Help with Voltage divider

Hello I'm trying to use a voltage divider to reduce the voltage from my solar panel (it's a kit) as it can produce a voltage of 7.2 V and I know that the analog pin on a Arduino Mega 2560 is limited from 0 to 5V .

For the circuit I'm using 2 180ohm resistors
The solar panel as the source and the GND of the panel is tied to the GND of the Arduino

When the circuit is operating I'm getting mV readings not what I expect
The solar panel has been outputing 2.6V and I'm expecting on the Vout that it will be 1.3V roughly

Now if I sparate the ground from the Arduino and build the solar panel in conjunction with the voltage divider circuit (so the Arduino ground is separate from the solar panel ground) I'm just reading the full voltage coming out of the solar panel it's not divided.

I'm curious if anybody can help me to get this to work I've been using my meter to measure all this before I damage my Arduino .

180 ohms sounds way too low

I had though it was too high at first because I had 2 1kohm in

Such a low resistance may be loading down the panel, causing voltage to fall. Try two 4.7k resistors. What is the maximum voltage the panel puts out in full sun with nothing connected but the volt meter? What is the size of the panel?

Voltage divider thingy Voltage Divider Calculator

JCA34F:
Such a low resistance may be loading down the panel, causing voltage to fall. Try two 4.7k resistors. What is the maximum voltage the panel puts out in full sun with nothing connected but the volt meter? What is the size of the panel?

So I put in the 4.7k resistors in and I got a bigger mV value now in the 70 mV range

I think I'll bump up the resistance once more

And in full daylight I read 7.18V as my max recorded and the size is 160mm X 70 mm

I bumped it up to 10k now and at around 1.6 volts conning from the solar panel I'm reading 115 -150 mV

I wonder if I just need really high resistance

With your resistor divider connected, what is the input voltage at the "top" resistor using a voltmeter?

So I put the panel to a constant light that produced about 4.5v
The first resistor measured about 2.1 volts
The second measure 451mV

Okay so I think I fixed it I put a 67k resistor in the first one too it and it gave me a nice Vout reading for 4.5v I read 2.21V

Then I got curious as to why such a high resistance was needed I put back in the 10K and it still producing the same great results

I am slightly confused as to this but thank you all for your help and have a happy new year

S1Sanichara:
So I put the panel to a constant light that produced about 4.5v
The first resistor measured about 2.1 volts
The second measure 451mV

So open circuit the panel shows 4.5V?

With 20K of resistance (your two 10K resistors in series) you see 2.1V at the top of the resistor. And with that 2.1V you see 0.45V at the middle of the divider?

It seems like the panel does not produce enough current to feed your resistor divider. When connected to the divider you see its output drops to 2.1V which means the panel has a high output resistance and even a small current draw is enough to produce a drop across it.

Consider putting an op-amp in a voltage-follower configuration between the panel and your resistor divider.