How to Charge Two 12V Batteries in Series and Parallel?
If you want your batteries to serve their purpose for a long time and save energy, proper recharging plays a key role. There are different methods to charge batteries, and using a battery charger is one of them. When we use a charger to charge a battery, an electrical circuit is created to increase its charge.
When it comes to charging multiple batteries at a time, series and parallel configurations help you do the job. Both configurations ensure precise control over distributing current and voltage across various components.
If you are searching for how to charge two 12V batteries in series and parallel, this article explains it all with a step-by-step guide.
What are series and parallel configurations?
Series and parallel combinations are two different options to increase voltage and current capacity by connecting two or more batteries.
Understanding the series configuration
While connecting two 12V batteries in series, you have to connect the positive (+) terminal of the first battery to the negative (-) terminal of the second battery. The same goes for the remaining two terminals of both batteries. The series configuration increases the voltage of the battery pack and maintains the overall current capacity.
For example, if you connect two 12V batteries in series, the combination will produce a 24V battery pack, while the current will remain the same throughout the circuit.
Understanding the parallel configuration
Connecting the positive terminal of the first battery to the positive terminal of the second battery and the negative terminal of the first battery to the negative terminal of the second battery creates a parallel configuration. When two batteries are connected in parallel, the current capacity increases, whereas the voltage throughout the circuit remains the same.
For example, when you connect two 12V batteries in parallel, the output voltage of the battery pack will be 12V, but it will have a higher current capacity.
Comparing series vs. parallel configurations
Let's quickly understand the key differences between series and parallel configurations of batteries.
| Feature | Series connection | Parallel connection |
| Voltage (V) | Increases | Remains the same as one battery |
| Current (C) | Remains the same as one battery | Increases |
| Capacity (Ah) | Remains the same as one battery | Increases |
| Power (W) | Increases | Increases |
Safety considerations before charging
Prioritizing safety is necessary before you start charging batteries in series or parallel. First, consider your personal safety. Once you are completely safe, you will be able to make sure the batteries are charging safely. Use acid-resistant gloves, goggles, and a costume to protect your hands, eyes, and body.
In addition, ensure the area where you are charging batteries is well-ventilated. This is especially important for lead-acid batteries. Don't forget to read the manufacturer's guidelines to understand the recommended charging method, current, and voltage.
If your battery is physically damaged, leaking, or swollen, don't put it on charge. Similarly, always use an original battery charger to ensure safe and stable charging. If you don't have the original charger, you can use the one that best matches your battery's specifications. If you want to purchase reliable battery chargers, explore the collection at Renogy.
Before you start charging your batteries, remember to ensure a secure connection and proper polarity. The tools you need while charging batteries include a digital multimeter, charger, and charging cables. The multimeter will help you determine the batteries' voltage to confirm whether they are fully charged or in process. Read more to learn how to use a digital multimeter to determine the battery's voltage.
How to charge two 12V batteries in series?
This section helps you connect two 12V batteries in series and start safe charging. Let's go through a complete step-by-step guide.
Step 1: Ensure safety
Safety must be your number one priority, as stated earlier. Use safety clothes, gloves, and goggles to protect yourself from the batteries' acid and chemical reactions. Moreover, make sure all electrical loads are disconnected from the battery.
Step 2: Get the tools needed
No specialized tools are required to connect two 12V batteries in series and put them on charge. All you need is a digital voltmeter, two jumper cables, and a charger that is compatible with 12V batteries.
Step 3: Connect both batteries in series
Once you have the desired tools, connect both batteries in series. But before you connect them, ensure they are fully charged. If they are, use jumper cables to connect the positive terminal of one battery to the negative terminal of the other battery. Now, you will get a combined voltage of 24 volts across both batteries.
Step 4: check the battery voltage
It is time to measure the voltage of the battery bank. The combined voltage of the bank should be 24 volts. If the voltage is lower, it means the batteries are discharged or weak. If this is the case, you should charge both batteries separately before you connect them in series.
Step 5: Connect the charger and adjust the settings
Once you make sure the batteries are connected properly and they are not weak or discharged, connect the charger. Connecting the charger to charge both batteries is simple. You just need to connect the positive wire of the charger to the positive terminal of one 12-volt battery and the negative wire of the charger to the negative terminal of the other 12V battery.
Adjust the charger settings for 12-volt batteries and choose the desired charging mode, e.g., bulk charge or trickle charge. If you don't know which mode to choose, read through the manufacturer's manual.
Step 6: Start charging
Now that the charger is connected and settings are adjusted properly. Start charging the batteries. Keep an eye on the charging process and make sure the charger is working effectively. Don't overcharge batteries to increase their lifespans and prevent them from damage.
Step 7: Disconnect and test
Disconnect the charger when the batteries are fully charged. Measure the voltage of the battery bank and ensure it is around 24 volts. If the voltage is still low, there might be an issue with one or both batteries. In this case, a detailed inspection is necessary.
Pro tip: Always make sure that the batteries have similar conditions and charge capacities before you connect them in series. Following the manufacturer's instructions is recommended.
How to charge two 12V batteries in parallel?
Now that you know how to charge two 12V batteries in series, it is time to learn to charge the same batteries while connecting them in parallel.
Step 1: Get the batteries ready
The two 12V batteries that you want to charge in parallel should be of the same type, and they must have similar states of charge and capacities. Ensuring these parameters helps prevent imbalances that may lead to overcharging or undercharging.
Step 2: Connect batteries in parallel
Connect the positive terminal of one battery to the positive terminal of the other battery and the negative terminal of the first battery to the negative terminal of the other battery with jumper cables. Make sure the connections are correctly tightened to avoid poor charging.
Step 3: Connect the battery charger
Since the positive and negative terminals of both batteries are connected to each other, connect the positive and negative wires of the charger to the positive terminal and the negative terminal of any battery, respectively.
Step 4: Start charging
Once you check and secure the parallel connection of two 12V batteries, turn the battery charger on. Keep monitoring the charging process. It is more important if you are doing it for the first time.
Step 5: Monitor and maintenance
Check each battery's voltage regularly to make sure the charger is charging the batteries correctly. Periodic inspection of cables and battery terminals is necessary, as it ensures there is no corrosion. If the terminals or cables are corroded, apply the mixture of baking soda and water to clean them instantly.
Tips for efficient and safe charging
You are now familiar with charging two 12 volt batteries in series and parallel. Below is a list of a few tips you should follow when charging batteries with either configuration.
- Use an advanced charger with automatic shut-off functionalities. Such chargers disconnect the batteries once they are fully charged.
- Always avoid undercharging and overcharging. Doing this will enhance your batteries' performance and increase lifespan.
- Prevent batteries from charging unevenly. To do this, you need a high-quality battery charger. In addition, keep the batteries away from extreme temperatures when they are on charge.
- Do not fully discharge the batteries before you put them on charge. If you have lithium-ion batteries, charge them before they reach 20% of their total capacity.
- Avoid fast charging when you don't need it. A slow charging process is recommended, as it extends the battery's lifespan and produces less heat.
Conclusion
If you are concerned about how to charge two 12V batteries in series, simply connect the positive terminal of the first battery to the negative terminal of the other battery. Then, connect the charger with the remaining terminals (positive wire to the positive terminal and negative wire to the negative terminal). The series combination will increase the voltage from 12V to 24V.
If you want to increase the current capacity, connect both 12V batteries in parallel and start charging. The discussion above has presented a step-by-step guide for both series and parallel charging mechanisms. Always follow the best charging practices to avoid experiencing hazards and ensure safe charging.
Batteries in Series FAQs
1. Can I charge two 12-volt batteries in series?
Yes, you can charge two 12V batteries in series. However, you won't be able to do that with a standard 12-volt charger. You need a 24V charger that matches the combined voltage of the battery pack - 24 volts.
2. Is it better to charge 12V batteries in series or parallel?
If you have a higher-voltage (24V) charger, connecting two 12V batteries in series would be preferable. If you want to use a 12V charger, connect the batteries in parallel.
3. Do you have to disconnect batteries in series to charge?
No. If the batteries are connected in series, you don't need to disconnect them to help them charge. The series connection always allows you to access the lowest battery.
