Crate battery_estimator 

Battery SOC (State of Charge) Estimator

A lightweight, no_std compatible Rust library for estimating battery state-of-charge (SOC) from voltage measurements. Designed specifically for embedded systems and microcontrollers using fixed-point arithmetic for maximum efficiency without FPU.

Features

• Fixed-point arithmetic - Uses fixed crate for efficient integer-based calculations
• No floating-point unit required - Perfect for microcontrollers without FPU
• no_std compatible - Works in embedded environments
• No heap allocations - Uses only stack memory and fixed-size arrays
• Multiple battery chemistries - Built-in support for LiPo, LiFePO4, Li-Ion
• Temperature compensation - Correct SOC readings based on temperature
• Aging compensation - Adjust for battery capacity degradation over time
• Custom voltage curves - Define your own voltage-SOC relationships
• Conservative battery curves - Extended battery life with conservative thresholds

Quick Start

use battery_estimator::{BatteryChemistry, SocEstimator};

// Create estimator for a standard LiPo battery
let estimator = SocEstimator::new(BatteryChemistry::LiPo);

// Estimate SOC at 3.7V (nominal voltage)
match estimator.estimate_soc(3.7) {
    Ok(soc) => println!("Battery SOC: {:.1}%", soc),
    Err(e) => println!("Error estimating SOC: {}", e),
}

Fixed-Point API

For embedded systems without FPU, use the fixed-point API for maximum efficiency:

use battery_estimator::{BatteryChemistry, SocEstimator, Fixed};
use fixed::types::I16F16;

let estimator = SocEstimator::new(BatteryChemistry::LiPo);

// Use fixed-point voltage for calculations
let voltage = Fixed::from_num(3.7);
let soc = estimator.estimate_soc_fixed(voltage).unwrap();

// Convert back to float if needed
println!("Battery SOC: {:.1}%", soc.to_num::<f32>());

Battery Types

The library supports multiple battery chemistries with built-in voltage curves:

Type	Full Charge	Cutoff	Description
LiPo	4.2V	3.2V	Standard Lithium Polymer
LiFePO4	3.65V	3.0V	Lithium Iron Phosphate (long cycle life)
LiIon	4.2V	3.3V	Standard Lithium Ion
Lipo410Full340Cutoff	4.1V	3.4V	Conservative LiPo (extended life)

Temperature Compensation

use battery_estimator::{BatteryChemistry, SocEstimator, Fixed};

// Create estimator with temperature compensation
let estimator = SocEstimator::with_temperature_compensation(
    BatteryChemistry::LiPo,
    Fixed::from_num(25.0), // Nominal temperature (°C)
    Fixed::from_num(0.0005) // Temperature coefficient
);

// Estimate SOC with current temperature
match estimator.estimate_soc_compensated(3.7, 20.0) {
    Ok(soc) => println!("Temperature-compensated SOC: {:.1}%", soc),
    Err(e) => println!("Error: {}", e),
}

Custom Voltage Curves

use battery_estimator::{SocEstimator, Curve, CurvePoint};

// Define a custom voltage-SOC curve
const CUSTOM_CURVE: Curve = Curve::new(&[
    CurvePoint::new(3.0, 0.0),   // 3.0V = 0%
    CurvePoint::new(3.5, 50.0),  // 3.5V = 50%
    CurvePoint::new(4.0, 100.0), // 4.0V = 100%
]);

// Create estimator with custom curve
let estimator = SocEstimator::with_custom_curve(&CUSTOM_CURVE);

Module Structure

• SocEstimator - Main estimator struct for SOC calculations
• EstimatorConfig - Configuration for SOC estimator (compensation settings)
• BatteryChemistry - Supported battery types
• Curve - Voltage-SOC curve representation
• CurvePoint - Individual voltage-SOC data point
• Fixed - Fixed-point type alias (I16F16)
• Error - Error types for estimation failures
• compensate_temperature - Temperature compensation function
• compensate_aging - Aging compensation function

Modules

prelude

Prelude module for convenient imports

Structs

Curve

A voltage-to-SOC curve for battery state-of-charge estimation

CurvePoint

A single point on a voltage-SOC curve

EstimatorConfig

SOC estimator configuration

SocEstimator

SOC estimator

Enums

BatteryChemistry

Battery chemistry types supported by the library

Error

Errors that can occur during battery SOC estimation

Constants

MAX_CURVE_POINTS

Maximum number of points allowed in a voltage curve

Functions

compensate_aging

Applies aging compensation to SOC value (floating-point API)

compensate_aging_fixed

Applies aging compensation to SOC value using fixed-point arithmetic

compensate_temperature

Applies temperature compensation to SOC value (floating-point API)

compensate_temperature_fixed

Applies temperature compensation to SOC value using fixed-point arithmetic

default_temperature_compensation

Applies default temperature compensation (floating-point API)

default_temperature_compensation_fixed

Applies default temperature compensation using fixed-point arithmetic

Type Aliases

Fixed

Fixed-point type for internal calculations

I16F16

FixedI32 with 16 integer bits and 16 fractional bits.