runsnbunsn
Member
- Joined
- Aug 29, 2018
- Messages
- 31
Hey Guys!
I found a good deal on solar panels, which made me think about my future solar setup when my powerwall is done. This is going to be a longer post, I'm happy about anyone who cares to read it and gives me some input. sorry in advance for my medium english.
First, the Deal:
I could get 5 x used 240Wp Mono Panels for about 500 - 600 euro. So 1200Wp, I dont know how old they are but my guess is max.10 years, closer to 5
My current setup:
12v setup,2x 50wp poly and 2x 100wp mono panels with 2x 12v lead acid batteries(which are pretty much done)
My future setup:
7s120p used 18650s, so I'll "upgrade" to 24v
Problems at the location:
Its a completely off-grid "shed", I only have a small generator there for those times when you need a bit more juice...
The shed and the whole location is "in the middle" of the woods, no elevation and no place without shadow. I'm not allowed to build anything there because its a "water reserve" location.
The place with the least amount of shade through the day is actually the roof of the shed, but there are trees all around, some of them I cannot cut down because I don't own them, and some of them which I will not because they are really old. I get about 2 - 3 hours of full sunlight on my panels atm, the rest of the day at least 1 - 2 panels are in partial or full shade.
Fun fact: I earn about the same solar power in march and april as in the summer months, just because the leaves are not fully grown at this time.
Because of the shading problem I go with a parallel setup, because in my opinion it makes no sense upping the voltage when most of the time at least one panel is shaded.
So the Problem is this:
Data of the new panels:
Pmax: 240W
Optimum operating voltageVmp: 32.2V
Optimum operating current Imp: 7.95A
Open Curcuit VoltageVoc: 37.3V
With 7s120p I want to stay in the 4.05 - 3.5V range, so maximum Voltage is 28,35V
The new panels need to be all parallel, because I have no other choice.
Because of the bigger space the panels use, I can almost definitely say that where will be almost zero time/day where all panels are in direct sunlight.
If you are still with me at this point, yay!
Is the 30.2V optimum voltage the voltage at pmax, or can it still drop? I'm a bit worried I'm not able to reach the 28.35V. Cables will be about 15m(thick solar cable, don't know the dimension)
The theoretical max will be about 40A, the real usage max around 30A with all panels parallel. Due to shading, it will be 5A to 20A most of the time.
And I guess with a voltage range of 30.2v to 28.35v a MPPT charger doesn't really make sense?(will go for a MPP Solar charger/inverter, either PWM or MPPT). Most MPPT have a minimum voltage of 30V
Should I take the deal or wait for another one with panels in the 40V to 50V range and use MPPT? I'm just not sure if it's worth it...
I found a good deal on solar panels, which made me think about my future solar setup when my powerwall is done. This is going to be a longer post, I'm happy about anyone who cares to read it and gives me some input. sorry in advance for my medium english.
First, the Deal:
I could get 5 x used 240Wp Mono Panels for about 500 - 600 euro. So 1200Wp, I dont know how old they are but my guess is max.10 years, closer to 5
My current setup:
12v setup,2x 50wp poly and 2x 100wp mono panels with 2x 12v lead acid batteries(which are pretty much done)
My future setup:
7s120p used 18650s, so I'll "upgrade" to 24v
Problems at the location:
Its a completely off-grid "shed", I only have a small generator there for those times when you need a bit more juice...
The shed and the whole location is "in the middle" of the woods, no elevation and no place without shadow. I'm not allowed to build anything there because its a "water reserve" location.
The place with the least amount of shade through the day is actually the roof of the shed, but there are trees all around, some of them I cannot cut down because I don't own them, and some of them which I will not because they are really old. I get about 2 - 3 hours of full sunlight on my panels atm, the rest of the day at least 1 - 2 panels are in partial or full shade.
Fun fact: I earn about the same solar power in march and april as in the summer months, just because the leaves are not fully grown at this time.
Because of the shading problem I go with a parallel setup, because in my opinion it makes no sense upping the voltage when most of the time at least one panel is shaded.
So the Problem is this:
Data of the new panels:
Pmax: 240W
Optimum operating voltageVmp: 32.2V
Optimum operating current Imp: 7.95A
Open Curcuit VoltageVoc: 37.3V
With 7s120p I want to stay in the 4.05 - 3.5V range, so maximum Voltage is 28,35V
The new panels need to be all parallel, because I have no other choice.
Because of the bigger space the panels use, I can almost definitely say that where will be almost zero time/day where all panels are in direct sunlight.
If you are still with me at this point, yay!
Is the 30.2V optimum voltage the voltage at pmax, or can it still drop? I'm a bit worried I'm not able to reach the 28.35V. Cables will be about 15m(thick solar cable, don't know the dimension)
The theoretical max will be about 40A, the real usage max around 30A with all panels parallel. Due to shading, it will be 5A to 20A most of the time.
And I guess with a voltage range of 30.2v to 28.35v a MPPT charger doesn't really make sense?(will go for a MPP Solar charger/inverter, either PWM or MPPT). Most MPPT have a minimum voltage of 30V
Should I take the deal or wait for another one with panels in the 40V to 50V range and use MPPT? I'm just not sure if it's worth it...