VICTRON BMV 700 Battery Monitor Question

[Danielelongo]

Hi everyone,
I just finished installing a 330-watt solar panel combined with a Victron 100 | 30 MPPT charge controller, a BMV-700 battery monitor, and two 145 Ah AGM batteries on my motorhome and need some help/clarification.

To start with, I'm quite satisfied with the system but quite confused with the battery monitor readings.

For instance, after a long day using DC appliances and charging laptops, I went to bed with the controller reading a 76% capacity left in the battery bank. Now this morning at 7 am I it checked it again and it still indicated a 76% capacity with a draw on the battery of around -1 amp. The sun was weak, we were mostly in the shadow, and we were drawing a -1 amp. To my surprise an hour later the battery monitor was reading full battery at 100%.

Here is my question how is that possible? I'm worried that the batteries are and may get damaged because the battery controller would not top them up?!
Another thing I noticed is that although the monitor indicates 100%, the voltage can vary quite a bit. I thought that voltage and battery percentage capacity would be linked?
Lastly, not sure why the monitor is not displaying the Ah, and the h, any idea?

Your help and clarification are very welcome. I would hate damaging the batteries.

Thanks
Daniel

 

[Lydart]

I have a SmartShunt in my VW California with Smart Solar 75/15 and Orion Tr Smart 12/12/30 charging 2 x110Ah Lifepo4. I installed my shunt with fully charged batteries. Performed a zero calibration then manually set SOC to 100%. Then I enabled both chargers. It has since worked as expected.

 

[tictag]

A negative draw on the battery means that it is being charged.

The BMV700 has a configurable 'fully charged threshold' value where it will assume the battery is fully charged. Check the manual for details.

 

[Mex Rider]

A negative draw on the battery means that it is being charged.

The BMV700 has a configurable 'fully charged threshold' value where it will assume the battery is fully charged. Check the manual for details.

Also early morning cold gives your panels a big boost in charge capacity.

 

[Rocketman]

> I'm worried that the batteries are and may get damaged because the battery controller would not top them up?!

The Battery Monitor and Solar Charge Controllers don't communicate much directly. Regardless what the Monitor says, the Charge Controller will run its program, so it will run through its charging profiles - Bulk - Absorption - Float.

The communications are if they have both with bluetooth (and you set-up a "network" - the BMV can send voltage and temp data. IF they are both connected to a GX device (i.e.CCGX) then that data can be shared also.
Study the manual of the charge controller on charging - there are a couple of settings that can be changed. How long of an absorption, etc.

Also you need to understand how the BMV resets the charge to 100% with tail current. One of the problems can be clouds can cut down your solar charge, and to the the BMV it can look like the batteries reached their tail current and then it will change to 100%. A bit later clouds go away, and the charge controller will continue to charge away (it doesn't know or care that the BMV says 100%).

 

[snoobler]

For solar charging, BMV should be programmed to 0.2V below the absorption voltage in the SCC. You need to ensure the tail current indicated by the % capacity in the BMV is actually a little above the tail current specified in expert mode on the SCC.

The charged detection time sets the number of minutes voltage has to be above the charge voltage AND the current has to be under the tail. This prevents the early termination due to clouds @Rocketman mentioned.

Here are my setting for my 48V system:





My BMV goes to 100% about 30 minutes before float.