BATTERY #101 Q&A:
HOW MUCH ENERGY STORAGE DO YOU NEED?
Figuring out how many batteries you need can be daunting.
If you don’t have enough battery capacity, you run out of power and need to fire up the backup generator.
On the other hand, if you buy too many batteries, you add unnecessary expense to your system, with extra components, complexity and maintenance.
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 over a period of time.
1,000 watts x 10 hours per day = 10 kWh per day
After estimating daily usage we need to 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:
FLOODED LEAD ACID
- Typical lifespan: 5-7 years
- Requires maintenance – add distilled water and equalize charge on a monthly basis
- Enclosure needs to be vented outside to expel built-up hydrogen gas
SEALED LEAD ACID
- Typical lifespan: 3-5 years
- No maintenance
- Enclosure should still be vented, batteries could off gas in certain conditions
- Typical lifespan: 10+ years
- No maintenance, no venting
- Highest efficiency, faster charging, more usable capacity (deeper discharge depth)
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.
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 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, 24 KWH 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
Other factors influence battery sizing:
- Ambient Temperature – Heat or cold has a big impact on battery performance and capacity.
- Seasonal Factors – People use more power at different times of the year. The sun produces more power in the summer than in the winter.
- Budget – Battery bank size is often a compromise between what you want to spend on batteries and how often you’ll need to run your backup generator.
This is not intended to be a comprehensive guide on off-grid design. Use this basic information, based on your energy usage, to get an idea of your desired battery bank solution, and then call us at #818-280-3091 for help picking the best battery for your needs. Thank You!
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How Soon Will BigBattery Ship My Order?
A: All BigBattery Products are shipped within (12-72) Hours.
(Depending on how complicated your order is to pack and if any tailored solutions are required).
Where does BigBattery Ship these products from?
A: BigBattery is a Direct US Manufacturer and Battery Supplier. All of our products are shipped domestically from California to your door.
(Unlike other sites, manufacture, own and stock all products sold right here in the USA!)
How will my products be shipped?
A: If your product is lighter than (45/Lbs) it will be shipped by FEDEX Ground. If over (45/LBS) it will be shipped on “Pallet(s)” LTL and dropped off at your location by a Truck.
(If you live in a residential area, we provide a truck with a lift-gate to quickly and easily unload said pallet at your location. The phone number that you have provided to BigBattery.com will be given to your truck driver so that he/she may contact you prior to delivery to confirm when you will be home and where you want said pallet delivered.)
Is there any benefit in shipping if I combine my orders?
A: YES, When we ship to you by LTL/Pallet – The cost of shipping said pallet(s) is not based on weight. So if you buy one (1) Battery or four (4) batteries – If they fit on a pallet, the shipping cost is the SAME. We understand that logistics can be expensive and we try our best to keep these logistics prices low by combining your orders to save you money. We recommend ordering multiples of the batteries that you need at the same (rather than separate orders) to save a lot of money on shipping. We offer Free Pickup as well in Chatsworth, CA.
Do you offer Faster shipping options?
A: Yes, we offer faster shipping options although they usually cost more, if this is your preference – feel free to choose a faster option upon checkout. We do not mark-up our logistics costs, they are simply a pass-through from the carrier to you. Our goal is to always ship the Fast, Safe and Cheap but if we can only get two of the three – we will choose Safe and Cheap unless you choose otherwise upon checkout.
Does your shipping include insurance?
A: Yes, all of our logistics providers carry heavy insurance policies. If your product was lost or damaged during delivery – it is covered.
Can I come Pickup My Product To Save On Shipping:
A: Yes, You can come to our warehouse (during business hours M-F/9-5) to pickup your order for FREE.
(Please choose this option at check-out. Be sure to bring a copy of your “Order #” to provide upon pickup.)
*** If you have any “Shipping Questions” Please – eMail: Emily@BigBattery.com (or) Call #(818) 280 – 3091 & (Press #2 for Shipping Dept.) **
Installation Of Our Batteries:
BigBattery does not take responsibility for the installation of our product. We are responsible for manufacturing and delivery of the most environmentally sustainable batteries in the USA at the best price (Guaranteed).
Due to the high energy density of our battery packs – we strongly recommend the use of a licensed electrician per any installation of our products.
If you have any further questions about installation of our products, please eMail “Info@BigBattery.com” (or) Call # (
Product Testing FAQ