Powerbank modules are ready-to-use modules that come with everything required to turn batteries into powerbanks.
Overview
Powerbank modules are breakout boards equipped with all components required by a powerbank. You just need to connect an appropriate battery pack and add a proper housing.
Such modules typically come with these features:
- Output Connectors: presoldered connectors for most or all common USB socket types. Some boards include Apple Lightning connectors.
- Charger: circuitry to safely charge the attached battery.
- BMS: protection circuitry to protect the attached battery from over-charge, over-discharge, and short-circuits. When protection was triggered, it is typically resettable by reconnecting the board to a charging current.
- Visuals: some sort of indicator to show state of charge
- Button: a button to wake up the electronics in order to draw power from the power bank
- Temperature Probe: good boards come with a temperature probe to stop operations on high temperatures. High temperatures can indicate a problem but can also occur environmentally: when the powerbank is exposed to direct sunshine, it can quickly heat up. Charging lithium batteries over 60 degree centigrade is dangerous and can lead to fire or explosion.
- Power Delivery: advanced boards come with power delivery ICs and support various quick charge standards. Simple boards only support the classic 5V USB charge.
Use Appropriate Batteries
Since powerbank modules already come with almost all required components, you often just need to add a suitable battery. Connecting a wrong battery can break havok and cause great damage, though.
Powerbank modules are designed for a particular battery type. Make sure the battery matches the board. This is extremely important because the charger built into these boards must match the battery requirements.
Battery Chemistry
Most modules require LiIon or LiPo batteries. Never connect such a board to a LiFePo4 battery, or else the battery will be overcharged and may be damaged or can catch fire. LiIon and LiPo batteries require different charging voltages and discharging voltage converters than LiFePo4.
Battery Voltage
Make sure the powerbank module is designed to work with the battery pack you want to use.
Small powerbanks and solar power banks use single batteries (1S). Larger and more powerful powerbanks often connect many batteries in series (2S, 3S, 4S, 5S, 6S, etc.).
The powerbank module must match the number of batteries you connected in series. A 1S powerbank module can only be used with single batteries (or a bunch of single batteries connected in parallel). Likewise, a 3S powerbank module always requires exactly three batteries connected in series.
The reason for this is similar to battery chemistry: when you connect batteries in series, this changes the charging and discharging voltage.
Building Battery Packs
Building powerbanks that use a single battery is the safest design and perfect as a start. All you need to care about is match the battery chemistry to the powerbank module.
Single battery powerbanks are typically not very powerful, though, which is why many users construct larger and more powerful battery packs. By connecting batteries in series, you can raise the voltage, and by connecting batteries in parallel, you can raise the current.
Constructing battery packs from more than one battery can be dangerous when done wrongly. Here are the most common mistakes:
- Unbalanced batteries: always use batteries of same type, same age, same vendor, and same state of charge. Their chemistry must behave similarly, and they must be charged to the same level before combining them. Even small imbalances can cause severe issues.
- Insufficient Electrical Connections: Powerbanks can draw enormous currents. When you power a notebook from a powerbank (provided the powerbank electronics support the required power delivery protocol and voltage), it may easily draw 65W. At 20V, that is a 3.5A current. At the battery level, the same 65W are drawn from 3.7V batteries, resulting in a 17.5A current. If you connected the batteries inside your battery pack with simple DIY wires, then these will probably soon go up in smoke.
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(content created May 02, 2024)