1. Calculating Capacity and Runtime of Parallel Lithium Batteries

Let's understand what "4 parallel 12v 100ah lithium batteries" means. When you connect batteries in parallel, you're connecting all the positive terminals together and all the negative terminals together. This increases the total capacity(Ah) while the voltage remains the same. 

• Capacity Calculation: In this case, you have four 100Ah batteries in parallel. So, your total capacity is:

  4 batteries * 100Ah/battery = 400Ah

  You now have a 12V 400Ah battery bank.

• Runtime Calculation: Calculating runtime is a bit more involved. It depends on the load (how much power your devices draw). The key formula:

  Runtime (hours) = Total Capacity (Ah) * Depth of Discharge (DoD) / Load Current (A)

  Let's break this down:

  Example: Let's say your total load is 17A and you're using an 80% DoD:

  Runtime = 400Ah * 0.8 / 17A = 18.8 hours (approximately)

  This means your 4 parallel 12v 100ah lithium batteries should power your 17A load for roughly 18.8 hours.

• Load Current (A): This is the total current drawn by all your devices. Add up the amp draw of everything you plan to run simultaneously. For example, if you have a 10A fridge, a 5A lighting system, and a 2A water pump running at the same time, your total load is 10A + 5A + 2A = 17A.
• Depth of Discharge (DoD): This is the percentage of the battery's capacity that you use. Lithium batteries can be discharged deeper than lead-acid batteries without harm. A common DoD for lithium batteries is 80%. This means you can safely use 80% of the battery's capacity. Some lithium batteries have even higher DoD, sometimes up to 90%, check with your manufacturer. 

2. Factors Affecting Lithium Battery Runtime

Several factors can influence how long your lithium batteries last:

• Load Size: This is the most obvious factor. The higher the load (more devices running), the shorter the runtime, as demonstrated in the calculation above.
• Depth of Discharge (DoD): Discharging your batteries too deeply consistently can shorten their lifespan. Lithium batteries can handle more than lead-acid batteries. However, it is still best to stay within the recommended DoD, which is usually 80-90%.
• Temperature: Extreme temperatures, both hot and cold, can greatly affect battery performance. Cold weather reduces capacity and runtime. High temperatures can speed up battery wear. Ideally, lithium batteries should work within their recommended temperature range. Check your battery's specifications for details. 
• Charging Rate (C-rate): The C-rate shows how fast a battery charges or discharges compared to its capacity. A 1C rate means charging or discharging the battery in one hour. Higher C-rates can create more heat, which may impact battery life. 
• Battery Age and Condition: Like all batteries, lithium batteries wear out over time. Their capacity slowly decreases with each charge and discharge. Good maintenance and storage can help extend their lifespan. 
• Internal Resistance: As batteries age, their internal resistance increases, which can reduce efficiency and runtime. 

3. Runtime Examples for Different Loads (Illustrative)

It's difficult to provide precise runtime figures without knowing the specific load. However, here's a table illustrating approximate runtimes for different loads with our 4 parallel 12V 100Ah (400Ah total) setup, assuming an 80% DoD:

(These are estimates. Actual runtime may vary.)


Wiltson Energy is a leading provider of cutting-edge lithium battery technology. Our product portfolio includes a diverse selection of 12.8V and 25.6V lithium batteries designed for optimal performance and durability. We also offer specialized low-temperature lithium batteries engineered to excel in extreme cold environments. At Wiltson Energy, we are committed to delivering innovative and dependable power solutions tailored to meet the evolving needs of our customers.