Li-Ion & LiPoly Batteries Created by lady ada Last updated on 2018-01-05 05:17:51 PM UTC
Guide Contents Guide Contents Overview Rechargeable Lithium Names Voltages Protection Circuitry "RC" Type Batteries Cell Phone & Camcorder Batteries Multi-battery Packs Proper Charging Conclusion Downloads Files Schematic & Fabrication Print © Adafruit Industries https://learn.adafruit.
Overview If you want to take your project portable you'll need a battery pack! For beginners, we suggest alkaline batteries, such as the venerable AA or 9V cell, great for making into larger multi-battery packs, easy to find and carry plenty of charge. If you want to go rechargable to save money and avoid waste, NiMH batteries can often replace alkalines. Eventually, however you may want to upgrade to the shiniest new technology - rechargable lithium ion/polymer batteries.
Rechargeable Lithium Names There are nearly a dozen different chemistries of rechargable lithium ion batteries but we will be specifically talking about Lithium Ion and Lithium Ion Polymer as a group. On the left you can see two Lithium Ion Polymer cells. On the right, two packs made of cylindrical Lithium Ion batteries Lithium Ion cells tend to be either rectangular or cylindrial. They are hard-shelled with a strong casing.
Voltages Depending on the design and chemistry of your lithium cell, you may see them sold under different nominal "voltages". For example, almost all lithium polymer batteries are 3.7V or 4.2V batteries. What this means is that the maximum voltage of the cell is 4.2v and that the "nominal" (average) voltage is 3.7V. As the battery is used, the voltage will drop lower and lower until the minimum which is around 3.0V. You should see the number 3.7V written on the battery itself somewhere.
You may also run across 4.1V/3.6V batteries. These are older than 4.2V/3.7V - they use a slightly different chemistry and you'll see the 3.6V marking on the cell. Nowadays you may also be able to purchase 4.35V cells! These are the latest chemistry, they have a little more power as indicated by the voltage being higher than 4.2V. They tend to be cylinder lithium ion's used for laptop batteries, and lights so its not terribly likely you'll just run into one unless you're looking for it.
Important Note! When charging batteries you must make sure that the charger voltage is less than or equal to the battery voltage. For the best battery performance/life you should have them matched. For example: 3.7/4.2V battery and 3.7/4.2V charger: OK - 3.7/4.2V battery and 3.6/4.1V charger: OK (but not ideal) - 3.6/4.1V battery and 3.6/4.1V charger: OK - 3.6/4.1V battery and 3.7/4.2V charger NOT OK! © Adafruit Industries https://learn.adafruit.
Protection Circuitry Lithium ion/polymer batteries are extremely power dense. This makes them great for reducing size and weight of projects. However, they are not 'safe' batteries and require extra care. Charging or using the batteries incorrectly can cause explosion or fire (as shown by this and many other youtube videos). There are five main things to watch for when charging and using batteries: Do not charge them above their maximum safe voltage (say 4.
Important Note! We suggest that you should never use lithium ion/polymer batteries without protection cells. Without the protection, a slight mistake in their use could destroy the battery and they have a much higher risk of exploding or catching on fire. © Adafruit Industries https://learn.adafruit.
"RC" Type Batteries When purchasing batteries, its good to be aware there are two families of batteries: Regular/Normal and RC (radio control) Regular/normal lithium ion batteries are what you find in your ipod, camcorder, phone etc. They are meant to last for over 500 charges, stay safe, and provide a C or two of current (For more details about **C** please read our basic battery tutorial) RC lithium ion batteries are meant for radio controlled cars, planes, UAVs, quad copters, etc.
Cell Phone & Camcorder Batteries You may end up using camcorder or cell phone batteries. These are removable batteries in a hard case. They tend have protection cells inside the case. This battery for example, is an old project battery from before you could buy lipoly batteries easily. © Adafruit Industries https://learn.adafruit.
Multi-battery Packs You may eventually find yourself needing a big battery, say because your project has twice as many LEDs or you want it to last twice as long. A lot of people think "well I know that if you parallel two batteries that doubles the capacity so I'll do that!" For example, we could take two 1300mAh batteries, that are 3.
You may be asking then, How come adafruit sells battery packs that are paralleled? These two packs are clearly two and three batteries. Since they are 3.7V they must be in parallel. Isnt this unsafe? The answer is that these batteries are assembled by a company that is experienced and certified to test and assemble battery packs. The individual batteries are tested and sorted by machine so that each pack has matching batteries with the same capacity and internal resistance.
This is also discouraged because the battery wont be able to be charged in a balanced manner. You should purchase a lithium ion pack that is preassembled. © Adafruit Industries https://learn.adafruit.
Proper Charging Now that you know how best to use your lithium ion/polymer battery, we'll finish up by making sure you know how to charge the battery. We'll have a longer tutorial for our chargers at some point but we want to get people started with how to best use our chargers! As we mentioned before, you must use a proper lithium ion/polymer battery charger. The good news is that nearly all batteries you will encounter are going to be 4.2V. And you can use a 4.
If you want to use the battery while also having it connected to the charger (less plugging and unplugging that way) you can simply use the BATTERY OUT connecion on the right. The IN and OUT ports are connected together on the circuit board so it acts as a pass-through To charge, connect a power supply to the top of the board. © Adafruit Industries https://learn.adafruit.
The PWR red LED on either board will light up to let you know its powered properly. While charging, an LED will also be lit. For the USB only charger, a green done LED will light when the battery is full. For the USB/DC charger, the charging LED will blink slowly (once every few seconds). You can change the charge rate of each charger by soldering a resistor into slot R4 (for the USB charger) or RPROG (the USB/DC charger). The max charge rate of the USB charger is about 1000 mA.
Conclusion Lithium Ion and Lithium Ion Polymer batteries are a great power source for projects but they require care during use and charging. They can be easy to damage or misuse and can hurt you or your property! All the batteries we sell pass testing and certification but you should still be careful with them.
Downloads Files MCP73833 Datasheet EagleCAD PCB files on GitHub Fritzing object in Adafruit Fritzing library Schematic & Fabrication Print © Adafruit Industries https://learn.adafruit.
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