Victron App and Multimeter Seem to Show Different States of Charge- Resolved

CrabTab

Recently I installed solar on my roof and an MPPT Victron 20Amp controller. It appeared to work well on a recent 3 week trip. Today I happened to check the state of charge on the 100AH AGM battery like I used to, with a multimeter. I got different readings than with the Victron App. I checked with a second multimeter and got the same voltage as the first meter, 12.4VDC. Below is a screenshot of the Victron App. As I understand it, the battery data tells me that I am at full charge, being in float mode with no current going in to the battery. I think that 13.57V reading in the app is a surface charge. The multimeter readings tells me the battery is only about 75% charged.

Edit: The battery switch is turned off on the trailer.

Can someone please provide some clarity for me? I apologize if this question has been covered in another post. Thanks in advance...

Dutch061

I guess my first question would be where are you taking the measurements with your multimeter in comparison to the MPPT.

Also, I do know that if you have a BMV-712 (I do) that you can network the readings that are directly measured at the BMV-712 (Voltage, Current, and optionally Temperature which I have also). Since these are read "at the battery" they are much more accurate than from the MPPT.

Not sure if this helps or makes the issue fuzzier. I believe the difference is in the location of where the measurement is being taken.

Brad

CrabTab

Thanks for the input @Dutch061. No BMV installed. Meter readings were taken off the terminals. Solar controller is in the tub with 10GA connecting wires, less than 12" long, to the battery. Here is the view inside my tub. It just seems odd to be in float mode at what appears to be 75% charge on a new battery. Thanks again...

Sharon_is_SAM

What kind of settings do you have on the controller?

BrianZ

Maybe this from our Victron controller manual would explain the current readings..
"PV voltage must exceed Vbat + 5V for the controller to start. Thereafter minimum PV 
voltage is Vbat + 1V."
Maybe the difference between your panel's voltage available to the battery & the battery's actual voltage you measured is not enough to restart charging if it had fallen below the 1V threshold to continue charging?
I would read that "battery voltage" as voltage available from the Victron to charge the battery, if it could push a current, but you're seeing zero watts and zero current, so it's like it's turned off as far as charging goes.  You're not showing the panel voltage - is it at least Vbat + 5V?  If so, it should have restarted.

Dutch061

@CrabTab, one other question are you comparing the voltages with the battery switch turned on or off (if applicable)? Yes, I understand that theoretically the MPPT should be connected directly to the battery via the fused lead.

Brad

CrabTab

Well, I figured out the issue. The ground wire leading from the MPPT had come loose. I didn't readily see it based on the location of everything. Open circuits don't function well, if I remember my electronics classes from so long ago. In a world of learning curves it sometimes seems I live in a spirograph.

Thanks @Dutch061, @Sharon_is_SAM and @BrianZ for offering help!

BrianZ

Glad you found it @CrabTab!
Loose connection had crossed my mind, but I was giving you credit for having checked that already. 😉
Those screw connections can be a little funky.