This is a very deep and large topic. While it would seem simple on the surface, it is actually complicated by all the different battery types and chemistrys.
In a nutshell, you have to be concerned that the charging current does not either boil the electroyte or is so strong it warps the plates of the battery. Fast chargers have to have safe guards to protect the battery. Normal, slow chargers limit the current by design and therefore are simpler. However, what it costs you is charging time.
Below is a link to info on Lead-Acid batteries. Other families have other requirements so each will have to be handled as a unique case. The charge recommendations depend both on the chemical family that the battery belongs to and the actual manufacturer's spec that built the batteries.
Be careful, remember that cell phones and laptops have caught fire due to improper battery charging. These were Lithium Ion batteries.
**broken link removed**