Step 29: Appendix A: Charging the Battery
Connect Battery to Charger Battery technology is great, as it allows us to bring a portable power source anywhere we go, including high into the sky. The unfortunate downside to battery technology is that batteries go flat after being used for a while; you already know this. Never fear though, this appendix to the SK340 Dead Cat quadcopter build tutorial Instructable will show you how to safely charge your batteries using the Accucel-6 charger.
The first step is to connect your battery to the charger. So, take a look at your battery and you will notice that there are two sets of wires coming out one end: the thick red/black set that we use to connect the battery to the quadcopter, and a set of four thinner colored wires with a thin plug at the end. We will plug both sets of wires into the Accucel-6 charger.
First, included with the charger were several wire adapters with red and black plugs on one end, and a variety of connectors on the other end. Locate the adapter with an XT60 plug on the end, this is the plug that matches the red/black plug on the battery. Next, on the right side of the Accucel-6, you will notice a red port and a black port. Connect the red and black plugs on the battery adapter into the matching colored ports on the Accucel-6. Now plug the XT60 plugs on the battery and on the battery adapter together.
Now let’s plug in the set of colored wires from the battery.Take a look at the right side of the Accucel-6 again and you will notice a bank of white female connectors with pins in them. Notice that each connector has a different number of pins. Now shift your attention to the group of four colored wires from the battery, notice that the connector at the end has four male pins. You can probably guess what we’ll do next. Connect the white battery plug to the slot on the Accucel-6 that has four pins.
Program Charger With the battery connected to the Accucel-6 charger, we now need to set up the charger to use the correct settings for charging our battery. Before we begin this process, I want to make a very important safety note: it is absolutely imperative that you use the correct settings for charging your battery. Failure to charge the battery with the correct settings could result in damage to the battery, the charger, or even catastrophic failure of the battery which could result in a fire/explosion. Also, during charging, always put your battery in a LiPo bag, which is a fire-proof bag designed to contain any battery failure. You should also never leave a battery unattended while it is charging.
I certainly do not wish to scare you with this information, but lithium polymer batteries are capable of high discharge rates and are made with some pretty volatile ingredients, like lithium, and it is important to be safe. In reality, if you handle, charge, and discharge the batteries with some care, you will be just fine. LiPo batteries almost never fail the way you see in some videos on YouTube.
So with the safety information out of the way, lets get started setting up the Accucel-6 to charge our battery. First, we will need to gather some information about the battery, which should be printed on the battery’s label, otherwise you can obtain information from the manufacturer’s documentation. The information we will need is: the number of cells in the battery, the voltage of the battery, and the maximum charge current of the battery. For the Turnigy 2200mAh 3S 20C Lipo Pack used in the SK450 Dead Cat quadcopter tutorial, the information we will need is as follows:
Number of cells: 3
Maximum charge current: 2.2 Amps
The first two pieces of information here, the number of cells and the voltage of the battery are easy to find, they are written right on the battery label. The third bit of information, the maximum charge rate, requires a little bit of math to figure out though, which I will take a moment to explain.
First of all, calculating the maximum charging current requires two other pieces of information: the battery’s capacity, and the maximum charging rate of the battery. The battery’s capacity is written right on the battery label. The battery’s capacity is expressed in units of milliamp hours (mAh), which basically describes how much power a battery can supply for how long. The capacity of the battery used in the SK450 Dead Cat quadcopter tutorial is 2200mAh. As for the maximum charge rate for the battery, the maximum safe charge rate for our LiPo battery is 1C. Here, the C stands for coulombs, which is basically a unit of electrical charge. This is probably a slower rate that you could technically pump into the battery, but we want to make absolutely certain that the battery does not start on fire, so we will go with the safe rate of 1C.
From the battery’s capacity, and the maximum charge rate of 1C, we can calculate the maximum charging current of our battery. First of all though, charging current is expressed in units of Amps. To find the maximum charging current for our battery, we will multiply the battery’s capacity in amp-hours by the maximum charging rate in coulombs. First, move the decimal point in the 2200mAh capacity listed on the battery label three spots to the left to convert from milliamp hours to amp hours. We end up with 2.2Ah. So, multiplying this figure by the maximum charging capacity of 1C, we end up with a maximum charging current of 2.2A.
So now that we did all that work and all that math, I am going to tell you that, unless you are in a big hurry, you should probably not charge the battery at the full 2.2A charging current. It will prolong the life of the battery if you charge at a lower rate. So in this tutorial we will use a charging current of 1A.
Now let’s finally get to programming the Accucel-6. First of all, plug in your 12V power adapter to the plug on the left side of the Accucel-6. As soon as you connect the power, the Accucel-6 will emit a loud beep. You should get used to these extremely loud beeps as the charger will be deeping a lot in the next few minutes. After the Turnigy splash screen goes away, you will be presented with a screen with “PROGRAM SELECT” in the first line and a battery type in the second line. If the battery type listed in the second line is anything but “LiPo BATT,” press the leftmost “Type” button to change the battery type. Once you have “LiPo BATT” in the second line, press the right-most “Enter” button.
On the next screen, the first line lists what action the Accucel-6 is taking. The device is capable of charging the battery, balancing the battery, fast-charging the battery, storing the battery, and discharging the battery. These functions are all useful and some are covered in other tutorials on this site, but for now, use the middle two arrow buttons to select “LiPo CHARGE” since we are interested in charging the battery right now.
The second line lists settings for the charging process, from left to right the settings are:
(battery cell count)
To change these settings, press the Enter button. The charging current setting should now be flashing. Use the arrow buttons to set the charging current to 1.0A. Now press the Enter button again to select the battery voltage/cell count setting. Use the arrow buttons again until “11.1V(3S)” is selected.
With the correct settings applied, we are finally ready to charge the battery.
Charge the Battery To start the charging process, hold the Enter button for three seconds. The Accucel-6 will beep a few times and then it will check the battery. After a couple seconds, a you will be presented with a new screen. The first line lists the settings you entered on the right, and the settings detected by the Accucel-6 on the left. If these settings do not match, press the leftmost “Back” button to return to the previous screen and double-check your settings. Otherwise, if the settings on the top line to match, press the Enter button to start charging.
The Accucel-6 will display the status of the charging progress. It lists the battery type and cell count, the current charging current, the current battery voltage, the charging time, and the battery capacity. Now you just need to wait for the battery to finish charging. Remember never to leave the battery unattended while charging. If you have to leave before the charging process is complete, stop the process by pressing the left-most “Stop” button. Lithium polymer batteries do not have a “memory effect” so you can always finish charging the battery at a later time.
When the battery is done charging, the Accucel-6 will start beeping. First press the Stop button, and then disconnect the battery from the charger. Now you are ready to fly some more.