Can You Wire Two Lithium Batteries in Series? What's Safe and What's Not
Aug 10, 2026
If you're upgrading to lithium batteries, there's a good chance you'll eventually ask this question:
Can I connect two lithium batteries together to get more voltage?
The short answer is:
Yes—but only if the batteries and the manufacturer support it.
Whether you're powering a 24-volt trolling motor, a 36-volt system, an RV, or an off-grid setup, wiring batteries in series is a common way to increase system voltage. However, doing it correctly is essential for both performance and reliability.
Here's what you need to know before connecting your batteries.
What Does "Wiring Batteries in Series" Mean?
When batteries are wired in series, their voltage adds together, while the amp-hour (Ah) capacity remains the same.
For example:
- Two 12V batteries in series = 24V
- Three 12V batteries in series = 36V
The overall capacity stays the same as a single battery, assuming the batteries are identical.
For example:
- Two 12V 100Ah batteries in series become 24V 100Ah
This is why series wiring is commonly used for higher-voltage trolling motors and other equipment designed to operate at 24V or 36V.
Why Would You Wire Batteries in Series?
Higher-voltage systems offer several advantages depending on the application.
Common uses include:
- 24V trolling motors
- 36V trolling motors
- Certain RV electrical systems
- Off-grid solar systems
- Industrial equipment
These systems are designed to operate at a higher voltage than a single 12V battery can provide.
Series vs. Parallel: What's the Difference?
This is one of the most common points of confusion.
Series Wiring
Series wiring increases voltage.
Example:
- Two 12V 100Ah batteries
- Result: 24V 100Ah
Parallel Wiring
Parallel wiring keeps the voltage the same but increases capacity.
Example:
- Two 12V 100Ah batteries
- Result: 12V 200Ah
Think of it this way:
- Series = More voltage
- Parallel = More runtime
Choosing the right configuration depends entirely on what your equipment requires.
Use Batteries That Are Designed to Work Together
One of the biggest mistakes people make is assuming any two lithium batteries can simply be connected.
For the best performance, batteries should be:
- The same chemistry
- The same voltage
- The same capacity
- The same brand
- The same model
- Similar in age and usage history
Mixing batteries with different characteristics can create imbalances that reduce performance and may interfere with proper Battery Management System (BMS) operation.
Check the Manufacturer's Specifications First
Not every lithium battery is designed to support series connections.
Before wiring batteries together, confirm that your battery manufacturer specifically approves:
- Series operation
- Maximum number of batteries in series
- Compatible charging equipment
- Recommended wiring practices
These recommendations exist because battery management systems vary from one manufacturer to another.
Start with Batteries at a Similar State of Charge
Before connecting batteries in series, it's generally recommended that they be at similar states of charge.
Large differences in charge level can create unnecessary stress during initial use and make it more difficult for the system to operate as intended.
Checking and charging batteries individually before installation can help create a balanced system from the start.
Use Proper Cable Sizes
The cables connecting your batteries become part of the electrical system.
Using undersized cables can:
- Create unnecessary voltage drop
- Reduce efficiency
- Generate excess heat
- Limit overall system performance
Choose cable sizes appropriate for your system's voltage, current, and cable length, following the equipment manufacturer's recommendations.
Don't Forget the Charger
One of the most overlooked parts of a battery upgrade is the charger.
If you've converted from a single 12V battery to a 24V or 36V system, make sure your charging equipment is compatible with:
- Your battery chemistry
- Your system voltage
- The manufacturer's charging recommendations
Using the proper charger helps protect both battery performance and longevity.
Can You Mix Old and New Batteries?
It's generally not recommended.
Older batteries and newer batteries may perform differently because of variations in:
- Internal resistance
- Capacity
- Usage history
- Charge acceptance
For the best performance, install batteries that match as closely as possible.
Common Wiring Mistakes
Mixing Battery Types
Avoid combining:
- Lithium and lead-acid batteries
- Different lithium chemistries
- Different capacities
A battery bank performs best when all batteries are closely matched.
Ignoring the Battery Management System
The Battery Management System is one of the most important safety and performance features in a lithium battery.
Always confirm that the BMS supports the configuration you're planning to use.
Buying Based Only on Voltage
Just because a battery is labeled "12V" doesn't automatically mean it's compatible with every series application.
Review the manufacturer's specifications before installation.
Overlooking Connections
Loose or improperly tightened connections can create unnecessary resistance and reduce system performance.
Inspect all terminals before putting the system into service.
Is Series Wiring Safe?
Yes—when done correctly.
A properly engineered lithium battery system using compatible batteries, appropriate wiring, and manufacturer-approved installation practices can provide years of reliable performance.
The key is following the battery manufacturer's instructions rather than assuming every lithium battery supports every configuration.
Is a 24V or 36V System Right for You?
If you're running:
- A higher-thrust trolling motor
- Larger boats
- Longer fishing days
- Heavy electrical loads
a higher-voltage system may offer advantages.
However, the correct setup depends on your equipment requirements—not simply personal preference.
Wiring lithium batteries in series can be done in certain applications when the batteries are specifically designed for it and the manufacturer approves the configuration. However, it's not the right solution for every battery or every setup.
At Summit Lithium, our batteries are engineered specifically for powering portable fishing electronics such as forward-facing sonar, fish finders, and portable shuttle systems. Because of that intended use, we do not recommend wiring our batteries in series.
If your application requires higher system voltage, it's important to choose a battery designed for that purpose rather than combining batteries in a way that falls outside the manufacturer's recommendations.
While wiring batteries in series is a common practice in some industries, the safest approach is always to follow the guidance provided by your battery manufacturer. Doing so helps protect your investment and ensures reliable performance every time you're on the water.
