few questions about solar power....

Grouinding has two or three major reasons to "exist".

First, is if there is a short between a hot wire (+12 VDC or 120 VAC) to the inverter case (as an example), then you want the "case ground" to connect (single point grounding) to the "return leg" of the VDC and/or VAC power. That prevents the case from "becoming" electrically hot and starting fires/electrocuting people. The grounded case provides an electrical return path to pop a fuse/circuit breaker/or internal over current protection circuit in the AC Inverter.

In the Philippines, I believe that your AC outlets are not polarized and no ground "blade" (the Hot/Neutral/ground wiring is not keyed like US and other countries). This makes grounding and such a bit more of an issue that is not "supported  by code and common practice". Instead, the AC equipment just relies on internal ~2,000 Volt insulation between the AC lines and (for example) your computer DC internal wiring. 

Second, a path to direct energy from a lightning strike (to your panels, house wiring, etc.) to earth Ground (cold water pipe, grounding rod, etc.). If you live in an area with a good chance of a lightning strike, grounding and surge suppressors are important. Note that a direct strike has more energy than any standard equipment can manage--But suppressors and grounding direct the lightning to "earth" instead of it jumping to phone lines, TV Antennas, computer networks, your AC power lines, etc.

The other reasons for "ground" are a bit more obscure but include starting florescent tube lights, electronic stove/water heater pilot lights, and other "things".

This makes your home brew solar system a bit more of an issue to "solve" if you are getting electrical shocks at times. I cannot tell you to do ABC to fix the problem. And any electrical shocks can be indicative of current or future problems.

-Bill

Not quite sure I know how to answer your questions... I try not to do a bunch of math that does not exactly relate to a poster's system requirements... It can cause more confusion vs clarity.

Can you give us a brand/model number/link to your solar charge controller?

There are a few "rules" that need to be followed to "optimally" connect a varied panel solar array to an MPPT controller.

Just like you should not connect various A/AA/C/D flashlight batteries in random series/parallel connections to a 12 volt car battery. Things are not going to work out well. From just not "harvesting" optimal energy from the array to actually risk of fire (probably not a big risk with your smaller array).

We always try to ensure that everyone's system(s) are as safe as possible--However with limited information, it is difficult to give "accurate" answers.

Having a DC Capable Clamp Current Meter so you can measure current (quickly and safely)--As well as the Volt Meter--Together it is easier to figure out what is going on with your hardware.

Could you use a low Ohm value resistor and measure the voltage drop across the resistor and get V=I*R / I=V/R type math--Yea--I have done that... But it does not make things quick and easy.

To even diagnose your panels (working or not, etc.)--Need the label (Voc/Isc/Vmp/Imp/Pmp ratings), or you can do things like measure Voc (voltage open circuit) and Isc (short circuit current in full sun) and figure out if the panels are working at all (there are other tests too--But keep things simple for now).

When we know more about the panels and charge controller, can then help with possible configuration and functional questions.

The problem with "random" solar hardware--It can be difficult to get the mix and match to make a system that operates anywhere near optimally. Very common that some things (I.e., miss-matched panels) will not play together well.

-Bill

Photo of solar charge controller does not really help much.

At this point, you need to measure the Voc (voltage open circuit) of each solar panel--Roughly, each panel should be Voc~20-22 VDC in sunlight. You can connect each solar panel in parallel with the others, up to 360 Watt solar array total.

If you do not have the panel mfg's labels (specifications), I guess you could go with a tape measure of you solar array total area using this rough calculation:

Panel square meters = (x*y) of each panel solar cell area + Panel 2 + panelxxx = total array area
Rough array max power = Total Array Area (in sq meters) * 1,000 Watts per sq-meter * 0.15 panel eff

This will give you a very rough idea of your solar array max power output.

If you can measure the array DC current--Then the max output current of the array would be:

Pmp = Vmp * Imp
Imp-array = Pmp / Vmp = 360 Watts / 18 VDC = 20 Amp max array output for your controller

If you measure 12.5 AmpDC Isc from your array (in full noon-time sun, clear day, panels pointed at sun, that is a good start.

Connecting panels all in parallel does not make optimum usage of your "MPPT" solar charge controller--But at least will work without damage/major issues.

-Bill

You are correct about the Omega/Ohm symbol... However you would not use that setting for basic Voc/Isc checks.

Since your meter is an AC current clamp DMM, you cannot use the AC Ampere function on this meter. You are pretty much left with the DC Voltage readings of the array/solar panel voltages. Voc (voltage open circuit--panel not connect) and Varray (voltage of the array when you panel(s) are connected.

Usually it is not very easy to measure voltages on connected arrays--You have to open connection (unplug MC4 connectors/etc.) or other methods to measure the voltages.

A single panel is usually pretty safe--But if you are on a ladder and accidentally short several panels/array--The spark(s) (or shock) my knock you have the ladder if you are not careful.

This is stuff that I/we cannot really train you about via a text forum/posts. There are lots of YouTube videos out there that can help--But finding specific help on measuring a "random" solar array setup--May not be easy to find or be that useful.

-Bill

Typically ("at best"), your solar panels would output around 50% to 77% to the battery bank on an average to very good solar day (cool, clear, dust free panels, etc.) into a battery bank (typically at 80% or less State of Charge--Especially for Lead Acid type batteries)...

If the batteries are >80% SoC (for Lead Acid), the batteries typically reduce the amount of charging current they will accept. The solar panel specifications are "laboratory" numbers... I.e., at Room Temperature and only a few seconds of "artificial sunlight). As panels become hot (under "real sun"), the Vmp falls, and Pmp=Vmp*Imp falls too (to roughly 82% of Vmp/Pmp of "factory numbers" on very hot day/noon time sun).

Note that the % numbers below are based on Battery Bank (lead acid) bank AH capacity... I.e., a 200 AH battery bank at 10% rate of charge is 20 Amps.

Bulk (or Boost) stage charging for a solar charge controller => maximum available solar current to battery bank (typically 10% to 25% of battery bank AH capacity)
Absorb stage charging => From 100% to less than 5% as the Soc goes from 80% to near 100% SoC
Float charging => From 2% to less than 1% charging current at 100% SoC

The outputs of solar panels is highly dependent on actual conditions... More or less Vmp-real=0.82*Vmp-std on a hot day (sort of worst case).

Imp=Amount of solar irradiance on panels. Full noon time sun, panel pointed at sun, clear day (no dust, humidity) equals approximately 1,000 Watts per Sq Meter... A solar panel can harvest about 15% of that energy into electricity.

Just variations in Solar Irradiance is a major topic in itself.

https://en.wikipedia.org/wiki/Solar_irradiance

For our needs, just using round numbers (rules of thumbs) is usually "good enough" for us to understand and debug our systems.

To say that a 50 Watt solar panel is outputting 50 Watts--Is expecting more than it can produce in real life. Again, at best, 50% to 77% of the panel's "rated output" will reach a discharged battery bank. Obviously, the solar harvest drops to 0% output late evening to early morning.

You may or may not have a true MPPT controller... As you have it connected now (a bunch of solar panels with Vmp~17.5 to 18.0 VDC) is operating (pretty much) in PWM mode.

A true MPPT controller would "optimally" work with Vmp-array roughly 2x Battery Charging voltage (minimum). Maximum Vpanel input voltage--Need controller specs. (some controller will fail at 60 VDC, others >100 VDC, others yet at 150 VDC, and some at >600 VDC). Without the specs, just don't know what yours requiters (typically as Vpanel voltage rating gets higher, the cost of the MPPT controllers increase too).

You can put panels in series for "better" MPPT harvest--But need to know the actual panel specs so that you meet the MPPT controller specifications, and the proper panel ratings for series connections (basically Imp of panels have to "match" for a series string).

Most stores are going to stock AC only current clamp DMMs... 90% of the people out there want to work on 120/240 VAC house circuits.

AC+DC Current Clamp Meters tend to be more expensive and need a bit more "reading of the manual" to use optimally on DC circuits. Not difficult, but you just need to "zero" DC clamp meter readings before measuring current. AC clamp meters do not need Zeroing for accurate current measurements.

-Bill

Again, current is very similar to liters per hour filling a 100 Liter bucket... So the current from each panel will add with each other panel to give you a total Ampere value... But like any water system, you need "pressure" (aka voltage) to fill a bucket that may be 50 feet above on a hill... Too little pressure, no water will flow. Too "much" pressure (voltage) and it is wasted. Yes, you can pump up to 500 feet elevation, but the bucket is at 50 feet.

Now with a MPPT controller, it can "use" the extra voltage and the current, and take the high voltage & current and efficiently down convert to the lower battery voltage and give a higher charging current.

At this point, you can have bad panels(s), bad connections, bad wiring, an MPPT controller that is really a PWM controller, running a true MPPT controller at Vmp~18 volts and the MPPT controller really is running in PWM mode, you could have "mismatched" solar panel Vmp voltages, your charge controller thinks the battery bank is near full, etc.

Don't have enough information to really know what is happening.

-Bill

I did not see any 400 Watt class panels in this photo... They should be roughly 1m * 1.83m (1.83 sq meters) in size (minimum for a good quality mono-crystalline solar panel). Example of a 400  Watt panel:

https://www.solar-electric.com/lib/wind-sun/REC_n-peak_3_black_series-DS.pdf

From the photo, I really cannot figure out the Voc of each panel... Ideally, the Vmp of a panel is 0.5 Vmp per cell * number of cells in series... Typically 36 cells in  series for Vmp~18.0 volts (for a "12 volt" panel)... You can find 60 cell; and 72 cell (in series panels) too--Especially for the larger format panels.

I would suggest that any panels that are 10% of your largest panel (I.e., 400 Watt * 10% = 40 Watts) is hardly worth the effort to mount/wire/maintain/test/etc. In engineering terms, anything 1/10th or less is usually "near irrelevant). And anything that is 1/2 or larger (I.e., 400 Watts * 1/2 = 200 Watts) is on the "same order" of magnitude--I.e., "makes a significant difference".

For example, I would suggest that any panels that are (1/2 of 1.83 sq meters) 0.92 sq meters or larger are "worth" pulling off the roof, testing (and measuring Voc/Imp in noon time sun) and documenting what you have. Any panels that are 0.18 meter or smaller, are not really worth working with.

Once you have the solar panel "specs" (again, round numbers are good enough). Note that a typical DMM with wired Amp function are usually limited to 10 Amps maximum. A 400 Watt panel can output more than 11 amps (or more) in ideal conditions.

Also note that 400 Watt panels are typically (but not only) around 36/60/72 Volts Vmp. A typical 140 Watt class panel is around 18 volt Vmp... And one of your small panels is around 15 cells (?) which would be Vmp~7.5 volts (and another panel may be a 12 cell or 6 cell panel?).

I understand that you are trying to do this on a budget... But really need actual panel specs (even Voc and sq meter per panel) would be a big help (sq meter can be converted to Isc/Imp roughly) to configure a "workable" solar array.

Your 70cm * 45cm panel would (at best) be around 60-68 Watt panel.

Or are you saying that "all of your panels" add up to ~400 Watts?

Anyway--Need some basic information to help more.

-Bill