E-Scooter battery not charging.

[unimatrix93]

Dear forum,

I have succesfully repaired a Ninebot Kickscooter E2 control unit, which had a burned MOSFET on it. (Thank you sam_sam_sam )

Now after replacing the faulty component, the scooter turns on and working as should but I noticed, that when I plug in the charger, the charging animation shows on the display, but it actually won't charge the battery.

After dissassmbling the battery, I found out that I can charge the battery trough the discharge plug (the big yellow one) If I connect it to my PSU. But I cannot charge it when I connect the PSU to the charging wires.

What could cause this issue?

[stj]

it could be protection,
check the voltage of each cell-bank - they should match or be very close.
also it probably wont charge if the cell voltage is too low.
unfortunatly "too low" seems to be a bit vague - some stuff thinks 3.5v and some will charge at 2.5 or even 2v

[unimatrix93]

it could be protection,
check the voltage of each cell-bank - they should match or be very close.
also it probably wont charge if the cell voltage is too low.
unfortunatly "too low" seems to be a bit vague - some stuff thinks 3.5v and some will charge at 2.5 or even 2v

Should I try first charge it to 100% with my PSU?

[stj]

not till you check the cell voltages

[unimatrix93]

not till you check the cell voltages

Allright, will check each bank tomorrow and report back. Thank you!

[unimatrix93]

not till you check the cell voltages

So the battery charge is at 16% now according to the display.
I disassembled the battery pack, the output plug has 15V on it.

Here is the top and bottom side of the battery pack:


How should I measure these banks to get the correct values?

[stj]

you have access to all the battery tabs so just meter the 6 groups of 4 cells and see if they match or are close to each other
now lets talk numbers.
it has 6 groups so 6x 4.2v is 25.2v fully charged.
15v divided by 6 meaans you have 2.5v per cell right now - witch is potentially below the safety threshold of the protection board.
if they all match then forcing them upto 18-20v will probably get it working on the original charger again.

[sam_sam_sam]

Be careful jumping the voltage up to high if your current is more than one amp going to the battery some BMS boards do not like this situation and will either turn on and go right back off or just refuse to charge now you can bypass the BMS board but if you do this only charge it up so that each has reached 3.00 and no higher than one amp and by all means keep an eye on the temperature of the battery cells if they start getting warm stop bypassing the BMS board and only use the battery charger that is for the battery pack

[unimatrix93]

Be careful jumping the voltage up to high if your current is more than one amp going to the battery some BMS boards do not like this situation and will either turn on and go right back off or just refuse to charge now you can bypass the BMS board but if you do this only charge it up so that each has reached 3.00 and no higher than one amp and by all means keep an eye on the temperature of the battery cells if they start getting warm stop bypassing the BMS board and only use the battery charger that is for the battery pack

The battery charger rated output amper is 1.5A. That measn I can safely charge the battery pack with 1.5A trough the discharge plugs. no? Or should I use 1A just to be sure.

The battery packs current voltage is 14V.
I measured the tabs in the following order:
B+ - B5 = 3.5V
B4 - B3 = 3.5V
B2 - B1 = 3.4V
B- - B1 = 0.0V

Based on this I assume B1 is dead, which causes the pack to become inbalanced so the BMS disables charging.
What do you guys think?

[kevingill]

That would only make 10.4v, so you must have missed out a couple of legs of cells.

You've only shown 4.

Report B- to B1, B1 to B2, B2 to B3, B3 to B4, B4 to B5, B5 to B+

[unimatrix93]

That would only make 10.4v, so you must have missed out a couple of legs of cells.

You've only shown 4.

Report B- to B1, B1 to B2, B2 to B3, B3 to B4, B4 to B5, B5 to B+

You are right!

B- to B1 = 0v
B1 to B2 = 3.4v
B2 to B3 = 0.4v
B3 to B4 = 3.5v
B4 to B5 = 3.3v
B5 to B+= 3.5v

[sam_sam_sam]

You are right!

B- to B1 = 0v
B1 to B2 = 3.4v
B2 to B3 = 0.4v
B3 to B4 = 3.5v
B4 to B5 = 3.3v
B5 to B+= 3.5v

Do not attempt to recharge this battery pack until you resolve the issue with B- to B1 and B2 to B3

It is very possible that the battery cells have an issue with self discharging sin drum and if this is the case it would be better just to replace all battery cells with brand name new ones or barley used ones

Here is how you can determine if you have the self discharge sin drum let the battery pack sit for 30 days and see if the voltage between the different battery cell rails right now you have a difference of 0.3 volts if it has discharge sin drum this difference will get bigger than what you see now

It is not a very good idea to just replace the battery that have no voltage or very little voltage with new ones

Now with that said you can use battery cells that are used BUT make sure that you test each battery cell for milliamperes hour and try to match them as close as possible you can for best results the brand and series is also important but milliamperes hours of each battery cell is more important than not matching them as close as possible

For best results if I were fixing this battery pack I would replace all the battery cells with brand new or barley used battery cells that are brand name battery cells

For best results you should test each battery cell to know what the actual milliamperes hours are because if they are more than 50 milliamperes some BMS protection boards do not charge and discharge battery cells unevenly unless they have a balancing function incorporated in the BMS so this is where you have to do the balancing the battery cells as close as possible for best results

Even if the BMS protection board has a balancing function it still important to balance the battery cells as close as possible for the best possible performance so the balancing function does not have to work harder to get the battery cells balanced

[unimatrix93]

Do not attempt to recharge this battery pack until you resolve the issue with B- to B1 and B2 to B3

It is very possible that the battery cells have an issue with self discharging sin drum and if this is the case it would be better just to replace all battery cells with brand name new ones or barley used ones

Here is how you can determine if you have the self discharge sin drum let the battery pack sit for 30 days and see if the voltage between the different battery cell rails right now you have a difference of 0.3 volts if it has discharge sin drum this difference will get bigger than what you see now

It is not a very good idea to just replace the battery that have no voltage or very little voltage with new ones

Now with that said you can use battery cells that are used BUT make sure that you test each battery cell for milliamperes hour and try to match them as close as possible you can for best results the brand and series is also important but milliamperes hours of each battery cell is more important than not matching them as close as possible

For best results if I were fixing this battery pack I would replace all the battery cells with brand new or barley used battery cells that are brand name battery cells

For best results you should test each battery cell to know what the actual milliamperes hours are because if they are more than 50 milliamperes some BMS protection boards do not charge and discharge battery cells unevenly unless they have a balancing function incorporated in the BMS so this is where you have to do the balancing the battery cells as close as possible for best results

Even if the BMS protection board has a balancing function it still important to balance the battery cells as close as possible for the best possible performance so the balancing function does not have to work harder to get the battery cells balanced

I see,
I just want to restore the recharge function of the battery. I don't mind if it's not a 100% fix, since I already spent so much time and money on it.

So I should proceed and replace the batteries between B- and B1 and B2 and B3.
The orignial batteries are GP brand inr18650/26l 2550mAh. I only have significantly smaller cells like 1850mAh sadly.
I checked around and I found some Tenpower INR18650-26ME 2600mAh cells from a reputable webshop.

can I use these to replace the dead cells between B- - B1/B2-B3?

[sam_sam_sam]

It would better than not doing anything however just be aware of the fact that your running time will suffer somewhat because of doing it this way

If you are going to do it this way just have each group of battery cells basically have the same amount of voltage before you put the battery pack on the battery charger

[stj]

it's a high current device,
look the batteries up here and see how much current they can dump into the load.
https://secondlifestorage.com/index..../cell-database

[unimatrix93]

it's a high current device,
look the batteries up here and see how much current they can dump into the load.
https://secondlifestorage.com/index..../cell-database

I couldn't find the original cells in the database but I think I found them via google:
GP INR18650/26L Low cost battery cell - 18650, 21700, 26650, LiIon and LiFe

[unimatrix93]

It would better than not doing anything however just be aware of the fact that your running time will suffer somewhat because of doing it this way

If you are going to do it this way just have each group of battery cells basically have the same amount of voltage before you put the battery pack on the battery charger

Understood, and is it safe to disconnect the BMS from the cells? I mean it shouldn't lock itself by doing this right?

[unimatrix93]

Also, I think I must remove all the metal tabs from the BMS, since I cannot open up the plastic case. I removed every screw yet the two part wont seprate. I guess The tabs are holding it together.

[sam_sam_sam]

You more than likely will have to remove the battery tabbing to get to the battery cells that you need to replace anyway so that why I mention about just replacing all of them that are more or matched hopefully

[sam_sam_sam]

it's a high current device,
look the batteries up here and see how much current they can dump into the load.
https://secondlifestorage.com/index..../cell-database

Thanks for sharing this information saves me a lot of time looking them up