Hi!
I am planning to build a few solar systems for a local allotment site.
The site is very big with around 100 plots. I want to have 4 stations with two batteries each. One for CCTV camera and Wifi repeater and a second one as a charging station for tool batteries and mobile phones. I want to keep it separately so they can drain one battery, when the other stays unaffected.
Panels: UL-250M-60 (250W, Voc 37.6V, Vmpp 30.5V, Impp 8.20A)
controllers: I bought some cheap mppt modules up to 7A, 10A and 13A but they are only for 28V max, so I am thinking about a step-down module with CC.
batteries: 3S7P own build (18650) with BMS upto 25A. The cells are NCR18650BD with max charging current of 1A, so for 7 of therm, I believe the 5A max should be ok.
I read about some projects using just a step down module with CC set on float charge voltage and that was working fine.
I know it is not MPPT, but I dont mind losing some energy as the panel is 250W, and the charging power per battery will be around 60W.
Do you have any experience in non-MPPT step-down modules used for solar?
Do you think, I should use a step down module, then another charging controller?
In case of any overvoltage problems, is the BMS going to take care about the battery? (I wish ;-)
What do you think, is it a good idea? Or shall I invest into an expensive MPPT controller? I could not find any with the Current Control for small batteries.
Thanks
I am planning to build a few solar systems for a local allotment site.
The site is very big with around 100 plots. I want to have 4 stations with two batteries each. One for CCTV camera and Wifi repeater and a second one as a charging station for tool batteries and mobile phones. I want to keep it separately so they can drain one battery, when the other stays unaffected.
Panels: UL-250M-60 (250W, Voc 37.6V, Vmpp 30.5V, Impp 8.20A)
controllers: I bought some cheap mppt modules up to 7A, 10A and 13A but they are only for 28V max, so I am thinking about a step-down module with CC.
batteries: 3S7P own build (18650) with BMS upto 25A. The cells are NCR18650BD with max charging current of 1A, so for 7 of therm, I believe the 5A max should be ok.
I read about some projects using just a step down module with CC set on float charge voltage and that was working fine.
I know it is not MPPT, but I dont mind losing some energy as the panel is 250W, and the charging power per battery will be around 60W.
Do you have any experience in non-MPPT step-down modules used for solar?
Do you think, I should use a step down module, then another charging controller?
In case of any overvoltage problems, is the BMS going to take care about the battery? (I wish ;-)
What do you think, is it a good idea? Or shall I invest into an expensive MPPT controller? I could not find any with the Current Control for small batteries.
Thanks
