Batteries in series and parallel
Two AA cells in series light a flashlight bulb, and two in parallel barely glow it: volts add in series, run time adds in parallel, and the rules for packing cells safely.
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Power and batteries
Where the volts come from and how to keep them: Ohm's law on a real meter, cells in series and parallel, a regulator, a LiPo on a TP4056, a boost converter, a battery gauge, and a power bank you build yourself.
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What you will build
2 projects, built step by step
7 lessons in 5 chapters, about 3 hours on a simulated breadboard. Free, in your browser, every step checked by the simulator.
A boost converter: one cell to 12 V
An MT3608 boost module turns one 4 V lithium cell into 12 V for a lamp, and keeps it at 12 V as the cell runs down: how a boost converter trades amps for volts, and why it cannot step down.
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Chapter by chapter
Each lesson opens when the one before it is done, and each chapter ends in a project.
Chapter 1
Volts, amps and cells
Ohm's law with a real meter, and stacking cells for volts or run time.
- Open187 XP
Volts, amps and ohms with a real meter
A bench supply, a 10 ohm resistor and a multimeter: what voltage, current and resistance are, Ohm's law in one line, and what a current limit does when the law asks for too much.
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- ProjectLocked374 XP
Batteries in series and parallel
Two AA cells in series light a flashlight bulb, and two in parallel barely glow it: volts add in series, run time adds in parallel, and the rules for packing cells safely.
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Chapter 2
Steady volts
A regulator that holds 5 V while the battery sags.
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A voltage regulator: 9 V in, 5 V out
A 7805 turns a 9 V battery into a steady 5 V: its three legs and two capacitors, the dropout when the battery runs down, the heat it makes, and an AMS1117 that needs far less headroom.
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Chapter 3
Lithium cells
Charging a LiPo safely, and boosting one cell to 12 V.
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Charging a LiPo with a TP4056
A solar panel charges a LiPo through a TP4056 while an INA3221 and an LCD show every milliamp: why lithium needs a real charger, the 4.2 V limit, and what happens when the sun goes down.
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- ProjectLocked410 XP
A boost converter: one cell to 12 V
An MT3608 boost module turns one 4 V lithium cell into 12 V for a lamp, and keeps it at 12 V as the cell runs down: how a boost converter trades amps for volts, and why it cannot step down.
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Chapter 4
How full is it?
A divider that lets A0 read a 12 V battery.
- Locked187 XP
Reading a 12 V battery with a divider
Two resistors scale a 12 V battery down so an Uno can read it on A0, and the sketch turns the reading back into volts and a charge level on an LCD and a traffic light.
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Chapter 5
Boss project
A power bank that charges, boosts and shows its charge.
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Boss project: a power bank with a charge gauge
Put it all together: a lithium cell charged from USB by a TP4056, boosted to 5 V by an MT3608 for a gadget, and an Uno showing the charge on an LCD and a traffic light.
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Syllabus
Every lesson in the course
All 7 lessons, in order, each with what it covers. Any of them opens in the editor right away.
Volts, amps and cells
- Volts, amps and ohms with a real meterA bench supply, a 10 ohm resistor and a multimeter: what voltage, current and resistance are, Ohm's law in one line, and what a current limit does when the law asks for too much.
- Batteries in series and parallelTwo AA cells in series light a flashlight bulb, and two in parallel barely glow it: volts add in series, run time adds in parallel, and the rules for packing cells safely.
Steady volts
- A voltage regulator: 9 V in, 5 V outA 7805 turns a 9 V battery into a steady 5 V: its three legs and two capacitors, the dropout when the battery runs down, the heat it makes, and an AMS1117 that needs far less headroom.
Lithium cells
- Charging a LiPo with a TP4056A solar panel charges a LiPo through a TP4056 while an INA3221 and an LCD show every milliamp: why lithium needs a real charger, the 4.2 V limit, and what happens when the sun goes down.
- A boost converter: one cell to 12 VAn MT3608 boost module turns one 4 V lithium cell into 12 V for a lamp, and keeps it at 12 V as the cell runs down: how a boost converter trades amps for volts, and why it cannot step down.
How full is it?
- Reading a 12 V battery with a dividerTwo resistors scale a 12 V battery down so an Uno can read it on A0, and the sketch turns the reading back into volts and a charge level on an LCD and a traffic light.
Boss project
- Boss project: a power bank with a charge gaugePut it all together: a lithium cell charged from USB by a TP4056, boosted to 5 V by an MT3608 for a gadget, and an Uno showing the charge on an LCD and a traffic light.
Keep going
The next course on your track
Power and batteries is part of the electrical track, a ladder of courses from zero to expert.
Sensors and measurement
Intermediate: thermistors and RTDs, strain gauges in a Wheatstone bridge, light and IR, current on a shunt and an INA219, ADC resolution and noise, and calibration, finished with a power instrument you check against Ohm's law.
Open the next courseElectrical track
Current and voltage you can see, then transistors, op-amps, filters, power and PCBs. Every circuit runs in a real circuit simulator in your browser.
See every course on the trackKits
Build it on your bench too
Every lesson runs in the simulator with nothing to buy. When you want the real thing, these kits have the parts.
Power Bank Kit
A 7805 regulator, a lithium cell, a TP4056 charger, an MT3608 boost module and an Uno gauge with an LCD.
Open the kitFind your kit
Pick the starter kit you own and run every lesson in its manual with the same parts on the same pins.
See every kitQuestions
About Power and batteries
Is Power and batteries free?
Yes. All 7 lessons of Power and batteries are free and run in your browser, with nothing to install and no parts to buy before you start.
Do I need any parts?
No. Every circuit is built on a simulated breadboard, and the simulator checks each step as you go. When you want to build it for real, the same parts and wiring work on a real bench.
How long does Power and batteries take?
About 3 hours: 7 lessons in 5 chapters, each one a few short steps. Your progress is kept, so you can stop after any lesson and pick up where you left off.
What will I build?
Each chapter ends in a project that puts it together: Batteries in series and parallel and A boost converter: one cell to 12 V.
Where do I start?
With "Volts, amps and ohms with a real meter", and each lesson builds on the one before it. New to circuits? Electronics basics is the course that starts from zero.