Solar panels appear to be draining Batteries

[middysafloat]

I have just installed 4 X12V 140Wp Mono. panels in series connected to an MPPT controller. I also have an inverter/charger connected to the batteries which are 6 X 6v Trojan connected in series giving 720Ah.at 12V.

The problem I have is as soon as the panels are switched on for the MPPT to charge the batteries they appear to immediately start draining. Indications on the inverter monitor are that the SOC% drops, now I understand that the % is only a rough estimate but why would it reduce so rapidly.

I have checked the cables and voltages all appear correct. The panel monitor snapshot displays panel output as 0.46A, 92.97V and 42.78W. Battery status is normal and charging status is "boost charge" battery voltage is 13.37V, 3.25A there is zero load on the batteries.

I have always used the inverter/charger monitor to give me a reasonable idea of the SOC%.

I am no expert on Solar technology so can anyone help please, any suggestions will be gratefully received.

[Mike90250]

I'd suspect a bad charge controller, if it's from ebay, you are out of luck. Or take it back to the vendor for replacement.
Most good MPPT controllers are first connected to the battery to begin their internal computer boot-up, and after a few minutes, you can connect the PV.

And on the odd chance you connected wires backwards, please double check the polarities with a volt meter, not the wire colors

[middysafloat]

Thanks for your suggestions I have double checked the cables and polarity is correct, in fact ,I have an Epever Tracer - BN series MPPT 4215BN which alarms if cables are wrong.

I have switched on the MPPT and connected the panels after a while once the MPPT had booted up and settled down. The batteries are fully charged by the Victron inverter/charger and show a voltage of 13.18V with zero load. Immediately the panels are connected the MT50 monitor shows 14.4V then drops to 13.4V with 7.4A charge and the Tracer goes into boost mode even though the batteries are full.

Is there an issue with how the Tracer and Victron inverter/charger are connected to the battery bank? as the Victron monitor SOC% drops from full but I know the batteries are really still full as before connecting panels I have checked the battery voltage after 1 hour of load and the meter shows over 12.5V.

What sort of Amps, Volts and Watts should I typically expect from 4 X 12V 140W Panals in series?, the VOC of these is 26V per panel. I have noted on low sun days that the arrays current is 1.46A, volts is 101.58V and power is 106.20W with boost charging the full battery, is this ok I have no experiance?.

I am getting quite frustrated with this problem, I can understand that my lack of knowledge may be causing my confusion.

.

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[SunEagle]

It may be possible that something is putting a load on the battery to drop the voltage which then triggers the charge controller to start it jobs. That shouldn't happen unless there is an issue with the panel wiring or the CC.

[ewarnerusa]

The remote monitor seems to indicate that the solar charge controller is making the right decision by applying 14.4V bulk charge voltage level upon startup and then dropping to a float-level voltage of 13.4V upon determining that the battery bank is full. But indicating that the charger is in boost mode does not make sense. I googled that charger controller and found a listing for it on Aliexpress. It mentions in it controls charging and discharging? I don't know anything about a charge controller that allows for and controls discharging. Usually you want it to prevent that from occurring. I recommend studying the manual to determine what the discharging feature is and how to disable it if it is on.
I also note your mention of "switching MPPT on" as well as the controller having a load on/off button. You aren't using the "load" terminals on the controller are you? You should only be using the battery terminals to connect the controller directly to your battery bank.
I'm not very savvy on MPPT controller ratings, but your combined panel wattage (560 watts) slightly exceeds the maximum input rating of that controller (520 watts). Maybe something got fried by having more panel wattage than the controller is rated for. Technical Specifications

• Electrical Parameters

Description	Parameter
Nominal system voltage	12VDC / 24VDC Auto work
Rated charge current	Tracer4215BN40A
Rated discharge current	Tracer4215BN20A
Maximum battery voltage	32V
Max. solar input voltage	150VDC
Max. PV input power	Tracer4215BN 520W(12V) 1040W(24V)
Self-consumption*	≤50mA(12V) ≤27mA(24V)
Charge circuit voltage drop	≤0.26V
Discharge circuit voltage drop	≤0.15V
Temperature compensate coefficient	-3mV/ºC/2V(default)
Communication	RS485(RJ45 interface)

[Sunking]

I have checked the cables and voltages all appear correct. The panel monitor snapshot displays panel output as 0.46A, 92.97V and 42.78W. Battery status is normal and charging status is "boost charge" battery voltage is 13.37V, 3.25A there is zero load on the batteries.

So what is the problem?

All that is telling you is the panels are sourcing current, not sinking current, and your batteries are near completely charged up.

[Raul]

You need to configure and set up the batt. monitor properly to give you a more realistic SOC, then the CC needs slightly higher voltages algorithm than the inverter charger as they are conflicting. You should charge with one or the other unless you come up with some com between the 2. They need to start the charging cycle at once to reach a compromise otherwise once you finished charging with the multi then the batt. will be on float and you turn on the pv the CC will see the bank as PCOC and will start a new charging cycle bringing the bank to absorb voltage.
It appears that al the hardware works as intended but user input understanding is poor .

[Sunking]

One thing to keep in mind, for lead acid batteries SOC voltages are completely meaningless on an operating system. I can give you a brand new fully charged battery, Put a load on it and it it will measure 7 volts. I can give a dead 12 volt battery, put a charger on it, and it will measure 14 volts. SOC voltage means NOTHING. Not only for lead acid, but really any battery type.

There is only one way you can determine the SOC of a flooded lead acid battery and only one way. Measure the Specific Gravity with a Temp Compensated Hydrometer. The only time voltage can tell you anything is if the battery is disconnected and allowed to rest for several hours. Even then it is only a Ball Park indicator and would require a Hydrometer to tel you what the real SOC is. So if you want to use voltage as an SOC Indicator, tonight before you go to bed, disconnect the battery and go to bed. Next day measure the voltage.

From what I have read here so far strongly suggest Operator Error.

What you are most likely seeing is your battery is already fully charged. When you cycle the controller it starts off in Bulk mode automatically, then the controller determines the battery is already charged up and lowers the voltage to Float to around 13.6 to 13.8 volts. Perfectly normal.

FWIW the OCV voltage of a fully charged 12 volt battery is 12.6 volts. So if 12.6 volts is 100%, then what is 13.8 volts?

Correct answer: It means nothing other than the charger has finished charging the battery. The battery may or may not be fully charged. Turn off the charger, turn a load on, and the voltage will drop immediately to something less than 12.6 volts.

The only thing your SOC meter will tell you is when you are in trouble. If it read 12 volts or less, you are in trouble. It is an Idiot Light just like cars with a Check Engine Light or Hot Light?