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

[ffontana]

You're always talking about stock cells to be lg-m50lt.  Aren't those cells only in the earlier batches?

I'm the owner of 3 s18. one with Samsung 50g, another one with Samsung 50e and the third one never opened it as I never had any battery issue on it (is the newest one, still no battery nickel Stripes broken).

A mate here recently upgraded to molicel and is trying to convince me to upgrade but I'm not sure as I never needed extra power as I'm  very light. I prefer the extra mileage, but he says mileage is almost the same on molicel as battery is less stressed. 

Does it have any sense?

Are LG significantly worse than Samsung?

 

[Tawpie]

I am not aware of any S18s that have spontaneously gone up in flames UNLESS they were damaged, usually by drowning.

That does not mean it hasn't happened.

But I'm not concerned about my S18 and have no idea what cells it has. I'm not concerned because I believe KS is overly conservative about allowing the rider to request so much current from the cells that the cells might suffer damage. I believe that they pay attention to cell rating and limit performance of the wheel accordingly.

This is a belief, not a verified fact!

The question of upgrading and range: I think the range reduction is small if you push the wheel hard, but being a light rider you have some advantage there because it just takes less current for everything. I think that if you do not push the wheel hard all the time, you will experience real range reduction because by going easy on the current you're not taking advantage of the main benefit of the high current cells (as much).

I considered upgrading when I wear out my existing packs, but I probably won't because the way I ride I almost never get over current beeps so I'm not approaching the limits of the existing batteries.

Edited August 24, 2022 by Tawpie

[Vince.Fab]

I've been looking into changing over to Molicels as a heavy rider that pushes top speed and 50+ amps regularly (non molicel).  For the price though, after some research, it looks like adding another 1P in the form of wiring two rear packs extra in parallel might be the answer.   $1100 VS $300.  

[NSFW]

Thanks for clarifying, dycus. But I'm still puzzled as to why you believe that "the firmware limits the max current to prevent damaging the controller." That's the assumption about which our opinions differ, and everything else follows from that.

The S22 firmware clearly does not do this. I know this because I have a dead S22 waiting for a new controller, and so do a couple guys in Portland, another guy in Seattle, a couple guys in Vancouver... and that's just in my little northwest bubble.

While I agree that in theory the firmware could do that, I don't see evidence that King Song actually does so. 

There's a message circulating that claims to be a communication from KS to their Chinese retailers, offering to upgrade S22 controllers preemptively. While I can't say for certain that it's authentic, I don't see any reason to think that it isn't.

Is there some reason to believe that King Song did a better job on the S18 firmware than they did on the S22 firmware?

Edited August 25, 2022 by NSFW

[chanman]

Not so much a better job, but more conservative perhaps. I have evidence I guess, when I had the hall sensors on the S18 connected wrong so that the wheel wasn't getting driven effectively, the controller limited itself to 45A or so draw and shut off after several seconds, nothing was damaged.

[Tawpie]

12 hours ago, NSFW said:

Is there some reason to believe that King Song did a better job on the S18 firmware than they did on the S22 firmware?

One thing KS is very guilty of is falling prey to "mine is longer than yours". They did this on the 16X and S18, upping their advertised max speed to the very edge of their acceptable operating limit just because BG was faster. Those wheels don't appear to damage their batteries to the point of bursting into flames, but they will drop you on your face if you push them too far.

I fear that early reports from expert level aggressive riders that the S20 torque was only at the RS level caught KS again—so they went closer to the limits. I am not expert level, nor am I an aggressive rider but I'm glad to have high discharge cells on my pending S22 because KS is operating closer to the design limit. And I want margin, particularly from fire. I'll take a motherboard failure, or getting dropped on my face, but fire… nope.

I am not concerned about my S18 or 16X—their history (and willingness to drop you on the pavement) is enough to assure me that I'm not damaging the high capacity cells.

[dycus]

17 hours ago, NSFW said:

Thanks for clarifying, dycus. But I'm still puzzled as to why you believe that "the firmware limits the max current to prevent damaging the controller." That's the assumption about which our opinions differ, and everything else follows from that.

The S22 firmware clearly does not do this. I know this because I have a dead S22 waiting for a new controller, and so do a couple guys in Portland, another guy in Seattle, a couple guys in Vancouver... and that's just in my little northwest bubble.

While I agree that in theory the firmware could do that, I don't see evidence that King Song actually does so. 

There's a message circulating that claims to be a communication from KS to their Chinese retailers, offering to upgrade S22 controllers preemptively. While I can't say for certain that it's authentic, I don't see any reason to think that it isn't.

Is there some reason to believe that King Song did a better job on the S18 firmware than they did on the S22 firmware?

It is, admittedly, only an assumption, but there are good reasons to believe there is a current limit. Most of all, if there wasn't, the S18 could easily burn up its controller, motor or (low-discharge, high-capacity) batteries. All three can only handle so much current before they would be damaged, the batteries and controller especially. The S18 seems to cut out before that happens.

And they specifically advertise a peak power, if there was no current limit then the theoretical peak power would be more like 11kW! (84V - 60V = 24V (max sag), 24V / 0.13ohm = 184A (max possible current), 184A * 60V = 11kW).

Kingsong is known for making safer wheels that will protect themselves (and not overstress their batteries). This isn't possible without a current limit. I've heard of very, very few S18 motherboard failures that resulted in blown MOSFETs, besides some water-damaged ones. The S18 actually seems to be one of their more reliable wheels, from what I've seen.

S22 controllers could possibly be blowing from overcurrent, but it could also be any number of things. Voltage spikes, improperly driving MOSFETs (if you drive them in parallel you need gate resistors on each one or they can develop oscillations and blow up under specific turn-on conditions, ask me how I know that...), etc. High-power electrical design is hard. Even if you had a perfectly robust design and you used the same schematic, but laid out the PCB differently, you could make it unreliable due to new parasitic elements (inductance mainly) causing problems. S22s are definitely blowing up, if it is from overcurrent I wouldn't guess it's because they have no overcurrent protection, but that it's not tuned properly.

If KS is considering preemptive controller replacements, that suggests it's not a current limit issue, as that would just be a firmware change. There's probably a different issue with the hardware.

Begode is smart to keep using the same tested and proven board in so many of their products, developing new PCBs for every wheel will always lead to issues that need to be hammered out.

 

Edited August 25, 2022 by dycus

[Chriull]

Yet another way to compare Molicel P42a with Samsung 21700 50E/G in a 20s3p config as used with the S18:

With the below estimated numbers the molicel S18 has some very very roughly estimated 30% (18% to 41%) more maximum torque (overlean limit) than a S18 with regular 21700 50E/G cells at the same no load battery voltage.

 

From datasheets (and lyfgte-info.dk) the internal resistence of the 21700 50E/G could be somewhere in the 35 mOhm range. There is just stated the the "initial AC impedance" is below this value. In the molicel P42 datasheet 10mOhm initial AC Resistance is stated and 16 mOhm after a 1 sec 10A burden as DC resistance.

So this 35 and 16 mOhm lead to an overall internal resistance of the 20s3p pack of 0,233 and 0,107 Ohm.

At the torque limit (overlean limit) the mosfets are "open" (~100% duty cycle) and battery current equals motor current. The available torque is proportional to this current. This (steady state) current is determined by the internal battery resistance and the motor coil resistance (and mosfet, connectors and wire resistance, which is magnitudes lower).

Coil Resistance was reported and could be estimated somewhere around 0.3Ohm (for two coils in series which is measuring between two motor wires)

This current is proportional to the whole systems resistance (voltage can be reduced from the formula) and leads to a maximum torque relation of (0.3+0.233) to (0.3+0.107) - where the system with the higher resistance has a lower maximum torque/overlean limit than the lower resistance system.

Unfortionately this value is determining the result of this conisderation - so this is just a very very rough estimation!

As example for the severity of not knowing exactly the coil resistance (and cell internal resistances) - if one assumes 0.2 Ohm the advantage of the molicell grows to 41%, with 0.6Ohm it's reduced to 18%.

[mil04042]

The question still stands and I want to know, is there anywhere you can get the monicel batteries themselves you if you have an older wheel you can upgrade. I'm big guy too and since I have to walk up 3 flights of stairs each day a sherman is out but I'm also not interested in a cutout, not looking for speed or distance just less sag. And I can't want to sell and buy a new wheel just upgrade my current wheel

[Tawpie]

2 hours ago, mil04042 said:

is there anywhere you can get the monicel batteries themselves

eWheels sells them but you have to ask at sales@ewheels.com

Sit down though. 1095USD

(I bought a set because I thought I had a bad battery)

Edited October 23, 2022 by Tawpie

[mil04042]

5 hours ago, Tawpie said:

eWheels sells them but you have to ask at sales@ewheels.com

Sit down though. 1095USD

(I bought a set because I thought I had a bad battery)

Oh gosh 1095, that's rough. If I thought I could get even half that out of my old batteries then I could chew on $600. Guess I'll keep riding on hopes and dreams that my helmet doesn't kiss the pavement from sag hahaha