Building a new 48v 30Ah pack. This all checks out yeah?

[Skoomd1]

Building a 48v 30Ah pack for an escooter (Ninebot Max G2).

I ordered 78 Samsung 50E 21700 cells for a 13S 6P configuration. 0.15mm*8mm wide nickel plated steel. Going to use a "Happy BMS" which is rated for 44a continuous discharge. 200mm wide shrink wrap, 21700 cell insulators. Plan on 70km/h speeds (with field weakening) and 2000w continuous discharge on the motor. Does this sound right?

 

[neptronix]

You're looking to pull about 42A at 2000W. That's 7A, which has a nice correlate on this graph:



As you can see the light blue line, 7A is pretty saggy on a brand new cell. That's going to create a lot of heat.
This is at perfect room temperature. In the middle of winter, this sag is 4x'd ( basically your battery is cutting off early and performing poorly )

I would chose a stronger cell since you don't have any head room on thermals or voltage sag.

Ideally you would have 33-50% of the sag at the continuous draw you are aiming for.


But before we even get to that - your vehicle has a big problem. It doesn't have adequate wheels or suspension to go that fast at all. Bikes with full suspension and 26" wheels start to get sketchy at that speed. I wouldn't recommend going this fast on this chassis in the first place. You hit the wrong small curb or small road irregularity, and you're going flying at that speed.

And at that speed on the road, it's hard to anticipate those kinds of things to slow down.

 

[Skoomd1]

You're looking to pull about 42A at 2000W. That's 7A, which has a nice correlate on this graph:

View attachment 370771

As you can see the light blue line, 7A is pretty saggy on a brand new cell. That's going to create a lot of heat.
This is at perfect room temperature. In the middle of winter, this sag is 4x'd ( basically your battery is cutting off early and performing poorly )

I would chose a stronger cell since you don't have any head room on thermals or voltage sag.

Ideally you would have 33-50% of the sag at the continuous draw you are aiming for.


But before we even get to that - your vehicle has a big problem. It doesn't have adequate wheels or suspension to go that fast at all. Bikes with full suspension and 26" wheels start to get sketchy at that speed. I wouldn't recommend going this fast on this chassis in the first place. You hit the wrong small curb or small road irregularity, and you're going flying at that speed.

And at that speed on the road, it's hard to anticipate those kinds of things to slow down.

Thanks! I appreciate your informative response. Unfortunately, I have already ordered the cells, so I am probably going to stick to them. If I turn it down to 1600w continuous (which I don't have a problem doing) I think it should be okay, according to that graph. Does that sound okay? The current stock 36v 15.3 Ah battery handles 1300w continous no problem.
As far as the safety of it. Don't worry, I have been running this scooter at 55km/h without any speed wobbles, and the suspension is massively upgraded to handle it.

 

[Chalo]

your vehicle has a big problem. It doesn't have adequate wheels or suspension to go that fast at all.

I was going to refrain from chiming in on this thread because it's such naked lunacy to put 2kW into an automated head and arm injury device. But I looked up the model in question, and as built it's limited to 22mph. That's probably 25% or more too fast for its handling and layout, but it's much less than you would get from a derestricted 2kW.

If it stays limited to 22, then the continuous draw on the battery won't be anything like the maximum power.

 

[Skoomd1]

I was going to refrain from chiming in on this thread because it's such naked lunacy to put 2kW into an automated head and arm injury device. But I looked up the model in question, and as built it's limited to 22mph. That's probably 25% or more too fast for its handling and layout, but it's much less than you would get from a derestricted 2kW.

If it stays limited to 22, then the continuous draw on the battery won't be anything like the maximum power.

That's what gear is for. I have over 5300 miles (8500km) on this thing, the only time I crashed was within the first 50 miles of owning it. It's really not as dangerous as you're making it out to be. It has significant trail in the front. I could link you studies showing how that benefits it. But I am looking for input on the battery though, not the logistics of the physical safety of the vehicle.

 

[neptronix]

5300 miles... on factory power levels, right?

Is this your vehicle, with what looks like 4 inch wheels?



Trail will help you with handling but there's no getting around the problems with small wheels.
Your front and rear ( none ) suspension are totally inadequate for this kind of speed.
Being thrown off this vehicle because you hit a pebble too fast will still injure even if you are wearing body armor.

 

[Skoomd1]

5300 miles... on factory power levels, right?

Trail will help you with handling but there's no getting around the problems with small wheels being susceptible to flying off little bumps.

I guarantee you will lose the argument with physics..

4000 miles with factory power levels, 1300 with 35mph settings. I don't ride that fast on roads I don't know. I am an experienced motorcycle/bicycle/scooter rider with 15 years of riding experience. I understand hitting a crack/pothole the wrong way at those speeds, with small tires is extremely dangerous.

 

[Skoomd1]

5300 miles... on factory power levels, right?

Is this your vehicle, with what looks like 4 inch wheels?

View attachment 370772

Trail will help you with handling but there's no getting around the problems with small wheels.
Your front and rear ( none ) suspension are totally inadequate for this kind of speed.
Being thrown off this vehicle because you hit a pebble too fast will still injure even if you are wearing body armor.

They are 10x2.5" tires. 4" would be madness at any speed. And I am using upgraded sharkset suspension

 

[neptronix]

Are those really 10 inches?

So yeah.. you have to ride streets where you already know the irregularities so you don't get hurt because you have no safety margin at 35mph.

I find it strange that you have a lot of experience with 2 wheelers, but you want to go fast on the kind that's the least suitable for that kind of speed.

Anyway you've been warned that this is super dangerous, i'll get off my high horse.

 

[Skoomd1]

Are those really 10 inches?

So yeah.. you have to ride streets where you already know the irregularities so you don't get hurt because you have no safety margin at 35mph.

I find it strange that you have a lot of experience with 2 wheelers, but you want to go fast on the kind that's the least suitable for that kind of speed.

Anyway you've been warned that this is super dangerous, i'll get off my high horse.

Yes, the exact tire size is 60/70-6.5". (6.5" is the internal motor/rim diameter)

Believe me, I do not ride fast on roads I don't know. Nor do I in areas with high traffic/pedestrian traffic.

The reason I do it is because it's fun. I know it's a poor argument, and I know it's dangerous, but that's why. I only ride this thing on back country roads, with bright aftermarket lighting to make sure any potential vehicles can see me.

 

[Chalo]

I could link you studies showing how that benefits it.

The studies that made me pay attention were the ones that reported how much emergency room visits in my area skyrocketed after the introduction of idiot scooters for folks who are afraid of much safer e-bikes.

 

[Skoomd1]

The studies that made me pay attention were the ones that reported how much emergency room visits in my area skyrocketed after the introduction of idiot scooters for folks who are afraid of much safer e-bikes.

Okay. Well I didnt make this post to argue about this. Just looking for feedback on my battery I am building. Not sure why I am met with such hostility. Thought we were all on the same page. Nothing about my ride is as dangerous as you exclaim. I take safety pretty damn seriously, hence why I made this post....

 

[Zambam]

How well do these scooters stop? Do you wear a helmet? Lot's of scooter riders here who are knuckleheads, no helmet, go through red lights, ride too fast etc.

 

[Skoomd1]

How well do these scooters stop? Do you wear a helmet? Lot's of scooter riders here who are knuckleheads, no helmet, go through red lights, ride too fast etc.

I can stop from 30mph within 15 feet. Yes I wear a full face motorcycle helmet, elbow/knee pads, and gloves every time I ride. I don't do stupid shit like many escooter riders. I agree many of them ride like maniacs. I am an advocate for safe escooter riding, just read my posts/comments on r/electricscooters on reddit (u/skoomd1). Here is a clip of my riding in a very mountainous region, with MANY potholes, if you would like to see

Can we change the discussion back to the battery please?

 

[Chalo]

You bought a turbo version of a common idiot scooter. Help us not draw the obvious conclusion.

High current on steel strip is working towards the obvious conclusion. Beating the snot out of your cells is working towards the obvious conclusion.

 

[Skoomd1]

You bought a turbo version of a common idiot scooter. Help us not draw the obvious conclusion.

High current on steel strip is working towards the obvious conclusion. Beating the snot out of your cells is working towards the obvious conclusion.

Can you provide advice about that? Instead of snobbery? I can always use 2 strips for each bank of cells. Is there a reason I cannot use nickel plated strip? I can upload the 3D CAD model for how I will lay it out....

edit: here's the cad files... Ninebot Max G2 - 48V 28Ah internal battery by DenisYurev

I came here seeking advice, not opinion. Many of the posts here are excellent, and have guided my way through DIYing ebikes/escooters for years. Again, I am not sure why I am being met with such hostility. It's genuinely turning me away from this forum... Have you even ridden a full suspension escooter before? Sheesh. You speak of this "obvious conclusion", and the obvious conclusion that I am getting is you think your above escooter users.... How do you feel about EUC and Onewheel riders? This entire thread has been derailed.... I just wanted help with my battery. I am sure if I didnt mention it was an escooter, it would have steered in an entirely different direction. Wtf.

 

[Chalo]

You speak of this "obvious conclusion", and the obvious conclusion that I am getting is you think your above escooter users....

I don't think it. I live among thousands of scooter users and I know it from conclusive observation. Duh. If they weren't defective, they'd be on bikes like thinking people.

Wrong way riding, sidewalk riding, dumping the things in the middle of the sidewalk far more often than not, parking the damn things right in the middle of the bike lane, clogging up bike racks with things that aren't meant to be locked up, riding drunk, riding two-up drunk, self-maiming... there's a formidable body of evidence. So it's very much up to you to demonstrate that you're not one of the same.

 

[Skoomd1]

I don't think it. I live among thousands of scooter users and I know it from conclusive observation. Duh. If they weren't defective, they'd be on bikes like thinking people.

Wrong way riding, sidewalk riding, dumping the things in the middle of the sidewalk far more often than not, parking the damn things right in the middle of the bike lane, clogging up bike racks with things that aren't meant to be locked up, riding drunk, riding two-up drunk, self-maiming... there's a formidable body of evidence. So it's very much up to you to demonstrate that you're not one of the same.

I explicitly show that I don't do that via my youtube channel, and my reddit account. I educate riders on how to properly select a safe scooter, explain the "right" and the "wrong" way to ride, and advocate for wearing proper gear. I already explained this earlier in the thread....
You know why? Because yea, a lot of people ride these things drunk running red lights and shit. I hate to see that. This is my main mode of transport. I don't want it to become banned. I would just like to go a little faster myself.

Btw, calling a group of people "defective" is absurd. And I am a "thinking people" as you say... gross terminology....

 

[neptronix]

Hey, i want to be helpful but, i've seen people get injured on things with wheels about the same size at slow speeds.
I've ridden one myself and was shocked at how bad they handled, how unsafe they are, and how small bumps affect them ( that one had a 6 inch tire )

It doesn't make sense why anyone would ride such a vehicle on backcountry roads. That sounds beyond miserable, unless these roads are perfectly smooth, and i'm envisioning it wrong.

I've seen very safe scooters with dual suspension and big wheels that go high speed built on this forum. They have motorcycle tires, WAY longer wheelbases, and a lot more than an inch of suspension on both axles.

You have absolutely the wrong chassis for high speeds and i would feel bad if i advised you further and you died or were greatly injured as a result. I think the possibility of that is very high here.

 

[Skoomd1]

Hey, i want to be helpful but, i've seen people get injured on things with wheels about the same size at slow speeds.
I've ridden one myself and was shocked at how bad they handled, how unsafe they are, and how small bumps affect them ( that one had a 6 inch tire )

It doesn't make sense why anyone would ride such a vehicle on backcountry roads. That sounds beyond miserable, unless these roads are perfectly smooth, and i'm envisioning it wrong.

I've seen very safe scooters with dual suspension and big wheels that go high speed built on this forum. They have motorcycle tires, WAY longer wheelbases, and a lot more than an inch of suspension on both axles.

You have absolutely the wrong chassis for high speeds and i would feel bad if i advised you further and you died or were greatly injured as a result. I think the possibility of that is very high here.

Thank you. I understand and respect your viewpoint, even if I inherently disagree. I appreciate your input very much