One shunt, two instruments

[pessimist]

I'm pretty sure this has been asked before but I'm damned if I can find it. I'd like to run two BM1s (one headless) from the same shunt. Can't see why not, but I'm prepared to be corrected by someone who knows more than me. Low bar

 

[roaringgirl]

Hmm, the bm measures the voltage across the shunt and also uses a tiny bit of current to run itself. If you use 2 bms I guess they'll take twice as much tiny current to run. If you use a victron, you can read the info on a bluetooth device, so maybe you won't need a second one?

 

[pessimist]

Thanks, but Victron's bluetooth interface is closed whilst Nasa's is open which makes remote monitoring possible.

 

[roaringgirl]

I believe victron has a remote monitoring solution too, but I haven't used it.

 

[northwind]

Thanks, but Victron's bluetooth interface is closed whilst Nasa's is open which makes remote monitoring possible.

Victron serial connection is well documented and there are library's available to parse it, you can connect it directly to signalk for example

 

[PaulRainbow]

I have a Victron Smartshunt, which can be wired to a Victron display and simultaneously be viewable on Bluetooth devices. I can view mine on my phone and tablet and i have it hard wired, using the Victron cable, to a Raspberry Pi running SignalK and Grafana. The Pi is then accessible from all devices via a web browser.

 

[KompetentKrew]

Open source [Victron Energy]

 

[Ian_Edwards]

Providing the devices measuring the voltage, have a very high impeadance, which I' sure they will, then the micro amps they take will not have any effect on a 500amp shunt. Any error they cause will be so small you'll never notice it.

 

[PaulRainbow]

I'm pretty sure this has been asked before but I'm damned if I can find it. I'd like to run two BM1s (one headless) from the same shunt. Can't see why not, but I'm prepared to be corrected by someone who knows more than me. Low bar

"Headless" would mean not having the display, so i'm not sure what it is you're trying to do. What do you currently have and what are you trying to achieve ?

 

[pessimist]

"Headless" would mean not having the display, so i'm not sure what it is you're trying to do. What do you currently have and what are you trying to achieve ?

I'm already monitoring the headless BM1 using a Raspberry and feeding it to local wireless devices and also over the web. The boat is not fitted with a standard ammeter so I'd like to have a second BM1 providing "at a glance" amp readings.

 

[Wing Mark]

The current drawn by an instrument will be small, so won't affect the voltage the other instrument sees on the shunt very much.
Way below the resolution of the instruments.

There are cheaper current/voltage monitors if you just want a 'quick look'?

 

[PaulRainbow]

I'm already monitoring the headless BM1 using a Raspberry and feeding it to local wireless devices and also over the web. The boat is not fitted with a standard ammeter so I'd like to have a second BM1 providing "at a glance" amp readings.

Still not clear what you have. As i said "headless" means no instrument/display, so in the case of the BM1 you can only have the shunt, or possibly the shunt and Bluetooth monitor. If you have the Bluetooth monitor i can't see why you couldn't connect the display to the shunt in parallel.

 

[andsarkit]

Try it and see what happens. Make sure nothing such as solar panels are charging then turn on some constant current devices such as all your lights to draw a reasonable current. Connect and disconnect the second monitor and see if the original reading changes. This will tell you if it is a reasonable thing to do. I suspect it will be fine as most measuring devices are designed to be high impedance.

 

[pessimist]

Still not clear what you have. As i said "headless" means no instrument/display, so in the case of the BM1 you can only have the shunt, or possibly the shunt and Bluetooth monitor. If you have the Bluetooth monitor i can's see why you couldn't connect the display to the shunt in parallel.

I have both the shunt and Bluetooth monitor, thus "headless". I would like to add a display unit to the same shunt. I'm guessing that "can's" in your answer should be read as "can't", In which case I have my answer and you have my thanks.

 

[pessimist]

Try it and see what happens. Make sure nothing such as solar panels are charging then turn on some constant current devices such as all your lights to draw a reasonable current. Connect and disconnect the second monitor and see if the original reading changes. This will tell you if it is a reasonable thing to do. I suspect it will be fine as most measuring devices are designed to be high impedance.

Thanks, this too seems a sensible suggestion. I do not understand why high impedance is important (told you more knowledge than me was a low bar to clear) but it seems I can do what I'd like to do.

 

[pessimist]

Open source [Victron Energy]

From the document you referenced -

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FAQ


Q1. Why is the Bluetooth API not public?

Making the bluetooth API an official public one would mean that we can’t change it as simply as we can today; and also it means that we’ll get questions about it: bluetooth is not simple. Far more complicated than a serial port.
And then only our developers will be able to answer them: taking away development resources. Hence we chose to not make the Bluetooth API public.
---------------------------------------------------------------------------------------------------------------------------------------------------
Which I take to mean that it's too hard for us mere mortals. NASA, on the other hand, provided me with details of their API 20 minutes after my requesting it.

 

[PaulRainbow]

I have both the shunt and Bluetooth monitor, thus "headless". I would like to add a display unit to the same shunt. I'm guessing that "can's" in your answer should be read as "can't", In which case I have my answer and you have my thanks.

Ah, makes sense now, yes should read "can't", will edit that.

 

[Ningaloo]

I have a Victron Smartshunt, which can be wired to a Victron display and simultaneously be viewable on Bluetooth devices. I can view mine on my phone and tablet and i have it hard wired, using the Victron cable, to a Raspberry Pi running SignalK and Grafana. The Pi is then accessible from all devices via a web browser.

Paul, this looks exactly what I am trying to achieve. Are are you using a Pi running Venus with a second one for display? If using a single Pi, presumably connected to the Victron devices using a VE Direct to USB cable, how do you get the data into SignalK?
I have a smartshunt, 2 Smartsolar mppts and a 500W inverter. My battery charger is mastervolt.

 

[PaulRainbow]

Paul, this looks exactly what I am trying to achieve. Are are you using a Pi running Venus with a second one for display? If using a single Pi, presumably connected to the Victron devices using a VE Direct to USB cable, how do you get the data into SignalK?
I have a smartshunt, 2 Smartsolar mppts and a 500W inverter. My battery charger is mastervolt.

I have a Smartshunt, one MPPT and a Victron charger, the charger doesn't have a VE direct connection, so that's irrelevant. I have VE Direct cables from the shunt and the MPPT connected to the Pi. I don't use Venus and the Pi is headless.

Initially i connected to the Pi via wifi and accessed it with a browser. I now have a wireless router which connects to a hotspot on my phone and the Pi, tablet, laptop etc all connect to the router. So each device has internet access and can share data or view information from the Pi. You could skip the router and connect to the Pi directly, by Ethernet or wifi.

SignalK deals with the incoming data from the two VE Direct cables using the "VE.Direct to Signal "K plugin. It's pretty straightforward to then vies data using the SignalK webapps. I've also installed the "signalk to influxdb" plugin, so i can use Grafana, which gives the display in post #6 (amongst others), for monitoring the batteries and charging.

I also have an Actisense N2K to USB converter, which connects to the Pi and makes all of the data on the N2K network viewable, for which i use the "MXTommy/KIP" webapp.

This isn't really my field, so i had to do some online research to set it up, i think i might have forgotten much of it already