Troubleshooting Drop in Charging

[BR549]

We’re parked in the open and have had the converter turned off, using our single solar panel to keep lithium batteries charged while powering lights and refrigerator. We have used about 10-20% of the battery charge during the night. The batteries were fully charged well before sunset. High temperatures have been 100-105.

The system is a Victron SmartShunt, Victron SmartSolar, Victron Smart Battery Sense, and 2-200aH LiTime lithium batteries.

Things have worked great until a few days ago when we returned to the trailer to find the charge was 82% after a day of full sun. Yield had dropped from about 890 Wh to 100Wh. I turned the converter on to make sure we are fully charged for the night.

There were no clouds. That seems like a drastic drop to be dust accumulation on the panel. So where should I start in trying to find the cause of the drop in yield?

[howson]

BR549

The screenshot shows the battery voltage reached 13.52v and VMax was consistent with previous recordings. (The latter reading suggests it's not a voltage output issue from the panel to the input of the controller.)

Could it be the % of battery SoC is inaccurate? Obviously, if the battery is actually full, yield will drop since there's no place for the power to go.

I'm not 100% familiar with the Smart Battery Sense so I watched Victron's intro video. Since I don't see a GX device in your component list, is the SmartSolar getting the voltage and temperature of the battery bank from the SmartShunt or Smart Battery Sense? (I must admit the two devices seem redundant, so very interested to understand the setup.) Are all your components connected via a VE.Smart Network?

Howard

[BR549]

I'm not 100% familiar with the Smart Battery Sense so I watched Victron's intro video. Since I don't see a GX device in your component list, is the SmartSolar getting the voltage and temperature of the battery bank from the SmartShunt or Smart Battery Sense? (I must admit the two devices seem redundant, so very interested to understand the setup.) Are all your components connected via a VE.Smart Network?

The solar controller and battery sense communicate just for temperature. The voltage from the battery sense is certainly redundant, but this was a way to get temperature to the solar controller that was cheaper and easier than a GX.

So if the panel output is okay, could this be a failure of the controller? Any thoughts on how I could test that?

[Thorvald]

I agree with Howsen, battery state of charge is a simple calculation that tends to get wildly inaccurate after time unless you are pulling it right from the BMS. Post the smartShunt and SmartSolar voltage/current charge graphs, I bet we will see the battery reach its max (likely 14.6 but depends on the battery) and drop down to 13.6 idle (which for a four cell lithium battery would be 3.4v per cell, fully charged). Can also check the current graphs for the Shunt to see if there is a trend.

I checked the LiTime website but they don’t really give much specs for the battery and cells inside let alone access to the BMS info. They state “Nominal Voltage: 12.8V” so that would be 3.2v per cell if a 4 cell battery. Charge voltage is 14.4v,@40 amps. Max. Yours is the 200ah so I suspect it is two banks of four cells in parallel. They don’t have much info on their webpage nor can I find the user manual for download to see if it has more, maybe it’s just buried.

Solar Yield will depend on draw, if the battery or load does not need the power, yield will be lower no matter how much sun is there.

[BR549]

I noticed the change in charge level at the end of the day on July 20. That’s when I turned the converter on to make sure that the refrigerator was powered while I’m away.

What puzzles me is why the watt-hr yield dropped from 890 to 100 with no change in sunlight or coverage.

[howson]

I noticed the change in charge level at the end of the day on July 20. That’s when I turned the converter on to make sure that the refrigerator was powered while I’m away.

What puzzles me is why the watt-hr yield dropped from 890 to 100 with no change in sunlight or coverage.

What myself and Thorvald are trying to convey, using an alternative example, is the "fuel tank is full". We wouldn't wonder why the gas pump won't add fuel to our vehicle if the tank is full--of course the automatic shutoff will keep shutting down the supply.

This is no different from the solar panels to the battery. Once the battery bank is full, the supply shuts down. The 100W could just be the maximum needed to keep the batteries fully charged.

Below is what's currently happening in my camper. Even though I have 1200W on the roof and the sun is blazing here in NW Florida, the yield is a measly 82W. Why? Because there's only a very small load on the camper's 12V system. Looking back over previous days note the high yield. That's because I was working in the camper and was utilizing power--solar provided as much as it could 'cause the loads were there to use it.



In other words, I suspect the 89% reporting, not the output of the solar controller, at this point.

How to fix this? There's a manual reset in the Victron Connect app for your SmartShunt. Click the small wheel in the upper right corner and then select BATTERY SETTINGS. At the bottom click SYNCHRONIZE when you know the batteries are 100% charged. See if that fixes the percentage reporting.

[ncitro]

I think the question here was if when you turned on your converter your batteries took more charge or not. If they did then you are right there is some kind of issue. If they did not then Howard and Thorvlad are right on and the batteries SOC was misrepresented. Check your sync settings in the Shunt config. Those are the voltage and current it uses to automatically set to zero and avoid drift.