Connecting BMS to 4x 4s Li-poly batteries

[whitep]

Hi All,

I am connecting 4x 4S batteries in series to make 16S. I have a 16S BMS I am connecting up and have a couple of questions. Bear with me....

The balancing wires on the batteries have 5 wires as you would expect and I assume are wired up P-NP-NP-NP-N to the 4 cells.

To connect the 4 batteries up I need to connect it P-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-N making 17 wires by connecting the red(+) from one battery and black(-) wire of the next together leaving a single red and black at the end?

Are the standard balancing wires connected to the power cables coming out of the batteries? If so the wiring diagrams for the BMS's I have seen around are a little wrong arent they? Because the Black wire that goes to the B- on the BMS board is connected to the main - power cable that goes to the Motor/Controller/Charger etc?

Any advice would be greatly appreciated.

Here is my efforts so far (I havent connected the red and black wires together yet.)

 

[Nobuo]

To connect the 4 batteries up I need to connect it P-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-NP-N making 17 wires by connecting the red(+) from one battery and black(-) wire of the next together leaving a single red and black at the end?

Yes, between each serial connection between 4s batteries, there are a "+" pin from one battery and "-" pin from the next battery that are connected together and goes to the same balancing wire on the BMS, because that counts as the same Bx+ balancing section.

BMS wires are always named as "B1+", "B2+", "B3+", etc. that, starting always from the main "B-" battery lead, "B1+" is the first series positive lead that connect with the second series negative lead. You can find 3 different ways of a BMS configuration wiring, that should be perfectly explained in a wiring diagram, or that you can predict just counting how many balancing wires are:

Imagine we have a 10s battery and a 10s BMS:

First type of configuration: the balancing plug has 9 wires

In this case there are 9 positive named connections in the wiring diagram to the balancing plug: "B1+", "B2+", "B3+", "B4+", "B5+", "B6+", "B7+", "B8+", "B9+".

The "B-" balancing connection that fits also with main "-" 10s battery lead comes separately because it is indeed the main negative lead wire from the battery to the BMS ("B-" named on the PCB that has or need a black thick wire from the battery)

The "B10+" balancing connection that fits also with main "+" 10s battery lead comes separately because it is indeed the main positive lead wire from the battery to the BMS ("B+" named on the PCB that has or need a red thick wire from the battery)

this type of configuration is not common, BMS's use to have only a "B-" main input connection from the battery.


Second type of configuration: the balancing plug has 10 wires

In this case there are 10 positive named connections in the wiring diagram to the balancing plug: "B1+", "B2+", "B3+", "B4+", "B5+", "B6+", "B7+", "B8+", "B9+", "B10+".

The "B-" balancing connection that fits also with main "-" 10s battery lead comes separately because it is indeed the main negative lead wire from the battery to the BMS ("B-" named on the PCB that has or need a black thick wire from the battery)

The "B10+" balancing connection it is only a balancing connector on the main balancing plug, so all the positive main connections for discharge port and charge port comes directly from the battery main positive lead to the main discharge connector (a thick red wire) and to the main charge connector (usually thinner wire to stand around 5A max continuous charge) The board has no B+ hole to connect from the battery, if it has the hole it is not needed to use in this case.


Third type of configuration: the balancing plug has 11 wires

In this case there are 10 positive named connections in the wiring diagram to the balancing plug and the negative: "B- / B1-", "B1+", "B2+", "B3+", "B4+", "B5+", "B6+", "B7+", "B8+", "B9+", "B10+".

The "B-" balancing connection that fits also with main "-" 10s battery is connected indeed together with the main negative lead wire from the battery to the BMS ("B-" named on the PCB that has or need a black thick wire from the battery)

The "B10+" balancing connection it is only a balancing connector on the main balancing plug, so all the positive main connections for discharge port and charge port comes directly from the battery main positive lead to the main discharge connector (a thick red wire) and to the main charge connector (usually thinner wire to stand around 5A max continuous charge) The board has no B+ hole to connect from the battery, if it has the hole it is not needed to use in this case.

This last configuration boards are useful when you only need to balance the paralleled groups of a battery and all the protections and limitations are installed separately from the BMS. So you can do it directly from the balancing plug

Are the standard balancing wires connected to the power cables coming out of the batteries? If so the wiring diagrams for the BMS's I have seen around are a little wrong arent they? Because the Black wire that goes to the B- on the BMS board is connected to the main - power cable that goes to the Motor/Controller/Charger etc?

Yes. the main black discharge wire from the first 4s battery goes to "B-" on the PCB, and the black balancing wire of this 4s goes to the BMS balancing plug if it has 17 wires, if the plug has 16 or 15 pins, there is not need to be connected, because the main "B-" on the PCB act as the "B-" main balancing negative

 

[wesnewell]

Different bms's handle the balance wires differently, so it depends. Yours appears to only have 16 connections, so it draws either the +,-, or both from the main leads at the end. Without knowing which, there's no way top know for sure. Typically, to turn 4 4s balance wires into 1 16s balance connection, you take the red + wire from low end pack and connect it to the first neg. wire of the next pack and so on.

 

[whitep]

Thanks Guys, My balancing plug to the BMS has 16 wires. Also you have confirmed what my limited knowledge was telling me. If you see a bright flash on the horizon, I have done something wrong later today......

 

[d8veh]

Don't make any assumtions about the BMS multi-pin connector. Some use the main negative pack wire as ground, and the pins are for each balance wire. Some use pin one as ground and the last cell voltage is taken from the cell-pack positive. Some do both of those. That means for a 12S BMS, you could have 15, 16 or 17 pins on the multi-pin connector, and if it's 16 pins, there's two different ways it could be wired.

If a schematic came with your BMS, you can use it, but be aware that often they don't relate to the BMS actually supplied. If it's a good BMS, it'll be properly marked. B- for cell-pack negative, B1 for cell 1, B2 for cell2, .......,B+ for cell-pack positive. If it's not marked, use a meter to see if pin 1 is connected to B- and the highest pib connected to B+ (if present). Not all BMSs have a B+ connection.

 

[whitep]

Don't make any assumtions about the BMS multi-pin connector. Some use the main negative pack wire as ground, and the pins are for each balance wire. Some use pin one as ground and the last cell voltage is taken from the cell-pack positive. Some do both of those. That means for a 12S BMS, you could have 15, 16 or 17 pins on the multi-pin connector, and if it's 16 pins, there's two different ways it could be wired.

If a schematic came with your BMS, you can use it, but be aware that often they don't relate to the BMS actually supplied. If it's a good BMS, it'll be properly marked. B- for cell-pack negative, B1 for cell 1, B2 for cell2, .......,B+ for cell-pack positive. If it's not marked, use a meter to see if pin 1 is connected to B- and the highest pib connected to B+ (if present). Not all BMSs have a B+ connection.

The BMS has B- and P- and no B+. I assume the battery packs first Balancing wire is connected to the main positive power wire, therefore this will be connected to the load/charger +.

I do have instructions with the BMS, but its written in Chinglish. I am confident I understand it all well enough now.

I have the reds and blacks soldered together accordingly and the spare black connected to B- now, so all I need o tdo is connect the p- to the charger/load-

 

[d8veh]

Like I said, don't assume. Check it with a meter.

 

[whitep]

Like I said, don't assume. Check it with a meter.

Right I have waved a meter at it and r-soldered the big - wite to the BMS board and put a new big - wire to the main connector from the BMS. SO all I need now is the heatshrink to fit it all together.