# Battery sizing

1. Aug 19, 2015

### Pula

Hi,

I have just got into the battery industry and i would like to understand a few things especially when it comes to sizing a battery.

For example:
if i have a load of 1600W
and the system voltage is -48V DC (for a telecom application). The main supply is AC which is converted into DC through a rectifier in order to supply the load.

But during loadshedding for instance, or somehow the AC power is lost, I still need to back up my system for a certain period until the power is back.
Lets say 5 hours is needed to supply the load from a battery during the loss of AC.

Question 1: How do i select a battery that will supply the load with the right current and voltage?
(Examples are welcome as i know there are various batteries with different nameplates)
the battery that is used is an example, may it indicate the voltage of the battery and the capacity as well as the volts per cell.
Question 2: How do i calculate the time it will take for my batteries to be fully charged back when the power is back?
Question 3: how does the "Ah" of the battery play part in this scenario?

I have attached a snapshot that explains my scenario.

Thanks

#### Attached Files:

• ###### Snapshot.jpg
File size:
9.9 KB
Views:
82
2. Aug 19, 2015

### Staff: Mentor

You first need to define the "right" voltage and current. You also need to specify number of charge discharge cycles and expected battery life.

Are you talking about lead acid batteries? If so, then then Peukert's Law may be helpful to you,

There are many charging schemes. This article can introduce you to the ideas.

3. Aug 19, 2015

### dlgoff

This link provides a very good place to gain the understanding you're going to need.
http://batteryuniversity.com/learn/

4. Aug 20, 2015