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Connecting a BMV 600 - by not using the official cable


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I have a old BMV600? It uses BMV-60xS Text (TTL) protocol.

This one: https://www.victronenergy.com/accessories/bmv-602-data-link-rs-232

Have the connector for the pins on the BMV600, other side a serial connector, but I cannot figure out what FDTI cable I must get that does not cost a arm and a left ... toenail, that will work on Pi and Windows.

Can anyone point me in the right direction?

Or, anyone prepared to built me one for a fee?

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Doesn't it just use the standard ve.direct cable? Should be easy enough to check it. Check if you have ground on the one end and supply on the other. If it does, then by a process of elimination the two pins in the middle are RX and TX. Getting those wrong won't blow anything up, you just won't get any data. Then it's merely a matter of finding the right baud rate. Chances are it will be 19200... :-)

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I got a CP2102 to work with a BMV 702. Only connect three pins GND => GND  RX=>TX and TX=>RX . Did not connect power since it is not isolated works perfectly. Now using an isolated TTL converter and don't trust that it is truly isolated so did not connect VCC.

Do a serial loop back test and check your wiring.

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20160404_185644.jpg

2 hours ago, The Terrible Triplett said:

Chris, did you use the CP2102 as is, one side the USB, the other side the BMV?

2 hours ago, The Terrible Triplett said:

Any USB to TTL Serial converter will do. Since they are not isolated do not connect the power. The module shown is not a CP2102. The CP2102 (I have) the PCB is naked. This little unit is neater and claims to be isolated. Since the CP2102 worked without the power pin I left the power pin off this one.

http://www.ebay.com/itm/1PCS-STC-Full-Series-SCM-Auto-Programmer-downloader-USB-to-TTL-Isolated-/181782102152?hash=item2a530ec088 (R70)

The 3 X CP2102s I ordered cost 66 bucks with postage (R22 each) so Victron's R1k cable is abuse between the cheeks in my book. I see they (Victron cables) are assembled in China so there is no excuse.

(All credit to Ed for putting me onto CP2102s - I had already ordered the isolated module but being in the Karoo I now have spares).

 

 

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The power pin is there to power the "other" side of the circuit. The isolator chips have two power supplies, one for each side, and then they use capacitive or RF signaling to get the data to the other side.

Check out, for example, the iso1050 can transceiver I used in my project. Note the vcc1 and vcc2, and the separate grounds.

When running non-isolated, you have to decide which side you want to use for the supply, and leave the other side unconnected.

In my Victron 150/70 I discovered accidentally that it has current limiting on the 12V supply it puts on the CAN plug. My circuit has an 800mA fuse for protection (which is what they recommend), but I still managed to short it during development and the charge controller just made that typical high-pitched wine you get from a SMPS when it's doing current limiting... and it didn't even pop the fuse.

I'm pretty certain the equipment on the other side probably doesn't have such protection though :-)

iso1050.png

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Kotz in 'n tuimeldroeer, is soos wat ek hier voel.

There is a trick to the old BMV's ... ANYONE game to build me a connector, that will read it and be safe?

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TTT give me you details and I will post you a CP2102 it will work. I ended up soldering the jumper wires to the pins because they were inclined to slip off. You make fun of your DIY ability but you will manage. There is no need for the power pin and it is therefore safe. Why Victron need to have such expensive cables beats me.

Screenshot (102).png

Proof of the pudding is in the eating.

 

 

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Thank you Chris. I sent you a PM. Trick is, and I HOPE this one works, is that the BMV is older tech.

If it was not for that it would have worked already. :D

But I am HAPPY to give it a go, send me the bill!

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Thanks Chris, I got that one.

I am so tired of buying stuff and then they are not exactly what I needed or I have the right stuff, and then the smoke escaped after I looked at it. ;)

Fierce Releaser of Smoke ... title was earned.

The MOMENT I can read the data, BMV 600-602 and 700-702 are all sorted, bar final testing.

All that is left then is the Victron inverter and the hopefully by end of next week, Voltronic data will miraculously also start appearing. :D

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It seems BMV 600/700 have the same pins. I predict it is going to be a doodle. 

33 minutes ago, The Terrible Triplett said:

Fierce Releaser of Smoke ... title was earned.

You should put it behind your name like recipients of the Victoria Cross (VC) Military Medal (MM) etc.

TTT(FRS).:lol:

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I think the reason for the expensive cable with the isolation is that you also want to separate your grounds. Imagine this scenario. You have a Dell laptop. Dells ground their negative to the earth pin on the power supply. The negative on the USB cable is therefore earthed. If you connect this to a non-isolated TTL converter, it grounds the negative of the battery via the USB cable and your laptop. Now your neutral on your inverter it's bonded to earth as well. And if you have one of these modern "transformerless" models neutral/ground is not the same as negative. You've just shorted a couple hundred amps through your computer.

Sent from my GT-I9195 using Tapatalk

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That's the thing. You actually have to think about these things and consider everything. The moment you isolate it, you can stop worrying. This is precisely why Victron does it (or I would guess that's why they do it), especially when their hardware is used with other hardware not just in solar power setups but on boats (where things tend to cost more simply because you're the kind of person who owns a boat). You just avoid a whole lot of "you blew up my computer/GPS/Fish finder/whatever" claims. Most likely from that litigious nation otherwise known as Americans.

I go through this sh*t every time I want to rig up my oscilloscope to anything :-)

If your computer's power supply doesn't have a ground pin, like my old netbook, or my raspberry pi, then you already have isolation. No need to worry about tying the negatives together. If it has a ground pin, you have to check if there is continuity to your USB negative. On my Dell, I found this to be the case. Good design really, they have the whole metal chassis on the inside grounded.

So not sharing the supply line (usually around 12V? Or maybe 5V) is essential. Strictly speaking, you need only two wires to the BMV. Ground... and TX->RX. But that shared ground... with some cheaper inverters, or these transformerless things that don't technically isolate the batteries from the line output... you have no such guarantees.

Edit: Thankfully we've ascertained that the more modern Axperts do in fact use ancient transformer technology just like those old fashioned Victrons... or else they'd be in trouble here :-)

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