Is something wrong with my BMS?

How-Tos & Esk8 mechanics Esk8 Mechanics
#1

Hi :wave:

My bluetooth 14S BMS is reading 0.1V (screenshot attached) for each cell of my battery pack while charging.
If I unplug the charger, I got 3.3V reading.

I don’t know if I did something wrong or if my BMS has a defect.

The battery pack is a 14s3p made of Samsung 30Q.
BMS is used in a charge-only configuration (diagram attached) for a Onewheel battery mod.

App: Xiaoxiang BMS (iOS)
BMS: https://www.lithiumbatterypcb.com/product/13s-48v-li-ion-battery-pcb-board-54-6v-lithium-bms-with-60a-discharge-current-for-electric-motorcycle-and-e-scooter-protection-2-2-3-2-2-2-2-2/?attribute_specification-selection=14S+li-ion+30A

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Thanks for your help :+1:

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#2

Are you sure your balance connector is pluged all the way? I have the xiaoxiang 12s BMS and my BMS won’t charge or let me do anything unless both of the temperature sensors show adequate temps. Your sensors are unplulugged as they show -30. Do you always have that? Mine won’t work with unplugged

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#3

The balance connector is plugged well.
I only have one temperature sensor, so even if I plug it, I’ll have the other one temperature as -30.

When you unplug the temp sensors, it won’t let you charge, but does it mess with the volt readings ?

#4

You need both temp sensors in

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#5

No the volt readings should be ok, it just won’t let me charge. Unplug the balance connector and replug it back in. You can hack the battery into several pieces and any reamining connected would still show voltage in the app. Even without + and - pluged into the bms it shows most voltages so it is either some software error or connector badly plugged… or a broken BMS.

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#6

Ok, I’ll try to find a new temperature sensor and test it again. Thanks :wink:

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#7

The sensor shouldn;t be the problem why it’s not showing the voltage, just try replugging the balance connecotr that goes to the BMS. To be sure, check the - connection from battery to BMS that it is not torn off. I don’t think it should kill all the voltages but to make sure…

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#8

I’ve tried replugging the balance connector, I got the same result.
I’ll try to check if it’s cut off, I have to reopen everything so I can’t do that right now.

I made a short video of what happened in the app when I plug the charger, and unplung it:

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#9

I figured what was wrong. B- and C- were switched, diagram is correct, I just messed up while soldering it, sorry … :frowning:

About the temperature sensor, I configure the BMS to allow -40°. Now it’s charging ok.

Thank you for your help ! :smiley:

#10

hehe, nice you figured it out, glad to help :slight_smile:

#11

What setting exactly do you change, so that the temperature sensors are not needed?

#12

@Schtekarsten knows this :face_with_monocle:

1 Like
#13

Sensorless

#14

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Check ntc 1 & 2
Min values to -90 or similar