UPS batteries charging rates

Basically charging rates for UPS batteries depend on type of batteries cell such as Lead-acid (Pb) or Nickel Cadmium (NiCd).This two types of batteries cell have a different method to charging up.

For Lead-acid (Pb) cells is used a ‘constant voltage’ method.It mean where the current varies as the state of charge changes.Different method for Nickel Cadmium (NiCd) cells,it  is used ‘constant current’ where the cell voltage varies as the state of charge changes.

When we try to charging batteries  from  Lead-acid (Pb) cells type,the basic process are from a constant voltage source the charging current starts high and slowly decreases to a constant value when the cells become fully charged.The constancy of the current is an approximate indication that the cells are fully charged.

But the process is not same with batteries from Nickel cadmium (NiCd) cells type.It must used the constant current to get a good charging . The best way to checked condition of nickel cadmium batteries (NiCd) cells is using the specific gravity of the electrolyte.

For more detail about charging method,we can refer from the manual instruction and wiring diagram or can request training from battery charger manufacturers.

We must follow step or technique provided by manufacturer to avoid possible to overcharge batteries and may cause internal damage if the current is too high.

How to calculate batteries charging time and ampere value?

Basically we can use a ‘rule-of-thumb’ guideline for  slow charging current method.We can divide the ampere-hour (AH) capacity of the battery (at a 10 hour rate) by about 7

Example :-

We have 1 unit battery with capacity 200 AH (ampere-hour),So how long time we take to charging up the battery and how much value of  current needed ?

Calculation :-

200 AH / 7 = 28.5 ampere

rule of thumb charging time = 10 hour

So the 200 AH battery would require a charging current of about 30 amps for 10 hours.