12 volts used to be a standard for extra low voltage power systems. Today, most systems are 24V or 48V You can use 2 -12 volt batteries in series for 24 volts 3 for 36 volts and 4 for 48 voltsA battery rated for 100 amp hours will provide 5 amps for 20 hours.If we have a 12 volt battery, we multiply 100 by 12 and determine that the battery will provide 1200 watt hours.A 24 volt 100 amp battery will provide 2400 watt hoursA 48 volt 100 amp hour battery will provide 4800 watt hours. Keep in mind, no matter what voltage you choose you always have the option of running 12 volt from 24 or 48 volt using a 12 volt 30 amp step down transformer or multiple step down transformers to still run all your 12 volt power needs example 12 volt led lighting.
Should I choose a 12 volt, a 24 volt or a 48 volt stand-alone power system? your energy consumption should determine the voltage of your power system.
Doubling the voltage effectively halves the DC loads and halves the voltage drop. Because the battery voltage is doubled, the percentage of the voltage drop in relation to the battery voltage is only a quarter of the percentage drop with the lower battery voltage. Hence, with a 24 Volt system the cable need only be one quarter of the diameter as it does with a 12 volt system.
Example Imagine that you have an air conditioner rated for 1500 watts on a fixed 120V circuit. How many amps is it?Amps = 1500 ÷ 120 = 12.5So the air conditioner is rated for 12.5 amps, although you'll often see this rounded to the next highest number.Example : Imagine that you want to know how many watts it takes to charge a laptop. If you know that the laptop is rated for 0.5 amp and a fixed household current of 120 volts, you choose the following equation and plug in the missing pieces:Watts = Amps × VoltsWatts = 0.5 × 120 = 60So the laptop draws 60 watts of electricity as it charges.
AMP HOURS VS WATT HOURS 12 volt batteries rated at 100 Amp Hours are connected in series the voltage would increase to 24 Volts, the Amp Hours would remain the same but the Watt Hours have increased to 2400 watts. Doubling the voltage effectively halves the DC loads and halves the voltage drop. Because the battery voltage is doubled, the percentage of the voltage drop in relation to the battery voltage is only a quarter of the percentage drop with the lower battery voltage. Hence, with a 24 Volt system the cable need only be one quarter of the diameter as it does with a 12 volt system.
To determine input PV max watts into controller. Take the watts of each panel times number of panels and divided by the volts of system, Then add 20% this gives you the max amps into the controller.
Charging Lithium with a alternator.It is important to understand using a alternator hooked directly to a lithium battery will over heat and damage your alternator. Lithium batteries can charge at 100 amps causing over load on the alternator. The way around this is a DC to DC charger. This regulates the amount of amps output from the alternator.