Extra wires on BMS

TheBikeMan

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Mar 23, 2018
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I've noticed that some BMS boards have more red wires than is necessary for the number of cell packs for that voltage. For instance, a 48V 16s board when you only need 13s to get to a 48V battery. What are these extra wires for and what can you do with them if you have more than is needed? I would suspect that the BMS would shut down due to the lack of balance if these extra wires are not connected? Thoughts?
 

Nealh

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Show us a link to the board.
Most BMS will have +1 extra sense wire for a B- connection to read 0v then the correct amount of B+ wires for sensing.
A board with 16 sense wires will be for 15s /54v battery and not a 13s/48v battery, so not suitable.
From what you have explained you are looking at a wrong BMS for the voltage you require.
 

Woosh

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May 19, 2012
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some boards have the soft switch wires on the same connector.
 

TheBikeMan

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Mar 23, 2018
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Show us a link to the board.
Most BMS will have +1 extra sense wire for a B- connection to read 0v then the correct amount of B+ wires for sensing.
A board with 16 sense wires will be for 15s /54v battery and not a 13s/48v battery, so not suitable.
From what you have explained you are looking at a wrong BMS for the voltage you require.
Yea, that's what I think as well but here it is: https://www.banggood.com/16S-48V-BMS-25A-35A-45A-With-Balance-Battery-Power-Protection-Board-Water-Proof-p-1306543.html?gmcCountry=GB&currency=GBP&createTmp=1&utm_source=googleshopping&utm_medium=cpc_union&utm_content=2zou&utm_campaign=ssc-gb-en-all&gclid=Cj0KCQiAoo7gBRDuARIsANeJKUZeLgk6dYP1GRzVffTHjTiZbGhuHRNJbuzwA5W47IZNC2ECvC4P6O0aAgcTEALw_wcB&ID=46103&cur_warehouse=CN
 

Nealh

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That is badly labelled/sold it is for 15s so a much higher voltage then 48v, you have to ignore the 48v claim. It has 15 red sense wires and the black one for B-/0v.
 

Nealh

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TheBikeMan

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Mar 23, 2018
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That is badly labelled/sold it is for 15s so a much higher voltage then 48v, you have to ignore the 48v claim. It has 15 red sense wires and the black one for B-/0v.
Ah, okay there there are no BMS boards with extra S wires. They are just mislabled.
 

Nealh

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I have had another look at the BMS listed on Banggood and their is little or no specs for it.
It does seem strange to list it as 48v 16s when in fact 16s is 60v, then it twigged Lifepo4 48v is 16s so expect the BMS is actually for that battery chemistry and listed correctly but with scant battery details for use and type.
For the uninitiated buying some products can be fraught and the wrong item bought in error.

The same 16s listed on Aliexpress are stated and listed as 60v.
 
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TheBikeMan

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Ah, so the Lifepo4 Max out at 3.2V rather than 4.2 so it requires more cell groups to reach the desired voltage.
That makes sense.
 

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