I have two smartshunt connected to two different systems.
Each one see a current consomption of 0.1a for my raspberry pi (venus os) or 0.1a for my Ethernet switch. Sometime the current for the raspberry pi is 0.2a. in documentation I red that precision for current measure is 0.01a but my measure are always 0.1 or 0.2. isn’t strange ?
I also see in documentation there is a parameter in the smartshunt to ignore small current could it be this ? But in the documentation this parameter is made to have a 0a value instead of a very small value…. That is not my case.
My Smart shunt came with a current threshold set to 0.05A.
Current display on V-Connect is to 2 decimal places, i.e.0.01A resolution.
For a/d converters, measurement is always +/-1/2 LSB, so some variation is always there. However, it looks like the 10mA resolution is being rounded to 100mA resolution, so that is most likely causing the change in your readings. Pi takes about 3W (@5V) so it depends what voltage you are measuring current at…
Measuring small currents accurately with large current (300A,500A) shunts is not possible.
Either directly in smartshunt data or in vrm, the current is always a 0.1a precision. With rising sun today I have 0.3Aa. when sun is falling I have -0.1a.
You talk about rounding, is there a setting for this ? I have the feeling that you have same precision than me right ? So either I don’t understand the smartshunt documentation, either the documentation is wrong about the precision…
I am measuring current on the 24v battery, so 3w should be around 0.125a.
I tried to reduce this consumption by disabling the Bluetooth or by rising the transmission period to the vrm but current is always 0.1A.
Directly (via Hex data requests) you can get 0.001A resolution (depending on software version).
in VE connect (Bluetooth connection to shunt) you can get 0.01A resolution.
From VRM, the current is rounded to 0.1A resolution in the GX device.
The power taken by a Pi varies with accessories and what the Pi is doing so the current may vary.
0.125A rounded will read as 0.1A, but if the power rises to 3.6W (0.15A@24v), then this will be indicated as 0.2A.
In order to reduce the current consumption of the Pi further, you need to reduce the system clock frequency, this is not a simple task.
Thanks for your help. I see that smartshunt could have it’s Bluetooth disabled, is there a real impact in consomption? I already disabled bluetooth of the pi but without any impact on consumption… (problem of precision I guess…).
typically “disabling” a bluetooth chip just turns the rf bits off, the power is still connected. Not much power saving, but more of a security feature. nothing to do with the precision of the device.