Small system design questions
The attached diagram describes a portable back-up on a small cart, mainly used for 12v power in a prolonged grid down situation. We are all electric here and will be camping inside our passive solar home. I am not intending to use this system for any high wattage appliances. The inverter would be used to run a skill saw for really short periods of time if I needed it.
PV 1 and 2 are 100W Renogy panels. Data listed on the panels follows.
PMax = 100W
VOC = 22.5V
Optimum operating voltage VMP = 18.9V
Optimum operating current IMP = 5.29A
ISC = 5.75A
Max system voltage = 600VDC
Max series fuse rating = 15A
All 3 switches are SPST appropriately sized for amperage. S1 & 2 = 30A DC, S3 = 20A DC
The 12V outlet will be used for LED lighting, and to run a 1 GPM pump, 2.5A max.
USB ports for charging cell phones if cell service is working.
The 7AH batteries are for LED lighting.
1. Having decided on an MPPT controller, could you suggest a brand and model that would work well, while keeping an eye on future expansion of the system.
2. If I added another panel or two, keeping the total VOC below the maximum for the controller, would that require more batteries also?
3. My guess was to get a 30A controller. Should it be larger?
4. Is the 30A fuse for the panels correctly placed and the correct amperage rating?
5. Could I attach my 18V drill motor battery to the MPPT battery ports to recharge it, after disconnecting the 12V system?
6. Is the correct order of connections as follows? For turn-on system: Battery to MPPT first, then Panels to MPPT.
For turn-off system: Panels from MPPT first, then Battery from MPPT.
I appreciate your help and welcome your questions and advice.