Begode Master 134V 2400WH Suspension

[BleepBloopBlop]

The series configuration of the master is scalable to the EX2S where a parallel arrangement wouldn't be. A parallel arrangement wouldn't offer a balance pack as the stanchion needs to be centered on the wheel.

-A parallel config would be 32s1p on one side and 32s2p on the other side of the stanchion.

-By going to a series arrangement you can do 8s6p packs on either side of the stanchion making things balance.

-An 8s BMS is also going to be more compact in the battery packs as well!

[supercurio]

7 minutes ago, techyiam said:

The question raised doesn't apply only when cells are faulty. With all healthy cells, can't a rider rides until the wheel force him off or cut out if the necessary safe guards are not implemented? Don't you need the same safe guards?

At the risk of extrapolating because it's not coming from the results of a test, I would guess there are two scenarios:

Let's put this scenario in place:

Rider accelerates strongly
Battery level: 30%

• packs and cells well balanced:
  wheel beeps an alert for low voltage during an acceleration with the voltage sag resulting, so the rider stops pressing on
• 1 significantly weaker cell group:
  wheel beeps and voltage rapidly to 2.5V and below sharply: possibly at 0V or negative polarity, while damaging irreparably the cells in the  weaker group. Because the voltage drops much quicker. However it's only one cell group of 32 so it can't affect total voltage that much.
  The risk of cutout due to cells going haywire and dropping voltage much quicker than expected still increases the risk of cutout compared to normal operation, for which the alarms are calibrated.

What do you think?

 

2 minutes ago, BleepBloopBlop said:

The series configuration of the master is scalable to the EX2S where a parallel arrangement wouldn't be. A parallel arrangement wouldn't offer a balance pack as the stanchion needs to be centered on the wheel.

Oops! Scalable indeed since the EX20S already exists!
Made with 4x 24s2p packs in parallel.

[Tawpie]

Thanks for the insights on some of the things 4x8s4p bring to the party @RagingGrandpa and @supercurio!

I still don't know what to think—there are benefits in that monitoring of the battery 'system' can now be more granular. I didn't see an obvious data connection between the packs and the motherboard but also didn't watch Kevin's teardown so I'm not seeing how BG is leveraging the potential insight. But they do have the opportunity to improve monitoring of the system health... paralleling batteries can mask impending problems.

On the other hand what does the controller do when it notices that one of its 8s stacks isn't performing as it should? I'm guessing for brownouts nothing will change—the total system voltage will sag and if you keep pushing it you'll cutout. Perhaps there will be additional diagnostics that will let you know that pack 3 isn't charging to 33.6V?

My gut says there won't be much user visible difference either in operation or during charging. But I still am curious as to why they chose this route! It just has to be better for something… maybe it's as simple as being "touch-safe".

[Rawnei]

5 minutes ago, Tawpie said:

I still don't know what to think—there are benefits in that monitoring of the battery 'system' can now be more granular. I didn't see an obvious data connection between the packs and the motherboard but also didn't watch Kevin's teardown so I'm not seeing how BG is leveraging the potential insight. But they do have the opportunity to improve monitoring of the system health... paralleling batteries can mask impending problems.

The battery connectors have 3 cables though, couldn't the middle white one be a data cable?

[Tawpie]

5 minutes ago, Rawnei said:

The battery connectors have 3 cables though, couldn't the middle white one be a data cable?

Yep! It's an available connection, so it can be used to send information. 🤞

[Paul A]

Begode has a Facebook page.

Could these queries be sent to them for answers?

[chanman]

Not totally sold, but please correct me if I'm misunderstanding concepts or implementation.

3 hours ago, RagingGrandpa said:

Regarding charging, there is no difference between [4x 8s4p] vs [4x 16s2p] vs [4x 32s1p]. It's always 32 cells in series.

The difference is that you can rely on the 32s BMS to balance at the correct voltage for each parallel pack. Some additional work is required to get 4x8s packs in series balanced. In series, one pack can't just decide to stop accepting current or accept less current without shutting off the flow to the other packs. There's also the matter of varying resistances of individual modules making the voltage drop across each one in series slightly different. 

Presumably this could be handled by a separate charging circuit (and BMS?) supplying the 8S charging voltage to each pack in parallel, but this seems more complicated, not less.

Couple of "strengths" mentioned that I find suspect.

3 hours ago, RagingGrandpa said:

Simpler cell balancing system: no need to duplicate components for parallel packs (reduces complexity; fewer points of failure)

I guess you can have fewer total BMS components if you monitor 4P groups instead of individual cells, but that loses you the individual cell granularity. See above on complexity.

3 hours ago, RagingGrandpa said:

Avoids module-into-parallel-module discharge: Low voltage in one module (short, cell failure, etc) will not discharge the other modules. Which avoids the problem of a good pack dumping its energy into a failing pack. 

I talked about in an earlier post. I think this has drawbacks. Assuming the problematic pack doesn't disconnect entirely, shutting off the wheel instead of inducing tiltback and getting you to stop with more parallel packs to fall back on, the bad pack will just continue to be discharged into a presumably even worse state. And it creates problems mixing old and new packs.

Edited April 25, 2022 by chanman

[mike_bike_kite]

I love my Nik+ but I'm still not convinced by a 134V Begode EUC. They still don't seem to know why their 100V battery packs randomly catch fire. Trusting them to design a 134V 2400Wh pack seems a bit foolhardy to me. 

[RagingGrandpa]

2 hours ago, chanman said:

Some additional work is required to get 4x8s packs in series balanced. In series, one pack can't just decide to stop accepting current or accept less current without shutting off the flow to the other packs.

Bear in mind the 'baseline' charge-stop method that most EUC's have today. 
There is no single group of cells that "stops accepting current." 
Instead, today, all cell groups are monitored for an overvoltage threshold, individually.
If any cell group exceeds the (4.25V) safety threshold, all charging is stopped. 

That old approach can work equally well with Master's modules, as it does with [Monster etc]. 
If any cell, anywhere, goes over 4.25V, charging stops for all cells.

(And in a hypothetical situation where the modules were at different SOC% before EUC assembly: it would be hard for a user to resolve, I agree... but discharging individual modules isn't something a normal user can practically do. So this initial voltage-matching becomes a challenge for the factory, not for us.) 

2 hours ago, chanman said:

if you monitor 4P groups instead of individual cells, that loses individual cell granularity.

But the thing we monitor is voltage. And it's forced to be equal for each 4P. 
So, Master will monitor the voltage at every cell quite confidently.

Master likely isn't "bluetooth BMS," so the user will not get to know the cell voltage values, which is disappointing in the same way Gotways always have been. Maybe some day...

2 hours ago, chanman said:

[about single-module battery failures]
the bad pack will just continue to be discharged into a presumably even worse state.
And it creates problems mixing old and new packs.

But I think it's the same situation we have today with 100V Gotways. 
If one parallel group in one pack becomes damaged, and the wheel continues to be ridden, it is forced to continue operating and continue damaging itself. 

  

1 hour ago, mike_bike_kite said:

They still don't seem to know why their 100V battery packs randomly catch fire. Trusting them to design a 134V 2400Wh pack seems a bit foolhardy to me. 

Never trust an EUC!  
Instead: learn and prepare.  

 

Edited April 25, 2022 by RagingGrandpa

[chanman]

21 minutes ago, RagingGrandpa said:

But the thing we monitor is voltage. And it's forced to be equal for each 4P. 

True, but will there be communication if a cell in a 4P group fails or is disconnected? Voltage might read the same until we start discharging and see lower voltages on the failed group.

Charging by applying the 32S voltage to the packs in series still seems problematic to me, I don't see how it can balance the pack voltages, which will vary from slight differences in the pack capacity and resistance. The current flowing between the parallel modules is actually a natural way of doing this. Again, separate charging circuit with parallel 8S voltage makes sense to me, but not sure if that is what is implemented in the master.

[Miko.cz]

Maybe I missed something - how is the user notified that something is wrong if system shutdowns (?) to prevent damage? there is no parallel power source that can supply system and signalize error, while disconnecting only the faulty pack.

[RagingGrandpa]

20 minutes ago, chanman said:

Charging by applying the 32S voltage to the packs in series still seems problematic to me

Sometimes diagrams help...
I would recharge all 3 of these examples by simply applying charging current to the output, and don't really mind where in the circuit the plastic enclosures appear.

7 minutes ago, Miko.cz said:

Maybe I missed something - how is the user notified that something is wrong

The same way as today's 100V Gotways: unable to recharge.

[chanman]

I think you're missing that the plastic enclosures in your diagram also come with a BMS that balances the cells and that the cells aren't necessarily identical, so the configuration does matter. *To be clear I'm not referring to different cell types being used, but small differences due to manufacturing tolerances between the same cells, age, wear, any number of factors. My diagram skills aren't up to par, but lets take an extreme difference here. Say cells in enclosure 1 have a significantly lower capacity than the ones in enclosure 2 but similar resistance.

Charging:
A: The voltages in module 1 start to rise significantly faster than module 2. The flow of current changes accordingly, eventually we end up with the modules balanced.

B: Individual cell balancing so we should be able to be smart and get everything to 4.2V nicely.

C: Both module 1 and module 2 see the same current. Module 1 quickly becomes at full charge while module 2 is not. Still way below charging voltage so current is still flowing. Module 1 needs to protect itself from overcharging. If the difference is much smaller, we could end up with some funny final voltages without overvoltage protection kicking in, say 4.23V and 4.17V respectively.
 

Discharging:

A: module 1 discharges faster, more current starts to be drawn from module 2 to balance this.

B: BMS magic keeps things nice hopefully.

C: Both packs must output the same current. Module 1 reaches low state of charge quickly while module 2 is still going. The controller sees a lowish overall voltage but not enough to enforce tiltback. The resistance in module 1 starts to increase as it reaches low state of charge and sags harder. Controller still demanding lots of current. Undervoltage protections trip and the circuit is open.
 

With different resistance values it also gets sketchy, namely with the difference in voltage drop across module 1 and 2 in C configuration, effectively giving the two modules different charging voltages.
 

Edited April 25, 2022 by chanman

[EMA]

we should have a wheel and check the top circuit with a tester...

[mrelwood]

 

7 hours ago, supercurio said:

It brings us back to the same questions:

1. Does the Master BMS monitor individual cell group voltage during riding
2. Are all the 4 packs BMS connectes to the mainboard to send alerts, trigger tiltback if any of the cell group goes too low.

That's the questions I would personally want to see answered before buying.

Me too, definitely. In addition, I'm kind of waiting that someone will disassemble the board far enough to be able to see at least a glimpse of the battery connections. And maybe even trace a small part of the schematic.

 

5 hours ago, Rawnei said:

The battery connectors have 3 cables though, couldn't the middle white one be a data cable?

It could, sure. I do wonder though that why would a cost conscious company like BG use a much more expensive thick cabling for data connection, when such connections have traditionally been made with much thinner cabling. Not a notable cost difference for a single wheel, but they plan to sell thousands of them. That's a lot of cable.

 

2 hours ago, chanman said:

Undervoltage protections trip and the circuit is open.

So far there haven't been any cell group undervoltage protections in EUCs. I don't think that the BG Master would be the first one to implement them. The only undervoltage protection currently present is for the total pack/wheel voltage.

2 hours ago, chanman said:

With different resistance values it also gets sketchy, namely with the difference in voltage drop across module 1 and 2 in C configuration, effectively giving the two modules different charging voltages.

This is a great point!

[supercurio]

Yes @chanman so far, the system that will balance the 4 packs in series has not been identified yet.

But it has to exist otherwise it'll eventually end up with something like:

• pack 1: 34V (4.25)
• pack 2: 34V (4.25)
• pack 3: 32.4V (7x4.25, 1 damaged cell group at 2.65)
• pack 4: 34V (4.25)

The catch with this one is that the charge stops at 134.4V as expected, but the user has no idea that there's a dead cell group in the middle which might get drained to 0V while riding and catch fire later.
 

Or just drifting apart until it one cell group reaches 4.25 and the whole thing stops charging like, with who knows which voltage during discharge.

• pack 1: 33.65V (7x4.2, 1x4.25)
• pack 2: 33.60V
• pack 3: 33.20V
• pack4: 32V

Total 132.45V instead of 134.4V, just because one cell group has higher capacity than others?

Edited April 25, 2022 by supercurio

[BlckRck2014]

Anyone know if we can fit a shinko 244 in the master?

[TantasStarke]

1 hour ago, BlckRck2014 said:

Anyone know if we can fit a shinko 244 in the master?

I think Chance said he was gonna put one on

[alcatraz]

Are you guys talking about a cell internally shorting while riding? I don't believe that would send a rider to the ground unless a fire breaks out.

The wheel would lose 1/32 ~ 3% of the voltage.

As opposed to an 84v wheel losing 1/20 = 5% of the voltage.

On Inmotion the control board won't turn on if a group is under 3v. On Begode there has previously (to my knowledge) not been any such communication between the battery and the board.

It means that if you have a cell group below 2.5v you can still turn the wheel on. I think this is a source of some fires. By riding wheels with groups below 2.5v. Fast charging them while braking, sending them to 0v while accelerating.

That's why it's important to ensure max voltage is reachable on the charger. You can't completely trust the voltage readout as it might not be calibrated but at least write down the value every few months and ensure you can reach the same value as when you first took ownership.

[Tawpie]

8 hours ago, RagingGrandpa said:

Sometimes diagrams help...

My arithmetic wants to stack all 4 blobs in series? Or am I being too literal since you mentioned the plastic boxes don’t count.

Edited April 26, 2022 by Tawpie

[goatman]

might be, its easier and cheaper to ship smaller battery packs, no Dangerous goods. i think, has to do with how many wh's in the pack for airplanes

 Grin Technologies was building ligo packs so you can take them on a plane.

heres their listing if want to research it for yourself

https://ebikes.ca/shop/electric-bicycle-parts/batteries/ligo-bundle-order.html

[Forwardnbak]

not sure what happened here maybe took a good crash? looks like it did from the mud where it cracked. 

Saw these on EUC.org Fbook 

[Rawnei]

6 hours ago, mrelwood said:

It could, sure. I do wonder though that why would a cost conscious company like BG use a much more expensive thick cabling for data connection, when such connections have traditionally been made with much thinner cabling. Not a notable cost difference for a single wheel, but they plan to sell thousands of them. That's a lot of cable.

Maybe they just bought them ready-made in bulk like that? What else could the third cable be for?

[Tawpie]

3 hours ago, alcatraz said:

Are you guys talking about a cell internally shorting while riding?

This would be no bueno no matter the configuration... but an internal short should open circuit the cell (built-in safety), so maybe it wouldn't go boom. When a cell open circuits, it depends a little bit on how they've setup the parallel arrangement. If they paralleled 4 cells into a group, then stacked 8 groups in series, an open circuited cell will stress its three neighbors because the group's three survivors will still try to supply a full group's current. If they stack 8 cells in series as a group, then include 4 groups, an open circuited cell in one of the groups will reduce you to a 3p arrangement in that module. Not great, but worse things have happened.

Edited April 26, 2022 by Tawpie

[Tawpie]

30 minutes ago, Forwardnbak said:

not sure what happened here maybe took a good crash? looks like it did from the mud where it cracked.

In the e-rides teardown, when Kevin took the rubber top/seat/rainhat off there was 3M release liner in that area... they didn't actually use the tape. Might have helped? Maybe not, but it'll help now. "Includes parts needed for quick field repair".

I can understand why the factory didn't tape down the rainhat though, if it was taped to the side you might tear the rubber getting it off. And since you seem to have to remove the batteries to get the protective plastic stuff off the back, you're probably going to want to take the top off. "Some disassembly may be required to complete initial setup".

All easy enough to deal with, it's good to see BG hasn't completely lost their sense of history and tradition.

Edited April 26, 2022 by Tawpie