Hi, when I use a smart shunt to monitor my battery and the battery disconnects between smart shunt and battery - (as an example, the bms shuts off the battery) - will the shunt have a problem with that?
Hi Roger, welcome to the Victron forum!
Victron Smart Shunts are connected to the negative terminal of a battery, both used for messurements, as well as power for the Smart Shunt it self, together with the small positive lead.
When the battery/BMS shuts off, normally the negative battery terminal is disconnected.
In this case the Smart Shunt will loose it’s minus power, and thus shut down instantly.
This is not a big problem, besides that the shunt messurements, and connections also stop.
If the battery/BMS starts up again, the Smart Shunt will also power up. The messurements will normally continue where they’ve stopped.
Only when the Smart Shunt is powered off, and the battery continues running, you will get wrong messurements when the Smart Shunt is powered on again later. Than you need to correct this, what is mainly the SOC value.
There is a setting called “SOC on battery reset”. You can choose for the SOC on restart to keep the SOC ftom shutdown, show 100% or show nothing. Details in the manual. I usually suggest “Keep SOC”.
You have to remember, if your battery self discharges or gets charged whilst disconnected the SmartShunt will be wrong at restart and a full charge with the SmartShunt connected is required to get the system reading correctly again.
Thank you for the quick answers.
I am asking because my shunt stopped working after only 3 days of usage.
The only thing that happened in the system is, that I shut off the battery yesterday.
When that happens, there is still voltage on the “load” side of the shunt because the MPPT are still working and producing power. Although yesterday at 10 pm, there was not enough sun outside to really push much into the “load” side. And today morning, I restarted the system - battery first.
This noon, I realized that my shunt is not reporting any data, so I went down and it was dead on bluetooth also. I checked the fuse and it was blown. I inserted another fuse and it lighted up instantly. So I removed the shunt from the system and put it to a 12V power supply. I limited the power to 12V and 0.1A. Device showed no function and voltage drops down to 1.5V - so there should be a short in the system somewhere.
I ordered a new one today but asked here if maybe it is a bad idea to place it behind the battery switch and the BMS.
Maybe this old topic helps you a bit futher.
Theoretically, a Victron MPPT should continue to work without a battery connected. However, I don’t know what the MPPT’s output does when the battery is disconnected, whether the output voltage remains stable, or whether it might generate voltage spikes, especially under light load.
Perhaps a Victron expert on this forum is reading this thread and can provide additional information.
In my opinion it’s best to shut down the MPPT before you shut down the battery for longer time.
If the battery unexpectedly disconnects during charging an overvoltage can happen. The power has to go somewhere while it ramps down.
Since yesterday night was not sunny, this could not be the problem , but it could be a general problem, when the BMS kicks in and shuts off the battery. And this is a general and probable use-case. Two independent batteries could reduce the effect but then I would also implement a watchdog which shuts down the whole system if one battery fails.
I really don’t know how long the shunt did not work. At the moment, I have no logging for the data because I did not have the VE.Direct cables. They came today and thats when the fault became visible.
Found this here: Smartshunt(s) keep dying - DIY - Victron Community
Hope I will not join his fate ..