Is it possible to upgrade my existing S18 with the new Molicell battery pack?

[balwit]

I am a new, heavier (250 lb) rider and i have become concerned reading about the perils of battery sag. 

I wonder if anyone has successfully upgraded to the molicell pack. I assume that a bms upgrade would need to accompany the battery upgrade. 

 

Thanks.

[OldFartRides]

Welcome to the forum ! 
I have not considered this myself, but here’s something on the topic I found with a quick search :

https://www.youtube.com/watch?v=7JxJ4rnIeTk

If you bought it new, kick it around w/ your dealer. 
 

The few times I’ve run my s-18s below %50 batt they let me know with beeps and tilt back.

Advice from an old fart : If it’s not a high performance wheel, ride it gently. 
 

Edit : I watched the vid. It’s worth watching. There are also 155 comments worth perusing. You might reply to a few of those. Sometimes people will respond. I read that the conversion does require a different board. One option would be to sell your wheel and get a new molicell wheel. 

Best,

Edited August 8, 2022 by OldFartRides

[Tawpie]

I am on the "let me know when they arrive" for Molicels from eWheels, they didn't indicate a board change requirement and that would imply that for eWheels packs anyway, the pack capabilities are not taken advantage of in any special way by firmware. It should be a drop in replacement.

I don't think you'll be able to tell the difference unless when the battery gets depleted you might be able to take advantage of less voltage sag. We do not know how the firmware decides when to beep—is it purely voltage? Is there some aspect of computed safety margin involved? What factors go into safety margin? The only thing I know for sure is that at around 40% SOC KS starts lowering the max speed limit and it's my belief that this is keyed to battery voltage (I should dig into my data, but am pretty lazy).

Normaly I would assume that the lazy way out is taken: voltage and voltage alone provides the trigger thesholds. If this is true, then having less voltage sag could possibly allow a teeny tiny bit more headroom, but you won't see it until the battery is below 50%.

Since you're a heavier rider, you will be demanding much larger currents on a regular basis than someone like me. Honestly, I wouldn't be looking at S18, it just doesn't have enough batteries for you. But if you must, and if you ride gently (street, like a normal person not a member of the NYC crew), then absolutely: Molicel.

 

Edited August 8, 2022 by Tawpie

[NSFW]

I was thinking real hard about finding a buyer for my S22 and buying a Molicel S18 instead, just to save weight since I rarely use more than half a battery charge per ride.

But then, after seeing the trouble that KS has had with S22 failures, I've decided that I don't want to be an early adopter for the Molicel S18. Those batteries might just find the weakest thing in the rest of the S18's electronics. I mean, if they just took an S18 and added more powerful batteries, then I have zero faith in the motherboard's ability to handle that power without blowing up. 

I'm going to see how they perform for the first batch of customers, and then decide.

$0.02

[dycus]

The batteries don't make the S18 more powerful. They have a lower internal resistance so the voltage doesn't sag as much when riding or under high-current conditions. It doesn't "inject" more power or anything, the motherboard delivers the same current as it did before.

I've been riding the Molicels for hundreds of miles and they're just fine.

[NSFW]

3 hours ago, dycus said:

The batteries don't make the S18 more powerful. They have a lower internal resistance so the voltage doesn't sag as much when riding or under high-current conditions. It doesn't "inject" more power or anything, the motherboard delivers the same current as it did before.

I've been riding the Molicels for hundreds of miles and they're just fine.

If the voltage doesn't sag, and the current is the same, then you're talking about more power. 

power = current * voltage

Having you been riding a Molicel S18?

Nobody doubts that the Molicel make great cells. I just wouldn't bet that the S18's electronics can handle more power reliably, given how many S22s can't even handle the battery that it was originally designed for.

[dycus]

1 hour ago, NSFW said:

If the voltage doesn't sag, and the current is the same, then you're talking about more power. 

power = current * voltage

Having you been riding a Molicel S18?

Nobody doubts that the Molicel make great cells. I just wouldn't bet that the S18's electronics can handle more power reliably, given how many S22s can't even handle the battery that it was originally designed for.

Sorry, you are right, I was using imprecise language!

If the voltage sags less under load, then yes, there is an increase in power for the same current. What I meant was that I don't think the current increases, if anything it would go down slightly if the wheel is trying to command a certain power rather than a certain current (seems plausible if you were accelerating at the same rate either way).

So there should be no additional stress on the wheel, when ridden the same way, just because it has Molicel packs. The main benefit it gives is reducing the likelihood you will overlean the wheel at high currents (like going up a hill, bonking a curb, hitting a pothole, etc), due to reduced battery sag. Especially at lower states of charge where battery ESR starts going up.

I rode my original S18 for ~300 miles with the stock packs and now have ~450 miles on the Molicel packs. It's hard to give a direct comparison because I was only just learning to push the S18 to its limits by the time I switched. It gives me peace of mind to have the increased overhead though. I'd have to try a stock S18 again at this point, with the same pad setup, to see how it compares.

Overall, it's been a great wheel for me (~135lb geared). I ride on trails and the wheel is very capable. Still, I can easily make it beep due to hitting the current limit on uphill sections or when climbing steep obstacles. On the street I don't ride over 25, I want plenty of overhead. Never crashed (on asphalt) yet.

[MetricUSA]

Why would you reduce your already small range wheel???

Edited August 13, 2022 by MetricUSA

[OldFartRides]

If your typical ride is less than 20 mi., range isn’t a factor. For myself, I’m going to wear out those stock packs.

Best,

[dycus]

5 hours ago, MetricUSA said:

Why would you reduce your already small range wheel???

This is my trail wheel, and I don't typically ride more than 20 miles of trails in a day. I'd rather have the increased overhead!

[NSFW]

On 8/13/2022 at 3:02 AM, MetricUSA said:

Why would you reduce your already small range wheel???

Why would you put up with a low-power EUC just get a few more miles out of it?

It's not often than I use more than half of my S22's battery, so a Molicel S18 would be great for most of my rides. The extra 30 pounds doesn't add much value if I'm only going 20-30 miles.

That is, if the Molicel S18 doesn't self-destruct like so many S22s have. I'm not confident that King Song's electronics will be up to the job, so I'm going to see how the Molicel S18s hold up before I make up my mind. 

[techyiam]

11 minutes ago, NSFW said:

That is, if the Molicel S18 doesn't self-destruct like so many S22s have. I'm not confident that King Song's electronics will be up to the job, so I'm going to see how the Molicel S18s hold up before I make up my mind. 

I understand the caution, but aren't Kingsong's 84V motor drive system tried and true? Isn't the concern of the S18 has more to do with reworking the sliders? 

[NSFW]

5 hours ago, techyiam said:

I understand the caution, but aren't Kingsong's 84V motor drive system tried and true? Isn't the concern of the S18 has more to do with reworking the sliders? 

It was tried and true with the stock batteries, but the whole point of the Molicel battery is to send more power to the motor.

The stock battery is clearly within the limits of the S18's power system - but that only means that we don't know where the limit is. S18 owner might be pushing right up against the limit on a regular basis, but since they don't pass the limit everything is fine.

Is there enough margin to upgrade to Molicel without blowing MOSFETs? We won't know until we try.

[chanman]

The main benefit of the P42A packs is reduced voltage sag. The stock S18 severely throttles you at lower charge because the voltage sags very low if you draw a lot of current, and will cut you off if you ignore the warnings. Also if you're at high speed, a big voltage sag can drop the voltage below what's needed to maintain that speed, resulting in an overlean.  With the P42A packs, 30% is just as good as 100% for accelerating, and the overlean risk is reduced. The maximum current draw bottlenecked by the controller is not changed, obviously.

Edited August 16, 2022 by chanman

[Tawpie]

S18 has a couple of problems... it's difficult to get the suspension "just right" because it requires pretty tight tolerances, and to save weight they only put in a 3P system. That means it's operating near the end of its battery system—and if you're going fast and goose it, it will drop you on your nose. Why exactly I have no clue, but do suspect that the 3P system under high load has too much voltage sag, and whatever combination KS uses to protect the drive system kicks in.

S18 is not known for blowing its board unless it get drowned. It runs cool even if it is lying about its MOSFETs temperatures. KS has gradually learned how to build the suspension system so most new ones are ok enough, and they seem to have stopped using the (stupid decision) split washers in the suspension linkage. So the suspension has been pretty ok/good since v2.

If I still have it and do manage to wear the stock batteries out, I'll replace them with Molicels. Not because they might give me extra thrust (I don't think they will because I believe the control board is the limiting factor), but because when I do demand more power there will be less voltage sag and that MIGHT keep the control board from shutting down due to voltage-too-low. It's probably dumb, but I'll likely never have to worry about it cuz hopefully I'll be riding an S22! At least, part of the time. When I'm not whacking it with a hammer.

Edited August 16, 2022 by Tawpie

[techyiam]

43 minutes ago, NSFW said:

It was tried and true with the stock batteries, but the whole point of the Molicel battery is to send more power to the motor.

The stock battery is clearly within the limits of the S18's power system - but that only means that we don't know where the limit is. S18 owner might be pushing right up against the limit on a regular basis, but since they don't pass the limit everything is fine.

Is there enough margin to upgrade to Molicel without blowing MOSFETs? We won't know until we try.

I see.

The high discharge cells would have less voltage sag. Although, Molicel's have a higher discharge rate, the controller can limit battery current. And the 16X is famous for low end torque for climbing. That means the mosfets were not weak to start with. Kingsong should be able to set the controller to ensure the mosfets are not more vulnerable than before. Not to say it can't happen. But I suspect the probability is low.

[NSFW]

1 hour ago, techyiam said:

That means the mosfets were not weak to start with.

We only know that they were strong enough for the original battery. 

1 hour ago, techyiam said:

Kingsong should be able to set the controller to ensure the mosfets are not more vulnerable than before.

King Song should have been able to set the S22's controller to ensure that its MOSFETs are not vulnerable in the first place, but I'm pretty certain they didn't, and now I'm waiting for warranty parts.

Just to be clear, I hope that the Molicel S18 turns out great. If they are reliable, I will get one. As much as I enjoyed my S22, I'm pretty sure I'd be even happier with something that weighs 1/3 less. 

[dycus]

3 hours ago, NSFW said:

It was tried and true with the stock batteries, but the whole point of the Molicel battery is to send more power to the motor.

The stock battery is clearly within the limits of the S18's power system - but that only means that we don't know where the limit is. S18 owner might be pushing right up against the limit on a regular basis, but since they don't pass the limit everything is fine.

Is there enough margin to upgrade to Molicel without blowing MOSFETs? We won't know until we try.

I don't think you quite understand the electrical system of an EUC...

For a given set of riding conditions (rider weight, rate of acceleration, hills, wind, etc), it will take some amount of power to accelerate. No matter what the electrical system of the S18 looks like, it will still require the same amount of power to ride under the same conditions.

Electrical power is voltage times current. However, only current, not voltage, causes heating in the MOSFETs. This means that if you are requesting the same amount of power from the motor, and your battery voltage is higher, then the current will be lower. This will cause the FETs to run cooler even though the power is the same. For example, 75V * 28A = 2100W, and 70V * 30A = 2100W (28A causes 13% less power dissipation than 30A). The wheel with the higher voltage (less battery sag) actually draws less current.

The FETs do need to be able to handle the voltage of the system (plus voltage spikes), but the Molicels don't change the system voltage.

Batteries have what's called ESR (equivalent series resistance). A lower-resistance battery is always better - less power is lost as heat within the batteries, and the voltage sags less. If you're cruising at a steady pace and hit a pothole, there will be a sudden spike in current needed from the batteries. This causes the voltage to drop, and if you're riding near the top speed, can cause a cutout as your voltage goes below the level needed to keep your current speed. With lower-resistance batteries, there is less sag and thus more overhead, possibly saving you from a cutout.

The Molicels have much less resistance than the stock batteries. As an electrical engineer, I promise you, there are only benefits to this. It causes less stress on the wheel's electronics and gives increased safety overhead. The downside in this case is the lower battery capacity, due to having to optimize the cells for lower resistance rather than greater capacity.

The bottom line is, if you trust the S18's electronics with the stock battery, then the Molicels only make it safer and more reliable.

Edited August 16, 2022 by dycus

[techyiam]

3 hours ago, NSFW said:

King Song should have been able to set the S22's controller to ensure that its MOSFETs are not vulnerable in the first place, but I'm pretty certain they didn't, and now I'm waiting for warranty parts.

Not the same thing. The mosfets would fried at low speeds under strong acceleration since it was still a S20. Either the mosfets or the driver board or both, were not stout enough, and it doesn't look like Kingsong have managed to fully resolve this issue yet. Phase current and battery current are not the same thing.

Edited August 16, 2022 by techyiam

[NSFW]

14 hours ago, dycus said:

I don't think you quite understand the electrical system of an EUC...

...it will still require the same amount of power to ride under the same conditions.

[....] This means that if you are requesting the same amount of power from the motor...

I don't think you understand what makes the Molicel S18 appealing to me.

I want to ride under conditions that the folks I ride with tell me would go beyond the original S18's capabilities. I weigh 200ish and I will be doing jumps and steep/rocky/rooty singletrack.

So "under the same conditions" and "if you are requesting the same amount of power" are invalid premises. I thought that was the case for everyone who is looking forward to the Molicel s18. I mean, if you're just going to ride within the limits of the original S18, then you'd be better off with the longer range of the original battery.

[dycus]

You may be falling prey to marketing wanketeering - I see eWheels says "Now equipped with the Molicel P42a battery pack, with up to >4x more battery power over the standard LG M50LT cells". While this is strictly technically correct, it's very misleading. Yes, these cells are capable of delivering much more power than the stock cells. Unfortunately, everything else about the S18 stays the same; simply changing the batteries doesn't make the EUC more powerful. The control board will still only deliver up to a certain amount of current (as dictated by firmware), and thus the heat generated will not go up (and in fact will go down slightly on average).

The main point I'm making is that changing to the Molicels does not stress the EUC's electronics or make it more likely to fail, as was your concern.

19 hours ago, NSFW said:

Is there enough margin to upgrade to Molicel without blowing MOSFETs? We won't know until we try.

16 hours ago, NSFW said:

We only know that [the MOSFETs] were strong enough for the original battery.

On 8/15/2022 at 12:52 PM, NSFW said:

That is, if the Molicel S18 doesn't self-destruct like so many S22s have. I'm not confident that King Song's electronics will be up to the job...

Edited August 16, 2022 by dycus

[NSFW]

Aren't you the same person who just said "power is voltage x current" and the Molicel batteries will have less voltage sag under high demand?

Aren't you the same person who said you were happy to trade off capacity for more "overhead?"

I took that to mean that you expect the motor to get more power than the stock battery, in situations where the stock battery would exhibit voltage sag due to high power demand. (Coincidentally, that's what brought me here in the first place.)

If you don't expect a Molicel S18 to ever send more power to the motor (because " Unfortunately, everything else about the S18 stays the same; simply changing the batteries doesn't make the EUC more powerful") then I'm suddenly curious... what exactly is it that brings you to this fine thread?

Are you planning to get one and then only ride it like you would the original battery, but with a nice warm feeling of safety? 

As for me... when I told a buddy that I was thinking seriously about selling my S22 and getting an S18 to save some weight, he told me that the sort of riding we'd been doing would just overpower it. He's been doing this a lot longer than I have, so I'll take his word for it. But then I read about the Molicel version, so here I am.

[techyiam]

12 hours ago, NSFW said:

As for me... when I told a buddy that I was thinking seriously about selling my S22 and getting an S18 to save some weight, he told me that the sort of riding we'd been doing would just overpower it. He's been doing this a lot longer than I have, so I'll take his word for it. But then I read about the Molicel version, so here I am.

If I may interject....

At the outset, the system voltage has not been increased.

Due to high discharge cells (lower internal resistance), the voltage sag is going to be less. Under load, more voltage becomes available than before with the standard LG M50LT cells. And hence, higher than before battery current is possible. Having said that, the controller can still limit battery current. You can read testimonies from owners of Molicel S18 to learn more about performance gains.

The important piece of the puzzle are the mosfets used on the board.

The 16X uses the larger TO-247 mosfets, and is known to have great torque. The S18 also uses 12 TO-247 mosfets. TO-247 mosfets are bigger than the more common TO-220 mosfets. They can dissipate more heat and can handle more current.  

Like I said before, the Kingsong 84 V motor drive system is well sorted. You can read more about the 16X. The S18 came after the 16X. It would be child's play for Kingsong to make the Molicel S18 as robust as the 16X. In short, the risk should be low. It isn't like buying an S22. 🙂

To learn about performance gains, and issues on YouTube, search using key words:

molicel s18

 

Below is one review on the Molicel S18, and talks about voltage sag. Time-stamped. 

 

 

Edited August 17, 2022 by techyiam

[Tawpie]

12 hours ago, NSFW said:

when I told a buddy that I was thinking seriously about selling my S22 and getting an S18 to save some weight, he told me that the sort of riding we'd been doing would just overpower it. He's been doing this a lot longer than I have, so I'll take his word for it. But then I read about the Molicel version, so here I am.

Riding style and weight really matter. Where (and how) are you riding? I ask because overpowering a wheel on a rock garden is disappointing, but shouldn't result in serious injury. A faceplant in traffic at 30 mph is something most riders strive to avoid.

My off-road experience with my stock-battery S18 finds me off the wheel before I overpower it. But I weigh nothing at all and have the Russian push pads that don't actually allow me to 'push' (they're more decorative/comfort than functional). The previous owner of my wheel over leaned it at 30+ mph, so I cap my speed at 28 and back off at 25—because I'm afraid the 3P system won't be able to keep me upright. Speed is where I would consider Molicels—the lower internal resistance of the cells should help with continuous high load.

If I need new batteries for mine, I don't know what I'll do. Molicel is tempting, but I already don't have enough range on the S18 so any range hit is a fools move for me.

[dycus]

On 8/16/2022 at 7:00 PM, NSFW said:

Aren't you the same person who just said "power is voltage x current" and the Molicel batteries will have less voltage sag under high demand?

Alright, I lied a bit for the sake of a simplified argument. The Molicels, versus the stock packs, increase the peak motor power output of the S18, but only while at ~95-100% SoC. Anywhere below that, the peak power attainable with the Molicels is the same as the peak power attainable on the stock packs.

Peak power would be peak system voltage (84V) times peak allowed current. I say allowed current, because the firmware limits the max current to prevent damaging the controller. For the sake of this argument I will assume 60A, based on the advertised peak power of 5kW. The peak current is always the same, but the voltage drops as SoC drops. So as the battery dies, the peak power you can get goes down.

For my stock S18 packs, eucWorld calculated 0.13ohm for "battery circuit resistance". eucWorld measures voltage sag vs current draw to calculate this. This was always around where it stayed, I rode them for a few hundred miles. My Molicels are 0.09ohm, also checked over a few hundred miles.

Let's say you have the stock packs, at 84V. If you draw 60A from them, the voltage will sag to 76.2V (84V - (60A * 0.13ohm)). Therefore, the peak power actually attainable would be 4.57kW (76.2V * 60A).
The Molicels at 84V and 60A draw would only sag to 78.6V, giving a peak power of 4.72kW. This is higher than possible with stock batteries (though only 3.3% more).

However, once the Molicels go from 84V to 81.6V (100% to ~95%), then at 60A they sag to 76.2V, and the peak power is then 4.57kW, the same as stock.

 

In other words, when my Molicel S18 reaches 95% SoC, the peak power is now exactly the same as a stock S18 that's just at 100%. Only for that top 5% SoC can you get a 3.3% higher peak power than stock. 95% and below, I will not experience a higher peak power than what I can get from a stock S18.

This is what I meant when I said "it's not more powerful". Whether that's 'valid' or not is up for debate, but that is what my thought process was. My apologies for not communicating it more clearly!

There's also the interpretation of "higher average power", which I think is what you were going for. Yes, for any given voltage, the Molicels will have more power available than the stock packs due to reduced sag. My thinking was that this isn't significant, as a stock S18 at just slightly higher SoC would work just as well.

 

On 8/16/2022 at 7:00 PM, NSFW said:

Aren't you the same person who said you were happy to trade off capacity for more "overhead?"

I took that to mean that you expect the motor to get more power than the stock battery, in situations where the stock battery would exhibit voltage sag due to high power demand. (Coincidentally, that's what brought me here in the first place.)

Yes, that is correct. While there is only a 3.3% increase in peak power during the first 5% battery (or 3.3% increase in average peak power all the time), the voltage overhead is much more significant and is present through the entire SoC range. Voltage overhead correlates to safety when at high speed or low battery voltages (where the difference between motor voltage and battery voltage is low, aka high PWM). If you have a current spike that sags the voltage below what it takes to keep your current speed, you will fall. The Molicels provide (edit: up to) about 10% more voltage overhead versus stock, all the time (based on my data).

The operating voltage range of the S18 is 60V-84V, a span of 24V. From peak power to low-voltage tiltback, all within that 24V. The stock packs sag 7.8V @ 60A, and the Molicels sag 5.4V @ 60A. This is 2.4V less than stock. Thus, over that 24V operating span, there is 10% less sag (2.4V / 24V).
Put another way, 7.8V is 32.5% of that 24V range. 5.4V is only 22.5%. 10% more overhead.

Edit: I realized you would only get the full 10% more voltage overhead at the max current draw. This is arguably where it's most important. But, at lower currents (and less battery sag for either system), the difference is less dramatic. For example, at 10A the stock packs would sag 1.3V vs Molicels 0.9V. Only a small 0.4V difference (1.7% of 24V). Though we already knew the Molicel upgrade was mostly pointless for those that don't push their wheel to its limits. Would still be good for emergency situations, as you'd also be able to brake harder without the voltage spiking over the maximum when near full charge.

 

This is why I say the capabilities of the S18 aren't (appreciably) increased, since I could have just done the same maximum-power stunt with a stock S18 at a slightly higher SoC, and gotten the same amount of motor power. Only in the first 5% SoC could I do a stunt that needed up to 3.3% more power than a stock S18 could ever provide. But I always did it 10% more "safely" because of the reduced sag and reduced chance of cutout. That is the whole point of the Molicels (as per my understanding, anyway).

 

On 8/16/2022 at 7:00 PM, NSFW said:

If you don't expect a Molicel S18 to ever send more power to the motor (because " Unfortunately, everything else about the S18 stays the same; simply changing the batteries doesn't make the EUC more powerful") then I'm suddenly curious... what exactly is it that brings you to this fine thread?

Are you planning to get one and then only ride it like you would the original battery, but with a nice warm feeling of safety?

I came to this thread to make the case that the Molicels don't increase the S18's peak power (much), and that the (more significant) reduced voltage sag is the main reason to get them. It's harder to overlean it at all states of charge. And, to explain that the Molicels don't stress the S18's electronics any more than stock (since the max current is fixed, and current, not power, determines heat dissipated in the FETs, and the voltage isn't any higher than stock). Your first post expressed concern about the control board blowing up from "more powerful batteries", and I wanted to let you know that wouldn't happen.

And yes, that is how I ride my Molicel S18.

My apologies for repeating myself on many points, I'm just trying to be very clear and exact in this post. And sorry for the wall of text.

 

Math disclaimers:
The exact numbers aren't going to be accurate, though I tried to base them on the best data I had. It's probably not exactly 3.3% more powerful and 10% safer. But the point I'm making is that the voltage overhead is much larger than, and more important than, the extra power.
Also, as the battery discharges, the ESR increases, I'm not taking that into account.

Edited August 18, 2022 by dycus