This seems to confuse me especially when I am looking at buying another portable solar panel. My current 120 watt solar panel made by rich solar & purchased off EBay (Bit Deals) is specified as 17.8 maximum power voltage with a maximum power current of 6.74 amps. I have been to Home of 12 volt in SA who tell me their 120 watt Blue apple panels are A grade panels & I will admit are in a better frame & a much better leg support. But the VMP on the blue apple is 19.5 volts so therefore the mpc is only 6.44amps I know this is negligible but I would like to know why & how there is a variation and two is a 19.5 volt panel better than a 17.8 volt panel. I do know that some cheap panels are sold that are 14 volt mpv and understand that they will struggle to fully charge a battery. As an aside are these cheaper panels on EBay a second grade panel or are they A grade as the sellers state.?? Thanks for your time to ponder, consider & reply Daz
This seems to confuse me especially when I am looking at buying another portable solar panel. My current 120 watt solar panel made by rich solar & purchased off EBay (Bit Deals) is specified as 17.8 maximum power voltage with a maximum power current of 6.74 amps. I have been to Home of 12 volt in SA who tell me their 120 watt Blue apple panels are A grade panels & I will admit are in a better frame & a much better leg support. But the VMP on the blue apple is 19.5 volts so therefore the mpc is only 6.44amps I know this is negligible but I would like to know why & how there is a variation and two is a 19.5 volt panel better than a 17.8 volt panel. I do know that some cheap panels are sold that are 14 volt mpv and understand that they will struggle to fully charge a battery. As an aside are these cheaper panels on EBay a second grade panel or are they A grade as the sellers state.?? Thanks for your time to ponder, consider & reply Daz
What part of the answer that I gave you on Exploroz were you not satisfied with?
If I had said something that was incorrect, you can be sure that others would have jumped in very quickly with their version of the truth.
This seems to confuse me especially when I am looking at buying another portable solar panel. My current 120 watt solar panel made by rich solar & purchased off EBay (Bit Deals) is specified as 17.8 maximum power voltage with a maximum power current of 6.74 amps. I have been to Home of 12 volt in SA who tell me their 120 watt Blue apple panels are A grade panels & I will admit are in a better frame & a much better leg support. But the VMP on the blue apple is 19.5 volts so therefore the mpc is only 6.44amps I know this is negligible but I would like to know why & how there is a variation and two is a 19.5 volt panel better than a 17.8 volt panel. I do know that some cheap panels are sold that are 14 volt mpv and understand that they will struggle to fully charge a battery. As an aside are these cheaper panels on EBay a second grade panel or are they A grade as the sellers state.?? Thanks for your time to ponder, consider & reply Daz
I think if you read Brian's post again you may understand but perhaps this may help
[your 120W panel with vpm of 17.8V & Peak current of 6.74A adds up to 119.972W
Good enough to be called 200W
Then the 120W blue apple panel with19.5V &6.44A =125.58W
The unknown is are they both working on the same test standard ?? [temp & light intensity]
If so the the Blue is giving slightly better output
Now regulators come into the story & this may be confusing
IF the regulator is a PWM [pulse width modulation ]type
The panel you have would actual put more Amps into the battery
IT 'at PPP' would put in 6.74A
But the Blue would only put in6.44A
But IF the regulator was a MPPT [Maiximum power point tracking reg]the 2nd panel uder the same conditions of operation would put in slightly more current[Amps] at times.
The old panel, in theory & neglecting conversion losses with a battery at 12V would put in10A
The new panel with a battery at 12V would put in 10.4A
put simply A PWM reg cannot change the AMPS output of the panel
& the lower the battery voltage the less ACTUAL Watts goes into the battery
A MPPT reg converts the Watts of the panel to suit the battery voltage & IN theory puts the full available WATTs into the battery
PeterQ
give
-- Edited by oldtrack123 on Friday 7th of February 2014 04:55:31 PM
Brian thank you. I was only looking to see what other opinions were about and the question about A grade panels still has not been answered. Obviously by your reply it got up your nose that I re posted on a different forum. Not everyone is on Exploroz.
With regard to the grade of the panel, it is impossible to know by the advertisement as retailers have been known to tell porkies in the past.
You are probably unlikely to get an A grade panel at a basement price, but a B grade panel will generally suffice as that grading allows for visual flaws which don't affect performance.
C grade cells will still produce about 90% of their rating, and a check of Ocv and Isc will soon disclose a C grade defect panel.
D grade cells just don't make it to the assembly line these days, so it's unlikely you'll get one that bad.
You don't often encounter mono panels of any less than B grade quality, so it may be best to stick to them.
With regard to the grade of the panel, it is impossible to know by the advertisement as retailers have been known to tell porkies in the past.
You are probably unlikely to get an A grade panel at a basement price, but a B grade panel will generally suffice as that grading allows for visual flaws which don't affect performance.
C grade cells will still produce about 90% of their rating, and a check of Ocv and Isc will soon disclose a C grade defect panel.
D grade cells just don't make it to the assembly line these days, so it's unlikely you'll get one that bad.
You don't often encounter mono panels of any less than B grade quality, so it may be best to stick to them.
Did you count the number of cells in each panel? The "normal" panels have 36 cells in a 9 x 4 or 6 x 6 configuration.
The 36 cell panels operate at a peak power of 17.something volts. Your 17.8 V MPP panel is a little higher than the normal (usually 17.2 - 17.4 V) but we will use that voltage. So the current panel is 17.8/36 = 0.494444 volts per cell. If the cell configuration is 10 x 4 cells this gives 0.494444 x 40 = 19.7777 V
I say again, did you count the number of cells in each panel?
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PeterD Nissan Navara D23 diesel auto, Spaceland pop-top Retired radio and electronics technician. NSW Central Coast.
Did you count the number of cells in each panel? The "normal" panels have 36 cells in a 9 x 4 or 6 x 6 configuration.
The 36 cell panels operate at a peak power of 17.something volts. Your 17.8 V MPP panel is a little higher than the normal (usually 17.2 - 17.4 V) but we will use that voltage. So the current panel is 17.8/36 = 0.494444 volts per cell. If the cell configuration is 10 x 4 cells this gives 0.494444 x 40 = 19.7777 V
I say again, did you count the number of cells in each panel?
Dazz, There goes another theory. The only explanation is they are stretching their specifications. The 19.5 MPP seems to far from the normal for me. If they are truely as labelled you will get less current from that panel if you are running it through a series pass (PWM) controller. I would not like to put it in parallel or series with the original panel if you are running them through an MPPT controller. With the panels being so different I think it will be difficult to track the panels performance.
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PeterD Nissan Navara D23 diesel auto, Spaceland pop-top Retired radio and electronics technician. NSW Central Coast.
Dazz, There goes another theory. The only explanation is they are stretching their specifications. The 19.5 MPP seems to far from the normal for me. If they are truely as labelled you will get less current from that panel if you are running it through a series pass (PWM) controller. I would not like to put it in parallel or series with the original panel if you are running them through an MPPT controller. With the panels being so different I think it will be difficult to track the panels performance.
