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Topic: Adding Victron 712S to Magnum System (Read 385 times) previous topic - next topic
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Adding Victron 712S to Magnum System
I offer this report for readers interested in a little technical information on battery monitors.

I have a Magnum Energy Inverter/Charger, Battery Monitor, and Remote Display, installed back in 2013. I read about neat features provided with newer equipment, which seems unlikely to be offered via upgrades to Magnum equipment, given the viability of Magnum Energy as a going concern.

My interest is viewing historical State of Charge (SoC) and Charge/Discharge Current in and out of the battery bank, on my iPhone or iPad. People here speak well of the Victron Energy 712 S Battery Monitor with Bluetooth, and it seems like it would satisfy my interest. But, how would it play with the existing Magnum equipment?

A battery monitor tracks the total amp-hours (Ah) stored in the battery bank by measuring the positive Ah going into the battery bank, less the negative Ah coming out of the battery bank. All it needs is to know the size of the battery bank in Ah, and the Ah in or out during each brief time interval, to calculate SoC in percent. It knows the current using a very small resistor in the battery circuit (called a “shunt”), which produces a very small voltage which is digitized and input to the battery monitor. The Magnum uses a shunt which produces 0.05V when the current is 500 A. Well, so does the Victron! This is convenient because the same shunt can work for both, and even at the same time. At least, that is my theory.

The two shunts are electrically identical, but different in shape. The Victron has its digitizer mounted right on the shunt, and the Magnum has its digitizer connected by wires a few feet away. I swapped out the Magnum to the Victron shunt because it was more convenient to attach the Magnum wires to the Victron shunt, than drill holes in the Magnum shunt to mount the Victron digitizer board.

Now the Victron and the Magnum coexist just happy as can be, not affecting each other. The Magnum continues to show its data on its remote display same as before. The Victron sends the historical and instantaneous data I am interested in to my devices via Bluetooth, so I don’t need to put its display in an easily viewable spot.

Some notes on alternatives: Victron offers a headless battery monitor (without the display), which would satisfy my needs, except that it locates all of its electronics on the shunt, which wouldn’t fit where I need it to fit. Using both shunts would also function correctly, but would be a little bit inelegant, and would require rebuilding three short sections of heavy 4/0 welding cable to fit both in.

Reality matched theory. I love it when a plan comes together.
Victron Energy BMV-712 Smart Battery Monitor with Shunt - 6.5-70 VDC -.../url]
2013 27’ Mid-Bath
2005 Honda CR-V
Re: Adding Victron 712S to Magnum System
Reply #1 –
Thanks for the update, Keith! I know many owners have Magnum equipment, so this should be helpful to lots of people.

Just one terminological quibble: as far as I know, there is no "Victron 712S" product. It's the Victron BMV-712 we're talking about here.
Andy Baird
2021 Ford Ranger towing 2019 Airstream 19CB
Previously: 1985 LD Twin/King "Gertie"; 2003 LD Midbath "Skylark"
 
Re: Adding Victron 712S to Magnum System
Reply #2 –
Quote from: Keith S  - 
A battery monitor tracks the total amp-hours (Ah) stored in the battery bank by measuring the positive Ah going into the battery bank, less the negative Ah coming out of the battery bank. All it needs is to know the size of the battery bank in Ah, and the Ah in or out during each brief time interval, to calculate SoC in percent. It knows the current using a very small resistor in the battery circuit (called a “shunt”), which produces a very small voltage which is digitized and input to the battery monitor.
This is a bit over-simplified. Current in and out of the battery bank is handled differently depending on environment and battery chemistry. Charge and discharge efficiency are major factors that will affect state-of-charge, and the battery monitor must compensate appropriately to avoid compounding errors over time. The algorithms used typically require pre-setting these factors.

Steve
2004 FL
2013 Honda Fit