Panel differences?

DMS11X

Why are some panels listed as use for "off-grid" and others are listed for "grid tie" ??? Are they not the same?

petertearai

same but diferent .
Off grid tend to be 22  or 44 volt open circuit .
grid tend to be 36 volt .... or there about  .
. But it realy tends to be how you arrange them , for battery charging a 12 volt battery  then the 36 volt grid panels would be a problem , except if you go for the more expensive  mppt  charge controller , see https://www.solar-electric.com/learning-center/batteries-and-charging/mppt-solar-charge-controllers.html
The mppt charge controllers  can have an input voltage of  generally 150 to 200 volts. So if you arrange the panels in series to be under this voltage all is well .
Grid tie  panels will often be connected to a string inverter , ie all panel's in series , so having a lower voltage per panel will often mean you can get more watts per string .
But to answer your question it is my understanding that the actual cells in either panel can be the same .

mcgivor

petertearai said:

same but diferent .
Off grid tend to be 22  or 44 volt open circuit .
grid tend to be 36 volt .... or there about  .
. But it realy tends to be how you arrange them , for battery charging a 12 volt battery  then the 36 volt grid panels would be a problem , except if you go for the more expensive  mppt  charge controller , see https://www.solar-electric.com/learning-center/batteries-and-charging/mppt-solar-charge-controllers.html
The mppt charge controllers  can have an input voltage of  generally 150 to 200 volts. So if you arrange the panels in series to be under this voltage all is well .
Grid tie  panels will often be connected to a string inverter , ie all panel's in series , so having a lower voltage per panel will often mean you can get more watts per string .
But to answer your question it is my understanding that the actual cells in either panel can be the same .

Additionally 

The difference in voltage is due to the cell count, a grid tie panel will typically have 60 cells, a 24V nominal panel will have 72, there are other configurations but these are by far the most common. Supply and demand governs the price, grid systems account for the vast majority of panels produced hence cheaper per watt.

Photowhit

There really isn't a difference at this point, some of the cheapest panels are 72 cell panels.

It use to be important, since until about 12 years ago MPPT type charge controller were uncommon. PWM charge controllers are less expensive and make use of panels designed in narrow terms to charge 12 volt nominal batteries, which require about 36 cells per 12 volts. Most of the small panels of less than 160 watts currently being made are 36 cell panels and will have a VMP (voltage under load) of 17.5-19 volts. A 12 volt battery charges at around 14.5 volts and some voltage is lost to wiring and heat. 

So a 12 volt battery bank is looking for roughly 36 cells in series, a 24 volt system 72 cells in series (a single 72 cell panel or 2 36 cell panels in series), a 48 volt system/battery want 144 cells in series, 4 - 36 cell panels, 2-72 cell panels. This is for use with a PWM charge controller.

Today, many system use MPPT type charge controllers, which maximize the potential wattage from arrays (group of panels) with a higher voltage than the system voltage. In fact they need to have about 30% higher voltage than the systems charging voltage.

BB.

You will find the GT panels are UL/NRTL Listed devices for use with grid tied solar inverters. And they are listed to 600 or 1,000 volts for use in high voltage arrays (typically GT inverters are used with 200-400 Vmp-arrays).

Battery powered systems may not be Listed devices.

Bill