These are some parts of charger, you can go to here to know the whole article.
Source: http://rcfpvplane.com/some-tips-for-buy-a-charger/
Cell compatibility

When buying a charger you should consider what LiPo batteries it can support. Some very cheap lipo chargers will only support 2S lipos or 3S lipos, where the fanciers ones will be able to support the full range from 1S to 6S. Other higher end chargers are also able to balance charge more than one LiPo at the same time.

Charging current

Most batteries specificy a maximum charge rate as 1C, 2C etc.. however most chargers you specifiy the charge rate in Amps, so sometimes there is confusion between these two values. To convert your battery C charge rate to Amps you simply need to multiply the battery capacity by the C rating. So lets say we have a 2200mAh battery with a charge rate of 2C. So the maximum current we can charge this battery at is 2.2Ah x 2 = 4.4A. Similarly lets say we want to charge a 5000mAh battery at 1C, the max current we will need to set on our charger is 5Ah x 1 = 5A. The maximum current you can for your charger depends on the power output it is cable of as described in the next section.

Power Output

All batteries have a certain power output level, defined in Watts, typically around 50W. This number represents how much power the charger can provide to your battery, ultimately the larger this is, the faster it can charge your battery. Watts are the product of current and voltage, so if you keep current constant (say at the recommended 1C value) you will use more power with higher voltage (bigger cell count) batteries. So having more power available it better. Lets look an example, if we want to charge a 3S 2200mAh battery at 1C we will need to use 12.6V x 2.2A = 27.72W. If we want to charge a 3S 5000mAh battery at 1C we will use 12.6V x 5.1A = 64.26W which is actually a little over the standard power rating for chargers. So we an only charge our 5000mAh battery at 50W/12.6V = 3.6A assuming we have a 50W charger.
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Power Supply

Some batteries include a built in power supply so you dont need to worry about this. But if your battery does not include a power supply you will need to make sure that the one you buy will match your charger in terms of specifications and also the connector is the same. At Unmanned Tech we have the option to add a compatible power supply on most of our chargers.

However the most important thing is to ensure that the power supply has the correct power (Watts). So if using a 50W charger, you will need to make sure your power supply will be able to provide at least 50W of power to the charger, however getting something a little over is best such as a 60W power supply.