11s bms wiring help

How-Tos & Esk8 mechanics Esk8 Mechanics
#1

alright, guys so I bought this bms from Litech and i am having some trouble figuring out the balance connectors on this bms. it’s baffled me and a few other experienced builders so I’m making a topic on it.

First, I had wired my 10 cells in normally so that cell 1 positive side connected here and so on.

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then b- to the pack negative and c- to charge port negative. and pack positive to charge port positive.

When I had it wired this way, the charge port voltage was different and the pack wouldn’t charge. the pack voltage was 38 and charge port voltage was showing 34 for some reason.

after talking to some people like @taz @DerelictRobot and @akhlut i moved up the cell one poostive balance wire to the pin where it says b1 on the pcb. like this

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Now the charge port voltage is the same as the pack voltage and it charges but there’s a suspicion that something still isn’t right.

I have checked for continuity between the first pin and b- and its a no go. @DerelictRobot pointed out that the first pin has a traces to a bleed resistor which would be weird for a b0 pin.

here is the data sheet for the bms which doesnt show a b0 pin on the wiring pin harness.

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any help would be greatly appreciated.

#2

To my understanding ,b0 is the same as B- so although there is b0 on pcb, as long as you have B- connected to Battery -, you don’t have to connect Battery- to b0.

In my mind here is how bms measures each battery.
Let bn = reading at bn and B- (multimeter red to bn and black to B-)
Bat 1 = b1
Bat 2 = b2 - b1
Bat 3 = b3 - b2
…
Bat 11 = b11 - b10

In the first case, you connected b0 to battery1+, which makes b1 = 0 but is supposed to be 4.2 if fully charged.

Simply put, b0 is the same as B-.

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#3

how do i know that, that is a b0 pin though? the first pin is not connected to b- and it doesnt say so on the data sheet.

#4

That I guess is just experience. I am not 100% sure either. Maybe try measuring b0 and b1 see if it is the voltage as battery 1?

#5

So, initially you had all the balance leads in the connector?

You said you had 10 cells in normally. Do you have 10S or 11S?

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#6

im running 11s. theres 11 connectors in the main balance lead which i had connected every wire in my first configuration. the bms also came with a 2s jst plug for the other 2 leads.

#7

Sorry, I misunderstood, I thought you said you had 10 cells wired normally.

Just wondering, if everything is working now what makes you suspicious that something isn’t right?

#8

i havent fully charged it yet. but @DerelictRobot pointed out that the first pin has a bleed resistor so it cant be “b0” it has to be b1. and he thinks the way i have it wired right now my 11th cell is in the 12th cell pin.

if you follow the traces on the resistors it leads to all kinds of confusion.

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#9

I agree it’s pretty confusing, but I like the way it’s wired now.

You have followed the schematic, with the exception of B11 appearing to go to B12, but as B11 doesn’t have a pad, and there is a spare pad to the right of B13, this just looks like a misprint on the pcb.

I’ve got a 10S Bestech BMS, which is split 8 and 2. You can see that B- isn’t used.

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