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Hello,

I finished an implementation of 4 ZEVA BMM8 (basic BMS) in a truck EV, I used UTP CAT5 and CAT6 cables to monitor cell voltages, there are 3 different modular cabling parts:

1) From the each cell, I have 1Amp mini-fuse, then the cable goes to a centralized panel where I have four RJ-45 wall mount network ethernet jacks "UTP rossettes"

2) From this rosettes, the cabling goes to near the car's dash, here I use 4 individual UTP female network couples, so each cable that comes from the batteries is plugged, then from the other side of the coupler, the cable goes to the final stage:

3) Cabling from the couple to the BMM8.

I see the design very serviceable, clean, structured as in small datacenter ethernet network. There is no "spaghetti" of cables. Because there is no display here, I can easily plug an 8cell monitor to see voltages in a module, using a "Y" connector for instance.

But I'm having problems having FALSE voltage readings: going from negative voltage readings up to higher voltages of 19 or 25volts in a single cell!

So the BMM8 LV or HV relays make the EV useless, perhaps the vibration in a car is one of the factors that make the connections very unstable.

I have changed couplers, cables, same issues. So I need to change all cabling and connectors completely. Before doing it I need your help asking you for good connectors and cabling AWG in an implementation like this.

Anyone that has experience with BMS cabling? I'd like to use 8-pin connectors, other than network parts, I will discard UTP cable, no twisted pairs. 8-pin connectors are nice because each BMM8 can monitor 8 cells, so one cable goes to one module.

Thanks a lot,

ekthor
 

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Solid, single strand Cat5/6 is asking for trouble. Guys use it all the time for Modbus cable with jobs I work on, and it breaks every single time. With cell taps, all it has to do is break and you're shorting to the next battery. Use stranded wire.

Connectors, you're on your own, just make sure they're rated for more than 12VDC. I'd connect directly using some 20/21Awg wire like they list on their site:
http://www.zeva.com.au/
 

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Any chances some stray currents are being induced ? Maybe go with shielded Cat5/Cat6 and connect the shield to the chassis ?
 

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Any chances some stray currents are being induced ? Maybe go with shielded Cat5/Cat6 and connect the shield to the chassis ?
DON'T USE CAT5/6. They're solid strand. They will eventually break in a high vibration environment. Doesn't matter if they're shielded. It's the wrong type of wire.

He could use shielded multi-strand wires. But please don't use Cat5/6. It's horrible in a car or anywhere there's vibration.
 

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DON'T USE CAT5/6. They're solid strand. They will eventually break in a high vibration environment. Doesn't matter if they're shielded. It's the wrong type of wire.

He could use shielded multi-strand wires. But please don't use Cat5/6. It's horrible in a car or anywhere there's vibration.
Cat of the communications cable isn't indicative of whether it is solid core or not, instead it is indicative of things like twist rate (frequency rating) and resistance, dictating the speeds and cable length runs for various speeds and loads when used in PoE capacity.

There is a separate thing that is going with these cables, which is whether they're solid core for fixed runs, or stranded for patch work (shorter runs between equipment and patch panels or outlets).

Here is an example of patch cable, which is standed and plenty flexible, but still shielded :

http://www.l-com.com/ethernet-category-5e-f-utp-pvc-patch-26-awg-4-pair-stranded-white-1kft
 

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Cat of the communications cable isn't indicative of whether it is solid core or not, instead it is indicative of things like twist rate (frequency rating) and resistance, dictating the speeds and cable length runs for various speeds and loads when used in PoE capacity.

There is a separate thing that is going with these cables, which is whether they're solid core for fixed runs, or stranded for patch work (shorter runs between equipment and patch panels or outlets).

Here is an example of patch cable, which is standed and plenty flexible, but still shielded :

http://www.l-com.com/ethernet-category-5e-f-utp-pvc-patch-26-awg-4-pair-stranded-white-1kft
I realize the Category 5 or 6 isn't indicative of being stranded or solid. But what I do know, is that most cat5/6 cable you see on the market is solid. If it is stranded, he's fine. My point was not to use solid conductor cable.

When you strip it, it can score the conductor, which weakens it. It's not good for high vibration applications.

I'm an Applications Engineer, and I've seen hundreds of people use cat 5 cable with solid conductor for wiring to terminals, and eventually they call and wonder why their equipment isn't working. It's because the conductor broke.
 

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I don't think it's really necessary for most applications. The Orion and Elithion and Zeva don't use shielded battery taps. They have Shielded CAN cable though, and I would recommend shielding that.
 
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