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DIY Msuper X Battery Pack? (batteryless model option)


taserface
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Hey-

EUC noob here... I have been lurking around here for a while, but I think I'm close to pulling the trigger on an EUC.  Due to the power/capacity, I am leaning towards the new MsX.  I noticed there is a battery-less option available for ~800 cheaper.  I don't mind wiring up some packs if I can save a few hundred bucks.  Does anyone have any feedback available for going that route?  Is it just a matter of building the packs and connecting them (IE: battery-less still includes the BMS?, etc)?  (I have built big packs for electric skateboards and bikes before, but not sure if there is anything special w/r/t EUC setups).  Is there any opportunity to increase the capacity w/o modifying the existing enclosure (over the 1600wh/Sanyo GA version)?

Also, I haven't been able to find much info yet on the MsX BMS, but I read that the old version didn't have any output protection at all... is that still the case?  Is their BMS just used for charging?  

Anything else I should know or recognize before I start seriously considering going w/ that option? (IE: could QC be worse, warranty implications, etc, etc).

Let me know if you need any additional info from me.  Thanks!

Edited by taserface
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4 minutes ago, taserface said:

Hey-

EUC noob here... I have been lurking around here for a while, but I think I'm close to pulling the trigger on an EUC.  Due to the power/capacity, I am leaning towards the new MsX.  I noticed there is a battery-less option available for ~800 cheaper.  I don't mind wiring up some packs if I can save a few hundred bucks.  Does anyone have any feedback available for going that route?  Is it just a matter of building the packs and connecting them (IE: battery-less still includes the BMS?, etc)?  (I have built big packs for electric skateboards and bikes before, but not sure if there is anything special w/r/t EUC setups).  Is there any opportunity to increase the capacity w/o modifying the existing enclosure (over the 1600wh/Sanyo GA version)?

Also, I haven't been able to find much info yet on the MsX BMS, but I read that the old version didn't have any output protection at all... is that still the case?  Is their BMS just used for charging?  

Anything else I should know or recognize before I start seriously considering going w/ that option? (IE: could QC be worse, warranty implications, etc, etc).

Let me know if you need any additional info from me.  Thanks!

No disrespect, but if you're asking the question you're wholly unqualified to take this task on. I certainly would never take it on.

The reason the battery-less option is available is because some people already have an MSuper V3s wheel and they may want to upgrade. They could take the batteries out of their existing wheel and stick them in the new one and they're done. The batteries are the most expensive part of any wheel. The battery packs are actually very complicated, which you would realize if you've ever taken one apart.

Sorry to deflate your inspiration :unsure:

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16 minutes ago, taserface said:

Heh, no disrespect taken, but I would still like an answer :). 

I don't think asking questions means you're unqualified to take a task on, but that's just my opinion.  At this point, I'm just trying to gather enough data to make an informed decision.

Anyway, as mentioned, I have built large battery packs before (half dozen or so 100+ cell battery packs (along w/ many more smaller packs)) and have never had an issue, so I'm not clear on why I'd be so unqualified here... but that is what/why I am asking.  I'm mostly looking for confirmation into what is or is not included w/ the batteryless version and if there are any gotchas that are EUC specific... the unknown unknowns for someone with EV, but not EUC building experience. 

If the biggest hurdle is just building and connecting a pack of batteries, I don't consider that all that complicated.  I even have spare nickel strips ready to go.

I have to assume that the battery-less option isn't solely for those looking to swap packs, especially w/ what I've seen so far re: people extending or replacing packs after purchase.

Thoughts?

I've avoided going down the EUC battery rabbit hole in favor of riding. But there are a lot of battery geeks in this forum. @US69 and @esaj pop into my mind as guys who might better direct you.

The reason that EWheels is offering the battery-less option is for the reason that I explained and no other.

Technically, all you need to do is provide 84-volts into the control board. The control board is not involved in the charging of the batteries so you can think of the batteries as a black box as far as Gotway wheels are concerned. How you get to the 84-volts is up to your ingenuity if your up for the challenge.

Good luck.

Edited by Marty Backe
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2 hours ago, taserface said:

I don't think asking questions means you're unqualified to take a task on

If someone sits in the captain’s seat in an aeroplane asking ”how does one fly this darned thing”, it does make him unqualified. No matter what the answer is.

Li-ion cells are dangerous, which is why many are hesitant in making howto’s and answering basic questions from people that seem beginners.

EUC batteries have the BMS built in each battery pack. There is also probably a separate temperature sensor.

Edited by mrelwood
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7 hours ago, taserface said:

Thoughts?

That's an interesting option because you may then build batteries using LG MJ1 instead of Panasonic/Sanyo GA that GotWay uses for top batteries, you can also add battery or two in empty space (the side without controller board has a lot of empty space).

By doing this, you may end up with a monster MSuper XXX with 2+ KWh battery, getting an interstellar range.

Edited by EZhel
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I'm no battery or BMS expert, but I've read a lot about them, and tinker around with electronics, so I do know some things.

I don't know if current Gotways have any signalling from the BMSs to the mainboard, if they do, then you either need to find the exact same type of BMS they use, or one that behaves exactly similarly, so the signalling is correct.

The BMS should have separate charging and discharge, you don't want overvoltage protection on the output side, as regenerative braking can push the voltage to above the maximum momentarily when braking with packs near full, and the protection would cut all power. On the charging side only, there should be overvoltage protection, so a wrongly calibrated or faulty charger cannot overcharge the packs and cause a fire.

As for output protections, there could be some, but for the output current, the limit must be really high, as I'd guess the big power wheels can draw >100A from the packs in momentary spikes, and you most definitely don't want the BMS to cut power due to that. Most wheels give the final battery warning around 3V/cell, so 2.5V/cell low voltage protection could still be ok. Don't know if the BMSs have temperature monitoring, maybe not? If they do, then you probably wouldn't want it to cut power, but maybe alarm instead.

No output protections or shunting them is a possibility, just be really careful not to ever short circuit the output on accident (not that you'd want to do that even with protections ;)).

EUC Extreme rides with totally unprotected (no BMSs at all, balancing is handled by the chargers) very low resistance Li-Po -packs, but then he has 2 x 1400W iCharger 4010 Duo's + bells and whistles just for charging (probably $1000+ just for the chargers and extras alone), and custom cooling in the mainboards. And destroys a lot of boards riding. 

 

Edited by esaj
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58 minutes ago, Keith said:

Now to answer the question. 

To be honest, it is your above statement that showed a lack of understanding of EUC’s plus expecting the supplier to supply the BMS. 

It is absolutely vital that BMS on EUC’s DO NOT HAVE OUTPUT PROTECTION, cheap wheels that have used eBike BMS have been death traps and there is a long thread on disabling output protection on them. Any and all output protection on EUC’s has to come from the main control board just as a warning to the rider to take action. Under no circumstances, even if the battery is on fire, is it acceptable to just cut power.

As @Marty Backe explained, the wheel is absolutely not sold without batteries for DIY enthusiasts so no BMS is supplied, nor directly available. You are quite correct that there is nothing stopping you, or anyone else building a pack. Gotway are really good at cramming the batteries in though so you might find that a self build results in lower, not necessarily higher, capacity. 

What, I cannot tell you, but hopefully someone with that wheel can, is whether the BMS has any additional signalling wires to the main control board to alert on individual cell failures? Some EUC’s such as the IPS brand have a wire from each series cell so that it can manage even a single cell (or cell group) fault. Some others have a BMS alert signal wire, However many do not and only total voltage of the pack can be monitored. This means it is also pretty vital that a matched, single batch set of cells are used in the build as poor cells will not be controlled by the BMS other than by balance charging.

No, the Gotway wheels have no BMS signalling to the control board

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well, i’ve built my own battery packs based on aliexpress bms boards and cells with pre-welded lips sold by Nkon (otherwise you need a spot-welder). saves a few bucks, but in the end not thaaat much cheaper and not worth the hassle imo

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1 hour ago, taserface said:

BMS that implements current throttling (not cutoff) that gets coordinated w/ the tiltback function,

Just to catch this, that could not be possible. When current throttling happens, no additional current goes thru. How does the wheel do tilt-back? By accelerating more until the wheel is in the front of centre of gravity. That requires more current. If the board detects current throttling, (unless it’s a very short peak) there is nothing it can do. The CoG is lost and the rider will fall.

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1 minute ago, mrelwood said:

Just to catch this, that could not be possible. When current throttling happens, no additional current goes thru. How does the wheel do tilt-back? By accelerating more until the wheel is in the front of centre of gravity. That requires more current. If the board detects current throttling, (unless it’s a very short peak) there is nothing it can do. The CoG is lost and the rider will fall.

I'm admittedly out of my element here w/ EUCs (and it was just a throwaway example that I don't think matters much at this point), but between starting tiltback before max continuous current is reached and then leveraging burst discharge for a short duration, if necessary, I would think it would still still be possible.  You'd want an overpowered battery pack for the BMS and it's not something you'd want to invoke except as a last resort, but I'd think it'd still be better than reaching burst discharge levels w/o any feedback and/or potentially frying the main board, assuming their aren't alternative safeguards in place that accomplish the same result.

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Coming to think of it, almost all my "info" regarding the 80% limit are hearsay and speculation based mostly on discussions on the need for such alert last year. So scrap that. More info and manufacturers required.

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  • 2 weeks later...
On 6/25/2018 at 4:27 AM, taserface said:

Ya'll are kind of a tough crowd.

Anyway, thanks for the all replies, ranging from slightly condescending [to be fair, I get why: power failures are inherently going to be more catastrophic on an EUC than other personal EVs] to helpful :).

Yeah can be a tough crowd at times, but in the short time I have been here and riding a wheel I have not only managed a complicated brake of my left Scaphoid taking many months to heal but likely never back to full motion or even pain free, but also seen others hurt themselves all the time and while some of them lucky enough and just a gash, skin scrape or a chipped tooth we have also seen long threads about more serious injuries like the one of Rehab1 for example.


I dare to take the liberty of saying it' s just for your own good my friend even if ok with building your own and capable, people care and seen some nasty accidents that's all I think.

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On 6/25/2018 at 3:13 PM, meepmeepmayer said:

can get EUC BMSes from 1radwerkstatt.de (1radwerkstatt@gmx.de), he's very knowledgable and can answer all your detailed questions. Or try your luck on Ali.

Unfortunately he doesn’t have 84Volt BMSs in stock.....at least not 4 weeks ago.

As he is KS specialist he didnt need that till now....as i requested a 84V pack for my Monster in the meantime he might have....but i doubt it ?

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17 minutes ago, m.s.g. said:

On a slightly similar note, can the 20s4p packs from the gotway tesla be used in the 84v monster msuper x, or does the msuper X pull too much amperage for a 4p setup?

Warning: this is a non-answer.

In theory, nothing should stop you from using that pack in the X. Put it it, plug it in, done.

Also, I don't believe the firmware explicitly expects a certain battery. There is (or at least was announced) a 650Wh or 800Wh option, so 3P, and I doubt they would write extra firmware for that (What if people later extend the batteries? Extra FW is way too much work for the effort avoidant Gotway anyway.). Not sure how a wheel detects when a pack of serial cells is at its current limit. Is there a voltage drop or something? Does the BMS refuse to give more? It has to be something.

Finally, as the 100V msuper X is 4P and seems to work...

So, I would strongly doubt there is any problem with using that pack. But that's still just a guess.

Edited by meepmeepmayer
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3 hours ago, meepmeepmayer said:

Also, I don't believe the firmware explicitly expects a certain battery.

The teardowns seem to indicate that the only cables between the battery and mainboard are + and -. So no, the brain has no idea how much food there is in the tummy.

3 hours ago, meepmeepmayer said:

Not sure how a wheel detects when a pack of serial cells is at its current limit. Is there a voltage drop or something?

There is, but I don't think any wheel recognises a voltage drop under load from just a near-empty battery. My Airwheel A3 battery still has decent capacity, but the amperes are done for; even a freshly charged battery goes to zero bars on a steep hill.

This is why for any fast power requirements (fast acceleration, sudden bump) any battery warning beep or attempt to tilt-back based on voltage drop alone is futile.

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