Victron BMK702 with two solar charge controllers.

[Eonicks]

First off, thanks to the many contributors to this forum. I was able to do a DIY install of four 100 watt panels in a series/parallel configuration based on the research both here and AM solar websites. Originally going to use the factory prewire, but after days of trouble shooting and a call to Alano, I determined that the wiring was somehow severed from the factory. I eventually ran my own wiring down to the controller.

So after the maiden camping trip this past weekend, I have an issue with maybe the readings/settings on the BMK 702 or I'm using it incorrectly.

I installed the following equipment. Victron 100/30 solar charge controller for the four panels, A separate 75/15 for a 100 watt portable panel, BMK702, Bluetooth dongles for all three, and two Lifeline 6volt batteries. I went with separate dongles so I could read the performance of each component on my phone from inside or outside the trailer.

Given the shaded campsite, I was using the portable to suppliment the roof panels. The issue is the BMK would show a SOC percentage greater than what the battery voltage would tell you. For instance, it would quickly ramp to 100% when only receiving an hour or two of adequate sunlight , and the voltage would indicate something closer to 25% discharge based on the lifeline user manual. (Understand not completely accurate unless sitting for 4 hrs with no load).

Looking for some troubleshooting advice. Could it be the use of two controllers, BMK settings? Thanks for any help.

[alano]

I'm curious where you installed both current shunts exactly? These monitors work by integrating the current into and out of the batteries. The BMV-702 monitor includes several parameters (charged voltage, tail current, charged detection time) that must be set for the monitor to acknowledge the 100% SOC point. Perhaps reviewing these with your Lifelines might address the issue?

[lewster]

There should be only one shunt in the system, as the BMV-702 only uses one and the Blue Solar charge controllers have none. The settings for your BMV-702 should be properly set for your battery bank with total capacity, tail current etc.

The Blue Solar controllers are similarly set for the absorb and float charge voltages and charging duration. These are easily done thru the Victron Connect app.

The readings from the BMV-702 should be consistent regardless of which solar controller you are using, but the actual voltages and charge amperages shown on the solar controllers will vary dependent on the number of panels connected to each system.

If you purchased the system from AM Solar, a quick call to their tech support team will probably resolve any monitoring inconsistencies.

[Mgieselman]

The exact settings for the BMV-700 series aren't always exactly what you would think.

I'd watch this video from Victron on how to setup your BMV-702 then let it go through a full charge cycle.

https://www.victronenergy.com/blog/2...nc-parameters/

[Eonicks]

Thanks for the posts so far. Just one shunt installed Alano. I'll have to get the trailer out of storage and give AM solar a ring for tech support.

[Eonicks]

Originally Posted by Mgieselman

The exact settings for the BMV-700 series aren't always exactly what you would think.

I'd watch this video from Victron on how to setup your BMV-702 then let it go through a full charge cycle.

https://www.victronenergy.com/blog/2...nc-parameters/

Think this may be my issue. I tweaked the charged voltage settings based on 0.3 volts less than the float voltage and should have 0.3 less than absorption voltage for a solar system. Will check out this weekend.