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Esperanto

Unicycle running with ninebot mini battery

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The battery of my unicycle died, so I decided to test it. It worked perfectly with Xiaomi's ninebot mini battery.

I'll test the range on the weekend. :)

 

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5 hours ago, Esperanto said:

The battery of my unicycle died, so I decided to test it. It worked perfectly with Xiaomi's ninebot mini battery.

Yes it would do, other than the fact that most EUC's, with the exception of Ninebot have a 16 cell 59.2 volt battery, the mini has a 15 cell 54V battery. So you will not do any harm to your EUC if it is designed for 16 cells but you might do some harm to yourself as you could find it running out of power to keep you upright at speed.

Providing you keep your speed down (or if your wheel has a very conservative top speed anyway) you may be OK but please be prepared for it to possibly suddenly try and face plant you. Alternately, if your wheel has good electronics it may simply decide the battery has got too low after a mile or two and just tilt back on you. Of course if the wheel is intended for 15 cells it will probably be fine.

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You're right, Keith. My unicycle is designed for 16 cells. In the first tests I felt less power than the original battery. I have not tested at high speeds yet, mainly because the battery is too heavy on the side and disrupts the balance - and also because I need personal protection equipment...

I'll fix it in the center of the wheel and try again. My unicycle certainly does not have good electronics, for the low price I paid for it, so I'll run slowly for now.

Edited by Esperanto

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my generic chinese EUC battery too died... it was purchased just a month ago.

i opened the battery pack. there was 16 cells in it.

I test each on voltage and each cells were found healthy, reads 3.7V plus or minus each.

on the multi tester it reads 67 something volts overall. 

but when this battery pack is connected back, it just powered my EUC for only 5 seconds and then turned off.

so I had to recharge maybe battery pack was just drained but charger always turned green all the time.

normally, charger will light RED upon charging and turned GREEN when full.

i borrowed the same battery pack from another EUC and connect it to it's board. it worked flawlessly.

so I suspect the BMS made this battery pack doomed. individual cells were found all healthy!

tear down time, battery pack was undressed again.

i bypassed all the connections with the BMS circuitry, cut off each individual cells to the BMS.

it turned out just a simple 16series battery pack.

Then i recharge it. the RED light on the charger glow! eureka moment!

i timed it and it was exactly 39minutes before the RED led turn into GREEN.

GREEN meaning the battery pack was fully charged.

connected it back with the EUC board and EUREKA... power!

check everything,

evening lights turned on brightly, bluetooth speaker sounds again, balancing effect on the wheel motor work.

this is it. it is rideable now. ride it until it drain. recharge again but this time it was short of 1 hour before the RED led turned GREEN.

redo this for 8 times cycle and it worked so well.

Conclusion: therefore the battery pack can work without the BMS.

 

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when a failed battery pack had its life back to work... maybe it can also work for your EUC.  after 3 weeks, someone had got interest in it and bought it after that.

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The BMS is there "just" for balancing the cells and for protections (like discharge short-circuit / overcurrent / overdischarge and charging overvoltage monitoring / reverse polarity protection). When the protections are not active during discharge, yes, it works just as a 16-cell battery with the BMS adding just a little bit of extra resistance (probably negligible in comparison to the total internal resistance of the cells themselves). Without the balancing mechanism, the cells can start to charge/discharge to different voltages over time, and an imbalance will occur. This can lead to some cells reaching too high voltage during charging or getting overdischarged during riding. Overcharged cells can catch fire or explode, overdischarged cells will age, lose capacity and drop the voltage faster and can even reverse their polarity. A large series battery pack with no BMS is a fire hazard, especially if there are no charging side protections. The typical reason for the hoverboard fires seems to have been caused by the cells overcharging (catching fire during charging), maybe they had bad BMSs?

Edited by esaj

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5 hours ago, vivzkice said:

Conclusion: therefore the battery pack can work without the BMS.

That is, not to put too fine a point on it, a bloody stupid conclusion! As @esaj points out above, the BMS is your battery's safety device, without some means of balancing the cells they will drift further and further out of balance until, one day - it might take weeks or months - either a cell will charge to over 4.3 volts and catch fire, that fire will quickly spread to the rest of the pack, or alternately one or more cells will discharge significantly below 3 volts and go permanently high resistance completely ruining the cell and pack. 

Either put a new BMS  on the pack or break up the pack and use its cells for something else, vaping, torches, whatever.

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1 minute ago, Keith said:

That is, not to put too fine a point on it, a bloody stupid conclusion! As @esaj points out above, the BMS is your battery's safety device, without some means of balancing the cells they will drift further and further out of balance until, one day - it might take weeks or months - either a cell will charge to over 4.3 volts and catch fire, that fire will quickly spread to the rest of the pack, or alternately one or more cells will discharge significantly below 3 volts and go permanently high resistance completely ruining the cell and pack. 

Either put a new BMS  on the pack or break up the pack and use its cells for something else, vaping, torches, whatever.

I concluded it can work without BMS... but I never said that battery pack can forever be reliably taken into consideration for good. how stupid people jump up saying into bloody stupid ending. the story is, there was a BAD BMS, since without yet the replacement BMS available in hand during the tear off, so better bypassed that bad BMS and a conclusion was made. 

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