Using Ni-MH AA Battery for Kids' Car and Bike | 6V 4.5Ah

Using Ni-MH AA Battery for Kids' Car and Bike | 6V 4.5Ah

Step-by-Step Guide

1. Understanding the Requirements

  • Voltage Requirement: 6V
  • Capacity Requirement: 4.5Ah (4500mAh)

2. Selecting the Right Ni-MH AA Batteries

  • Voltage of Each AA Cell: 1.2V
  • Capacity of Each AA Cell: Typically 2000mAh to 2500mAh for high-quality AA Ni-MH cells

3. Determining the Number of Batteries

Series Configuration for Voltage: To achieve 6V, you need 5 AA batteries in series (1.2V x 5 = 6V).

Parallel Configuration for Capacity: To achieve 4.5Ah, you need to combine multiple series strings of 5 AA batteries to match the required capacity.


  • Capacity per Series String: If each AA battery has a capacity of 2500mAh, a single string of 5 batteries will have a capacity of 2500mAh.
  • Number of Parallel Strings Required: To achieve 4.5Ah, divide 4500mAh by the capacity of one string (2500mAh), which equals approximately 1.8. Since you can't have a fraction of a string, round up to 2. Thus, you need 2 parallel strings of 5 AA batteries each to achieve a total capacity of 5000mAh (5Ah), which is slightly above the required 4500mAh, providing some extra capacity.

4. Connecting the Batteries

  • Series Connection: Connect 5 AA batteries in series to achieve 6V.
  • Parallel Connection: Connect 2 such series strings in parallel to achieve 5Ah.
Diagram: Battery Configuration
Series String 1 Series String 2
[1.2V AA] — [1.2V AA] — [1.2V AA] — [1.2V AA] — [1.2V AA] [1.2V AA] — [1.2V AA] — [1.2V AA] — [1.2V AA] — [1.2V AA]
Total: 6V, 5000mAh (5Ah)

5. Assembling and Housing

  • Battery Holder: Use appropriate battery holders to secure the AA batteries. You’ll need two 5-cell series battery holders and connect them in parallel.
  • Wiring: Use reliable connectors and wiring to ensure secure and stable connections. Soldering or using battery connectors can help ensure connections are strong and reduce resistance.
  • Housing: Make sure the battery pack fits into the battery compartment of the car or bike. If the original compartment is too small, you may need to modify it or find a suitable enclosure that can be securely attached.

6. Charging

  • Charger: Use a Ni-MH charger designed to charge the combined capacity and voltage of your new battery pack (6V, 5Ah). Ensure the charger can handle the series and parallel configuration.

Important Considerations

  1. Current Draw: Ensure that the Ni-MH batteries can handle the current draw of the vehicle’s motor. High-quality AA Ni-MH cells should be able to handle moderate to high discharge rates.
  2. Safety: Ni-MH batteries can overheat if over-discharged or over-charged. Use a Battery Management System (BMS) or ensure your charger has overcharge protection.
  3. Balancing: Ensure that the charge is evenly distributed across all cells to prevent imbalance which can shorten the lifespan of the batteries.


Using Ni-MH AA batteries as a replacement for a 6V 4.5Ah battery is feasible with careful planning and the correct configuration. By using 2 parallel strings of 5 series-connected AA batteries, you can achieve the desired voltage and capacity. Ensure proper connections, secure housing, and use an appropriate charger to maintain safety and performance.

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