# When do you go higher in voltage of solar system

Registered Users Posts: 17
Greeting,

When do I need to use 12volt battery, 24v, 48v, and 96volt, is it higher wattage system is higher to use in voltage.

For example 5000w, I can go for either 24v battery connection or 48volt connection. I can not use 12volt connection!

What is better to use 24v system or 48v system?

Best regards,

Re: When do you go higher in voltage of solar system

More or less, I like to use 100 amps as the point at which to go to a higher battery voltage...

100 amps * 12 volts = 1,200 watts
100 a * 24 v = 2,400 watts
100 a * 48 v = 4,800 watts

If you do the math, you find that even a 100 amp nominal inverter needs much heavier wiring for safe/reliable operation. For example:
• 1,200 watts * 1/0.85 inverter eff * 1/10.5 volt cutoff * 1.25 NEC wiring/breaker/fuse derating = 168 amps minimum

For charge controllers, they are rated at a maximum output current (say 60-90 amps for larger units) at 12/24/48 volt battery banks:
• 5,000 watts * 0.77 mppt controller+panel derating * 1/14.5 volts charging = 266 amps @ 12 volt bank
• 5,000 watts * 0.77 mppt controller+panel derating * 1/29 volts charging = 133 amps @ 24 volt bank
• 5,000 watts * 0.77 mppt controller+panel derating * 1/58 volts charging = 66 amps @ 48 volt bank

So, higher voltage systems typically allow you to use much smaller diameter wire and/or send current farther distances from the bank. And, your charge controllers can "manage" a larger array with higher battery bank voltages.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset