There are a variety of battery chargers in different sizes and strengths.
The first thing to consider is if they are automatic or manual. An automatic is designed to automatically shut off when the battery is fully charged and there is no danger of forgetting you left in going which could ruin the battery. The downside to this is that many chargers shut off too soon leaving you with a seemingly charged battery. With a manual charger you can control how long to charge the battery for.
Battery chargers come in 6/12/36/48/60/72 Volt settings. Depending on which battery, or how many, you are using will determine which charger is right for you. 12 Volts is by far the most common.
A 12 Volt battery charger will have various amp selections. Typically something like a 2/12 setting. This means to trickle charge a battery you would put it on the 2 amp setting. To give the battery a bigger charge you would put it on the 12 amp setting. This is useful for a discharged battery, where the trickle charge would be suited for things like maintaining the battery.
Every battery there is needs to be in use. If you have a quad or motorcycle a little 1 amp maintainer is great to keep the battery alive during storage. If you have deeply discharged 6 Volt camping batteries, they should be charged with more like 25 amps before storing, then be maintained on about a 4 amp maintainer. Storing your hot rod? If the battery is fully charged then a little 1 amp maintainer works good.
Table top chargers are good for recharging a battery when you left your lights on. If the battery is stone cold dead they won't do much for it. Floor chargers come in home use, and commercial use. These can jump start your vehicle, and their settings range from 2 amps up to 400 amps. If you need to give a good charge to a lot of batteries fairly often, these are a great choice.
The more heavy duty the components of the charger, the better job they do, and the longer they last. They cost more but they work.
We are always available for advice and information.