RC Battery Chargers are one of the single most important items you need to purchase when getting into electric flight or any electric powered RC vehicle for that matter.
They are also one of the most misunderstood items in the hobby and most people just get what the sales person recommends without doing a little research first.
This generally leads to getting an inadequate charger for your needs; either overpowered, but in most cases under-powered or without some very important features. I will also be talking about how you power your charger because I get so many e-mails on that single topic alone and once again, there are many misconceptions.
Since LiPo and various forms of lithium chemistry such as LiFe, and lithium ion, are so popular these days, good lithium battery charging & balancing support is what makes or breaks a computerized charger in my opinion.
In this day and age with all the good computerized RC battery chargers on the market, the only chargers that I am going to talk about and recommend support all rechargeable battery types (NiCad, NIMH, PB, and of course lithium); the reason being, one charger will support all your charging needs.
Myself, I'm an iCharger guy... iCharger in my opinion offer the best bang for your charging buck..
Getting a quality computerized battery charger should be seen as an investment for your long term enjoyment of this hobby, most certainly if you are into electric powered flight. Computerized chargers have all sorts of benefits, but there are three that stand out in my opinion:
The first item to consider when looking at a computerized RC Battery Charger is how much power it can deliver and maximum cell count it will support. Cell count is pretty easy to figure out, and most good computerized RC battery chargers support at least 6S LiPo cell counts and up to 15 or more NiCad, NIMH celled packs. The confusion for most comes into play with the maximum charge current.
This is where many people select the wrong charger for their actual needs. From my LiPo battery write up , you have a good understanding of the amount of charge current measured in amps that your specific battery can handle. You must understand that before you can determine what size charger you need; so if you haven’t read my LiPo page, or it is still a little foggy, have another look.
Let’s take a popular size LiPo used in a 450 class heli for example such as a 2200 mAh 3S pack. At a 1C charge rate, the charge current for this battery would be 2.2 amps. A 2C charge rate (getting to be very normal these days) would be 4.4 amps. So when you go out to get your RC Battery charger, your thought is to get one with at least a 5 amp charge rate – right? Well, there is another very important specification on RC battery chargers that you must also look at, and that is the wattage output rating (measured in Watts).
The problem is so many RC battery chargers manufacturers just boast of the maximum charge current.
Without the wattage rating, you may be in for a big surprise the first time you go to charge your battery and select a high current charge rate only to find out that the charger won’t deliver it.
Watts are calculated by multiplying the voltage by the amps.
So our 2200 mAh 3S LiPo battery when it is near a full charge voltage of 12.6 volts will be drawing about 27 watts of power (12.6 volts x 2.2 amps).
If it is charged at a 2C rate that wattage number would increase to around 55 Watts (12.6 x 4.4) and so on.
This doesn’t take into account any efficiency losses in the charger or the input voltage to the charger which also both play a roll. However, for ease of explanation, let’s just say if that’s the largest battery you will ever charge at nothing higher than a 2C charge rate, you need to get a charger rated not only at a 5 amp charge rate, but also a 55 watt or higher power rating.
If the charger is only rated at 45 watts for example, but boasts a 10 amp charge rate, it would still be able to only deliver about 3.6 amps when a 3 cell lipo is nearing it’s full charge voltage of 12.6 volts (45W divided by 12.6 volts = 3.57 amps).
As you can see, even though the charger is rated at a maximum 10 amp charge rate, it would only be able to deliver 3 amps at 12.6 volts and that is not taking into account any efficiency losses that are usually in the 10 to 20 percent range reducing the charge current even more.
So why can the charger manufacturer in this example claim a maximum charge rate of 10 amps?
Well, depending on the voltage of the battery you are charging, a 10 amp charge rate is possible. If you were charging a single cell lipo pack for example (4.2 volts fully charged) on this 45 watt charger, at that voltage it will be able to deliver about 10 amps (45W divided by 4.2 volts = 10.71 amps). The manufacturer is certainly not lying about the maximum charge rate, but if they also don’t include the wattage rating of the charger, you are not getting the “full story”...
With more advanced charging methods such as multiple pack parallel charging becoming very popular, even if you never got into larger models that required higher voltage/capacity battery packs, even that 60 watt charger would still be somewhat limiting.
Considering where electric powered flight is heading these days (bigger and bigger birds), getting the most powerful charger you think you would ever need will save you money down the line – as I said, it is a good investment.
The good news is some of these very high wattage RC battery chargers don’t really cost that much more than lower powered ones.
If you intend on getting into 500 size and larger birds down the road and want to charge at higher C rates or want to charge multiple packs in parallel to save time, you really have to start looking at more powerful chargers in the 200 to 400 Watt range. For instance, a typical 550 size electric helicopter such as a T-Rex 550 will use a 5000 mAh 6S battery pack.
At a 2C charge rate, the charger would have to not only support
both a 6 cell count and a 10 amp charge rate, but would have to be rated
at about 250 watts or higher (10 amps x 25.2 volts). A 3C charge rate
would push that number to around 378 watts (HUGE).
As I mentioned, this one gets lots of email time, and in fact many folks are pretty upset when they get any computerized RC battery charger to find out it doesn’t come with any way to power it – yes, you generally need to purchase or build a separate power supply. WHY?
There are several reasons, cost and size being the biggest two, followed by charging out at the flying field. Almost every computerized charger on the market is built to accept a 12-14 VDC input from a vehicle battery or flight box battery to charge your batts out at the field.
Some of the better RC Battery charges on the market will accept over 30 volts DC in order to charge higher voltage packs more efficiently at higher charge and wattage ratings but will still operate at lower voltages as well.
There are certainly some computerized chargers on the market that have the ability to support both a 12 VDC input and household 120 AC using a built in power supply. The problem with all these “built in power supplies” is they offer very low power and only work with lower power chargers up to about 50-80 Watts maximum.
The reason the output is limited comes down to size... To pump out 100 watts or more at 14 VDC, the power supplies get large; much larger than the chargers in fact; not to mention the heat that large power supplies generate that would cook the charger without adequate cooling fans and heat sinks that would make them even bigger.
There are a few 100 – 125 watt RC battery chargers on the market that have built in power supplies but they are usually big, heavy, and expensive not to mention 125 Watts is nothing these days. You can get into a nice 250 to 350 Watt charger and separate power supply for much less money since the price of high amperage power supplies and chargers has plummeted in recent years with higher power RC electric flight becoming so popular.
Depending on the RC battery charger you get, will dictate the power supply you need. For example if you were to get a 250 Watt charger, you would need a power supply rated at about 20 amps @ 14 volts output (20 amps x 14 volts = 280 Watts). Remember, no charger will run at 100% efficiency, there are always losses so if the charger is rated at 90% efficiency for example, that 280 Watt number comes in at about 252 watts at 90%.
These are very basic calculations and things like how the power
supply is rated and the output voltage all come into play, but this
should give you a good starting point when choosing a power supply. If
your power supply is under rated, a good computerized RC battery charger
will simply limit the amount of charge current it is able to deliver,
it won’t ruin the charger, but it could perhaps overheat the power
supply if you are pushing it to its maximum rating. In other words, it's better to over-size your power supply then under-size it.
Most power supplies these days, even the fairly cheap ones will have over current and over heat protection so it is generally not an issue, you just wouldn't be able to charge at the maximum charge rate your charger is rated at as the power supply automatically starts limiting output if it is being overworked.
Many of the features to look for in a good computerized RC battery charger I already covered on the LiPo Battery page, but here is a recap plus other important features:
Most RC battery chargers these days are very similar in operation and menu/button layout which is convenient. The generic name "4-button charger" is used often to describe them. It goes without saying, all the chargers I list support all common RC battery chemistries such as NiCad, NiMh, PB, and of course all lithium types (LiPo, LiFe, LiIon).
These are a few recommendations based on features, price, and quality. These of course are just my recommendations and new chargers are hitting the market all the time, but my recommendations should give you a good idea of what is out there and what to look for in a good computerized RC battery charger.
I feel one of the better value and quality RC battery chargers that you can easily find is the SkyRC iMax B6AC V2.
It's a combination AC/DC charger meaning the power supply is built right into the charger so you can just plug it into any standard household AC outlet.
It can also be powered from a DC power source such as a vehicle battery for field/track charging.
At around $65.00 USD, the value is good. Like most chargers with built in power supplies, it's low on power at only 6A & 50 Watts. This not a charger for people who need more serious charging power in other words, but for newbies just starting out that don't have too many packs to charge, it makes for a nice first charger.
The Keenstone 10A 100W AC/DC charger represents really good value considering the higher current and power rating; again with a built in power supply for powering from a household AC outlet as well as DC powering.
It hasn't gained the same brand loyalty as others, but it gets good reviews by most and at under $50 is certainly one of the least expensive 100 Watt chargers with built in power supply on the market right now.
Once past the realm of the lower power chargers, if you are getting into larger birds or multiple pack parallel charging, it's time to start looking at higher power options such as this iCharger 208B.
You may be surprised to find out they don't cost much more than low power chargers, and in a few cases maybe even less!
As I already mentioned, my personal top pick when it comes to computerized RC battery chargers goes to the iCharger line from a company called Junsi. These chargers offer the best charging bang for buck in my opinion (best power to cost ratio).
Most everyone loves them! The lowest power one (The 106B+) is rated at 250 Watts. Their highest power one is the 4010 Duo rated at a whopping 2000 Watts!
The pricing for these chargers as I mentioned is outstanding with all the advanced features they offer including PC interface data logging, automatic variable speed cooling fan, internal resistance measurements, and intelligent balance charging just to name a few of my favorite features. Here are the basic specs for the full line up and the approximate costs.
Another very good name in computerized RC battery chargers is CellPro/PowerLab. They get great reviews all the times, however, not quite the same power to cost ratio bang for the buck as iCharger's I feel.
REMEMBER, don’t forget about your power supply with any of these good hi-output chargers.