What is the C Rate for Lead-Acid and Lithium Batteries? How to Calculate

In this video, I will unravel the concept of C-rate in battery systems and why it's crucial for anyone involved in solar power to understand it. My name is Nick, and my mission is to make solar power understandable for everyone. C-rate, a term often encountered when discussing battery specifications such as nominal voltage, internal resistance, and ampere-hours, essentially tells us how fast a battery can be charged or discharged. It's usually represented as C followed by a number, for example, C20 or 0.05C, which can sometimes lead to confusion.

C-rate is derived from the battery's capacity in Ampere hours, serving as a guideline for its charging and discharging speeds. For instance, a lead-acid battery with a C-rate of 20 means if the battery has a 100 ampere-hour rating, it can safely charge and discharge at 5 amps. Similarly, for lithium batteries at a 1C discharge rate, we can charge and discharge at 100 amps, which significantly impacts how we design and utilize our solar systems.

Understanding the difference between placing the number before or after the "C" is crucial. If the number precedes the "C", like 20C, you multiply it by the battery's capacity. If it follows, as in C20 or 0.05C, you divide the capacity by that number. This distinction affects how we calculate the necessary charge and discharge currents for our batteries, especially when considering their application in solar power systems.

When we delve into practical applications, the importance of C-rate becomes even more apparent. For solar power systems, especially in settings where batteries like lead-acid or lithium are used, knowing the C-rate helps in accurately sizing the system. Lead-acid batteries typically have lower C-rates than lithium, meaning they can't handle as high charging or discharging currents. This is a critical consideration when planning to power high-demand appliances or when deciding on the battery type for your solar setup.

Moreover, the built-in Battery Management System (BMS) in lithium batteries plays a vital role in managing these rates, shutting down the battery to prevent damage if high currents are drawn. This protective measure is something lead-acid batteries lack, making the understanding and application of C-rates even more essential for ensuring the longevity and efficiency of your solar energy system.

Today, I've covered the essentials of what is c rate, what is c rate of a battery, and how to apply the c rate formula and c rate battery calculation to optimize your solar setup. Whether you're dealing with the discharge rate of lithium-ion batteries or calculating cable thickness for solar panel wires, understanding C-rates is key to a successful solar power system.

[daviddwyer]

Thank you for the information. Well done

[macrobertgellado]

Thank for info. Very clear explanation.

[robertostazzoni]

Hello @cleversolarpower and thank you for the video. Could you please confirm if the formulas and numbers in minute 1:05 are ok? with a C rate of 20, a battery rated 100 Ah should discharge or charge at 2000 A in 3 minutes, like you shown in the table.

[hasz]

hope this finds you well and safe, can you provide us about connecting solar panels to batteries with MPPT

[carloosgongora]

nice video, 1 suggestion can you make a video doing a diagram about Off the grid solar system with Micro inverters and batteries with all the parts needed 👍🏻

[RK-nlhn]

Can you calculate the c rate? I have panasonic up-vw1245p1 seald lead acid battery and i would like to know the c rate. 12v 9ah

[keithjacobson]

Thank you for the many excellent videos you have produced. Many people have had seemingly good results employing used forklift batteries as the storage for home systems. They find used batteries and often spend about $100 US for them, then spend a month or more reconditioning the batteries, often using a single solar panel to “boil” the batteries which removes the stratification from the plates. Eventually the batteries have very high capacity. They also contend these batteries can be drawn well below 50% of capacity regularly and still bounce back for many years. This runs against the normal lead acid logic but I believe them. They are running off grid homes and are running normal grid tied loads daily. Do you have any experience or opinion on these batteries? Thanks ColoradoKeith

[SiBex_ovh]

Now in LiFePo4 batteries cells specification we see the P Rate from Power Rate, 0, 5P is half Wh of battery.

[martinkendal]

Thank you so am I right in saying for an AGM leisure battery the lower the C rate the better?

[hakan_ozturk]

hi. 5200 mAh, 3 H and 50 C are given. Voltage is not given. How to calculate power of this battery? Thanks.

[jeffcampsall]

Should power consumption include inverter losses in addition to appliance consumption?

[phrsmith]

thank you finally a video on C ratings that is easy to understand, although my battery has 2 C ratings C20 82ah and C100 90ah I'm guessing the C100 rating is max capacity so would the 82ah C20 rating be it's usable capacity?

[ririanakmuslim]

Saya memiliki battery lifepo 3, 2v, 50amp....apa artinya?

[ibrahimbadara]

Can you clear the contradiction please? Because in another video, you said the C-rate for a lead acid battery is 0.2.

[samirgunic]

You got me confused. 1:20 Why do you multiply capacity of 100 Ah by 1 for a Lithium battery with a discharge C rating of 1, but in the previous example you divide (you don't multiply) capacity of 100 Ah by 20 for a Lead-Acid battery with a C "rating" (unspecified type of rating) of 20? You also go on to say that the Lithium battery can charge and discharge at 100 amps. How do you know that the charge and discharge C ratings are the same for the Lithium battery, and if they are the same, why would they not be the same for the Lead-Acid battery?