DIY Solar Shack
Let's find out yes or no (and why!)
First, some of the basics - learning is good! Let's get into it --->
Voltage & discharge
it's where it all begins
When you buy an appliance rated for 12 volts, this is an indication that it's designed to operate at 12 volts - it's the nominal voltage. It could operate on 11 volts or 13 volts, which is OK if it doesn't change more than 10 to 12%. Car batteries also have a nominal voltage - 12v. It's terminal voltage can be below or above 12 volts.
Voltage vs Discharge
Lead acid Depth of Discharge can be found by measuring terminal volts. 12.73 volts means fully charged.
Battery voltage indicates state of discharge
BATTERY DISCHARGE TAKEAWAYS
NOMINAL VOLTS CAN VARY 10%
LOW VOLTS = NO POWER HIGH VOLTS = BURNOUT
VOLTS INDICATES DISCHARGE
HOW TO DO IT
GOOD FOR ...
Delivering hundreds of amps in a short time (cranking car engines.)
CAR BATTERY CHARACTERISTICS
Supplying medium currents for long periods - discharge limit 20%
GOOD FOR ...
Delivering medium to high current over extended period so time - can be discharged to 80%
DEEP CYCLE BATTERY CHARACTERISTICS
Supplying heavy currents quickly
Marine batteries are the best of both worlds. They can deliver sustained current of boat lights and pumps and also have enough quick power to crank an engine.
WHAT ARE MARINE BATTERIES?
PRICEY BUT WORTH IT ...
Lithium iron phosphate batteries are naturally dee-cycle and can be discharged to 95%. Maximum of 80% is recommended for life of 2000 cycles. 50% discharge will give life of 5000 cycles.
BATTERY DEEP-CYCLE VS AUTO TAKEAWAYS
Max lead-acid discharge 20%
Pb deep-cycle heavy and short life - discharge 50 to 80%
Lithium iron phosphate natural deep-cycle
ITS ALL ABOUT THE VOLTAGE
A 100W panel will charge a battery great - until it's fully charged. Panel output voltage is 22V and will push a charge battery V up to 15 volts, damaging the battery.
WHY NOT CONNECT SOLAR DIRECT TO BATTERY?
DIRECT CONNECT ONLY 5 WATTS OR LESS
MONITOR DIRECT CONNECTED SOLAR PANEL IF NO CONTROLLER
ALWAYS USE AN MPPT CHARGE CONTROLLER