Single Cell LiPo Battery Care

2023-05-23 | By SparkFun Electronics

License: See Original Project

Courtesy of SparkFun

Guide by BBOYHO

Introduction

Note: This tutorial was ported over from the older LiPo Battery Care tutorial. Tips from the LilyPad ‎Basics: Powering Your Project (Power Options: Rechargeable Lithium Polymer Batteries) were also ‎added to this tutorial.‎

Lithium-Ion Polymer (LiPo) batteries are a favorite of ours. Very light weight and some of the ‎highest energy densities available. We affectionately call this battery the 'car battery' because it's ‎huge. Not physically (it's 110 grams!) but because this 6Ah LiPo in capable of outputting 6 Amps ‎over the period of one hour! This is a very large amount of power in our low-power embedded ‎world. Please don't confuse this with a real car battery!‎

Single-Cell-LiPo-Battery-Care

A LiPo battery capable of producing 6 Amps for one hour!‎

Required Materials

To follow along with this tutorial, you will need the following materials at a minimum. You may not ‎need everything though depending on what you have. Add it to your cart, read through the guide, ‎and adjust the cart as necessary. Below is a wishlist of the parts that you need to get started if you ‎were to charge a LiPo battery and then remove the connector.‎

Wishlist for 1S LiPo Battery Care SparkFun Wish List

VIEW WISHLIST FOR 1S LIPO BATTERY CARE ON SPARKFUN.COM

Single Cell LiPo Chargers

There are a variety of development boards and breakout boards with a dedicated single cell LiPo ‎battery charge circuit. Below are a few examples from the SparkFun catalog that have the ‎MCP73831. The charge IC used, and charge rate will depend on the design.‎

Single Cell LiPo Battery

Of course, you will also need a single cell LiPo battery. Below are a few LiPo batteries to choose ‎from in the SparkFun catalog.‎

Tools

Need some help removing the single cell LiPo battery from the JST connector? Try grabbing a ‎needle nose plier or diagonal cutters. Or you can use a hobby knife to whittle down the JST-PH's ‎locking tabs.‎

Note: If you decide to not use needle nose pliers, we recommend getting a low cost diagonal ‎cutters instead of flush cutters. This will prevent users from damaging their nicer flush cutters when ‎pulling the JST connector out.‎

You May Also Need

For strain relief, you can use some electrical tape and scissors to secure the wires on the single cell ‎LiPo battery. You may want a marker to label the battery.

Electrical Tape
Scissors
Marker

Suggested Reading

If you aren’t familiar with the following concepts, we also recommend checking out a few of these ‎tutorials before continuing

Connector Basics: Connectors are a major source of confusion for people just beginning ‎electronics. The number of different options, terms, and names of connectors can make selecting ‎one, or finding the one you need, daunting. This article will help you get a jump on the world of ‎connectors.‎
Battery Technologies: The basics behind the batteries used in portable electronic devices: ‎LiPo, NiMH, coin cells, and alkaline.‎
How Lithium Polymer Batteries are Made: We got the opportunity to tour the Great ‎Power Battery factory. Checkout how LiPos are made!‎
How to Use a Multimeter: Learn the basics of using a multimeter to measure continuity, ‎voltage, resistance and current.‎
What is a Battery? An overview of the inner workings of a battery and how it was invented.‎

Charging LiPo Batteries, Safely

‎Warning: Never ever charge a LiPo with anything but a special LiPo charger! We recommend ‎you do not leave a charging battery unattended.‎

Back in the old days, there were only two chargers available in SparkFun's catalog. The standard ‎charger based on the old MAX1555 IC and our faster charger based on the newer MCP73831 IC. ‎You will notice the MAX1555 and MCP73831 populated as a 5-pin IC as shown in the images below. ‎The MAX1555 was great but its limited charging current (300mA) and diminishing market availability ‎way back when pushed us towards creating chargers based on the MCP73831 (500mA per hour ‎charging rate.)‎

charger_1

Retired USB Single Cell LiPo Charger with ‎MAX1555‎

charger_2

USB Single Cell LiPo Charger with ‎MCP73831‎

You will notice the MCP73831 populated on select development boards and a variety of breakout ‎boards with different USB connectors. Below are a few examples with the MCP73831 populated on ‎different boards found in the SparkFun catalog.‎

Other notable LiPo chargers in the SparkFun catalog is the BQ24075 populated on the Battery ‎Babysitter - LiPo Battery Manager, and LT3652 populated on the Sunny Buddy - MPPT Solar ‎Charger. Both can be used to charge a single cell LiPo battery through USB or a solar panel, ‎respectively.‎

Recommended Charge Rate for Single Cell LiPo Batteries

To avoid explosions (which are only very briefly fun), you should not charge these LiPos at a ‎current over the battery's capacity, typically 1C for fast charging. To be safe ^[1], you should keep the ‎charge current at or below 1C of your battery as indicated in the datasheets.‎

What does this mean? Well, let’s take a look at the datasheet for the 850mAh LiPo battery. The ‎image shown below highlights the recommended standard charge rate and maximum continuous ‎charge current, where C is the capacity of the LiPo battery. For a standard charge rate of 0.2C, an ‎‎850mAh LiPo battery can be charged at a rate of 170mA. When charging at the maximum charge ‎rate of 1C, an 850mAh LiPo battery can be charged at a rate of 850mA.‎

datasheet_3

Datasheet highlighted for the 850mAh LiPo Battery's Charge Rates

What does this mean with the LiPo chargers available? Well, if you have an 500mAh single cell ‎LiPo battery, it should not be given a charge current over 500mA. You should use a charger that is ‎able to charge the LiPo battery with a dedicated single cell LiPo charger set at or below 500mA. ‎The minimum LiPo battery that SparkFun has available currently that is compatible at this rate that ‎you can safely charge is 850mAh. Other larger single cell LiPo batteries can also be charged at this ‎rate.‎

What about a 100mAh LiPo battery? Yeah, those should not be charged higher than 100mA. ‎Make sure to find a single cell LiPo charger that is set at or below 100mA. The minimum LiPo ‎battery that SparkFun has available currently that is compatible at this rate that you can safely ‎charge is 110mAh. Other larger single cell LiPo batteries (like the 400mAh shown below or any of ‎the ones shown earlier) can also be charged at this rate.‎

Depending on the designer, the charge rate can be set to a default rate of either 500mA or 100mA. ‎Certain boards can have a 3-way jumper, switches, and/or PTH footprint to solder a resistor to ‎adjust the charge rate. Below is a schematic of the USB LiPoly Charger. As you can see, this ‎particular board is set at a default rate of 500mA with a 3-way jumper. Cutting the jumper and ‎adding a solder blob between the center pad and the other jumper pad will set the charge rate to ‎‎100mA.‎

diagram_4

But what about that lone 40mAh LiPo Battery in SparkFun's catalog?! If you look closely at the ‎schematic shown earlier, there is also a footprint (not currently highlighted but it is connected to the ‎same net) that allows users to solder a PTH resistor. This allows a user to set the charge rate to a ‎value other than 500mA or 100mA. There's not that a lot of development boards and breakout ‎boards that have the footprint available. Make sure to be careful when connecting a USB cable to ‎those boards when a 40mAh battery is attached. You will want to remove the battery and connect ‎the LiPo battery to a separate LiPo Charger that is set at or below 40mA.‎

Polymer Lithium Ion Battery - 40mAh‎

To calculate the resistor needed on a board with the MCP73831, you can use the following formula ‎from its datasheet. Note that this equation is specific for the MCP73831 charge IC.‎

calculate_5

We'll just skip ahead of the calculations and tell you that the value to charge at a rate of 40mA is... ‎‎25kΩ! This is quite an odd number for a resistor value in SparkFun's catalog. You'll need to wire a ‎few resistors wired in series and parallel to connect to the two PTHs (i.e., 10kΩ + 10kΩ + (10kΩ || ‎‎10kΩ) ). Or you could use resistor with a larger value like 47kΩ that is included in the resistor kit. ‎However, the charge rate will be less: 21.28mA.‎

‎[1]: Most batteries include over-current protection -- implemented on the little circuit board under the yellow tape -- which will keep the battery from ‎blowing up if you supply too much current. But it's best to not rely on that circuit: you'll save power and your sanity.‎

Note: For users using R/C LiPo batteries (i.e., more than one cell., make sure to use a dedicated ‎LiPo battery balance charger to safely charge the LiPo batteries.

Connecting and Disconnecting a LiPo Battery's JST ‎Connector

Depending on the manufacturer, there are different packages and connections for Lithium batteries. ‎We will be going over how to connect and disconnect batteries with a JST-PH connector in this ‎section. They will usually have a protection circuit under the yellow Kapton tape, and a silver ‎packaging (of course the exception is the 6Ah LiPo battery that is blue).‎

‎1250mAh LiPo ‎battery with JST ‎connector‎
110mAh LiPo battery ‎with Solder Tabs‎
2600mAh Lithium Ion ‎Battery 18650 Cell‎
24.5mm CR2450 ‎Coin Cell Lithium Ion ‎Battery

JST Connector Locking Tabs

Typically, single cell LiPo batteries are terminated with a two pin JST-PH female connector. These ‎are polarized connectors with pin 1 as +VBATT (red wire) and pin 2 connected to ground (black ‎wire). These mate with the two pin JST-PH male connector (shroud).‎

connector_6

‎Danger: Always double check the orientation of the power and ground wires on the battery, ‎depending on the manufacturer they may be reversed!!! All single cell LiPo batteries in the ‎yellow/silver packs carried by SparkFun and SparkFun original boards use this standard ‎configuration.‎

If you look closely at the JST female connector, there are two locking tabs on the top of the ‎connector for a secure connection. However, this can make it hard for anyone that wants to unplug ‎and replug the battery back into the board. After a few inserts and removals, the locking tabs on the ‎JST connector will wear down slightly to the point that you will be able to remove the connector by ‎hand.‎

tabs_7

‎Danger: Certain ecosystems use a JST connector for power as well. One example is the ‎micro:bit. Note that the input voltage for the connector is different: it is typically around 3V and is ‎intended to be used with 2xAA batteries. The battery chemistry is different for the AA batteries ‎‎(usually alkaline with a nominal voltage of about 1.5V). Make sure to not connect the LiPo battery ‎directly to the micro:bit's JST connector unless you have a regulated voltage.

disconnect_8 ‎ ‎

Disconnecting JST Connectors on the micro:bit from the Wireless Remote Control with micro:bit Tutorial

Connecting JST Connectors

Inserting the LiPo battery's JST connector into its mating connector is a breeze. Simply hold the ‎JST female connector with your index finger and thumb. Then hold board in a similar fashion using ‎your other hand. Align the two JST connectors together. Insert the JST connector into the socket.‎

insert_9

Disconnecting

Now disconnecting the LiPo battery is a different story. Earlier, we talked about some locking tabs ‎on the side of the JST connector which can make it difficult to disconnect it from a female JST ‎connector. Depending on the manufacturer, the material of the female JST connector can add an ‎extra layer of difficulty if it is rigid. Below are a few options if you decide to disconnect the LiPo ‎battery.‎

Using Your Bare Hands Fingers!
Needle Nose Pliers
‎3D Print a Special Extraction Tool!!!‎
Diagonal Cutters
Shaving Off Locking Tabs

Warning! Make sure to not pull one the wires to disconnect. You may end up ripping the wires out ‎from the connector.‎

Using Your Bare Hands Fingers!‎

You will need to carefully remove the connector out by pinching the sides of the JST female ‎connector with your index finger and thumb. With your other hand, hold down the JST male ‎connector.‎

wiggle_10

Wiggle the JST female connector side to side while carefully pulling away the connector from the ‎board.‎

jst_11

The JST connector will slide out of the socket. Congratulations! You have successfully ‎disconnected the LiPo battery from your board.‎

socket_12

Needle Nose Pliers

For those with long nails, you will want to use some needle nose pliers. We recommend using ‎needle nose pliers with teeth like the one below:‎

Needle Nose Pliers

Grip the sides of the JST female connector using the needle nose pliers in one hand. With your ‎other hand, hold down the JST male connector.‎

grip_13

Wiggle the JST female connector side to side while carefully pulling away the connector from the ‎board. Using needle nose pliers will make it easier to remove but make sure to not angle the tool ‎too much as the pins can be damaged if you angle the connector at an extreme angle.‎

slide_14

The JST connector will slide out of the socket. Congratulations! You have successfully ‎disconnected the LiPo battery from your board.‎

disconnect_15

Diagonal Cutters

Of course, you could also use some diagonal cutters as well. Wire cutters have thin jaws that allow ‎you to grip the head of the connector. However, there is a risk of cutting the wires if the diagonal ‎cutters slip.‎

Diagonal Cutters

Depending on the design of the board, you may need to grip from the top or bottom of the JST ‎connector. We'll show in the following images how to remove the connector from the bottom. ‎Position the wire cutter between the between the JST female connector's flanges on the side and ‎the JST male connector's socket. With your other hand, hold down the JST male connector. Don't ‎go squeezing hard on the wire cutters either. They are simply there to grip the edge of the ‎connector.‎

cutters_16

Diagonal cutters holding JST connector from ‎the top of a PCB

cutters_17

Diagonal cutters holding JST connector from ‎the bottom of a PCB

Note: You can also use round nose pliers similar to the method used with diagonal cutters. ‎However, they won't have the thin jaws like a diagonal cutter.

round_18

Use the edge of the PCB as a fulcrum point and lever out the connector. Pull the JST female ‎connector away from the board by wiggling the connector sideways back and forth.

edge_19

The JST connector will slide out of the socket. Congratulations! You have successfully ‎disconnected the LiPo battery from your board.‎

disconnect_20

Removing the Locking Tabs

Another option is to remove the locking tabs using a hobby knife. Cutting the tabs will make it easier ‎to remove by hand. While it will not be as secure as it was before, we have found that it still holds ‎pretty well in the JST male connector socket.‎

Hobby Knife

Pinch the sides of the JST female connector with your index finger and thumb. With the hobby ‎knife, slice the locking tabs off each side of the JST female connector until it is flush with the top of ‎the connector. There's not a lot of space to work with so make sure to not cut your fingers and ‎angle the hobby knife away from your fingertips!‎

pinch_21

The JST connector on the left shows the locking tabs intact. The JST connector on the right shows ‎the locking tabs removed after. If the connector is still too tight, you can also cut down part of the ‎fin (the slot between the two locking tabs) on the top of the connector as well.‎

intact_22

How Much Power is Left?‎

You might be asking yourself; how much power is left in my LiPo battery? This is useful to ensure ‎that you have enough charge to power your project or storing the LiPo battery.‎

Multimeter

One way to check the voltage of a LiPo battery is using a multimeter. You can set a multimeter to ‎measure the voltage and connect to the terminals of the JST connector. Of course, you can also ‎connect to the +VBATT and GND pins on a PCB if the battery is connected to a board as well. Just ‎be careful not to accidentally create a short between the two terminals when measuring with the ‎probes.‎

multimeter_23

Using a Multimeter to test the voltage on a LiPo Battery.‎

LiPo Fuel Gauge

Another method is using a dedicated LiPo Fuel Gauge to output the voltage and charge remaining ‎on a display. You are less likely to short the battery terminal pins using a LiPo Fuel Gauge ‎‎(assuming that you are connecting a LiPo battery to the LiPo Fuel Gauge's JST connector or have it ‎soldered to the PTH) compared to using a multimeter. Below are a few LiPo Fuel Gauges that you ‎could use.‎

gauge_24

LiPo Fuel Gauge (MAX1704X) Hookup Guide

Monitor your LiPo battery with the LiPo fuel gauge! In this tutorial, we will be using the MAX17043 ‎and MAX17048 to monitor a single cell,

LiPo battery over the Arduino Serial Monitor.

We will also ‎connect a display to view the output without the need to connect the microcontroller to a computer.‎

babysitter_25

Battery Babysitter Hookup Guide

An introduction and getting started guide for the Battery Babysitter - a flexible LiPo battery charger ‎and monitor.‎

Reinforcing the Power Cables

One of the down sides to using these LiPo batteries is their fragile power connections between the ‎wires and protection circuit. These types of batteries are manufactured for a permanent install in ‎devices, and not being removed often as can sometimes happen with projects. For users ‎prototyping or frequently removing the battery from boards without ON/OFF switches, it can be ‎easy to accidentally pull or break the power wires from the terminals on the protection circuit built ‎into the battery. Luckily for us, a little electrical tape goes a long way!

tape_26

The red and black wires on a LiPo will tend to wear out and break off if you swing the battery ‎around too much. This fix is so simple, but we find that many people don't realize what a little ‎stress-relief can do. You can provide strain relief to the wires by placing them to the side and ‎securing with electrical tape - this will help with strain on the connection to the battery.‎

On your LiPo battery, fold the red and black wires to the side. With electrical tape, start in the ‎middle of the battery and tape over the top. Use a little bit of tension on the tape as you go over the ‎top of the battery. I use one and a half full wraps around the battery.‎

cut_27

Cut the tape with wire cutters or knife to make a clean cut. Tearing the tape can leave ugly ripples in ‎the electrical tape.‎

cut_28

To make it even more secure, you can add another piece of tape across LiPo battery.‎

tape_29

These one or two wraps around the battery serve as a simple stress relief. All the mechanical stress ‎is transferred to the tape instead of to the soldered terminals inside the top of the battery. Now ‎when you use (or misuse) the battery, you won't have to worry about breaking the red and black ‎wires from the top of the battery!‎

Labeling Batteries

We've had a surprising collection of LiPos for various projects (they just seem to be replicating at ‎this point!). A problem that came up was identifying the battery. What was I doing with this battery? ‎What torture had I put it through? A Sharpie marker is perfect for marking your battery. A name ‎such as 'heater' or 'costume' makes a world of difference. Dating the battery will let you know when ‎you first used it. After a few years, these batteries will start to lose some of their capacity. A date ‎code helps to indicate that general health of a cell.‎

collect_30

Remember, a protection circuit is usually built into yellow and silver pack that we sell. The protection ‎circuit board is usually under the yellow Kapton tape where the wires are connected.

battery_31

The protection circuit will prevent:‎

over voltage (over charging)‎
over current (the battery will turn off if there is a short in your system)
under voltage (the battery will turn off before it runs down too low)‎

This protection circuit prevents most misuse of the battery and we have definitely misused some ‎batteries. You can be re-assured the protection circuit will protect you and the battery.‎

Battery Storage and Handling

Warning: LiPo batteries can explode or catch fire if mishandled or damaged. They can become ‎unstable and dangerous if punctured or exposed to high temperatures.‎

While LiPo batteries are a great option for providing rechargeable power to your project, they do ‎have some safety considerations. This section will cover a few tips for safe handling and use of ‎LiPo batteries for your projects.‎

Storage

When not in use for long periods, it is recommended to discharge the LiPo battery to about ‎‎3.9V to 4.0V
Always store your batteries in an enclosure free of sharp objects. When installing a battery in ‎your project, take care to keep it away from parts of your project that could pinch, poke, or ‎strain the battery
Do not transport or store a LiPo battery with metal objects, such as hairpins, necklaces, or any ‎other conductive object or material
Keep or store the battery in a cool and dry place/environment while installed in a project or in ‎storage. If you are not planning to use your project for a long time, remove the battery and ‎store it separately

‎Keep Away from Heat and Moisture

Keep your LiPo battery away from environments that will damage it. Do not immerse a LiPo ‎battery in liquids. Remove the battery from your project if it needs to be washed (such as e-‎textiles and wearable projects)
Do not use or store the battery near any source of heat. To secure a battery to your project, ‎Velcro is a temporary option or sew into a pouch or place in a plastic enclosure. Never iron or ‎hot glue directly on or around a LiPo battery

‎Inspect Battery Before Each Use

Short circuits or damage to LiPo batteries may not always be noticeable - check the battery for ‎puffiness, heat, or other changes. If the battery looks damaged, remove immediately
If the battery gives off an odor, generates heat, becomes discolored or deformed, or in any ‎way appears abnormal during use, recharging, or storage, immediately remove it from your ‎project or battery charger and stop using it. Make sure to dispose of your batteries properly - ‎do not throw them in the trash! Contact your local e-waste disposal organization for details on ‎how to discard batteries in your area

Resources and Going Further

Looking for more resources on LiPo batteries? Check out a few below. There are many websites ‎available online with this information. While the articles linked refer to multi-cell LiPo batteries, the ‎information is still relevant for general guidelines for handling LiPo batteries and storing.‎