HOW MUCH
ENERGY STORAGE
DO YOU NEED?
Determining how many batteries you need can be a daunting task. If you don’t have enough battery capacity, you run out of power and need to fire up a backup generator.
Conversely, if you buy too many batteries, you add extra components, complexity, and maintenance, resulting in unnecessary expenses to your system.
Sizing solar batteries is one of the first steps in designing your off-grid system. The amount of battery storage you need is based on your energy usage. Energy usage is measured in kilowatt-hours (kWh) over a period of time.
Example: 1,000 watts x 10 hours per day = 10 kWh per day
After estimating daily usage, we will consider which type of battery will work best, as they have unique performance characteristics and are sized differently.
PICKING THE RIGHT BATTERY
There are a few different battery types commonly used for off-grid storage systems:
Price: $399 / kWh Storage
(Per Usable kWh Capacity)
LITHIUM
- Typical Lifespan: (10) Years
- High Power Density
- Small Footprint
- No Maintenance
- No Toxic Venting of Gas
Price: $300-450 / kWh Storage
(Per Usable kWh Capacity)
SEALED LEAD ACID
- Typical Lifespan: (6) Years
- Low Power Density
- Medium Footprint
- No Maintenance
- No Toxic Venting of Gas
Price: $300-450 / KWh Storage
(Per Usable KWh Capacity)
FLOODED LEAD ACID
- Typical Lifespan: (2-3) Years
- Low Power Density
- Large Footprint
- High Maintenance
- Toxic Venting of Gas
The Two Main Categories are Lithium & Lead-Acid.
1.) Lithium Batteries are more efficient, weigh less, lose less power in the charge/discharge process, and have the highest power density. [Batteries in this category are Lithium-Ion, LiFePO4, and NMC.]
2.) Lead-Acid Batteries are less efficient, weigh more, lose more power in the charge/discharge process, and have a lower power density. [Batteries in this category are Flooded, Sealed, AGM, Gel, and Deep-Cycle Lead-Acid Batteries.]
People used to buy “Lead-Acid” was because it was cheap; however, we are now offering “Lithium Batteries” at the same price per Usable/KWh that last (3x) as long and require no maintenance. Lead-Acid batteries have limited usable capacity and can be discharged to 50%.
Due to better efficiency and deeper discharge depth, lithium battery banks only need to be HALF the size of a comparable lead-acid battery bank! Lead-acid batteries are sensitive and need to be fully recharged every day, whereas lithium batteries can stay at a partial charge without any adverse effect!
BigBattery was created to make Lithium Batteries affordable for everyone. We now offer new “Lithium Batteries” at the same price per usable/kWh that last (3X) as long and require no maintenance. There is NO reason to buy Lead-Acid today. Lithium Batteries are clearly the better solution, and BigBattery manufactures and supplies these batteries to you at the Best Price in the USA!
(We’ll beat any competitor’s price by 10% Guaranteed!)
SIZING YOUR BATTERY BANK
The exact math for sizing your battery system is based on your daily power usage and the battery type.
Based on the usage of 10 kWh per day, here are some examples:
LEAD ACID SIZING:
10 kWh x 2 (for 50% depth of discharge) x 1.2 (inefficiency factor) = 24 kWh
LITHIUM SIZING:
10 kWh x 1.2 (for 80% depth discharge) x 1.05 (inefficiency factor) = 12.6 kWh
Battery capacity is specified either in kilowatt hours, or amp hours.
Example:
24kWh = 500Ah at 48V → 500Ah x 48V = 24kWh
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, 24 or 48 volt depending on the size of the system. Here are examples of battery banks for both lead acid and lithium, based on an off-grid home using 10 kWh per day.
FOR LEAD ACID, 24 kWh IS EQUAL TO:
- 2,000 Ah at 12V
- 1,000 Ah at 24V
- 500 Ah at 48V
FOR LITHIUM, 12 kWh IS EQUAL TO:
- 1,050 Ah at 12V
- 525 Ah at 24V
- 262.5 Ah at 48V
Other factors that influence battery sizing:
- Ambient Temperature – heat or cold has a significant impact on battery performance and capacity.
- Seasonal Factors – Power usage varies throughout the year depending on a few factors. For example, the sun produces more power in the summer than in winter.
- Budget – battery bank size often compromises what you want to spend on batteries and how often you’ll need to run your backup generator.
Based on your energy usage, use this information to get a general idea of the minimum battery bank size, and then call us at #(818) 280-3091 for help pricing the best battery for your needs!
Disclaimer: This is not intended to be a comprehensive guide for off-grid systems & design.
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