Ask me Anything Solar

Please what does these values with ? mean as displayed on a CC

Pv

Voltage-pv voltage

Current-?

Battery
Voltage-Battery voltage

Current

Load
Current

When the current value under the battery parameter has a negative value, what does this mean?

From  therealMcCain:

Pv

Voltage-pv voltage

Pv voltage refers to the amount of electrical voltage a solar panels can produce. For most solar panels there are generally 2 types of Pv voltages. 

VOC which is the open circuit voltage. The voltage of the panel when it is not been used to connected to any load. 

VMP which is the Voltage maximum power. The optimum voltage of the Pv for it to be able to produce its maximum power. 

Current-?

This is usually measured in a ampere or amps for short. Again solar panels usually have 2 types of currents. 

You gave the ISC and IMP (I in this case represents currents just as v represents voltage) 

The first is current short circuit. The is the total energy that is released from a solar panel when it is short circuit that is positive and negative are connected together. Again this figure is not useful as it only use the potential of the solar panel when the current is not flowing through a circuit. 

The next figure is the IMP. Current maximum power. This is the total amount of currents or amps a solar panel can produce under standard test conditions. 

The IMP is produced when voltage is at VMP. 

Things to note electricity is measured in watts. Watts is a combination of voltage times amps. Hence a solar panel of 220w could have the following 33. 8v (VMP) and 6.5 amps (IMP) 33.8 ✖ 6.5  = 219.7 roughly 220w.

Battery

Voltage-Battery voltage

Battery voltage is the general nominal voltage of a battery. Batteries generally have nominal voltage. Which is their standard designed voltage. Like 12v, 6v, 2v. For off grid application the voltage of a battery is determined by how many cells it has. A battery cell is nominally 2v.

The voltage of say a 12v battery can vary between 15v and 10.5 depending on its state of charge, use or amount of current energy being drawn from the battery (also called battery load). 

Current

This represents the total amount of current  stored in the battery. This usually measured in amps hours. (not to be confused with amps). Amp hours is the amount of amps or current that can be drawn from a battery within a specified time period usually an hour. Hence a 200AH battery means theoretically 200Amps can be drawn from the battery in an hour before the battery becomes fully discharged. Or 10 amps can be drawn for 20 hours or 5amps can be drawn in 40 hours.  Although the situation in real life use is not linear thanks to what is known as battery peukert effect

Load
Current

When the current value under the battery parameter has a negative value, what does this mean?

Most charge Controllers and battery monitor indicate a Battery being discharged by putting a negative symbol – infront of the amps or watt figure. e.g -12A means 12A is being discharged from the battery.