

-Mike

 

[tropmonky]

awesome info. The Deck space for the batts are
3.25in deep
15.5in long
7in wide

I was thinking a pack made from the 20ah cells here would be great: http://endless-sphere.com/forums/viewtopic.php?f=31&t=14832 ... I THINK I might be able to fit a 12c pack in there which would give me 37v but I'm not sure that it will fit yet. Those cells can handle pretty much anything I'd be able to toss at it with this scooter. By sticking to a single cell pack it will make it that much easier to charge, heck I may have room for the charger in the scooter with that pack even!

I'll get into looking about how to add the hall sensors and how to change it form delta to wye... I have a feeling I'll be doing a lot of learning and that's a great thing. I'd think that this motor will pull more than 35a at full throttle going up a hill, but I just don't know enough to back that up...

I gotta start making decisions and getting to work on this if I want to get it one in the next couple months!

Thanks again for the info!

 

[mwkeefer]

Cell_man cells are apparently (from all testing posted) awesome but I think you may just want to do the Turnigy LiPo pack build very similar to what others have done... given your dimensions (huge) let's just argue and say a 15AH 12S pack - that would be 6 6S packs... turnigy 20C lipo were just on sale at hobby king not too long back 5000mah versions in 6S for 50.XX usd each.. so it would have been 300 for that 12S3P pack total.

My folder is using a 20" hub motor with an 8:1 reduction and 15S (55.5v nominal) with bursts of current reaching 69A on a simple 9FET infineon - a bit larger than the 6fet but also more common and the FETs inside are 75v/75a rated with caps for 63v so higher voltage or currents aren't too bad.

Adding halls is simple, they are just little sensors which are placed at 90 or 120 degrees apart (based on magnet and pole count, etc).... which is why i don't expand but some people make a disc to mount them on, some embed them inside the motors, etc... do a search for RC and Hall Sensors.

The halls give you immediate startup torque and dead stop starts without kicking to go... since your reduction won't be that high (as in 20+ :1 like in most eBikes) it may pay to look into a motor with a higher kV and reducing more..

Under 5hp #10, #35 (bike chain) and belts will work fine... 219 works well too but it's a bit overkill for < 5hp peaks.

The controller will limit the current per your configuration... 35a @ Low Voltage Cutout on 12S is = 1386 watts or 1.86hp which is not just more power than your current configuration (Direct Currie Drive - sorry, calling a chain direct always makes me giggle) but would be perhaps 20% more efficient than a brushed motor...

Add to that the improved discharge capacity of the Lipo over SLA -- even with your current 1HP (that's what the 750 means btw) at 36v nominal you are pulling 54 Amps peak... thats a 5C discharge rate which SLA would hate... it would reduce the 10AH batteries down to more like 6 AH... pulling from a 36v lipo pack the same current and the Lipo will shrug it off and give you well past the 100% rated capacity (I get this with 4.15v charge max and 3.3v cutout) which is just the nature of the chemistry and 20C ratings...

By raising the voltage and lowering the current you would reduce generated heat (losses) - someone has a slogan here... Volt Up Amp Down, there is a logic to it when possible.

If you use a higher kV motor and reduce it further it will allow for more power to develop and more torque to be put to the wheel... and the scooter platform unlike most eBikes has weight distributed in such an even form (power and passenger in center mass) so your less likely to flip but stil...

One other item to be aware of... you may want to look into alternate rims / tires with a lower rolling resistance to further increase the efficiency... This may not be practical, I don't know what's available in 12" offerings.

If you don't want to run huge gearing and make your convert utterly obvious.... I would say convert a higher kv motor from delta to wye to gain torque and efficiency while lowering idle currents then try to form fit as close to stock as possible... I don't think you need more than 3hp but your the boss = )_

-Mike

 

[tropmonky]

Hmm, lots of food for thought.

On the battery note I want to keep things simple for charging reasons... I don't want to dis-assemble 6 packs to charge up is the main thing. I'd like to set it up so I can install charging plugs on the scooter itself so I don't even need to open the deck, but that's not totally necessary as it's super easy (one hand tightened screw) to open it up.

Having a single 12cell battery pack with a BMS that handles charging means that I could carry around a simple ac/dc 5a charger with me and juice up on the run if needed with is a huge plus. One thing I've learned already is that it totally sucks when you run out of power and you're still a mile away!

I just don't know of any easy charging options for a setup with 6 or more packs, do you?

Oh, and my scooter has the street tires that come on pretty much all the currie scooters like the stealth, not the knobbies you see in the picture.

 

[mwkeefer]

Charging is a whole nother issue...

Do some searches here for bulk charge lipo, meanwell s-350-48...

Those are CC/CV 350w power supplies which work well for chargers of higher rate and lower prices...

10S - there are tons of chargers available

6s is more or less the hobby cheap zone but nothing prevents you from building the BMS/Balance hardware into the deck.

I think you have a power brick charger now right... about 1.5A or somthing? A meanwell 350 would be similar in size (slightly different shape though) weighs about 1.5 lbs and with a 12S pack at 4.15v per cell you calibrate the output voltage for exactly 49.8v and hook it up to the pack (watt meter inbetween) and connect some form of pack powered balancer (I use cheap 25.00 hobby king battery medic type balancers) to the 2 final paralleled 6S connections (equaling your 12S, so 2 plugs not one) and add a deans jack for charging power...

Believe it or not - I use this method for charging 15S2P on a modified Meanwell supply which will fit nicely (actually 3 of them would fit) in my topeak trunk... my pack balance when I am done is about 7mv out of balance... no big deal.

Most of us use CellLog8s for LVC/HVC indicator and interrupt... they are accurate enough and tiny... you would need 2 of them.

You could also do an 8S system and just find a motor to give the right RPM at 8S lvc (26.4v)... that would require 84 A of current to provide 3hp and that would be pushing the stock infineon but again, do a search for low voltage infineon mods and you will find Mr. Jermey Harris has already worked those mods out (for use in his boat power system). 84A is pushing it but 60A would be okay.

Hope it helps!

-Mike

 

[Metallover]

I have a similar scooter, a schwinn s-350, and I fitted an outrunner to it.

I would suggest finding the lowest kv outrunner you can. (your choice looks good) You will want it. On my scooter I really want to get a smaller tire so I can run more voltage, because with the current gearing I am limited to a 6s lipo. This summer I plan on getting a new (regular ebike) controller to make my throttle usable and enable higher voltages (before I was using an RC esc with a servo tester for a throttle), a smaller tire to allow higher voltages, a fan on the motor from a computer fan, and some instrumentation including a VT monitor from hobbycity for a temp monitor/alarm and another battery monitor, to act as a lvc alarm. My e-bike stole that.

I used the original sprockets and chain - The motor sprocket just happened to fit my new motor. I don't have a freewheel, and it does fine. I don't know what a freewheel on a scooter would feel like..

I will also note that I am using a smaller outrunner, a 63-54. I would go for a larger one, especially with a bigger scooter and probably someone over 150lbs.


[you can find my thread on it if you search for it; It started out as a pocket bike thread then I traded that for this scooter]

For range, I figure I can get around 10 miles on a 15ah 6s lipo (333wh) pack with no current limit. I am reaching about 20mph (only) so it will be less efficient with any higher speeds. Effeciency decreases expodentially with speed. :x I have never hooked it up to my watt meter so I don't have any figures for that.

I have to say I like the e-bike more for practical use becuse you can pedal if you run out of batteries and pedal to extend your range. A scooter, however, is a very fun project and it's fun to ride.

 

[tropmonky]

Nice! Good info... Yeah with regards to the motor I feel the bigger the better, LOL... even if I'm not going to use all of it. The new Monster 2000 RC ESC has current limiting built in so I'm still kinda leaning toward that right now. I figure the next weekend or two I'll start to really crunch some numbers and take a really serious look at thing and make my decision then.

So you're going to change to a ebike ESC? Are you going to install hall sensors to allow that?