Resistor identification on a shunt PCB of a battery manager - Page 1
Forum section: electronics / beginners

author: mwiens
author_rank: Newbie
timestamp: February 06, 2023, 09:19:54 pm
content: 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

author: Kim Christensen
author_rank: Super Contributor
timestamp: February 06, 2023, 09:39:47 pm
content: 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?

author: mwiens
author_rank: Newbie
timestamp: February 06, 2023, 10:11:23 pm
content: 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

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: February 06, 2023, 10:19:04 pm
content: Perhaps this:https://www.digikey.com/en/products/detail/littelfuse-inc/RXE010/99603

author: Kim Christensen
author_rank: Super Contributor
timestamp: February 06, 2023, 11:52:51 pm
content: Same thing, but a Bourns MF-R010.See page 6 for markings:https://www.bourns.com/docs/product-datasheets/mf-r.pdf

author: mwiens
author_rank: Newbie
timestamp: February 07, 2023, 05:24:44 pm
content: 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.