ELF: upgrade motor and controller for more power.

[theGoPedal]

We met someone who recently purchased an ELF trike:

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His goal is to use it as his primary vehicle for an eco-friendly handyman business. To do this, he will need to haul a trailer loaded with his equipment in and around downtown Kansas City at 20-25 mph. The total vehicle weight is 800 lbs (trailer, 400 lbs; rider, 200 lbs; trike, 150 lbs). The steepest hill he will need to climb is from the city market to downtown on Grand street, a 6% grade.

The trike is currently equipped with a 48v 11ah Li-Ion batttery, what looks like a 12T MAC motor mounted in a mid-drive position and 30A controller.


After a few test runs it is clear that the trike doesn't have enough power to do the job. It will slow to 5mph on the hill and the battery will cut out due to voltage sag if stressed for too long. We'd like to increase the trike's power to make it more useable for the owner.

We plan to increase the battery capacity from 11ah to 30ah by replacing the 48V 11ah battery with two 48V 15ah batteries run in parallel.

We plan to replace the motor and controller with more powerful ones. For the motor, we're looking at this one:

http://www.9continent.com/nkt/products_show.asp?id=119

The main reason is we already have one here in our workshop. We can start testing it right away. But will be powerful enough? Should we be looking at Cromotor or Midmonster? We'd like to model our system on the ebikes.ca simulator but we're not sure how to set up the ELF's mid drive system. We'll continue to investigate this question until we're satisfied that the motor we select will be up to the job.

For the controller, we'll probably go with a Kelly.

Will keep this thread updated with info and pics as the project moves forward.

 

[Drunkskunk]

Their website claims they use a 600 watt motor, that should be a more powerful motor than the 9C, but it's hard to say without knowing more about that motor. If the motor is running through the gears, yet the bike can't make it up hills in Kansas, I'd say there is a problem with the setup. What sort of controller are they running, what's the amp limit, and which rear hub are they using?

Midmonster motor sounds interesting, but you'll probably need a motorcycle back wheel to keep from simply spinning it into smoke. 10kw+ motors also do bad things to frames if you don't modify them to handle power 20 times more than stock.

An Infineon based controller should handle any power requirements an ebike could come across better than a Kelly, and still be compatible with devices like a Cycle Analyst.

 

[alsmith]

As an aside- the bike looks nice.

You'll need to get proper technical details about the drive train before updating anything- What is the motor make and model/variant and wheel size, What controller is used (make, model, fets, amp rating, programmable?), and battery details (voltage, capacity, discharge rate- continuous and max-, chemistry). It may be some bits will meet his target needs, but there again maybe not but you'll get some good advice if people know just what he is starting with.

I definitely like the look of that trike though- if I get a big lottery win tonight ........

 

[alsmith]

As an aside- the bike looks nice.

You'll need to get proper technical details about the drive train before updating anything- What is the motor make and model/variant and wheel size, What controller is used (make, model, fets, amp rating, programmable?), and battery details (voltage, capacity, discharge rate- continuous and max-, chemistry). It may be some bits will meet his target needs, but there again maybe not but you'll get some good advice if people know just what he is starting with.

I definitely like the look of that trike though- if I get a big lottery win tonight ........

update- the site says 11.25 Ah 48V Li NMC battery from Samsung - I doubt that's good enough for what he wants. It probably means the controller won't be up to the job so I'd guess a more powerful controller and higher capacity batteries are needed as a minimum. I don't know anything about the '3 speed motor' is it really a 3 speed motor or a motor driven through a 3 speed hub?

 

[oldwahoo54]

I believe it's a 3-speed hub, and you can upgrade to a Nuvi.

I wonder if he could cut down on what he's hauling around or lighten it somehow. Or use the cargo capacity of the Elf, w/o the trailer. Maybe it won't fit in the cargo area behind the rider? Or he wants to be able to leave the trailer at the job?

When I was at the Elf factory, they mentioned that some people were rigging up wiring harnesses so they could hook up multiple batteries in parallel, and some were just carrying spares so they could switch them out when needed. There's certainly plenty of room for multiple or bigger batteries.

 

[mvly]

Controller should be kelly. But I think the MAC motor should be good for up to 1.5KW. Though that would be the maximum limit. I would keep the gearing to be the lowest as possible for climbing hills. DD like the 9C would be better, but you will need to hack it up I suspect. But a 48V is a must I think if you want to climb any hill without much assist.

 

[amberwolf]

It looks like a multiple-cause problem; probably isn't any one thing to do to fix it, but a few "little" things.

AFAICS in the pics, it's not really a middrive thru the gears, as it appears to run the output chain on the left side of the motor and wheel. That means that essentially it's just a straight hubmotor but not mounted in the wheel.

So if the gearing is set up on motor and wheel to give a top speed that is higher than needed on the flats, you could then change that gearing so the on-flats top speed is lower, down ot the max he needs, which will increase the torque available for startups and hill climbing, without adding any more load to the motor or controller.


Additionally, it's very likely that battery, being so small, is sagging on the higher loads of hills, and the voltage drop is one reason for the slowdown. You will need to monitor voltage during the problematic times and see what it is vs the times it works as expected, and also monitor current at those times. If it does have significant sag, you may need a larger pack (multiple paralleled packs of the same kind, for instance, which will also give more range), or one of the same capacity that is capable of a higher C-rate without sagging in voltage, which will help.

If you have any batteries of your own that are the same voltage, you can test that theory by simply paralleling htem with the existing pack, and see if it helps. Or if you have packs of similar but not identical voltage but that have much higher capacity / C-rate, same thing.


You could also up the voltage on the pack, to whatever the max the controller can safely handle is, and change the motor/wheel gearing to reduce the max wheel speed back down to whatever the needed top speed is, and that could also help.




Replacing the controller with a higher current capable one would also help, if hte battery can handle it, but it will also make the motor hotter, and if it's a geared motor then depending on what those are made if it could eventually cause problems with them. It could also overheat the halls in the motor and cause temporary failures while it's too hot, even if it doesn't permanently damage them (did this with a Fusin on DayGlo Avenger).