Avoid Alternator Damage: Charge Lithium Batteries Safely

Table of Contents

1. Introduction
2. Challenges of Charging a Lithium Battery from an Alternator
3. Understanding the Setup for Testing Alternator Charging
4. The Efficiency of Alternators and the Issue of Heat Generation
5. The Impact of RPM on Alternator Cooling and Charging Capacity
6. Testing Lithium Battery Charging at Different RPMs
7. The Importance of External Regulators in Controlling Alternator Temperature
8. The Balmar Alternator and its Temperature Monitoring Features
9. Results of Testing Alternator Charging with the Balmar Alternator
10. Conclusions and Solutions for Charging Lithium Batteries with an Alternator
11. Victron's Solutions for Protecting Alternators and Battery Systems

Article

Charging Lithium Batteries from an Alternator: Challenges and Solutions

Introduction

When it comes to charging a lithium battery from an alternator, things are not as straightforward as charging a lead battery. In this article, we will explore the challenges associated with using an alternator to charge lithium batteries and discuss the solutions available to overcome these challenges.

Challenges of Charging a Lithium Battery from an Alternator

The first challenge when charging lithium batteries with an alternator lies in the difference between the charging requirements of a lead/acid chemistry and a lithium chemistry. Due to the internal resistance of a lead-acid battery, the charge current is naturally limited. However, with lithium batteries, the charge current can potentially exceed the maximum rated amperage of an alternator, leading to a significant risk of overheating and wear on the alternator. This risk is especially prominent at low alternator speeds, where the crucial cooling needed for the alternator is lacking.

Understanding the Setup for Testing Alternator Charging

To explore the effects of alternator charging on lithium batteries, a setup was created at Ati Energy in Bucharest, Romania, within the Victron Dealership. The setup consists of a 230-volt three-phase motor on the left, accurately measured using a control box. The motor is attached to a frame, and on the right side of the frame is the alternator being tested. The main battery used in the tests is a 300Ah Lithium battery, without a Battery Management System for the purpose of testing. A Victron BMV 712 Battery monitor and shunt are used to measure the current flowing into the battery.

The Efficiency of Alternators and the Issue of Heat Generation

Before delving into the testing process, it is important to understand the efficiency of alternators and the heat they generate during charging. Typically, alternators have an overall efficiency of around 50%, which means that when they charge with 1000 Watts, they also generate 1000 Watts of heat. To dissipate this heat, alternators have fans on the rotor, which cool down the unit. The faster the alternator runs, the better it cools. This information sets the stage for the subsequent tests conducted at different RPMs.

Testing Lithium Battery Charging at Different RPMs

The first test was conducted at 3000 RPM, resulting in a healthy 78.9 amps from the alternator. This speed ensured the temperature of the alternator remained cool, around 43 degrees Celsius, thanks to the built-in fan. However, when the speed was reduced to 1500 RPM, still above idle speed, the cooling effect decreased significantly, leading to a rise in temperature. At this lower RPM, the alternator started overheating and eventually burned the internal coil. This test clearly demonstrates that charging lithium batteries at low RPMs can result in alternator overheating and potential damage.

The Importance of External Regulators in Controlling Alternator Temperature

To address the issue of overheating during alternator charging, external regulators play a vital role. The Balmar alternator, used in the testing, includes an external regulator that monitors both the alternator and battery temperatures. By adjusting the field output, the regulator automatically lowers the output current when the temperatures rise, effectively preventing overheating. This temperature regulation feature ensures that the alternator remains within a safe operating range, even during extended charging.

The Balmar Alternator and its Temperature Monitoring Features

In the tests, the Balmar alternator was equipped with an optional temperature probe attached to its exterior casing. This probe serves as a crucial component in the temperature regulation system. The regulator uses the temperature readings from the probe to adjust the output current and prevent the alternator from exceeding the allowed temperature range. The tests conducted with the Balmar alternator demonstrated its effectiveness in keeping the temperature within acceptable limits.

Results of Testing Alternator Charging with the Balmar Alternator

Initial testing at 2114 RPM produced a steady 50 Amps, with the ambient temperature at 24 degrees Celsius and the external casing of the alternator at 42 degrees Celsius. As the speed increased to the maximum achievable speed of 3600 RPM, the Balmar alternator delivered around 94 Amps. However, with the rise in temperature, the regulator automatically reduced the output current to prevent overheating. Despite the internal temperature reaching 130 degrees Celsius, the Balmar alternator continued to function properly, showcasing its ability to withstand high temperatures.

Conclusions and Solutions for Charging Lithium Batteries with an Alternator

Based on the tests and observations, it is evident that charging lithium batteries with an alternator poses unique challenges. The main difference lies in the charging requirements and the need for adequate cooling. Many alternators can only deliver their rated current at high RPM speeds, which works well for lead batteries but not for lithium batteries. The high current draw at low speeds can cause alternator overheating. To address these issues, several solutions exist. One option is to install an alternator that can deliver the required current even at idle RPM. Another solution is to use an alternator and regulator equipped with a temperature sensor, such as the Balmar alternator showcased in the tests. This sensor ensures that the alternator's temperature remains within acceptable limits even during prolonged charging. Additionally, current limiters or DC to DC Chargers can be installed to regulate and limit the charging current. These solutions offer effective ways to mitigate the challenges of charging lithium batteries with an alternator.

Victron's Solutions for Protecting Alternators and Battery Systems

Victron, a leading provider of power solutions, offers three equipment options to protect both alternators and battery systems. The Buck-Boost, BMS 12/200, and the upcoming Orion Tr Smart DC to DC Charger are designed to safeguard alternators and batteries during the charging process. These products provide added peace of mind and ensure the longevity of both the charging system and the battery.

Highlights

• Charging lithium batteries with an alternator presents unique challenges due to differences in charging requirements and cooling needs compared to lead batteries.
• Alternators have an efficiency of around 50% and generate significant heat while charging.
• Charging lithium batteries at low RPMs can lead to alternator overheating and potential damage.
• External regulators, like the Balmar alternator used in the tests, monitor and adjust the output current to prevent overheating.
• The Balmar alternator with temperature monitoring features showed excellent performance in controlling temperatures during charging.
• Solutions for charging lithium batteries with an alternator include using larger alternators, regulators with temperature sensors, and current limiters or DC to DC Chargers.
• Victron offers a range of products to protect alternators and battery systems during charging, including the Buck-Boost, BMS 12/200, and the upcoming Orion Tr Smart DC to DC Charger.

FAQ

Q: Can I charge a lithium battery with any alternator? A: Charging a lithium battery with an alternator requires careful consideration of the alternator's capacity to handle the high current draw of lithium batteries. It is recommended to use alternators specifically designed for lithium battery charging or to employ regulators and temperature sensors to control the charging process.

Q: Why does charging a lithium battery at low RPMs cause overheating? A: Lithium batteries draw a high current even at low speeds, which can exceed the maximum rated amperage of an alternator. The reduced RPMs limit the cooling effect of the alternator, leading to overheating and potential damage.

Q: How do external regulators with temperature sensors help in charging lithium batteries? A: External regulators monitor the temperature of the alternator and battery and automatically adjust the output current to prevent overheating. Temperature sensors enable precise temperature control and protect the alternator from excessive heat.

Q: Are there any alternatives to prevent alternator overheating when charging lithium batteries? A: Installing larger alternators capable of delivering the required current at low RPMs or using current limiters or DC to DC Chargers can help regulate and limit the charging current, reducing the risk of alternator overheating.

Q: What products does Victron offer to protect alternators and battery systems? A: Victron provides a range of equipment, including the Buck-Boost, BMS 12/200, and the upcoming Orion Tr Smart DC to DC Charger, designed to protect alternators and battery systems during the charging process. These products ensure safe and efficient charging of lithium batteries.