A long term investment you’ll be making in the RC hobby is a good charger. Chargers come in all flavors – simple, cheap, expensive, robust – it’s a matter of finding the best lipo charger for your needs and situation.
How to charge lipos
Lipo batteries are not run-of-the-mill batteries. Their chemistry is quite unique, and they must be charged in a specific way, or else BOOM.
A single lipo cell’s minimum voltage is 3.7 volts, and lipos can be charged up to 4.2 volts. Although you could theoretically push it a little higher, you should not unless you absolutely know what you are doing and are aware of the risk involved. Also, pushing lipos to greater than 4.2 volts will significantly decrease their life span.
The lipos used for fpv racing quadcopters are usually 2, 3, or 4 cells hooked up in series, which means the voltage compounds. A 2 cell lipo is 7.4 volts, a 3 cell lipo is 11.1 volts, and a 4 cell lipo is 14.8 volts.
When charging lipos, each cell must be charged equally to 4.2 volts. This is called balanced charging. Most hobby chargers have a balance charge option that monitors the voltages of the individual cells and makes sure each cell gets to the same 4.2 voltage.
Charging is done by C. In charging, the C rating is the same as the number of amp-hours the battery is of. So charging a 2000 mAh battery at 2.0 amps is considering charging it at 1C.
If you wanted to charge at double the speed(make sure your battery is capable of this before you do so – read the label!) you’d charge at 4.0 amps, considered charging at 2C.
Features to look for in chargers
Computerized or not?
Some RTF quadcopters ship with regular chargers that will simply bring up the voltage of the lipo to 4.2 volts per cell and stop. These chargers are usually compatible only with 2 and 3 cells, and some may support 4 cells. There are no advanced charging options – you just plug and charge.
Getting into the hobby, you most definitely want to invest in a computerized charger. Computerized chargers have a ton of different functions and support different battery types such as NiMH, NiCd, LiOn, and of course LiPo.
They also have a wide variety of charging functions such as charge, fast charge, balance charge, discharge, and storage charge. They’ll also let you check the battery’s cells, check internal resistance, and even save a profile of your regular charging routines.
Lipo chargers can also have safety features built in to make sure too much charge is not pushed into the battery. A basic safety feature is verifying how many cells are in the pack and how many cells the charger is set for.
My Imax B6 charger rings an alarm and refuses to start charging if the cell count I selected is different from the cell count of the battery.
Some chargers will also have a temperature cutoff where they will stop charging once a certain temperature is reached. Prolonged exposure to excessively hot temperatures can result in nasty consequences when it comes to lipos.
Additionally, there can also be a timeout function that stops charging once the charger has been running for a set period of time.
Some chargers also support connecting to your phone or computer to change settings and monitor charging.
How much power does the charger output?
The power output of a charger is measured in watts(voltage x amps). If your charger has less watt capacity than the batteries you are trying to charge, your batteries will charge slower than they could be.
So to charge a 3S 3000 mah battery at 1C, you’d require 12.6 volts x 3.0 amps, or 37.8 watts. If your charger was rated for 50W, then you wouldn’t have a problem with this battery(the problem in this case being charging it as fast as it could be charged).
If you wanted to charge the same battery at 2C on the 50W charger, your charger would not be able to supply the 75.6 watts required, so you’d end up charging slower.
Wattage becomes even more important if you are parallel charging. I run into this problem quite a bit with my Imax B6 when I try to parallel charge 3 or more 4S 1300 mah lipos. My charger can’t supply enough power to charge all the batteries at 1C, so it takes a little longer to charge them.
Note: But still shorter than charging them one by one. Parallel charging is awesome!
The Imax B6 is the charger I use. I must confess I bought it along with my first quadcopter and radio, and being on a tight budget, I went for a mid-range charger. At $40 from HobbyKing, the Imax B6 does what it’s supposed to do just fine: charge your lipos! It’s a fully computerized charger, and can take DC power(from a power supply/car battery) and AC power from a wall outlet. It’s fine for charging one lipo at a time, or even small lipos in parallel, but charging 1.3 lipos in parallel slows it down a little. Still, it’s served me well so far.
Note: The Imax B6 is a heavily cloned charger, so get it from a reputed source.
Turnigy Reaktor 300W
The Reaktor is a whopping 300W charger. It’s a fully computerized charger that takes both AC and DC power, which is great, so you don’t have to muck around with a power supply at home. 300W can easily parallel charge batteries for your racing quadcopter(1.3-1.8) even in parallel, and at $115 or so, it’s a slightly pricey but good investment. If you have the cash, go for the Reaktor instead of the Imax.
Venom Power chargers
Venom Power chargers are top of the line chargers. If you have the cash, spend it on these chargers. Venom offers one charger which has four outputs rated at 100 watts each. So if you have 20-30 lipos that you need to charge quickly and safely, the Venom charger will do it in a breeze. You could set up four parallel charging boards and you’d have multiple packs ready in less than an hour.
Venom also has more economical dual and single chargers, too.
This tiny little charger is awesome, easy-to-use, and cheap at under $50. It charges a wide variety of batteries, can output 8A and 150W, which is more than enough for charging 6 1300 lipos in parallel. You will need a power supply, or you need a large lipo battery to provide power for charging a smaller battery.
You can also see my detailed review here.