Fuse LEDs on a Lynx Distributor without a Lynx Smart BMS – how do others solve this?

Q&A and troubleshooting
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1

The Lynx Distributor has a detection circuit with a red or green LED for each fuse. That circuit requires 5 V, which the Distributor does not generate itself.

It normally receives this via the RJ10 connection from a Lynx Smart BMS or a Lynx Shunt VE.Can.

Neither is present in my installation. The Pylontech BMS communicates directly with the Cerbo via CAN, and the DC side is protected with separate MEGA fuses for each branch. As a result, the LEDs remain dark, even though the RJ10 cable between the two Distributors is connected correctly.

The manual states that, for standalone use, you should connect pin 1 of the RJ10 to 5 V and pin 4 to ground. The problem is that this connector is not protected against reverse polarity, and there is no ready-made cable that does this.

Making one myself therefore feels risky. How have others solved this? Has anyone else encountered the same issue with an installation using managed batteries?

System: 3x MultiPlus-II 48/5000, 2x Lynx Distributor M10, 4x Pylontech US5000, Cerbo GX MK2, Venus OS v3.75.

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4

I’d just make it myself, checking and measuring everything several times before connecting it.

I have a similar system myself, but built my own busbar.

5

I don’t want to take any risks. In the meantime, I found this video: https://www.youtube.com/watch?v=8h-E1lkYCKg There ought to be a market for this, surely? I’d be happy to pay €35 to get the LEDs working. I’d really like to be able to buy a ready-made product somewhere that is fully supported by Victron. I have such a professional installation, and then I’m expected to solder things myself? That doesn’t feel right.

6

@WiFikid

Nice setup….

I used this software and bought a USB-I2C adapter from AliExpress.

Details and parts are linked in my system build overview on my profile.

7

@BjoernK Thanks a lot, that’s exactly the information I was looking for.

Interesting that the RJ10 turns out to be an I²C bus that changes the picture completely. So the fuse status can end up in Venus OS and VRM
after all, not just as local LEDs?!

Two questions if you don’t mind:

  1. Which USB-I2C adapter exactly did you order? The README mentions the
    FT232H and the C232HM-DDHSL-0 cable, and that 3.3V works better than 5V
    for the I²C lines. Did you need the pull-up resistors separately, or were
    they on the adapter?

  2. Does the adapter also supply the 5V on pin 1, or do you feed that separately? With two Distributors daisy-chained I want to be sure the
    supply is adequate.

And a broader point: this is exactly why I think Victron should offer this. The protocol is known, the hardware is a few euros, and the software already exists thanks to @twam. A supported cable or small
module would turn a reverse-engineered workaround into a standard accessory and give installers the fuse alarms in VRM that the Distributor was designed to provide.

Is anyone else here running Lynx Distributors without a Smart BMS? I’d like to know how large this group is.

8

@WiFikid

More Details with pictures in my build thread:

USB-I2C adapter:
https://de.aliexpress.com/item/1005006984824882.html
Additionally you need a resistor, some thin cables and a RJ11 cable.

Yes, the adapter powers the Lynx electronics. You just have a 4 pin cable from USB adapter to I2C in at Lynx.

Yes, the alert is shown on Venus OS, VRM and optionally as email, Victron App.

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9

@BjoernK Thanks again, your setup is brilliant and even offers more possibilities than I originally asked for!

But it also confirms my point. To get a function that is already built into the Lynx Distributor as standard, I apparently need the following: an adapter board from AliExpress, a resistor, some wire, a soldering iron and software reverse-engineered by a third party. And all of that connected to a connector which Victron warns in its own manual is not protected against reverse polarity. If I connect it incorrectly, I could damage the unit, and that damage would be at my expense.

That is not something I want to do on a professionally installed system (which cost a lot of money).

For me, the simple version would be sufficient: a red/green indicator light for the fuse status on the Distributor itself. I don’t need to see this in VRM. I would happily pay €35 for a moulded USB-to-RJ10 cable with a fixed polarity.

There therefore seem to be two product solutions:

Basic: a moulded USB-A-to-RJ10 cable, using only pins 1 and 4, with a fixed polarity. This powers the fuse-detection circuit from the USB port of any GX device, thereby removing the risk that the manual itself warns about.

Advanced: a small USB-I²C module that also reads the fuse status into Venus OS and VRM. The protocol is known, and the hardware costs only a few euros.

For the basic version, Victron would not actually need to develop anything. It is simply a cable!

Is anyone from Victron reading this thread and able to put this to product management? The number of installations with managed batteries (Pylontech, BYD, Pylontech-compatible) and Lynx Distributors without Smart BMS is only increasing. At the moment, each of these systems has a documented feature that does not work, and the only way to resolve this is through a DIY solution using unsupported hardware?!

I would be happy to make my installation available as a test site, and I have the full technical documentation available.