Triple Motor Electric Goped Build

[caliusoptimus]

Hi folks,

short time lurker here ready to share my project! I've been in the goped community for over ten years and I've learned a lot about 2 stroke engines and their nuances. A while ago I started talking to some RC guys and the verdict seems to be that electric setups are capable of more power output than any of the gas or nitro setups...so I started thinking about how this could be applied to a scooter.

I've already typed a build log on another forum (the only one left in the goped community with active members) so I'll just jump to the point!

Build Parameters (Goals)

60mph top speed
enough torque to climb any hill in the average urban area
built around a goped GSR roller
charges in 2hrs
20-30 mile range

Equipment choices:

3x 48v 1000w unite motors
2x chinese controllers
112x LG HG2 18650 cells, configured as 14s8p (tested on a battery analyzer, came out to a solid 22.4aH)







[youtube]F1BttmfZGJA[/youtube]


As you can see I've already put quite a bit of time and testing into this baby and it has actually worked out really well!

With current gearing I am at a top speed of about 45mph with enough torque to climb any hill I've encountered including some pretty gnarly dirt trails and hills. I took it out for a long relaxed ride to see what kind of range I could get from the batteries. At an average speed of 16mph with a top speed of 28 I was able to get 23.7 miles of range on a variety of terrain. I'm almost certain these motors are capable of pulling me to 60mph but the gearing I would need might be too taxing on the motors when climbing even a modest hill.


Anyway, I've come here to endless sphere to seek your advice!

The motor controllers I chose for this project were very generic and had to be significantly modified to work together. They ended up working really well, however they don't have any of the advanced features I am looking for. I would like to either buy or build a single controller that has battery current monitoring/protection, motor current limiting, current control throttle, and some sort of way to monitor this data in real time. Is there something out there that has these capabilities for a reasonable price? Or should I start filling my digikey cart? lol

Here is what the controller must handle:

58.8 max battery voltage
battery current 200A peak (160A continuous)
350A motor current (peak)
90A continuous motor current

 

[Ianhill]

I can not help with the controller issue Ive been collecting bits so I can move to the brushless version 48v 1600w boma motor because of lack of controller options,
I bet with three motors it can really climb like a mountain goat, but do you find the motors get warm the 90amp continuous seems realistic but the 350 amps peak 117amps per motor I can't see how they will hold up at 60amps mine was getting so hot it was close to failure but I have used an old CPU heatsink few pics in my thread and it has made a big difference with my temps I can run 60amp bursts to 30mph and maintains top speed then to cover 15miles no heat issues, but the fact these motors have a fairly high resistance and commuter sparks the downside is a lot if heat wastage if you had a triple brushless boma motor I think you would get your 60 mph goal with the right gearing and little overvolt and need less input say around 6kw, 100amp on your current 18650 pack with tons of controller options.
Thing with having three motors means three times the heat losses input current etc so I would still say that one strong motor beats three weaker ones but it looks great and is executed well and is truly a one off well done.

 

[whitepony]

great build and sick video, that thing is mad!!

 

[caliusoptimus]

Thank whitepony!

@ianhill I ended up going with a kelly controller (KDZ72301) and it is almost perfect for this setup. I was looking at alltrax controllers at first but the kelly has way more options like the current meter output and the option of another pot or hall effect sensor for regen braking.

Yeah it definitely climbs without a complaint! The motors only get hot when I maintain full speed. Riding 30mph with mild hills the motors barely go above ambient temp. Going full speed gets em' pretty warm. I would say they get to about 160F after a few minutes of full speed riding. I've got the controller set to 300 amps motor side and 200 amps battery side. I've heard these motors tend to fail at the commutator, so I've been taking it easy and keeping my speeds around 30-35mph. I've been thinking a lot about brushless motors... if I were to do this all over again I would probably choose one large brushless. I built it down to a price and that's why I ended up with these motors. Maybe one day I will do another build... with the experience I've had with this scooter I think I could get more efficiency and speed. All that said this thing is a blast to ride! My favorite goped to date

 

[Ianhill]

Glad to see you got a decent controller for the old girl.
Budget was the reason I ended up with the brushed motor and fair play you have done well I have not seen any thing similar, I found a simple CPU heat sink keeps the temp down on the commuter plate so I just got to keep from overheating the windings the brushes last around 400miles to half worn where I like to change them and the commuter segments are merely bonded and tend to melt in great fashion ive melted a few my1016's but the larger my1020 seem a bit better touch wood not one has failed yet but I have 2 spares lineing up to be killed.
Throttle problems I got mainly as its a pot controller and I need the hall effect voltages so I'm running by twisting a pot to go ive tried to get the halls to work but I lose throttle range or the board makes a strange squeak sound like its out of sync and i don't know what components to use to fix it.

 

[beetbocks]

i have built a MTB scoot using a single 6374 brushless outrunner and 12S (50v) lipo and single ESC ..which gives a very similar performance but under 9kg weight...
scroll to the last few pages..
your looks to have some nice power..
https://endless-sphere.com/forums/viewtopic.php?f=35&t=55997

 

[caliusoptimus]

i have built a MTB scoot using a single 6374 brushless outrunner and 12S (50v) lipo and single ESC ..which gives a very similar performance but under 9kg weight...
scroll to the last few pages..
your looks to have some nice power..
https://endless-sphere.com/forums/viewtopic.php?f=35&t=55997

I saw your thread, very nice projects! I'm probably going to build another scooter of this style at some point but from the ground up, taking everything I don't like about this scooter and making it better. What would you recommend as far as brushless motors and controllers?

And yes the power on this thing is impressive! It is faster than most of the 2 stroke engines for these scooters... I just wish it had more range

 

[beetbocks]

well i use Alien Power 6374 motor and ESC ..and a 12S 10,000mah battery pack..but as yours range is limited to around 15-20 miles max...if i take it steady on flat terrain..but i tend to just ride mine for fun and not commuting..so its not so bad
i suspect you would be more happy with a 80mm motor for more power..and maybe a 20,000mah pack..
this is always the issue with electric -range versus power... ideally fit a BMS for easy on board charging..that's my next mod..

 

[caliusoptimus]

I got the regen feature working today! The controller has a handful of different options for regen. There is one setting that engages it when you let off throttle and it feels just like a gas engine with that setting. I don't like this though, because it takes away the ability to coast. Instead I'm going to hook up a proximity sensor to the brake lever. I'm going to set it up where the regen engages with just a slight pull of the lever, and if you need more brake you just pull the lever further until the brake pads grab. The sensor on the brake lever will also be great for turning on a brake light!

I haven't tried regen on a full battery yet. It might be a problem, because the controller settings aren't by any means precise. If it overcharges I can install a circuit on the brake sensor that doesn't allow regen until the battery is below a certain voltage.

Made some progress on my custom computer/digital readout. I've got the case, the LCD and the arduino to run it. Once it's done the computer will have functions like max speed, avg speed, trip distance, max current, max regen current etc. I'm also going to add a feature that calculates the current "miles per kw/hr" so I can figure out what speed and gearing will provide the best range. Those 3 holes are for buttons which I haven't made yet.

Here is the main screen.


Shows battery voltage, current, speed and efficiency. Speed is in MPH and efficiency will be in miles per kW/hr. Or maybe miles per W/h? Got the voltage meter and the speedometer dialed in. The program takes multiple samples of the speed and averages them together to provide less jitter in the reading. I'm using two wheel magnets to double the refresh rate of the speed reading. It's very fast and updates about 5 times / second above 10mph unlike a typical bicycle computer which updates maybe once/second.

The amperage reading goes from -50 to 200 amps so I can see regen in action. Max regen I'm comfortable with is 32 amps which is the 4A/cell specified on the datasheet. It actually brakes pretty hard at 15 amps so I may not need to go that high.

I'm working on a second and maybe third screen to show some statistics. I'm not very good with arduinos so I don't know if they have user accessible rom. Hopefully they do so I can save statistics between power ups.