Battery Management System wiring

MakeLoveWork

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May 8, 2020
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Hello everyone,

before I am going to share my motorcycle conversion project in the future, I could need some help with the wiring so I wont burn my cells before things even started. :)

I got a two wire BMS with a B- and a C- pad. Honestly, I didn't find too much info about these.
Anyway, so I createdtwo diagram sketches, which show my attempts on the whole wiring.

Would be lovely if you guys could take a look at them and tell me, which ones shows the right BMS wiring and also, if the diagram itself looks like it should work. :)

Thank you very much in advance. Great to have a place like this. :)

Kind regards
Simon

[size=small]Sketch 1:[/size]

image_ylbdpm.jpg


[size=small]Sketch 2:[/size]
[size=small]image_pgykau.jpg[/size]

Additional information:The battery pack is 72V 75Ah; motor is 72V 8000W so... about 111A; the BMS is rated for 100A (200A peak); charger is 84V 5A
 

Redpacket

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Not an expert on these, but those diagrams don't look right to me?
Are they from the manufacturer?
Can you post links to where you bought them?

On the "controller" shouldn't the wires from the motor connect to motor - & motor +?
Linking motor + to motor - might be effectively shorting the controller? (first time you touch the throttle, the conntoller blows or overloads)

I'd be 95% sure the discharge connector XT90 -(minus) wire should connect to B- not the BMS C- terminal
Typically the C terminal is to disconnect the charger once the cells have reached cut-off voltage
 

MakeLoveWork

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Redpacket said:
Not an expert on these, but those diagrams don't look right to me?
Are they from the manufacturer?
Can you post links to where you bought them?

On the "controller" shouldn't the wires from the motor connect to motor - & motor +?
Linking motor + to motor - might be effectively shorting the controller? (first time you touch the throttle, the conntoller blows or overloads)

I'd be 95% sure the discharge connector XT90 -(minus) wire should connect to B- not the BMS C- terminal
Typically the C terminal is to disconnect the charger once the cells have reached cut-off voltage
I made these diagrams myself with the little kind of knowledge i gathered through the internet and from pictures of the controller for example. So it was more like a guessing game so far.
Thats why I asked, if someone could tell me, what I'd have to change about the diagram so it would work.

For the C- pad, I got the following picture, which said that C- was connected to the negative side of the charger and the negative load, if I understood correctly.
My BMS looks just a little different but I assume, that the functionality is still the same.


image_qqdzrt.jpg


For the controller/motor thing - I didnt mean to connect motor + and motor -
It is meant to show the 3 wire bundle going from the controller to the motor.

The second motor label on the top is for readings which will be displayed i guess.
 

daromer

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You need to look at the diagram from the supplier of the bms you bought. Not every bms is wired in the same way
 

MakeLoveWork

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daromer said:
You need to look at the diagram from the supplier of the bms you bought. Not every bms is wired in the same way
Okay. I tried to contact them before and dint get a response. I will try it again.
Unfortunately the package didn't even include a very basic explanation.

Thanks for the advice. I thought they were probably more or less the same.
 

OffGridInTheCity

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Looking at this - it strikes me that you don't typically hook both + and - (from the battery) to a BMS. The BMS power leads are on the - only... the idea is to interrupt the load if things are out of spec. Typically, one side of BMS hooks to - side of the battery and the other side of the BMS hooks to the - side of charger/load. In the original post, it looks like actual + is hooked to B+ - which will likely cause a short.

As suggested, manufacturer wiring diagram is a must.
 

MakeLoveWork

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OffGridInTheCity said:
Typically, one side of BMS hooks to - side of the battery and the other side of the BMS hooks to the - side of charger/load. In the original post, it looks like actual + is hooked to B+ - which will likely cause a short.
Isn't that basically, what the first diagram shows? Minus side of the charger is connected to C- on the BMS and B- on the BMS is connected to the minus side of the battery. I possibly just miss understood.

I messaged the BMS manufacturer for a diagram or at least an opinion on the diagrams I made. I hope to get a response on monday.

By "+ is hooked to B+" you mean that Charger + is connected to B+?
I've taken that information from eBikeSchool.com (Youtube). He hooked B+ to charger + and Discharge +. So all three wires soldered together.
 

OffGridInTheCity

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MakeLoveWork said:
Isn't that basically, what the first diagram shows? Minus side of the charger is connected to C- on the BMS and B- on the BMS is connected to the minus side of the battery.
My bad, I was misreading the diagram and focused on the LARGE B+ assuming the 'green' was the BMS rather than the battery - e.g.missed the small BMS square.
 

MakeLoveWork

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OffGridInTheCity said:
MakeLoveWork said:
Isn't that basically, what the first diagram shows? Minus side of the charger is connected to C- on the BMS and B- on the BMS is connected to the minus side of the battery.
My bad, I was misreading the diagram and focused on the LARGE B+ assuming the 'green' was the BMS rather than the battery - e.g.missed the small BMS square.
Yea, the green mess was meant to be the battery. Just a 2D of the 3D battery pack I modeled in CAD so I wouldnt fuck up the nickel strips.
 

Korishan

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Why is this in the Electric bikes section instead of the BMS section? :huh: :huh:

It's a BMS question that is pertinent across all applications.
 

MakeLoveWork

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Korishan said:
Why is this in the Electric bikes section instead of the BMS section? :huh: :huh:

It's a BMS question that is pertinent across all applications.
I did not see the BMS section. I skipped reading, when i saw solar and wind, cause my actual project was about electric vehicles.
Sorry for that...
 

Korishan

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MakeLoveWork said:
Korishan said:
Why is this in the Electric bikes section instead of the BMS section? :huh: :huh:

It's a BMS question that is pertinent across all applications.
I did not see the BMS section. I skipped reading, when i saw solar and wind, cause my actual project was about electric vehicles.
Sorry for that...

Then you looked right past it ;)


image_vfcdgx.jpg


Being that it's under Solar and Wind, I can see how that can be a little confusing at times.
 

MakeLoveWork

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To close this thread, I just want to give a quick response with the solution I received.

For the BMS I bought, the BMS manufacturer said that Sketch 2 is the right way to connect everything.
But since I assume that this can differ between BMSs I'd advice everyone with a similar problem to reach out to their manufacturer.

Thanks for your replies. :)
 
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