In order to benefit from the cold temperatures which raise vmp you will need an mppt controller.
Do solar panels put out very little amperage.
This is the open circuit voltage the solar panel will produce at stc or standard test conditions stc conditions are the electrical characteristics of the solar panel at airmass of am1 5 irradiance of 1000w m 2 and cell temperature of 25 o c.
If the panels are connected in series the voltage of each panel is added but the amperage stays the same.
For example if the solar panel is rated at 175 watts and the maximum power voltage vmp is given as 23 6 volts then calculate the current as 175 watts divided by 23 6 volts which is equal to.
To ensure that you don t blow your device s fuse set the maximum amperage sensitivity to well above your expected reading.
Hopefully it is less than the solar panel controller output voltage.
The second fuse between your solar panels and charge controller is a little bit different to figure out.
Standard temp and conditions stc is how panels are rated.
Connect the ve solar controller output lead to the ve.
Solar panels usually range in wattage output from around 250 watts to 400 watts but some panels exceed the 400 watt mark.
I had the exact panel op did and in direct summer sun the highest i measured off the back of the panel was just over 7 amps.
Measure the solar panel controller output voltage try to get maximum voltage by angling the panels.
The solar panel with the highest watt is the sunpower e series a commercial solar panel line.
The top panel in the e series comes out at a whopping 435 watts.
Measure the battery voltage.
Solar panel voc at stc.
Rarely do you achieve stc output because in the hot sun the panels heat up and their output is reduced to normal operating cell temperature noct output.
To test solar panel amperage output put your solar panel in direct sunlight set your multi meter to the dc amps setting.
The size of this fuse is dependent on how many solar panels you have and how they are connected series parallel or series parallel.
It may be that you can never get more than 12 13v.
If it is proceed.
Ask someone who knows and they should tell you that for a small setup like 150watt system a mppt is a waste of your money.