Live Demo — Battery C-Rate Calculator
Select your battery type and enter capacity, voltage, PV charge current and load power to verify the C-rate instantly.
Battery C-Rate Calculator
Free professional calculator that verifies battery charge and discharge C-rate for solar street lighting systems. Select the battery chemistry, enter capacity and system voltage, then provide the PV charge current and load power to compute the C-rates and check them against the allowable limits of lead-acid AGM, gel, LiFePO4 and NMC batteries.
Key Features
Battery Chemistry
Select lead-acid AGM, gel, LiFePO4 or NMC batteries with their recommended charge and discharge C-rate limits.
Battery Parameters
Enter battery capacity in ampere-hours and choose the system voltage (12V / 24V / 48V).
Operating Inputs
Provide the PV charge current from the MPPT/PWM controller and the connected load power in watts.
Charge C-Rate
Computes C-rate_charge = I_charge / C and checks it stays below the battery's maximum charge rate.
Discharge Verification
Computes C-rate_discharge = (P_load / V) / C and flags marginal or overloaded discharge conditions.
Reference Limits
Built-in allowable C-rate table for AGM, gel, LiFePO4 and NMC batteries to guide high-power load sizing.
Technical Specifications
| Platform | HTML5 Web App | Android (via WebView) |
| Core Calculation | C-rate_charge = I_charge / C; C-rate_discharge = (P_load / V) / C |
| Battery Types | Lead-acid AGM, Gel, LiFePO4, NMC |
| Capacity Input | User-defined (Ah) |
| System Voltage | 12V / 24V / 48V |
| Charge Current | PV controller output (A) |
| Load Power | User-defined (W) |
| Allowable Charge | Lead-acid 0.1-0.2C, LiFePO4 0.2-0.5C, NMC 0.3-0.5C |
| Allowable Discharge | Lead-acid 0.25-0.3C, LiFePO4 1C, NMC 1-2C |
| Industry Standards | IEC 61427-1, IEC 62620, IEEE 485 |
| Output | Charge / discharge C-rate with pass or marginal status |
Frequently Asked Questions
What is a battery C-rate?
The C-rate is the ratio of the charge or discharge current to the battery capacity. For example, charging a 100Ah battery at 12A is 0.12C. It indicates how intensely the battery works, and excessive C-rates accelerate aging and reduce usable capacity.
How is the C-rate verified?
The charge C-rate equals I_charge / C, and the discharge C-rate equals (P_load / V) / C. Both are compared with the battery's allowable limits; the calculator returns a pass or marginal status so you know whether to resize the battery or split branches.
What are typical allowable C-rate limits?
Lead-acid AGM charges at 0.1-0.2C and discharges up to 0.25C, gel up to 0.3C, LiFePO4 charges at 0.2-0.5C and discharges up to 1C, and NMC charges at 0.3-0.5C with 1-2C discharge. Street lighting systems normally run below 0.1C.
Why must high-power loads be checked?
A high night-time load can push the discharge current far above safe limits. For a 12V 100Ah LiFePO4 battery, a 1200W load equals 1C, right at the boundary. Sustained high C-rates degrade capacity quickly, so the C-rate should be verified whenever loads change.
Thank you for choosing Open Solar Design