Comparing slow and fast chargers is usually based on personal requirements and usually include two major characteristics. Completeness of charge and reduced stress due to heat are the two top factors that determine a good charger.

Fast charging gets your batteries charged faster but usually results in more stress due to heat. This can reduce a rechargeable battery’s useful life. Also, fast charging may not provide a complete charge.

Slow charging usually means that the battery is stressed less and does not heat up as much. It also may result in a more complete charge. Remember, this is not always true. A bad slow charger can overcharge your batteries resulting in excess heat and permanent damage.

A good charger will not overheat or overcharge the batteries which can lead to damage and a shorter rechargeable battery life span. Good and bad chargers are not based on whether they are slow or fast chargers. Good chargers are built on technology that can monitor and react to changes in  the rechargeable battery temperature and voltage appropriately.