quintinha
New Member
Hello all,
This is my first post here. Thank you to everyone who contributes to this forum, it's a goldmine.
After a lot of reading I'm just about ready to buy stuff. The project is very basic and I'm trying to keep it as plug-and-play as possible: my goal is to place approximately 25-30 1w and 2w LED bulbs around my yard for nighttime lighting. I'm shooting for somewhere around 30 watts running for 4-6 hours per night.
Here are the specs of the items I'm planning to buy (Please excuse the Portuguese, I'm American but live in PT):
TLDR
1x 100W panel, 5ish amps, 18ish volts
1x lifepo4 12v 20ah battery, 10amp max charge, 4amp max discharge
1x victron 75/10 mppt controller
a bunch of low-watt outdoor lights
Panel
https://www.castroelectronica.pt/pt...taico-silicio-monocristalino-100w-12v--proftc
Potência nominal: 100W
Corrente de Potência Máxima (Impp): 5.39A
Tensão Máxima de Energia (Vmpp): 18.56V
Tensão de circuito aberto (Voc): 21.76V
Corrente de curto-circuito (Isc): 5.72A
Tensão máxima do sistema: 100V
Battery
https://innpo.pt/baterias-recarrega...ah-innpo-baterias-recarregaveis-de-litio.html
Tecnologia LiFePO4
Tensão nominal 12,8 V
Capacidade 20 Ah
Corrente máxima de carga 10A
Corrente máxima de descarga 4A
Controller
https://innpo.pt/controlador-de-car...ictron-energy-controlador-de-carga-solar.html
Tensão da bateria 12/24V
Corrente de carga nominal 10A
Potência nominal FV, 12V 1a,b) 145W
30w from a 12v battery is 2.5A, so the battery's max discharge of 4A should be good.
Running the lights an average of 5 hours per night is 150w of power. The battery should provide more than 200wh so at least on a sunny day it should be groovy.
I'm open to suggestions if I've overlooked anything, please let me know what you think.
The one question I have remaining in general about how this all works is about the relationship between the controller and the battery: the battery says 10A max charge current (although it states 20A in the spec sheet, I need to clarify this with the manufacturer) and the controller says 10A charge current. The panel produces max 5.39A and 18.56V. From reading this thread I understood that that controller will drop the voltage received from the panel to match the battery it's charging thereby increasing the amps:
So (dirty example) if a panel sends the controller 20V at 5A, that's 100w, but the battery wants 14V not 20V, so the controller sends it 14V at 7.1A for the same ~100w it received from the panel (ignoring system loss and whatnot). As long as the battery's max charge current rating is greater than what the controller is sending, and the controller's max current rating is greater than what it's receiving and sending, it's all gravy. Is that right, if a bit oversimplified?
Thanks! and happy building
This is my first post here. Thank you to everyone who contributes to this forum, it's a goldmine.
After a lot of reading I'm just about ready to buy stuff. The project is very basic and I'm trying to keep it as plug-and-play as possible: my goal is to place approximately 25-30 1w and 2w LED bulbs around my yard for nighttime lighting. I'm shooting for somewhere around 30 watts running for 4-6 hours per night.
Here are the specs of the items I'm planning to buy (Please excuse the Portuguese, I'm American but live in PT):
TLDR
1x 100W panel, 5ish amps, 18ish volts
1x lifepo4 12v 20ah battery, 10amp max charge, 4amp max discharge
1x victron 75/10 mppt controller
a bunch of low-watt outdoor lights
Panel
https://www.castroelectronica.pt/pt...taico-silicio-monocristalino-100w-12v--proftc
Potência nominal: 100W
Corrente de Potência Máxima (Impp): 5.39A
Tensão Máxima de Energia (Vmpp): 18.56V
Tensão de circuito aberto (Voc): 21.76V
Corrente de curto-circuito (Isc): 5.72A
Tensão máxima do sistema: 100V
Battery
https://innpo.pt/baterias-recarrega...ah-innpo-baterias-recarregaveis-de-litio.html
Tecnologia LiFePO4
Tensão nominal 12,8 V
Capacidade 20 Ah
Corrente máxima de carga 10A
Corrente máxima de descarga 4A
Controller
https://innpo.pt/controlador-de-car...ictron-energy-controlador-de-carga-solar.html
Tensão da bateria 12/24V
Corrente de carga nominal 10A
Potência nominal FV, 12V 1a,b) 145W
30w from a 12v battery is 2.5A, so the battery's max discharge of 4A should be good.
Running the lights an average of 5 hours per night is 150w of power. The battery should provide more than 200wh so at least on a sunny day it should be groovy.
I'm open to suggestions if I've overlooked anything, please let me know what you think.
The one question I have remaining in general about how this all works is about the relationship between the controller and the battery: the battery says 10A max charge current (although it states 20A in the spec sheet, I need to clarify this with the manufacturer) and the controller says 10A charge current. The panel produces max 5.39A and 18.56V. From reading this thread I understood that that controller will drop the voltage received from the panel to match the battery it's charging thereby increasing the amps:
An MPPT solar controller can be imagined as a specialized DC-DC converter that feeds the battery its desired charging voltage. By lowering the output voltage, a higher current can be drawn by the battery, so in a way, voltage is „turned into current“. However, there is no „waste“ in the sense that energy is purposely converted to heat, it is merely a side effect of the process that is not 100% efficient.
So (dirty example) if a panel sends the controller 20V at 5A, that's 100w, but the battery wants 14V not 20V, so the controller sends it 14V at 7.1A for the same ~100w it received from the panel (ignoring system loss and whatnot). As long as the battery's max charge current rating is greater than what the controller is sending, and the controller's max current rating is greater than what it's receiving and sending, it's all gravy. Is that right, if a bit oversimplified?
Thanks! and happy building