How to Connect Two 12 Volt Batteries in Series: A Comprehensive Guide

Understanding Series Connection
A series connection adds the voltage of two batteries while keeping the capacity (Ah) unchanged. For example, connecting two 12V 100Ah batteries in series results in a 24V 100Ah system. This setup is ideal for applications requiring higher voltage rather than increased capacity, such as solar inverters or RV systems.
Benefits of a Series Connection
- Increased Voltage: Perfect for devices and systems that require higher operating voltage.
- Simple Wiring: Series connection is straightforward, requiring only one connection between batteries.
- Cost-Effective: Easier than purchasing a single higher-voltage battery.
Tools and Materials Needed
- Two identical 12V batteries (LiFePO4 or deep-cycle)
- High-quality battery cables
- Wire connectors
- Wrenches
- Protective gloves and goggles
Step-by-Step Guide to Connecting Batteries in Series
1. Preparation
Ensure both batteries are of the same type, capacity, and age. This prevents imbalanced charging and extends battery life.
2. Safety First
Wear protective gloves and goggles. Keep tools and work area dry to avoid short circuits.
3. Position the Batteries
Place batteries close together for easy access to terminals.
4. Connect the Batteries
- Connect the positive terminal of the first battery to the negative terminal of the second battery using a battery cable.
- The free negative terminal on the first battery serves as the system ground.
- The free positive terminal on the second battery connects to your device or system.
5. Secure the Connections
Tighten all connectors with a wrench. Loose connections can cause voltage drops, heat buildup, or safety hazards.
6. Verify the Setup
Use a multimeter to check the voltage across the free terminals. A correct series connection should read approximately 24 volts.
Tips for Maintenance and Troubleshooting
- Inspect Connections Regularly: Look for corrosion, loose cables, or wear.
- Monitor Battery Health: Check for consistent charging and discharging.
- Balanced Charging: Charge each battery individually with a 12V charger when possible to maintain balance.
- Use Appropriate Cables: Ensure cables can handle the current without overheating.