asked
Is it possible to have 2 bmv units operating from one shunt i.e display in two locations please?
To clarify, I have a shunt on house bank with a bmv on fuse board to enable easy monitoring.
This is in an electrical cupboard.
However, it would be useful to have the bmv in a main companionway to enable easy day to day monitoring of state of charge.
Is there any way to split cat5 from shunt to send to two bmv units?
Many thanks
Best regards
J
You can absolutely do this. You need to put two of the BMV shunt circuit boards on a single shunt, so you'll have to get creative and add a little wiring to make that work.
Once you do, however, both BMVs will read off the same shunt. I have this setup full time in my configuration.
Nice idea.
Is there a slight difference in calculations, or are the readings exactly the same?
There is a difference in readings -- the raw sensor error and the nature of the way the error accumulates over time mean that one will probably always be different than the other.
That said, as long as you have a setup where both of your BMVs can "resync" to 100% from time to time, in my experience they don't get too far apart. Maybe 3-4% after several weeks in my case?
Hey Ben, that's great. Thankyou for the input! Any risks/tricks to be aware of when mounting second bmv driver?
Cheers
J
No tricks, it's pretty straightforward. I mounted both of them on one of the two shunt holes using the same screw. That leaves one side hanging off the edge, and you can make a small lead from it back to the one that's installed normally. You just need to put them in parallel with each other, in other words.
Someone at Victron told me there could be measurement error as a result of doing this, but it wasn't obvious to me how that could be the case, and I don't see it in real life. I think they were just being cautious.
Hi Ben,
I would attempt the parallel mounting you experienced.
1. I am not quite sure to understand this mounting. On the shunt, the card is held by 2 screws. But it's not possible to add a second card, due to the RJ12 connector, unless the second card is tightened with only 1 screw and makes a quite big angle with the first one. Futhermore, you need to draw a wire to connect to the other screw.
Thus, this makes a parallel mounting : the current between the "Battery" and the "controler" screws will then be divided in 2. Will this affect the measures ?
Thanks to clarify.
2. I personally imagined another solution : using a male-female-female RJ12 connector, to connect directly the 2 BMV to the same shunt. Will this work ?
Yes, I have the two cards at 180 degrees with each other, and a wire connects the two far screws.
Shunts work by measuring a voltage, not a current, so having two cards in parallel does not divide the measurement.
I don't think you can split the RJ12 signal up. I didn't try that myself, but I think I remember being told it was not possible. Then again, you could give it a try and see for yourself.
I am not sure if it is possible, but I don’t think the displays are sold individually either.
Why not just run two shunts side by side?
Just to be clear to everyone, when multiple shunts are used, they need to be in series.
Allan.
I'd buy an older droid or iOS device and just stream data to where you want it. You could attach to a wall, or move around. This assumes you have a Bluetooth device. This is what I do.
I have an equal but opposite issue, my battery bank was originally 24V, consequently the copper cables were huge and many.
I don't want to swap them now I've gone 48V.
I want to know if I can run multiple shunts, parallel on the primary, series on the secondary, to 1 BMV.
