Battery Bank Calculator
Fill Battery Bank Sizing Calculator Calculator
The two main battery chemistries for off-grid are Lead Acid (flooded or sealed) and Lithium. These two chemistries have unique characteristics. Lithium batteries are more efficient, which means less power is wasted in the charge/discharge process. They also have a greater discharge depth allowing you to fully utilize all of your battery capacity.
Lead acid batteries are sensitive and need to be fully recharged every day, where Lithium batteries can stay at a partial charge without any adverse effect. Lead acid batteries also have a more limited amount of usable capacity and are typically discharged only 50%.
Because of the better efficiency and deeper discharge depth, Lithium battery banks tend to be only 50-60% of the size of a comparable lead acid bank! The Lithium batteries we use are purpose-built for off-grid solar, and utilize a special Lithium chemistry called Lithium Ferro Phosphate (LiFePO4, commonly called “LFP”).
This type of Lithium battery is engineered to provide a long service life (over 10 years) while also being safe, with a stable chemistry and sophisticated electronic protection features.
The exact math for sizing your battery system is based on your daily power usage and the battery type. Based on usage of 10kWh per day, here are some examples:
Lead Acid Sizing
10kWh x 2 (for 50% depth of discharge) x 1.2 (inefficiency factor) = 24 kWh
10kWh x 1.2 (for 80% depth of discharge) x 1.05 (inefficiency factor) = 12.6 kWh
Battery capacity is specified either in kilowatt hours, or amp hours.
For example, 24 kWh = 500 amp hours at 48 volts → 500 Ah x 48V = 24 kWh
It’s usually a good idea to round up, to help cover inverter inefficiencies, voltage drop and other losses. Think of this as the minimum battery bank size based on your typical usage. You may want to consider 600-800 amp hours of capacity, based on this example, depending on your budget and other factors.
Battery banks are typically wired for either 12 volts, 24 volts or 48 volts depending on the size of the system. Here are example battery banks for both lead acid and Lithium, based on an off-grid home using 10 kWh per day:
For Lead Acid, 24kWh is equal to:
- 2,000 amp hours at 12 volts
- 1,000 amp hours at 24 volts
- 500 amp hours at 48 volts
For Lithium, 12.6 kWh is equal to:
- 1,050 amp hours at 12 volts
- 525 amp hours at 24 volts
- 262.5 amp hours at 48 volts
AMRtechnologies Inc. Solar & Electrical Systems
Tel: (+506) 7037-8077 or Toll Free: 1(800) 2130227
Solar Systems in United States & Latin America