Resistor identification on a shunt PCB of a battery manager

[mwiens]

Hi everyone,

(I'm new here, so pardon me, if its the wrong section)

I am trying to "reverse engineer" a shunt PCB from my battery manager (Victron Energy BMV-602S) The manager is able to monitor two batteries - "advanced" monitoring of a leisure battery (B1) and "basic" monitoring of a starter battery (B2.)

The board of my shunt is lost, so I reconstructed the original circuit (I once ordered one and just traced the PCB paths and sent it back again) and want to  etch my own PCB. The board consists of:

• RJ25 connector (to the management unit)
• two terminals for positive poles of the batteries (+B1 and +B2)
• two contact pads (to each end of the shunt)
• two capacitors (C1 and C2)
• one resistor (R1)

The resistor (marked R1 on the PCB) does not look like a "usual" resistor. For me it seems to be a sort of non-linear thermistor or varistor and may have something todo with this "advanced" monitoring functionality for the leisure battery (B1).

A photo of an original shunt with a board is below in the images section, the bespoken resistor is in the red box. The resistor has a label "R010 B7V" on it.

I could identify both caps by their marking (104J250), but the resistor looks very odd to me.
I already searched around which resistor types exist and which it could be. From a form-factor it may be a thyristor or thermistor to me.
A week ago or so I tried my luck on the electronics stack exchange but with no luck.

Can you help me to answer this questions:

What type of resistor is it?
What function does it have?
What resistor can I use as a replacement in my PCB?


Images:

Original shunt with a board (red box is the bespoken resistor R1):


Close-up picture of the resistor R1:


The circuit of the PCB I reconstructed (Box meanings: red: resistor R1, green: battery positive terminals, blue: RJ25 connector):


General connection guide (documentation) of the shunt and the monitoring unit for two batteries:


Thank you for your help!

Max

[Kim Christensen]

I would guess that it's some sort of PTC fuse for the +12V power to the BMV-602 battery monitor.
Can we see a clear photo of the markings on R1 so we can guess at the manufacturer?

[mwiens]

Hello Kim,

thank you for your quick answer.

Unfortunately I do not have high resolution photos.
Still, I have this one from the days I had the original PCB and also found three more-or-less detailed images on the web.
(attached)

Greetings

[Wallace Gasiewicz]

Perhaps this:

https://www.digikey.com/en/products/detail/littelfuse-inc/RXE010/99603

[Kim Christensen]

Same thing, but a Bourns MF-R010.

See page 6 for markings:
https://www.bourns.com/docs/product-datasheets/mf-r.pdf

[mwiens]

Thank you, Kim and Wallace!

It really looks like a PTC fuse.
After further search it is most likely Bourns MF-R010, as Kim proposed.
Based on the datasheet which Kim sent, the fuse which I had, was produced in the 22nd week of the year 2017 - hence "7V"
I also found an image which looks quite the same, (besides the year and the week of manufacturing):



Thanks again, this topic can be closed.