Ninebot One S2 - Only one side charging?

[LDW]

I have a variant of the above problem.  The attached photos show the state of the two batteries after charging FULLY (they both say "100% charged).  The Voltage on both is relatively equal, but the Current and Wattage show the discrepancy.  The red arc on the third photo grows and shrinks, depending on the state of discharge, but never gets smaller than shown here.  The unit shows all Green lights when powered on, until it runs out of juice.  Then one side shows blinking red.  The time allowed to ride before the unit starts beeping and becomes unstable is pretty short--maybe 1.5 to 2 hours.  The unit is less than a year old.  

[Chriull]

1 hour ago, LDW said:

I have a variant of the above problem.  The attached photos show the state of the two batteries after charging FULLY (they both say "100% charged).  The Voltage on both is relatively equal, but the Current and Wattage show the discrepancy. 

Maybe battery 2 is disconnected (bms shut off for whatever reason) showing no current flowing?

Maybe also a connector problem?

Quote

 

 

Battery 1 has 6387 mAh of a total capacity of 2850 mAh left?

Edited November 20, 2017 by Chriull

[Knifa]

It sounds like you could have a dead/dying cell like me? I think remaining power is the same as how much mAh it put in during charging (e.g., my battery with the cell that's slightly larger capacity reads a little more than the other now).

I've had similar experiences with LiPo packs for drones with dead cells. It'll just continuously pump in power for ages trying to balance but it won't go anywhere or take forever.

I think only one battery (specifically battery 1) showing a current pull/wattage while stationary is normal. Mine does the same. See if you can get a look at it while riding it?

Edited November 20, 2017 by Knifa

[LDW]

>See if you can get a look at it while riding it?

Good idea; will try it.

[LDW]

>Battery 1 has 6387 mAh of a total capacity of 2850 mAh left?

Yeah--didn't even notice that!

[Actonpro]

On 2017. 11. 13. at 5:32 AM, Knifa said:

With this, we can get a look at the back of the BMS board. The chip on the back here is the actual BMS IC. It's a TI BQ7694003 (datasheet) which is a series of battery monitor ICs providing current monitoring, short circuit protection, low voltage protection, yada yada. The chip on the front of the BMS board is a STM 8L151K6T6 (datasheet) which is a basic 8-bit MCU, presumably doing comms with the main board and handling the BMS IC. There are also two MOSFETs (following the design from the BMS IC datasheet, I guess) one of which is 100V 40A (MDD1902) and the other was larger but I couldn't read the numbers off.

 

The large size IC's (STH15810) STripFET POWER MOSFET.  100V, 110A. It feature  is Gate(1), Source(2,3) Drain(TAB).

 

Have a nice repare and wheeling life..

 

datasheet_15810FET_ST.pdf

[Knifa]

36 minutes ago, Actonpro said:

 

datasheet_15810FET_ST.pdf

These same MOSFETs are used on the control board for driving the motor!

[Ogeezy8]

I received that same error yesterday on battery 1. My concern is that I'm not quite the electrical-hands-on kind of guy to do the kind of troubleshooting you were getting into. At the least, I'd like to remove the good battery and try charging the suspect battery on its own. Which side is battery 1? Left foot side or right foot side? 

[maxdiati]

On 11/12/2017 at 9:32 PM, Knifa said:

So today we replaced the cell and, again, it seems to work! I also got some more information on the BMS during this so see below for details.

We measured the suspect cell (1, bottom left). It read 3.4V, where the other cells were reading 3.8V. Definitely a damaged/failing as mentioned above --- so it was time for it to come out.

First step was to liberate the cells and boards from the casing. Thankfully, nothing is glued down and everything is screwed in place with nice holders, etc. There are a good few screws, all covered in silastic, however if you squeeze hard enough with a screw driver (philips), they will twist out. We also had to tear away the silastic around the XT60 and BMS comms cables. Once that's done, the whole thing just kinda lifts out.

With this, we can get a look at the back of the BMS board. The chip on the back here is the actual BMS IC. It's a TI BQ7694003 (datasheet) which is a series of battery monitor ICs providing current monitoring, short circuit protection, low voltage protection, yada yada. The chip on the front of the BMS board is a STM 8L151K6T6 (datasheet) which is a basic 8-bit MCU, presumably doing comms with the main board and handling the BMS IC. There are also two MOSFETs (following the design from the BMS IC datasheet, I guess) one of which is 100V 40A (MDD1902) and the other was larger but I couldn't read the numbers off.

Some interesting tidbits from the BMS IC:

• There's mention of a SHIP/NORMAL mode (low power for shipping vs. normal operation) and a button shown in the example circuit. Maybe this is what the button is for?
• The IC is capable of balancing using either its own internal drivers or externally (I guess a whole ton of external MOSFETs like a normal charger?). In this case, it looks like Ninebot have opted to use the internal drivers as there isn't really anything else on the board. Internal balancing is limited to 50mA which is gonna be hella slow --- is this what happens during trickle charging? Balancing is controlled by the host (the STM) rather than by the BMS IC

After that adventure, we ripped the dud cell out. We pried at the welding tabs with a stanley knife until it simply came free. There is enough room to get in there (at this edge cell, at least) however I'm not sure what it would be like trying to do it in the center. The plastic casing around the batteries is weirdly flexible so it makes it pretty nice to work with. At this point, the LED started blinking red (surprise!) which at least confirms it's not pulling all power from one cell. Pushing the tab back into the battery made it turn a happy green.

With the cell gone, it was time to put in our new cell. The new cell is a LG HG2 Series 3000mAh from Amazon directly, which fits the bill for this perfectly. As far as I could tell, the HG2 is the step up from the cells that are already in this. The chemistry is the same (INR) and it provides the same/higher constant discharge rates so all seems good. I should have really double checked the capacity at this point, to make sure it was legit and not a fake, but some visual checks (plus coming straight from Amazon) made me feel OK. If I was doing it again, I would double check.

I didn't get any pictures of the soldering process, unfortunately, but the gist is this:

1. We used a good temperature-controlled soldering station (Hakko 888D) with a very large tip, good solder (MG 63/47), and good flux (MG liquid something...). The iron was set to 450C.
2. The positive and negative sides of the battery were tinned with a reasonable dollop of solder, after applying a lot of flux. We double checked for heat at this point, and the battery didn't get hot at all.
3. With lots of flux on the tabs, the battery was placed in the plastic holdery-thing and held firmly in place. The positive end was soldered first (near the BMS board). My friend pushed the tab firmly towards the battery with a stick while I gave it a quick tap with the soldering iron.
4. Repeat above for the other end.  The battery had a warmth to it afterwards but not warm enough to count as "hot". The light started flashing green again, so seems like everything went together well.

 After this, we basically did everything in reverse. Everything back into the casing, screws all in, bit of hot glue to make up for the missing silastic. Nothing in particular to report here.

Once all back together and screwed into the Ninebot (on it's own, other battery disconnected), it all seemed to work OK! No shouting from the app, reporting around 60% capacity. I rode it around for a good bit, then to the store and back, and it seems to be dropping at a fairly reasonable rate. Battery temperature also reports reasonable temps, no huge voltage sag, etc.

So that's it! All seems to be in working order, for now. That said, a couple of things still to test:

• Run the battery to near empty, and charge it up again. Haven't tried charging it with this new cell yet.
• Test with the other battery installed. Do they drop in capacity at the same rate?
• Go through a couple of cycles, crack open the battery again and check cell voltages. Are they all within reasonable limits?

 

 

Hi there,

Thank you really much to Knifa for this topic, a great piece of work ! 

I'd like to repair a battery with a similar problem. Following the method, I just don't know how to remove properly the "welding tabs" which are really tight and I'm personnaly afraid to break them by following the same method with the knife... Does anyone have any advice or clue to make this step easier ?

Thank you in advance.

[null]

Thanks for sharing all your info @Knifa 

I am in the same operation (supposedly, dud pack, opened it) Just a small technical question: do you remember how you managed to measure the batteries that are not on the edges? The four accessible ones of my pack have different voltages, so I feel I should measure them all.. Thanks and sorry for the bother.

Edit: never mind, I found, using the opposite side bridges

For the general info in the thread: the case clips are where the bumps are, + one set on the sides.

Edited March 16, 2019 by Mimolette

[Knifa]

Good to hear you managed to measure it @Mimolette! Getting to some of them is pretty awkward without removing tape, etc.

I thought I'd say as well, I've been riding on these batteries every day for like a year since (hitting 1500km+) with no issues. Worse things have happened since then like dropping the entire unit in a huge puddle and having to replace MOSFETs but it's still going!

Edited March 17, 2019 by Knifa

[null]

Thanks for the comment @Knifa, and good to hear about the followup!
Mine had very different charge on all cells (everything between 4,2 and 3,6v), but no remarkably so, luckily a couple of overnight charges seems to have balanced them out. Sorry for tagging on your thread but as it was linked to measuring individual cells.

Cheers.

[Matahalii]

Nice little how-to here. I stopped by to hopefully get advice. My battries are somehow weak now. I can ride approx 15-18km with fully charged packs. In the app all is very even. No bigger discrepances between both packs. But where has capacity gone? I was able to ride 25km+ on one charge at minimum?

I Pulled the packs out at about 65% Charge (app) and measured the cells:

Pack 1:
long row: 3,80 3,81 3,80 3,81 3,79 3,87 3,86 3,87 3,87  3,86
short row: 3,88 3,87 3,88 3,88 3,88 (V)

Pack 2:
long row: 3,76 3,77 3,76 3,77 3,77 3,87 3,86 3,86 3,86 3,87
short row: 3,88 3,88 3,89 3,88 3,89 (V)

both read the same data via the app, but Pack 2 has more of the weaker cells, whilst in both packs the short row has the strongest cells.

No cell seams to be really odd.

Any suggestions?

[Giggi]

Hello for everybody that have this kind of problem there is this usefull tool that will show the single battery level only connecting with bluetooth https://mimod.ru/en_US/ninebattery/ it totally works on ninebot s2 I've tested it ! 

Also would be possible to change each cell of the pack with better capacity cell type of the same specs of the original to increase the capacity of the batteries? 

[anandsbisht]

On 11/8/2017 at 2:56 PM, Knifa said:

I think I fixed it!

Against better judgement, my friend and I took the battery apart.

There is one main board inside (the BMS, presumably) and a daughterboard that helps connect the two rows of batteries. There are 15x 18650 Li-on cells, at 4.2V when charged.

You might spy from the picture of the BMS board, that there is a hidden push button on there. My LED was originally flashing red (totally flat?). I pushed it once, and it turned solid green for a few moments, and then back to flashing red. A few moments later I tried holding it down, and it started blinking green, and then back to blinking red. Since then, the button does absolutely nothing. No idea what the LED codes mean, nor what this button is for.

We inspected the cells and found all to be fully charged (4.2V) bar one --- the very first cell in the bottom row, which was at 2.8V. Total speculation but, before the LED turned blinking red, it was previously solid green. We were wondering that, perhaps, the BMS is powered from the first cell on pack. Over time, maybe it's just really drawn out this battery?

Next step was to try and charge this low cell. We used a good charger (iSDT SC-608), and some patience, to poke at the two accessible battery tabs with a pair of multimeter probes.

As soon as the cell hit 3V, the LED instantly turned solid green again. After about 45 minutes of holding it like this (ouch) the cell charged up fully without any problems. No heat build up, even when charging at 3A.

After all this, we plugged it back into the Ninebot. No more complaints from the app or machine! Reports 100% charge from the battery. I ran it around a bit to see if the cell was dropping off too quickly, but it appears to be totally fine. Voltage drops in line with the other cells.

I suspect the cell may still be a bit goofed, but at the very least it looks like it's easy(ish) to replace.

Hi Dear...Please Confirm Which One Out Of 2 Chip ( Orange or Black ) Charges The Battery & Which One Goes Parallel To Motherboard To Operate The Wheel...Thanks..  

[Nehmet]

Hello everyone,
I write here because I have a similar issue to the one first described by @Knifa, however my wheel charges and seams to use both batteries.
The problem is that I manage 10Km when I'm lucky and the two batteries discharge at wildly different rates. For example after a few kilometers I would see: Battery1 al 86% and Battery2 at 54%.
Now, reading this thread i finally decided to have a look at the batteries and find out what the deal was.
The first thing I found was that Battery1 (left side) had a blinking green led while Battery2 (right side) had a solid green led and both batteries showed at 100% charge. I also tried to disconnect one battery at a time and the unit powers on and shows 100% charge on the single battery in both cases.

At this point I decided to go all in and open up Battery2 (the one the solid green led), and the inside exactly as described by Knifa. However, when I started mesuring the voltage on the single cells I found a strange situation: the 5 cells in the top row all had similar voltages (between 4.12 and 4.14 volts), the 5 cells on the left in the bottom row all had slightly higher voltages (between 4.24 and 4.28) lastly, the on the right side of the bottom row all 5 cells had lower voltages (all 5 between 3.64 and 3.66).

Another thing I noticed is that the little button on the BMS does absolutely nothing to the led which has stubbornly remained solid green through all of my attempts.

After that I connected only the foulty battery to the right side of theunit and powered it on, with the unit on I held down on the little button on the BMS and all the leds on the back side of the unit turned solid red (from solid green) while the bottom half of the leds on the front of the unit turned solid yellow (also from solid green). Doing the same action with the battery connected on the left side of the units turns all the back leds solid green while all the front ones turn off... Uh?

I left the wheel with only Battery2 to charge overnight (about 12h) and it started and ended with both the charger and the battery having solid green leds.
I disconnected the charger, closed up everything with only Battery2 connected inside the wheel and went outside for a 1,5Km ride.
Keeping the app open and my speed between 10 and 14Km/h I coud see the charge dropping steadily from 100% all the way to 71%. I came back inside without turning it off and kept checking the app with the unit on while leaning against a wall, thats when wierd things started to happen.

I'm unsure how to insert images in here but this is what the (old)app showed when I arrived home:

• Km left: 11Km
• Km traveled: 1,6Km
• Travel time: 27m 24s
• Charge left: 75%
• Energy: 2154mAh
• Status: Normal
• Tension: 58,2V
• Current: 0,08A
• Power: 4,66W
• Temperature: 26°C
• Capacity: 2850mAh

While in the new app things are slightly different and less detailed:

• Km left: 11,1Km
• Km traveled: 1,5Km
• Travel time: 27m 53s
• Charge left (in the overview): 81%
• Charge left (in battery details): 76%
• Tension: 58,21V
• Current: 0,08A
• Power: 4,66W
• Temperature: 26°C

So, I left the wheel on for a while and checked the apps again, surprise!

• Km left: 12,3Km
• Km traveled: 1,6Km
• Travel time: 39m 15s
• Charge left: 79%
• Energy: 2325mAh
• Status: Normal
• Tension: 58,4V
• Current: 0,08A
• Power: 5,21W
• Temperature: 26°C
• Capacity: 2850mAh

Now it has been sitting there idle for 1h 40m and the situation is:

• Km left: 2,1Km
• Km traveled: 1,6Km
• Travel time: 1h 41m
• Charge left: 21%
• Energy: 603mAh
• Status: Normal
• Tension: 58,2V
• Current: 0,09A
• Power: 5,19W
• Temperature: 25°C
• Capacity: 2850mAh

I turned it off and took it apart again and the battery led is flashing green... with this voltages: Total pack is 57,8V; the 5 cells in the top row are between 3,77 and 3,78; the 5 cells in the left bottom row are between 4,05 and 4,06: then we have from left to right: 3,57 - 3,57 - 3,56 - 3,34 - 3,51.

Now I put the battery back in the unit and connected the charger: solide red on the charger and blinking red on the battery. If I disconnect the charger the battery returns to blink green.
After less than a minute, the charger and then the battery become solid green. Disconnecting the charger and waiting a minute or two lets the battery return to blinking green. Rinse and repeat, I did it 5 times with the same result. After that I mesured again the voltages: Total pack is 58,9V; the 5 cells in the top row are between 4,06 and 3,78; the 5 cells in the left bottom row are at 4,13V; In the bottom right side 4 cells are at 3,63V while the second to last reads 3,49V.

Any Idea what's going on here?
I'm not as skilled in electronics as Knifa or others, I can easily find my way around a tester and a soldering iron but that's about it. I know jack about the actual components.

[UniCycler]

Hi guys, very interesting thread. Thanks for sharing all your information.

I´m a little bit concerned about the batteries of my NB One S2 which is 3 years old and has about 400km on the clock. I´ve learned EUC riding on this wheel and after that it wasn´t used very often because I bought another wheel. I only used it for training and short range trips. I never discharged it lower than 50% and got 12-15km out of this with a lot of stop and go driving. So I guess the capacity is in a normal range. But I´ve seen with the EUC World app that the imbalance of the battery packs is quite high (pack 1: 150mV and pack 2: 130mV)

The first 5 Cells of each pack are having quite low voltages and I´m wondering why the balancing doesn´t seem to work. I charged it a couple of times 1-2 hours longer then the charger indicated charging (during green light phase) because I thought that at the end of charging the balancing would begin but my experience is that even than no real balacing takes place and all cells are charged with 50mAh (trickle charge). I stopped this process when the highest cell was at 4.23V because I don´t think that more overcharging is good but it may be that the overvoltage cut off is set to higher values and only then the real balacing begins.

Does anyone know more about the balacing process of this BMS? When does balancing begin?

What was your highest cell voltage after overnight charging? 

Are there any other ways to bring the cells in a better balance?

Thanks!