I recently decided to make an off-grid "portable" solar car charger and finished my project yesterday.
I designed the system to charge my car during the day based on my daily kWh usage (I typically use 10kWh/day and work from home a good portion of the day). The system has a some (required) battery storage (2.4kWh) and a 2.6kW solar array (8 x 320W panels). The power output is sufficient to charge the Model Y with the 120VAC @16A NEMA 5-20 adapter (33% more current than the normal 5-15 adapter that comes with the vehicle). Ultimately this system may end up on a trailer, but for now it is home based and can be disassembled in a few hours in case we move to a new home. I've spent around $7k so far but I may double my battery bank for another $1.8k.
The 24VDC system I made includes the following:
I designed the system to charge my car during the day based on my daily kWh usage (I typically use 10kWh/day and work from home a good portion of the day). The system has a some (required) battery storage (2.4kWh) and a 2.6kW solar array (8 x 320W panels). The power output is sufficient to charge the Model Y with the 120VAC @16A NEMA 5-20 adapter (33% more current than the normal 5-15 adapter that comes with the vehicle). Ultimately this system may end up on a trailer, but for now it is home based and can be disassembled in a few hours in case we move to a new home. I've spent around $7k so far but I may double my battery bank for another $1.8k.
The 24VDC system I made includes the following:
- Two 1.2kWh 14.4V LiFePO4 Battle Born batteries, connected in series, with internal battery management system (prevents over/under charge)
- 8 x 320W Silfab solar panels (two parallel strings, four panels per string)
- A Victron charging controller with maximum power point tracker
- The MPPT finds the peak of the current-voltage curve of the solar array input
- The charge controller steps down the voltage (from ~150VDC at the solar array to 24-28.8 VDC at the battery) and ups the current (from ~16A at the array to ~80A into the battery)
- A 24V 3000VA (2400W) Victron inverter that lies in parallel with the batteries that turns DC into 120V AC
- If there's sufficient sunlight, the inverter draws current from the solar array and puts excess current into the battery
- If there's a cloud, the inverter pulls current from both the battery and solar array to meet the AC power requirement
- If it is dark, the inverter pulls only from the battery (the current battery bank will charge the car for about 1 hour)
- A (not required) brain & monitor that dumps all data to the internet and allows you to easily adjust charge settings for all the equipment from one spot
- A (not required) battery monitor (the inverter can do clearly, but the additional monitor allows you to measure the two batteries individually)
- Two 15A DC circuit breakers and disconnect for the two solar array strings (not your common AC fuses at your hardware store)
- Two 150A DC fuses for the monster power cables that connect the battery bank to the charge controller & the inverter
- A DC battery disconnect switch
- A 20A AC circuit breaker
- Ground rod/wiring to ground the metal frames of the array (lightening protection) and to act as a single ground point for the DC and AC sides of the system
- Rain tight metal conduit for all outside solar DC wiring
- Tons of additional wiring/hardware
- Twenty plus trips to Lowes and other random electrical supply stores