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tjorg avatar image
tjorg asked

Using the BMV-700 relay

I have the BMV-700 installed in a solar powered camper van with AGM batteries. My understanding is that I can set the BMV relay to disconnect power so that I do not overdraw the batteries. I have set the floor parameters in the settings and done some tests. I set the SOC% floor and also the battery voltage floor and ran a bunch of power through to draw the batteries down. The BMV shows that the battery percentage and voltage are both lower than the floor that I set but it did not alert or use the relay to shut power down. I drew it all the way down to 11.4V and it read that as 35% remaining. That was as much as I felt comfortable draining them.


What am I doing wrong? Or am I misunderstanding the capabilities of this unit?


Thanks!

BMV Battery MonitorRelay
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ripper avatar image
ripper answered ·

The manual and the quick hint in the app just describes it wrong. Took me hours to finally get there.

First of all the BMV does not disconnect the power itself in case you misunderstood. It needs extra devices such as a relay. The build in relay can be used to drive for example an external relay.


To use the internal relay you would have to select standard under relay preferences, probably inverse the relay, adjust the bell for soc for the low limit when it should shut off and adjust the bell with a bar through when usage is okay again. Unlike stated int the manual, the relay is not on while being between the two values, rather it is hysterisis. Means on till its hitting lower limit, then stays off till higher limit is reached, it then goes back on. For some reason if you put bell with bar to a hundred, it shows zero and does something stupid. You can do 99% max. Also make sure to disable high and low voltage underneath unless you want it. It stays on if you played around up top and selected charger mode or whatever and messes with your selection.


The alarm buzzer is indipendant and you can play around in the same mannor.

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tjorg avatar image tjorg commented ·

Thanks for the help! I did misunderstand what this thing can do then. The product description says "Programmable relay, to turn off non critical loads". So what it actually does is send a signal to a separate external relay (at the SOC% or low voltage that I program)? Would this be something like the Victron Battery Protect? What relay setup did you end of using for your system?


I did get the alarm to work at least.


Thanks!

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niteman131 avatar image niteman131 commented ·

@ripper

It appears from your answers, you have become very familiar with the BMV relay. I have a pretty good understanding of the relay except for the actual contacts. Are both contacts completely floating, or is one contact internally connected to power or ground ? I would expect they are completely isolated so that I could connect Power OR Ground to one contact as needed, and use the remaining contact to control a relay.

Any help will be greatly appreciated !

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mohsen-alserri avatar image mohsen-alserri commented ·

hello friend, i am building a system using 3 quattro inverter, 4 smart solar charge controller and CCGX device. when i purchase these devices and all their accessories. the engineer in the store told me that i must buy the bmv-700 device to run the system without issues. So i want to know is he correct? or can the system run normally without the bmv-700

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