Advice wanted. Electric downhill.

[Ohmygodlandshark!]

Hey! So I'm mostly brand new to this. And most electronics. I've installed a crank case 1500 w in a old steel frame racer, and I've ridden alot of dirtbikes.
Now to my questions.
According to the guy I bought it from this is the Bike: 72v 30 Amp battery, 60 Amp bms.
200 lg cells. 10 series. 20 parallel.
"84 watt gives 60 Amp"
50 cells was changed last service. Along with a new bms from dayli.
4000 w vektor controller. Changed from a 6000 w annoy bikes controller. ( I have it in a box, and it's huge)

8000w cromotor in a 24 inch rim. (This is peak power right ? They will advertise this one as 4000w or something? )

Double rock shock dampers in the back.
Dmn volcano racing shoxs (usd-8)

Gt hub with 20 mm axell.
Shimano slx brakes and Saint 4 piston calipers.

He also said the frame is a " horizon" and It looks slightly better than other Chinese rip off frames. ( I'm assuming it's Chinese by the welds and such)
But ive broken a dirtbike in half some I'm not too confident in this bike.


My questions to the experienced stealth Bomber type bike builder :
Did the original guy choose good stuff ? Any weak links ? If I don't care about range for a day, would it hurt to put on the 6000w controller again ?
I've heard about some little "sine wave " controller or something like that , that supposedly everyone is putting on their bike? So it's less noisy and have a more controllable power down low ? I think I need that. Also he said there's no overheat warning from the hub motor ? Is that really bad ?

My long term goal is to learn this Bike and how to repair and modify it, and in the end, create an easy to use, reliable, turnkey , fun alternative to a gasoline dirtbike/enduro. ( I'm limited to the forrest of my family farm and two local tracks)
Flat to somewhat steep hills, and open pinewood forrests.
I'm already looking to buy a Nyx frame (that's what grabbed my attention years ago.
But I'll install parts for it when I've gotten some experience.

Is 800 usd a fair price for a nyx frame ?
I can upload pictures as soon as I figure it out.

 

[amberwolf]

According to the guy I bought it from this is the Bike: 72v 30 Amp battery, 60 Amp bms.
200 lg cells. 10 series. 20 parallel.

Are you sure about the numbers? They dont' sound right.

10 cells (assuming typical cylindrical LG cells) in series is only a 36v battery, not 72v.

If it's actually 20s 10p, then it's 72v, and would make more sense as a 30A battery if the cells can provide only 3A each (perhaps 1C, at a guess).

"84 watt gives 60 Amp"

That doesn't make sense. Could you explain what was intended by the statement?

(you could get 84W output by putting 60A at 1.4V thru a load, but it doesn't seem relevant to the bike or the discussion....)

50 cells was changed last service. Along with a new bms from dayli.

Do you happen to know why they were changed? If it was from aging, you'll want to know that all the other cells would be the same age and so would also need to be replaced "soon", as they will age at similar rates to each other. If it was from a failure, knowing what the failure was may help you troubleshoot a problem later.

8000w cromotor in a 24 inch rim. (This is peak power right ? They will advertise this one as 4000w or something? )

You would need to know *which* cromotor it is, specifically, to know any of that. And if it is an actual Cromotor, or if it is a clone, or even just a random motor they're calling Cromotor because they think that makes it sound powerful (happens more than a little). Getting a link from the seller to the actual page the motor was purchased from would help you know a lot more.

Motor watt ratings don't necessarily mean much in regards to their actual abilities, anyone can call any motor anything they want (and often do).

Did the original guy choose good stuff ?

You'd have to provide links to each of the actual items' sale pages for us to know exactly what they are for us to tell you if they are "good stuff".

Any weak links ? If I don't care about range for a day, would it hurt to put on the 6000w controller again ?

To answer that, we need more info.

Why was the original controller removed and replaced? That could be important, such as if it is damaged and is what caused the failure of those 50 cells, for instance. Or some other issue.

Weak links would definitely include the battery itself. The rest we'd need more info to figure out.

A 36v (10s 20p) 30A-capable battery for a 6000w or even 4000w controller is going to be quickly destroyed by overheating the cells, and will have tremendous voltage sag under load, giving way less watts than it would if used within it's actual limits.

To get 6000w at 36v, you'd need 167A, about five and a half times the 30A the pack is capable of.

At a guess the cells may have voltage sag of half their actual voltage, or more (depends on the specific cells used; you'd have to look at the manufacturer test chart on their spec sheet, then extrapolate to the even worse loading you'd be putting on them). (note that this wasted power from cell voltage sag is all converted into heat inside the cells themselves, heating them quite a lot quickly).

Since this would take a 36v pack down to about 18v, your controller would probably shut off due to it's internal LVC. If it doesn't, your BMS should do it, assuming it can survive that level of overcurrent itself.

The 60A BMS, if it actually monitors current and shuts down output to protect it, will, if it isn't itself damaged or destroyed by the severe overcurrent, shut down every time you try to use anything above just a little bit of throttle. Similarly, if it doesn't monitor current but does survive the overcurrent, it would still shutdown from voltage sag on the cells.

Even the 4000w controller will require 111A at 36v, almost four times as much as the batteries can handle, and twice the BMS ability.

If it's actually a 20s 10p 72v pack, then a 6kw controller will still need over 83A to generate full power, nearly three times what the cells can handle, and still well over the BMS limits.

A 4kw controller would need nearly 56A, almost twice the cell's capability, though at least it would be within the BMS limits.

I've heard about some little "sine wave " controller or something like that , that supposedly everyone is putting on their bike? So it's less noisy and have a more controllable power down low ? I think I need that.

All a sinewave controller does is use a smoother waveform to control the motor with than the trapezoidal controllers do. Many high-power controllers already do this, so there's a good chance yours is already this type.

What you probalby are really looking for is an FOC controller with a current-controlling-throttle. That means you are controlling not the speed of the motor, but the phase current of the motor, which means you are controlling it's torque directly, and that gives you much better control over how it pushes the bike around. Typically you must setup these controllers to work with the specific motor, battery, etc that they are being used with, so they're not "plug and play", but they are "better" for some purposes (possibly including yours).

Some throttles are more responsive than others, too, with greater mechanical range of the throttle movement giving greater output range to send to the controller. Some of them require programming the controller differently to accomodate them.

Also he said there's no overheat warning from the hub motor ? Is that really bad ?

"overheat warning" is just a temperature sensor, that you can then monitor either with a display of the temperature yourself, or by the controller and have it automatically scale back or shutdown power if it increases too much.

It's only needed if you expect to use the system in a way that is likely to overheat it. (running high loads at low speeds, using higher power than the motor is designed for, etc).


If the motor doesn't have one and you want/need one, you can open the motor and install one, but that's only "easy" if it already has wiring present for one. (a single extra unused signal wire is sufficient; it can usually share ground with the halls). If no wire exists for it, it may be difficult to add one.

My long term goal is to learn this Bike and how to repair and modify it, and in the end, create an easy to use, reliable, turnkey , fun alternative to a gasoline dirtbike/enduro. ( I'm limited to the forrest of my family farm and two local tracks)
Flat to somewhat steep hills, and open pinewood forrests.

For reliable, you want to build starting with a battery that can handle the max continuous load your system would ever demand from it. The one you have can't even handle part of the demand your system could ask of it, certainly not the full demand.

To find out how much power the system needs, you'd need to measure the actual slope and length of the worst-case hills, and at least guesstimate the worst-case weight of the whole system (bike, rider, battery, motor, etc). It helps to also assume worst-case headwinds at the same time.

When you have that info, you can use things like the http://ebikes.ca/tools/simulator.html to determine how much power it takes to go up that kind of hill with that kind of weight with whatever winds you might see, at a particular max speed. You may need to use the "custom" option for battery, motor, and controller to reach the ability for the simulator to show the power you need for your system to do the work. There are instructions below the simulator on how it works.

If you don't want to do any of that, it's ok; you just wont' be able to be certain of the system's ability to do what you want until you actually try it out and see how hard you have to push it.



Regarding pictures, just click the Attachments tab, then Add Files, then browse to the pictures on your ocmputer and select one (or all of them) and click Open. The forum will then show a list of the files below the Add Files button, and a green progress bar as it uploads them and resizes them automatically. When it's done, just click Submit and they'll be in the post. (if you don't wait for it, they wont' be there and you'll have to do it again).

 

[E-HP]

According to the guy I bought it from this is the Bike: 72v 30 Amp battery, 60 Amp bms.
200 lg cells. 10 series. 20 parallel.
"84 watt gives 60 Amp"

The battery info doesn't pencil out.

Since a lot of the info doesn't make sense, one has to make assumptions. The seller could be describing a 72V 30Ah battery constructed with LG cells, in a 20S10P configuration. That would make a little more sense than the description above. This would indicate the LG cells have a 3000mAh capacity, so 3Ah x 20 = 30Ah

However, LG cells with 3000Mah capacity seems to indicate HG2 cells, but those can provide 20A continuous when new. That would be 200A at 10P. Doesn't seem likely, since the BMS is only 60A.

If the are LG MJ1 cells, those are 3500mAh, then at 10P, that would be 35Ah, not 30Ah. Since those are 10A continuous, that would be 100A for the pack, not 60A. Neither the capacity or discharge current line up with the seller's specs.

I don't know of any LG cells that are rated at 3000mAh capacity, with 5A continuous discharge, which would appear to match the seller's specs of 20S10P 30Ah, 60A continous discharge.

Did the seller put this info in writing, or is this from notes that you transcribed? 60A continous is nowhere close to enough for that bike, so I suspect that figure to be off at the very least.

 

[larsb]

Pictures say more than a thousand words :wink:

Picture of
- controller and any labels on it
- battery pack insides with cell marking and cell count
- bms with any labels or markings, top and bottom
- motor with any labels or markings. Both sides.
Measured motor shell diameter and width

From the description it’s clear that seller didn’t know what he was selling and there are some question marks on the system matching - there’s a risk that this bike is a dud.

 

[Ohmygodlandshark!]

Wow im Stunned guys. I've been on quite a few forums. But never have i seen felt so welcome.
Damn. So much good information!
Regarding your questions. I can see the batteries don't make any sense. I'll take photos tomorrow.

 

[Ohmygodlandshark!]

Okey guys , he has answered me. The thing is , I have a contract that says i can return it in a week.
So if it's a "dud" You can imagine my joy if we figure it out
(But I got i pretty cheap and theres not alot of bikes like this here)

Heres his reply to the statement about the battery info not adding up :
I understand what they mean, but they misunderstand (?)
What they say is true, but this batteries have a "discharge rate of 3c " Theres 20 cells with 10 pieces in cells (?) One battery is 3a but you can pull 3c max , that is 9 a per cell.

He said He can't remember the name/nr of the batteri but they are purple cells from LG used for w bikes. El sykkel. 3.7/4.2v , 3a ,3c (?)

I also took some pictures, but the battery is kinda stuck in there and on the inside of the layer of duct tape, there is some thin metal sheet I didn't dare cutting thru. But with the updated info on the battery, and the pictures , I figured I'd hold on.

The battery box measures : 15,5 " x 6" /6,5" x 4" inch

 

[larsb]

At least it’s more understandable
20 series, 10 parallel of 3Ah 9A max discharge LG cells
Could be true, could be false :wink:
Peak power on a balanced system would be 6.5kW but it would stress the batteries quite a lot.

Total energy would be 2.16 kWh for the battery, i don’t know what to assume for consumption, 70wh/km? about 30km range if that’s the case. Maybe we have some cromotor guys that know what to expect.

Does the controller have any markings? To know what it is could basically define the rest of the performance you’d expect. Check all sides.
What’s the max speed with no load (max throttle wheel lifted)? What voltage during test?

 

[Ohmygodlandshark!]

Ok, we can disregard everything now. I'm giving it back.

 

[larsb]

No, might be something totally different inside than sellers info, they are just estimations IF his data is correct
The cell i could find that roughly matches the data is LG-18650-MG1, an older cell with decent performance for the time but not at the top today. I think it’s from 2012 or thereabouts and batteries have come a long way since then.

..then again, you need to get a peek into the pack to be able to know. Could be a chinese low cost cell inside also.

 

[E-HP]

The cell i could find that roughly matches the data is LG-18650-MG1, an older cell with decent performance for the time but not at the top today. I think it’s from 2012 or thereabouts and batteries have come a long way since then.

MJ1’s would fit all the specs if the pack were 35Ah instead of 30Ah, so maybe the Seller has that spec wrong. The 60A BMS would be a conservative rating.

 

[larsb]

Ok, we can disregard everything now. I'm giving it back.

What did you pay for it?

 

[Ohmygodlandshark!]

Yeah. They might have been from 2012 for all i know. But we had a written contract so he took it back. I payed 2700 usd. But the used market for bikes like that is non existant in Norway. Loads of e scooters and GT / haida bikes everywhere.