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The most common types of battery chargers

30 May, 2023

The most common types of battery chargers

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Just as all batteries are not the same, all chargers are not the same too. In this article we examine the most common types of battery chargers and their applications.

Constant Current (CC) and Constant Voltage (CV) chargers

In constant current charging, the charger provides a constant current to the battery until it reaches a specified voltage level. This mode is commonly used for lithium-ion batteries and other battery chemistries that can accept a higher current during the initial charging stage. Once the battery voltage reaches a certain threshold, the charger switches to constant voltage charging. In this mode, the charger maintains a steady voltage while gradually decreasing the charging current. The charger adjusts the output voltage to a specific level suitable for the battery being charged. As the battery charges, its internal resistance increases, causing the charging current to decrease naturally. Constant voltage charging allows the battery to reach its full capacity without overcharging.

Here’s a diagram that shows the difference between the two chargers:

Constant Current (CC) and Constant Voltage (CV) chargers diagram showing the difference in charging

Constant Current (CC) and Constant Voltage (CV) chargers diagram showing the difference in charging

Fast Chargers

Fast charging is a mode that applies a higher charging current to quickly replenish the battery’s energy. This mode is useful when you need to charge the battery rapidly, such as in emergency situations or when you have limited time available. However, fast charging can generate more heat and may not be suitable for all battery types or capacities. Therefore, it’s important to follow the manufacturer’s recommendations to avoid damaging the battery. Our recommendation is to avoid fast charging your batteries when you can, so that you can prolong their life.

Maintenance or Float Chargers

Once the battery is fully charged, some chargers enter what is called a maintenance or float charge mode. In this mode, the charger provides a lower voltage, typically slightly above the battery’s nominal voltage, to compensate for self-discharge and keep the battery at its optimal charge level. It helps prolong the battery’s life and ensures it’s ready for use whenever needed.

A battery float charger

A battery float charger

Trickle Chargers

Trickle charging is a low-current charging mode used to maintain a fully charged battery. It provides a small amount of continuous current to compensate for self-discharge over time. Trickle charging is often employed when the battery is not in use for an extended period, such as on a vehicle that is used only in the summer and is stored in the winter. It helps prevent the battery from discharging completely and keeps it ready for use when needed.

A battery trickle charger

A battery trickle charger

What is the difference between trickle chargers and maintenance or float chargers?

Trickle chargers provide a low-current charging mode that passes a continuous small amount of current to the battery. This mode is often employed for long-term storage or infrequently used batteries, such as for vehicles that won’t be used for a few months but need to keep their battery from discharging completely.

Maintenance or float chargers are designed to maintain a battery at its fully charged state, but without overcharging it. It is mainly used for batteries that are subjected to repeated charge and discharge cycles, such as those in Uninterruptible Power Source (UPS) systems that keep computers running during power cuts, or electric vehicles, renewable energy storage systems and some electronic devices.

How does a battery charger actually work?

Battery chargers vary according to the battery chemistry they are designed to charge. The main principle though is very similar in all of them.

As mentioned above, a battery charger usually has different charging modes, such as trickle charge, fast charge, and maintenance or float charge. Whatever the mode though, the charger requires a power source to operate. This is usually the grid (meaning the socket in our house), but can also be a solar panel or other renewable energy source. Some chargers can convert the AC (alternating current) power from the wall outlet to DC (direct current) power that can be used to charge the battery.

Inside the charger, there is a charging circuitry that controls the charging process. It consists of various components, such as:

  • Voltage Regulators
    They regulate the voltage provided to the battery during the charging process. Different batteries have specific voltage requirements, and the charger adjusts the output voltage accordingly to prevent overcharging or undercharging. This voltage regulation is crucial for the battery’s longevity and safety.
  • Current Controllers
    They control the charging current flowing into the battery. Depending on the battery type and capacity, the charger adjusts the charging current to an appropriate level. This helps prevent overheating and damage to the battery caused by excessive current flow.
  • Charging Algorithm Circuits
    These circuits (microchips) use pre-programmed charging algorithms to optimize the charging process. These algorithms may include various stages, such as bulk charging, absorption charging and float charging. Each stage applies different charging parameters to ensure efficient and safe charging, as well as to prolong battery life. There are cases where a charger may also automatically recognise the chemistry of the battery we connect to it and adjust the charging parameters accordingly.
  • Safety Features
    Battery chargers often incorporate safety features to protect the battery and prevent potential hazards. These features include short-circuit protection, temperature monitoring, reverse polarity protection or overcharge protection. For example, once a battery reaches its fully charged state, the charger may automatically switch to a maintenance or trickle charge mode to prevent damage or fire from overcharging.

What does the charging process involve?

All batteries have a negative electrode (anode) and a positive electrode (cathode). The process of charging a battery goes through the following stages:

  1. Ions or electrons are removed from the positive electrode and are absorbed into the negative electrode
  2. The electrolyte allows ions to move between the electrodes.
  3. Ions migrate from the positive electrode to the negative electrode through the electrolyte.
  4. This movement of ions increases the battery’s stored energy.
  5. The voltage of the battery increases as it charges.
  6. Once the battery is fully charged, the charging stops to avoid overcharging.

Here’s a simple video showing the process

Can I charge a non-rechargeable battery?

The answer is a strict no, and you shouldn’t even try it.

Non-rechargeable batteries are not designed to handle the charging process. When you attempt to charge them, they may leak corrosive or toxic substances, causing damage to the battery itself and potentially harming the surrounding environment or individuals nearby. In some cases, overcharging can lead to the battery rupturing or exploding. This is because if you attempt to recharge a non-rechargeable battery, its temperature will rise and excess heat as well as a buildup of gas within the battery will occur. This will result in the battery becoming unstable and potentially lead to a fire or explosion. Non-rechargeable batteries do not have built-in safety mechanisms to handle the charging process and mitigate these risks.

Furthermore, certain types of non-rechargeable batteries, such as zinc-carbon or alkaline batteries, may release toxic gases like hydrogen gas when subjected to improper charging. These gases can be flammable and pose health risks if inhaled. Also, trying to charge a non-rechargeable battery can even damage the charger itself. The charging process may overload the device’s circuitry, leading to malfunctions or permanent damage.