Broken MCM5 V2 BMS - Begode Unable to Honor Warranty

[cegli]

Looking to see if anyone has any advice to get Begode to actually honor their warranty.  I bought an MCM5 V2 new ~June 2022 from Aliexpress.  It worked for 4 months, until it refused to charge.  Plugging it in results in it charging for 1 second, then the charger starts flashing green/red/green/red.  Wheel works fine, except it won't charge.

Taking it apart, I see the battery voltage is fine on both packs (73.1v).  The ground voltage on the BMS lead of the small pack is way off though at 25.1v instead of 0v.

This was connected to larger battery pack's ground lead, which is at 0v as expected.  This is/was pretty concerning.

I tried charging just the small pack with the bad BMS voltage, and it refuses to charge.  I tried charging just the big pack, and it charged to 84.2v, but then charger's over voltage protection kicked in and the charger started flashing (green/red/green/red) (!!).  Scary once again, so I rode the wheel for a bit get the voltage back down, and the wheel is sitting unused.

Looks like both BMSs are fried, because the small pack fed 24V into the ground of the large pack that now doesn't seem to provide voltage protection.

I contacted the aliexpress seller, and they told me that Begode doesn't have the batteries in stock anymore.  They've been saying that Begode will eventually get them in stock and send them to me for 3 months now, with no progress.  My wheel worked for about 4 months, and now has been dead for about 4 months... with no end in sight.

I looked at buying 2 new BMS's but they're quite a bit of money and it would take a lot of soldering, etc.  Anyone have any idea how I can get Begode to honor their warranty?

It seems like a bad idea to buy a Begode wheel, if they can't even provide parts for a 4 month old wheel.  It becomes trash as soon as it the first thing breaks on it, if you can't source any replacement parts.

Anyone have any advice?

[Chriull]

7 hours ago, cegli said:

Looking to see if anyone has any advice to get Begode to actually honor their warranty

Begode has no responsibility for any warranty against you - they are in no way your contractual partner. Everything they do would be their free and voluntary decision - a gift to you.

Afaik Begode have themselves no aliexpress shop?

That's an unfortunate situation if one buy's via aliexpress. You imported the wheel from china and so everything is your responsibility. Any promises the aliexpress vendor made could be legaly enforced in china ;(

One can only name and shame or take the things as they (unfortunately) are - one buys (hopefully) cheaper from alierpess and if it does not work out it's a calculated loss one is ready to take.

BMS/batteries could be checked by some electricion/e-bike service center? Although BMS used in wheels have some additional features - like a wire to syncronize the packs.

With google search and search terms like:

site:forum.electricunicycle.org bms gotway

site:forum.electricunicycle.org bms begode

you'll find some additional detailed information.

[alcatraz]

If you can't file some sort of claim with the seller then try to speak to Begode but try a different attitude. Having to go around the seller will put you in a requesting position other than entitled. Try asking of what can be done and if they can help to provide replacements at reduced cost. 

Another way around this problem is to go third party bms. It's a lot of work, but the end result could be better than original. The cost could be as little as 50usd for the unit itself, with bluetooth and some cabling. It assumes the cells are ok.

[Cerbera]

9 hours ago, cegli said:

It seems like a bad idea to buy a Begode wheel, if they can't even provide parts for a 4 month old wheel. 

Partly yes. But also it is a bad idea to buy this stuff off AliExpress - there are many many posts before that show the horrible problems people get when stuff goes wrong.

I do sympathize of course, and hope you get it sorted out eventually, but my Begode dealer has been able to source replacements for all the dodgy parts my Master needed, and has sent them all to me free of charge, sometimes without me having to ask. It's like the polar opposite of what you get on AliXpress. So it is not, in itself a bad idea to buy a Begode wheel, but you do have to get it from the right people, who understand the problems, ride the machines themselves, and have a constantly open channel to the manufacturer, who is motivated to help them because they want that dealer's next order.  I think AliXpress are just too big and diverse in what they sell to care as much.

But if you can approach Begode independently, with a polite and deferential tone, I have seen examples before where they have been extraordinarily helpful when they are of a mind to be so ! Of course I have also seen them just say no, and shut conversations down, and that's the end of that, so YMMV ! Genuinely, best of luck...but being nice can only help...

Edited February 24, 2023 by Cerbera

[alcatraz]

Warranty or not, they want to help their customers.

I sent them a burned board, out of warranty, and they made a serious attempt to repair it, changing several components and after being unable to fix it they sent it back to me for just the shipping cost. 

So my point is. Warranty or not, expect some support. But help a little to bridge the costs etc. The only way to not have to do this is to buy from domestic sellers which will bring initial cost way up.

Most aliexpress purchases are without problems. Sadly you had some bad luck. Personally I'd still keep using the cheaper platform but put some of the savings into repair costs etc. 

[cegli]

12 hours ago, Cerbera said:

Partly yes. But also it is a bad idea to buy this stuff off AliExpress - there are many many posts before that show the horrible problems people get when stuff goes wrong.

This doesn't really seem like an Aliexpress problem, this is a Begode problem.  The vendor is unable to get batteries from Begode, because they haven't kept stock around.  All vendors that don't manufacture their own batteries would have the same problem (basically most vendors outside of ewheels).

12 hours ago, Cerbera said:

I do sympathize of course, and hope you get it sorted out eventually, but my Begode dealer has been able to source replacements for all the dodgy parts my Master needed, and has sent them all to me free of charge, sometimes without me having to ask. It's like the polar opposite of what you get on AliXpress. So it is not, in itself a bad idea to buy a Begode wheel, but you do have to get it from the right people, who understand the problems, ride the machines themselves, and have a constantly open channel to the manufacturer, who is motivated to help them because they want that dealer's next order.  I think AliXpress are just too big and diverse in what they sell to care as much.

If the above experience extends to future models, this is only because the Master is still in production.  If Begode stops providing parts for the Master when they stop manufacturing it, your vendor would no longer be able to source parts.  Thus a dead Master board or battery in 18 months might mean a useless Master.

12 hours ago, alcatraz said:

So my point is. Warranty or not, expect some support. But help a little to bridge the costs etc. The only way to not have to do this is to buy from domestic sellers which will bring initial cost way up.

Most aliexpress purchases are without problems. Sadly you had some bad luck. Personally I'd still keep using the cheaper platform but put some of the savings into repair costs etc. 

This is a "they don't have replacement batteries at any cost" problem.  There's no option to give them some money to help cover shipping, etc.  Begode is apparently telling the vendor they will eventually make more, but they've been saying that for months with no progress.

15 hours ago, Chriull said:

Begode has no responsibility for any warranty against you - they are in no way your contractual partner. Everything they do would be their free and voluntary decision - a gift to you.

Yes, I haven't been talking with Begode.  Just the vendor.  Begode is violating their promise to the vendor, which seems to be the issue.

I think my best option at this point is to open up the battery packs and see what's going on with the BMSs.  Generic BMSs won't work as drop in replacements, because there is communication between the two packs.  Worst case, perhaps I can build a 21700 pack upgrade myself, but what a pain.

[Cerbera]

6 hours ago, cegli said:

If Begode stops providing parts for the Master when they stop manufacturing it, your vendor would no longer be able to source parts.  Thus a dead Master board or battery in 18 months might mean a useless Master.

Not necessarily. Most dealers buy a certain number of spare parts (and especially mainboards) along with their orders of the wheels themselves, which they keep to service their own customers' who will have problems. Where parts can't be sourced from Begode, responsible dealers like Speedyfeet in the UK for example are already looking at where else they can get (for example) the suspension brace bar that can warp and crack manufactured locally and to a higher quality. THAT sort of thing is difference between them and AliXp.

[Chriull]

7 hours ago, cegli said:

This doesn't really seem like an Aliexpress problem, this is a Begode problem.  The vendor is unable to get batteries from Begode, because they haven't kept stock around.  All vendors that don't manufacture their own batteries would have the same problem (basically most vendors outside of ewheels).

Seems the vendors did not make a "service/parts availability contract" with begode - which would cost extra 

So this could be an aliexpress vendor problem, not begode's too. Like some western vendors keep their own stock, as begode does not guarantee anything in this direction to their business customers.

7 hours ago, cegli said:

This is a "they don't have replacement batteries at any cost" problem.  There's no option to give them some money to help cover shipping, etc.  Begode is apparently telling the vendor they will eventually make more, but they've been saying that for months with no progress.

Begode is the manufacturer and not responsible for all this stuff.

On the other side the vendor has a contract with you and an open promise he broke or is about to break!

I'm not aware of business practices in china, but i'd not expecting vendors as business partners getting any guarantees from manufacturers comparable to western standard consumer rights.

7 hours ago, cegli said:

Yes, I haven't been talking with Begode.  Just the vendor.  Begode is violating their promise to the vendor, which seems to be the issue.

That's an interesting assumption.

I'd be careful to believe and publish such a statement of a vendor who breaks or is about to break his own promise he guaranteed you...

Likely the vendors just bought the wheels "as is". Once there are problems with the customers they'll talk to keep up customer satisfaction somehow. Legally they are not obliged to too much and they can open a new store if things go too wrong.

[cegli]

If that's really the way things work in the EUC world, it's a terribly inefficient system.

Imagine if cars, motorcycles, mountain bikes, etc worked like that.  Every single dealership/store in the world would have to keep a supply of every part for every vehicle in local stock forever, or else you'd not be able to fix it.  It couldn't possibly scale.  Hopefully that changes, or most EUCs are destined to be garbage in not too long.

No local dealer is going to make their own clones of boards + FW.  It's probably not legal to do that, even if they wanted to.  Plus the effort involved...

Even cheapo Aliexpress scooters I've gotten don't work like that.  The manufacturer keeps stock of parts of older models, and I buy and install them when needed.

[Chriull]

On 2/26/2023 at 1:04 AM, cegli said:

f that's really the way things work in the EUC world, it's a terribly inefficient system.

Imagine if cars, motorcycles, mountain bikes, etc worked like that.  Every single dealership/store in the world would have to keep a supply of every part for every vehicle in local stock forever, or else you'd not be able to fix it.  It couldn't possibly scale.  Hopefully that changes, or most EUCs are destined to be garbage in not too long.

As EUCs are legally in many states/counties in some gray area (forbidden/ignored/...).

Chance to injure oneself is given and legal responsibility is at least questionable - in many countries the importer/reseller is likely succesfully sued. So not many dare to take money in their hand...

And buying from aliexpress is a very own topic for itself. ;(

 

EUCs exist in a legal gray area in many states/counties, which means that their status may be forbidden or just ignored.

There is a risk of injury associated with using EUCs, and the legal responsibility for any resulting harm is at least questionable. Importers and resellers may be successfully sued in many countries, so few are willing to take the risk.

Purchasing EUCs from AliExpress is a separate issue altogether.

[alcatraz]

Don't despair. It's a fantastic wheel. Try to sort it out.

Begode is great in one way and that's that they don't require you to use their own proprietary bms. 

You know those wheel fires? You can install a smart bms and have a wheel safer than 90% of all wheels out there.

[cegli]

I cut open the smallest battery shrink wrap over the weekend to get a look at what might be wrong:

If you zoom in, you can see that the B4 and B15 tabs are both broken.  There's a lack of strain relief on many of these tabs, and only shrink wrap holds the battery halves together, so any flexing or vibration could allow them to break.

Some advice if you are cutting off the shrink wrap to work on these yourself:  Cut very carefully on the side that does not have the BMS, between the cells.  You can tell which side is which by looking for the MOSFETs in the lower left.  They're visible through the shrink wrap.

These tabs are not used for charging/discharge, but are used for balancing and measuring over charge and over discharge.  Thus they are "low current" tabs.  I splinted the B4 tab with solid copper wire on either side, then soldered the whole thing back down.  B15 was near the top of the battery, so it was easier to access and I soldered a piece of 14 gauge wire from the pad and a long length down the tab.

After that, the voltage on the "C-" port was 0V again, instead of 25.1V, which was a good sign.  I took the opportunity to check for cell balance.  The max drift was fairly small, but then again, I was in the "flat" portion of the discharge curve (~3.7v).

At this point, I unhooked the bigger battery, plugged this one in, and tried to charge it.  The battery now charges, which is one step forward.  As the charge got to the top, one of the cells hit 4.25v before the others reached full voltage, and the OC functionality kicked in, which is good.  I measured the difference in cell voltage, and could see they varied by about 0.12v max, now that we're out of the flat region.

I waited for the row of resistors to kick in to do top balancing by discharging the cells above 4.20v, but nothing happened.  I tried with charger plugged in, not plugged in, etc.  It doesn't work at all, and there's a good chance it never really worked given the difference in the cells that has built up over only 500km of riding.  I tried probing the resistor network, etc, but there's conformal coating over them, so it's not easy to peak at the circuit and see what's going on.

----

At this point, I've lost the little faith I had in Begode's BMS circuits for top-balancing, so I had to decide what to do with this wheel.  I ended up going with this solution:

JK Li-Ion Battery Balancer (Active Equalization) 2A 24s - https://www.aliexpress.com/item/4000151477995.html
JK Li-Ion Battery Balancer Adapter Board - Same link above
XH 2.54mm 10P 30cm Cables (QTY: 4) - https://www.aliexpress.com/item/32996835431.html
Shrink Wrap (1 Meter Blue 18650 Lipo Battery PVC Heat Shrink Tube Pack) (QTY: 3) - https://www.aliexpress.com/item/1005004612057938.html
^Widths 165mm, 228mm, 285mm.  These three widths should hopefully work for a double wrap of each battery, from each orientation.

I'm going to solder two of the 10p cables to each battery, one pin to each of the B-, B1, B2, ..., B18, B19, B+ leads.  This will give me balancing leads on each battery.  From there, the end of the cable can be plugged into the battery balancer whenever I'd like to balance the batteries.  This will also allow me to monitor the cell voltage of each of the cells through bluetooth when I'm doing this process.

The shrink wrap is to seal up the batteries after I'm done with them.  The balancing lead will stick out of the battery shrink wrap, like the main power cable.

I'm not sure if the other battery has the same balancing problem, but I don't trust it either, so I'm going to do this to both of them.  The most annoying part will be taking off the side to balance them every now and then, but I can't think of another method that isn't a serious pain.

----

As another note, I manually balanced this battery for now using about 20 1/4 watt 70 ohm resistors in a breadboard in parallel.  I used a multimeter probe to check for each cells at load voltage of 4.05v, which seemed to work pretty well.  I thought perhaps getting the voltages closer together might trigger the top balancing, but no luck.

[cegli]

The balancing leads and balancer came today.  Some things I learned:

--You actually need 21 leads for a 20s battery (oops).  So I should have gotten an 11p and 10p harness instead of two 10p.
--The XH 2.54mm 10P 39cm Cables linked above already come in a 10 pack, so ordering 4 bundles of them was also unnecessary (double oops).

Still worked out!  Here's a picture of it soldered, before I taped everything up.  I ended up using a 10pin + 6pin + 5pin harness due to my mistake. 

They plug into this adapter board, when I want to balance the battery.  The red wires go to the balancer.  The plugs left in it are to block off the pins I don't want to use, so I don't accidentally short anything.

The balancer worked well, and put every cell within 0.004v fairly quickly.  I'm still waiting on the shrink wrap.  Once it's here, I'll wrap up this battery and then cut open the other one.  I'll post pictures of that one as well.

[cegli]

Some other interesting things I've found about this version of the MCM5 v2...

Mine has a little board below the mainboard, that obviously looks like an afterthought:

Only one screw is connected, because they didn't plan for it to be there originally.  I couldn't find any information on it.

It has 4 MOSFETs on it with the following part number (IRF135S203).  Doing some reverse engineering, it looks like it was made to stop the batteries from dumping voltage/current into the motherboard when the batteries are first connected.  B- is connected to the "source", P- to the "drain" and B+ goes to the "gate" with some resistors or something in-between.  When the battery is first connected, the MCM5 won't turn on, because the voltage between P- and B+ is very small.  If you probe it, you can see the voltage slowly building, until after about a minute it gets up to battery voltage and then stays steady.

This circuit caused me some momentary panic.  I had the batteries unhooked for a while, and then I plugged one back in.  I was a little suspicious there was no spark, so I tried to turn on the MCM5 and nothing happened.  After reverse engineering this, I now know you just have to wait a bit.  Once the circuit gets to ~70V, then everything works as expected.  It also looks like this circuit could be bypassed entirely, but I'm guessing it's a nice thing to have.

[cegli]

More battery fix updates.  I've opened up and wired balancing leads to the big battery now:

^Side 1
 

^Side 2 (With balancing lead)

Whole battery with balancing lead:

^There it is balancing.  This battery was also pretty out of balance:

Post balancing:

I'm quite unimpressed with the build quality of this wheel:

--BMSs barely work and don't seem to balance properly.
--There were a few missing screws inside on the trolley handle (seems they just forgot them).
--One of the battery braces was broken because they tried to bend it around the MOSFETs on the BMS.  Doubt that was good for the MOSFETs either!
--The bottom trolley handle plastic retaining bit is broken, due to them not being sized quite right for the metal it's retaining.
--No spare parts to buy on a wheel that was still selling less than a year ago.
--Came with random little bits of plastic bouncing around in it when I first got it.  They were junk from assembly that they didn't bother to remove.

This wheel only has about 500km on it and was only ridden for a few months!  Just waiting now for the shrink-wrap, and I'll give a final report on whether we're all back in action.  I'm also curious to see how often the batteries go out of balance.  Not looking forward to having to open it up every time I need to balance it, but not sure how else to do it!