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I have had the BMV-702 for about 6 months. Everything has been working fine but a few days ago I get in the van to check it and all the info is reading backwards. If there is nothing using energy but the solar is charging it then it will read a negative wattage, will be depleting my AH’s and my % but if I turn off the mppt and turn on appliances I get positive watts and all my levels start to go up. Does anyone know why this is happening and how I can revers it?
@Drewglic it sounds like your shunt is connected backward (ie, the "loads and chargers" side is connected to the battery and the "battery" side is connected to the loads and chargers).
Are you sure you haven't recently re-wired the installation or, perhaps, recently replaced the PCB and installed it in reverse, something like that?
If you install a Victron BMV 702 battery monitor in reverse polarity (that is, if you connect the positive cable to the negative terminal of the battery and the negative cable to the positive terminal), it can damage the BMV 702 and potentially cause a safety hazard.
When you connect a battery monitor in reverse polarity, the device's internal circuitry will be exposed to excessive current and voltage, which can cause permanent damage to the electronics. Additionally, if the battery is charged, it may cause a spark or explosion, which can cause injury or damage to property.
If you have accidentally installed a Victron BMV 702 in reverse polarity, it is important to disconnect the device immediately and correct the polarity. You should also check the device for any signs of damage and consult with a qualified technician or the manufacturer for further advice.
Reversing the battery and load connections on the shunt does not cause reverse polarity damage. Think about it. The polarity on the shunt reverses all the time during normal operation. When the battery is charging you have one polarity and when the battery is discharging you have the opposite polarity. The current in the shunt flows both ways all the time depending on battery charging mode or battery discharging mode. This means that the polarity of the current sense signal seen by the monitor normally changes polarity. No damage will occur and it is not a safety problem.
Regarding the problem stated. If the system was once working properly and now all of a sudden the reading are showing charging when it is discharging and discharging when it is charging and no changes have been made to the configuration then I have no idea how that can be happening short of failure in the head unit which I doubt. Recheck the system operation to be sure it is really doing what you say it is doing. Are you sure it was once working properly? Are you sure there have been no changes to the system configuration?
It just occurred to me that aec-den-benz is not talking about reverse polarity on the shunt but but reverse polarity on the power supply to the head unit. I don't know how that can happen or why you would mention that here. That could definitely damage the head unit but possibly not. It is easy to provide reverse polarity protection in the head unit. Victron engineers are very smart and they may well have provided reverse polarity protection in the head unit. If they did not then it would be damaged and it would not be working at all but it is working at least to some degree. At this point there is not reason to believe that the power lead to the head unit have been reversed or that the head unit is damaged.
