Bought used (12Kw Stealth Bomber w 72v 48ah batt)

overal the bike rode really well at first.... I never use the pedals ecept for show when riding on streets just for plain observatory purposes knowing I should be riding a 750w bike not a 12,000w one.When I ride I stick to under 30mph but open it up where its appropriate... Which is where i got into trouble mechanically.At first I changed a few options so that my left thumb pushes to number (1) on the display-- top speed 12mph .It would climb or say walk up any steap hill offroad as long as the tires would bite in. Then thumb pushing the botton to (2) would be 30mph, (3) 48mph, (4) 60mph, (5) to skeered ... untill one day but when i pushed the bike on that half mile stretch then everything cut out ..That day i got some excersice pedaling,as getting home was only option.
The next day I dissconnected the battery and reconnected as basic BMS reset instructed and that worked!!!


but.....
some things have not worked right since...
So I grab a drink and sit and read hundreds of posts all night even till morning. Not knowing how to offer any ideas yet I am overwhelmed at how much craftsmanship so many take time improving and reinventing the wheel in an area thats so new frontier , where information is at best scarce,coming from China and factories that where technical product information is lost somewhere between the spokesperson they hire to answer phones, emails, a Department or customer service relations whom speaks english somewhat but it is impossible for their engineers to teach the ones hired to answer deep technical questions about of the products they sell to America.
I am truely impressed with the knowledge everyone here has aquired regaurdless to the handicap of missing technical specs from China ! And warming to see evryone helping each other here.. whereas then i now come in and hvae nothing to offer...
andf ,only more questions to ask

some things have not worked right since...

Click to expand...

So you reset the BMS and it fixed most of the problems but some still linger.

What are those problems?

Do Steath Bomber bought bikes have fuses ? another thing is the MQCON bluetooth reads after connection (Lack Voltage) all the menues read zero

Sounds like you need to unplug the bluetooth module cable connector

it seems the inverter was the culprit,maybe why the mqcon app showed ( lack voltage ) .On the new inverter Of the 3 wires that come out of the inverter 48v-96v to 12vdc . black neg -ground; +red input; yellow output dc12v . The old inverter had two black wires , a red wire, and a yellow wire.Of the two black wires one is a ground . The other black wire is the problem. because i dont know where or what its function is!
I had a maddog icebear scooter, in Nevada you stil need a drivers Lic. to operate one ,anyways the ticket was written up as 50 in a 35mph and driving on suspended Lic. Been using the scooter for 4 years untill now i needed a new ride. Fines are steep here.
On ebay I kept seeing these ebike but for way more than I ever would of imagine paying for one or would of ever had the $$$ to do so. Still unaware of how much Hub sized differant powers and batteries make all the differance in the world too.
I scouted all major cities in the US . and missed out on a two bikes each with 32 fet 72v 48ah 12,000 hubs both for $4700 but hadnt the cash yet so lost out on that deal- but still looking more , but than here came the stimulus check, i thought ok i will fine a bike, use it to get groceries,and get around and pay off my fine.
So i finally bought my dream bike. it seem like the frame was pitched into all fast off road on road bike the same design.anyways , hiccups i see are a normal thing for electic bikes and nothing is ever 100% reliable without maintence but even then the road of inncodence is still wide open , glass on the road , a car pulling out in front suddenly, and talk about strange bad luck , I'm riding and a bee flew in under my sunglasses and couldnt fly away as the wind pressure kept the glasses pressed to my face...Sucker stung me in the cheek.... Ok my problem getting back to focus on the part of my bike i think is damaged is the inverter, the headlight doesnt work and the controller says ,lack voltage, and if the inverter is the reason,than happy rides again!!
The converter i bought on ebay is smaller in wattage and had 3 wires to it , red , yellow , black with a connector, the bike old one has two black wires and the red, and yellow as well--- i need to know the purpose of the other black wire... Red is input positive voltage, yellow is converted voltage output and black wire being the common ground.
Thats were i'm at so far, hey and good luck to all your builds , and stay aware , stay safe!! I never did pay off my Fine,lol !!

Completly unaware of power requirements an ebike requirers, to get moving. I was wise though on the throttle first tmes to ease on the power . Then eventually whatever the bike had to offerpower wise, I enjoyed confidently at the approriate moments, but since the laws are quite clear on the legal limits of wattage ,and being the bike is just that a bicycle lmfao ,,i do best to not demonstrate its speed ,and i was never intentionall going go thrashing off roads , but that one is what cause my electical problem now, plus the bike settings and full throttle , cause the bike to just quite ,i am 240lbs and was an asphalt uphill climb was just trying to catch up to that harley, so , there was my first glimse at electric speed. i was impressed . 70mph in my mind was my limit, but learned it takes much amperage which i wasnt watching.
After bms reset , the controller app was stuck on "lack voltage" ,and i thought ok i have parameters set improperly .
All in all it was a blown inverter , the voltage regulator that feeds power to the turn signals, lamp , tail light, horn ,.etc and to the controller too!
Now we wait for parts.....
One other thing, is the display TFT 750c quite, and not sure why at the time so i opened the case checked around nothing loosened, no i fiddled with the button battery and in doing so bent the soldering thats fastens it to the board - so that fiasco project is going on too..

You said you live in Nevada where where were they bother to ticket you. Vegas Reno ?
Let us know how this works out.

Oh the ticket ,yes I turned onto Vegas Dr Las Vegas 89128 riding a 50cc maddog scooter .about a mile and the lights came on. Impounded my scooter too, officer wouldnt trust me to push it home 3 blocks .Impound fee =$280
The lesson learned here might be "never stop observing , use mirrors constantly

Hi guys!

First post on this forum.

I'm borrowing this thread because I have similar bike with similar problem. This is 12kW noname chinese enduro with 72v 48Ah battery.

I bought the bike used a few weeks ago. I'm from Finland, it's quite cold here. I bought spiked wheels (4mm spikes!) so I could drive forest routes during winter. But so far not so good!

The trouble is, BMS is shutting down if I use full throttle. I have to do BMS reset, either by connecting the charger, or unplugging the big battery connector. This is super annoying if you are far away from home because then obviously you can't use charger, so it takes some time to disassemble the side panel and unplug the battery.. Is there an easier way to reset the BMS?

I have to lower the power all the way to 2kW to allow full throttle, and still I don't feel very "safe" about it. It's not fun to drive if you a afraid that the bike might stall at any moment.

I'm pretty sure it is caused by cold weather. It works much better if I keep the bike in warm garage overnight, but even then it detoriates very quickly as the battery gets colder. I guess the power draw is not enough to keep the temperature up.

Even with 2kW power, I see quite big voltage sag. Even with full battery it can drop to 65V, then rises back to >80V when releasing the throttle. Must be dropping much lower with 12kW! So I guess it hits some low voltage limit on the BMS.

Now the questions.. I know BMS is internal to the battery. Has anyone disassembled the battery, how easy it is to access the BMS? Is there any way to adjust or disable the limits? Does it have separate FETs for charge and discharge? In that case it would be possible to bypass the discharge side, and rely on similar limits on the Sabvoton controller..

Zuikkis said:

Now the questions.. I know BMS is internal to the battery. Has anyone disassembled the battery, how easy it is to access the BMS? Is there any way to adjust or disable the limits? Does it have separate FETs for charge and discharge? In that case it would be possible to bypass the discharge side, and rely on similar limits on the Sabvoton controller..

Click to expand...

BMS is protecting as designed, and not safely adjusted/bypassed.

Best to configure LVC in your controller so it trips first, before the BMS LVC, so you don't have such trouble resetting the BMS.

Zuikkis said:

I bought the bike used a few weeks ago. I'm from Finland, it's quite cold here.
<snip>
BMS is shutting down if I use full throttle.
<snip>
Even with 2kW power, I see quite big voltage sag.

Click to expand...

So yes, the cold, and probably the battery's age (especially if it's years old), mean teh cells cannot handle the current required without great voltage sag.

The fix for the cold is to add easily-removable but airtight insulation to the battery case, to preserve the heat that is in the battery before you ride, so air doesn't carry it away. Needs to be removable so that you can take it off when it's in a warm area to get the heat into it, but put it back on easily when you then go ride.

Next fix for the cold is to add heating to the battery, but unless you have a separate battery to run that, it takes power from the battery to run the heating (not a lot, but you don't have much now anyway), and it sounds like you need to heat it while riding as well as a preheat, so it takes power away from riding to heat it. If you build in temperature-controlled heating that you can keep running all the time without risk of overheating the battery, then you don't need to be able to remove the insulation, which greatly simplifies the insulation process (which is also needed for the built in heating).


The fix for the age is to replace the battery itself. (or at least, all of the cells).

It is possible it's not *all* of the cells...it could just be one or a few bad groups of parallel cells. You can test this by measuring the voltages on each group while riding (or with an equivalent test load). The ones that sag lower on a ride are worse than the others. If they are all about the same then the whole pack is just old and needs to be replaced, or it's just plain so cold there that that's how it is going to operate unless you add heating to keep it warm.

Some chemistries are more susceptible to the cold...if this is a LiFePO4 pack, for instance, it may sag a lot more in teh cold (depending on the specific cells used) than some of the LiCo or NMC types.

Now the questions.. I know BMS is internal to the battery. Has anyone disassembled the battery, how easy it is to access the BMS? Is there any way to adjust or disable the limits? Does it have separate FETs for charge and discharge? In that case it would be possible to bypass the discharge side, and rely on similar limits on the Sabvoton controller..

Click to expand...

You do NOT want to do this. You could damage the battery in a way that may result in a fire, at an unpredictable time (usually while charging, but could be just while sitting there, someday, randomly, whne you're not there to do antyhing about it, or when you're asleep, etc). While the chance of fire from the damage is small, the result is overwhelmingly catastrophic when it does happen, and is not worth the risk.

The BMS is your last-ditch protection for the battery, and will generally already be set to the worst-case-allowable limits, before reaching overdischarge and cell-damage.

The controller, if you set it to similar limits, will do exactly the same thing the BMS does already, and stop you from damaging the battery by shutting you down. If you set it to even lower limits, (while bypassing the BMS) then you are probably actively damaging the cells. Even if it never catches fire from one of the several possible failure modes or cell-damages, it will age the pack even faster and further than it already is, and you'll have to buy a new battery that much sooner anyway.

If you instead do this:

fatty said:

Best to configure LVC in your controller so it trips first, before the BMS LVC, so you don't have such trouble resetting the BMS.

Click to expand...

then you'll be safer (though the problem will happen with even less power application, making the bike even harder to ride without keeping a tame hand on the throttle).




If you live in a house by yourself, then it's your choice. If you live in a place where other people will be affected by the fire that can happen from the cell damage from overdischarge, etc., then please don't bypass the protection that helps prevent this.

fatty said:

BMS is protecting as designed, and not safely adjusted/bypassed.

Best to configure LVC in your controller so it trips first, before the BMS LVC, so you don't have such trouble resetting the BMS.

Click to expand...

You are probably right. I have ordered the USB cable and Bluetooth dongle for the Sabvoton, but they haven't arrived yet.. So I have no idea what settings there are.

The bike has CA3. Now that you mentioned LVC, I see there is also LVC setting in CA3 setup. I could try that for starters!

It seems the BMS protection kicks in most often if there is very sudden change in power draw. For example if rear wheel suddenly digs through packed snow and reaches good grip on the ground below --> instant power loss..

amberwolf said:

If you live in a house by yourself, then it's your choice. If you live in a place where other people will be affected by the fire that can happen from the cell damage from overdischarge, etc., then please don't bypass the protection that helps prevent this.

Click to expand...

Thanks for you long response!

Just to clarify things, the bike is almost new, although I bought it used. It has only been driven 30km. According to CA3 statistics, it had never been charged by the previous owner!

Anyway, the problem is not battery overdischarging. After BMS reset, voltage raises back to 82-83V, that is, it's still almost a full pack.

It is 72V Li-Ion, 20S pack..

I wasn't going to remove the protections "completely", I just would like to have softer limit. It's ok to limit power if voltage gets too low, but it's not OK to shutdown completely requiring disassembling half the bike to make it go again.

I just checked CA3 settings, it currently has LVC of 60V.. That is probably lower than the setting in BMS. I'll try what happens if I raise it to 65V for example.

Zuikkis said:

Anyway, the problem is not battery overdischarging. After BMS reset, voltage raises back to 82-83V, that is, it's still almost a full pack.

It is 72V Li-Ion, 20S pack..

I wasn't going to remove the protections "completely", I just would like to have softer limit. It's ok to limit power if voltage gets too low, but it's not OK to shutdown completely requiring disassembling half the bike to make it go again.

I just checked CA3 settings, it currently has LVC of 60V.. That is probably lower than the setting in BMS. I'll try what happens if I raise it to 65V for example.

Click to expand...

She meant that if you bypassed the BMS, then overdischarge and cell damage could occur in any scenario, not just the LVC you describe here.

It seems you are considering the BMS to be the "problem" here, but the BMS LVC still tripping on a lighter 2kW load indicates that may not be the case. Still, raise CA and controller LVC to trip before BMS, then re-evaluate.

I suspect BMS is operating as desired and intended. Pack may be cheap Chinese cells that respond poorly to low temperature.

Zuikkis said:

Just to clarify things, the bike is almost new, although I bought it used. It has only been driven 30km. According to CA3 statistics, it had never been charged by the previous owner

Click to expand...

Or that stat was reset. (but probably not). Do you know how low or high the battery was at when you got it, and how long it had been that way?

FWIW, many (possibly most?) of these "generic" clones have pretty bad quality batteries, many of which don't even match the specs the bike was sold as having. You could be lucky and have a much better pack, but it doesn't sound like it especially if the bike really is that new.

Some of the packs are even made of literal garbage cells, recycled from scrapped batteries, and so are not actually new batteries, even though the battery / bike might have been sold as new to it's first owner (and the place that sold the bike wouldn't necessarily even know this, as they probably don't bulid their own batteries, but rather buy them from the cheapest source they can).

They may even be reshrinkwrapped to look like "brand name" cells, and sometimes the really impressive cheap cell places install new endcaps under the shrinkwrap (that are NOT welded to the cell, just held on with the SW, so they have a much higher resistance causing higher voltage sag under load!) so that you can't see the broken off spotwelds where they took the cells out of the old dead packs they came from.

There are some good battery builders out there...just not as many as there are bad ones, making it more likely, especially due to the cost differences, that there's a bad one in there than a good.

So...I would still give the same recommendations, in the same order: insulation, heating, pack testing/replacment (with a good quality well-built pack, which is going to be expensive for something to handle the power levels you want out of it...not what some seller *claims* it can do, but what it can *actually* do...if the pack costs way less than another claiming the same thing, it's a good bet the cheap one is not really capable...the one that's more expensive may not be either, but it has more of a chance than one that is "too good to be true").

The battery is the heart of the entire system. If it can't supply the current needed without significant voltage sag, then the system can't get the power to do what it's designed to do. (or at least, what it's ad copy says it can do :lol: ).

So a good battery is the first best thing to make sure any EV has. If it's not good enough, it doesnt' matter what else the system has, it can't do what you want it to.

Anyway, the problem is not battery overdischarging. After BMS reset, voltage raises back to 82-83V, that is, it's still almost a full pack.

Click to expand...

It may not be overdischarging as far as capacity...but it *is* as far as voltage during the event is concerned--it's dropping low enough to reach the completley discharged cell-level LVC in the BMS to cause the BMS to shut off, right?

So the effect on the cell can be similar. (depends on the specific cell, etc)

And if you bypass the BMS, then the problem will *be* overdischarging because you then have no protection or warning of any cell groups going too low. Knowing the whole pack voltage only helps if you know *for sure* that all groups are the same voltage, which is not typical with these sorts of packs.

It is 72V Li-Ion, 20S pack..

Click to expand...

Do you know how many "P" it is? Or what actual cell brand and model it claims to have? (this info is not usually available, and not always real if it is available, so no worries if not.) The number of parallel cells directly affects how much current it can provide without as much voltage sag.

I wasn't going to remove the protections "completely", I just would like to have softer limit. It's ok to limit power if voltage gets too low, but it's not OK to shutdown completely requiring disassembling half the bike to make it go again.

Click to expand...

That I can definitely understand.

Zuikkis said:

I just checked CA3 settings, it currently has LVC of 60V.. That is probably lower than the setting in BMS. I'll try what happens if I raise it to 65V for example.

Click to expand...

60v is about 3v/cell for a 20s pack. It's unlikely the BMS has a *higher* LVC than that--usually those are down around 2.8v or even less, though some are higher, or programmable.

So the most likely thing is that there are cell groups in the pack that are dropping below LVC because they are not as capable as other cells in the pack. The cold doesn't help.

Sometimes just leaving the pack on the charger for as much time as is possible while you can watch it (just in case something goes wrong) will rebalance a pack like that so that it works "better" for a while, at least...but if it's in that state already at new condition, it's only going to get worse over time.

amberwolf said:

Or that stat was reset. (but probably not). Do you know how low or high the battery was at when you got it, and how long it had been that way?

Click to expand...

Oh, battery was almost full, over 80V.

The battery has very good capacity at least. I rode the bike for like 2 hours in harsh conditions with the 2kW setting (which works without cutting), and it still showed about 80V idle voltage... Only issue is the voltage sagging.

It may not be overdischarging as far as capacity...but it *is* as far as voltage during the event is concerned--it's dropping low enough to reach the completley discharged cell-level LVC in the BMS to cause the BMS to shut off, right?

Click to expand...

But surely there is a big difference in voltage under load, and idle voltage. It's a bit odd to use same LVC level without taking current into account?

Do you know how many "P" it is? Or what actual cell brand and model it claims to have? (this info is not usually available, and not always real if it is available, so no worries if not.) The number of parallel cells directly affects how much current it can provide without as much voltage sag.

Click to expand...

No idea. It's this bike:
https://www.aliexpress.com/item/32971912560.html

No mention on the battery brand. The battery is very big and heavy. It looks like it's made from 18650 cells, and by outside dimensions it could easily have 200-300 cells.. Hmm, the claimed 48Ah hints perhaps at 16P 3000mAh?

60v is about 3v/cell for a 20s pack. It's unlikely the BMS has a *higher* LVC than that--usually those are down around 2.8v or even less, though some are higher, or programmable.

Click to expand...

Cycle Analyst has a "gain" setting for LVC:

[ Batt->LoVGain ]
The feedback gain setting for the low voltage rollback. A higher number results in the power scaling back more abruptly when voltage falls below the VltCutoff.

It's possible voltage drop happens so quickly that CA3 does not react quickly enough? I'll try increasing that too.

As I said earlier, the cutoff usually happens when there is a really quick change in power, if there is a quick change of grip for example. These kind of things don't really happen in the summer where grip is more constant, so that combined with the cold weather makes it even worse.

I just was on 1 hour test drive, full power enabled and no BMS cuts!

I simply set the LVC in CA3 to 64V, no other changes. Works perfectly.

Full throttle acceleration on road the voltage is steady about 68-70V, and power is not limited.

I only saw lower voltages in the special cases where there's lots of snow and rear wheel is spinning wildly and suddenly gets grip and bike jolts forwards.. These are the cases that break gasoline motorcycles too, too much sudden momentum.

But now with 64V limit it did not BMS fault at those situations, which is great.

Thanks for your help on this!