Battery charger sizing

[navin34]

Dear All,

Can anybody give reference of standards and formulas / useful websites etc used for sizing of battery charger for industrial AC /DC UPS and Navigatonal aids systems used in OFFSHORE PLATFORMS.
Thanks in advance.

Rgds

Navin

 

[itsmoked]

There probably isn't any one unified site with the info you are searching for. There are many rules for all the different types of batteries.

Can you get a whole lot more specific?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[nightfox1925]

For a DC Battery Charger,

A = Kt x {(SF x L) + [(BIF x Ah)/ RT ]}

Where:

A = Ampere Rating Of Charger
SF = Service Factor
L = Sum Of Continuous DC Loads
BIF= Battery Inefficiency Factor
RT = Recharge Time
Kt = Temperature Correction Factor

For UPS systems, you should list down your UPS loads accordingly and determine the total UPS loads. Normally, we provide the total UPS loads and the required back-up time and the UPS vendor will size both UPS charger and batteries.

See also IEEE-1115 and IEEE-1184.

In addition, as itsmoked said, be more specific with your applications and your back-up time requirements. The size of both DC and UPS chargers depends on both battery and load requirements and consequently, your batteries depends on both load and back-up time requirements.



GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata

 

[navin34]

Dear 02101972,

Can you provide reference of standard which specifies this formula for DC BATERY CHARGER.In my application Batteries are Nicd type and charger is parallel redundant configuration. Duty cycle is 600A for O.5hr and 450A for 7hrs.
What is the value of Kt , SF, BIF for Nicd Batteries.
Pl explain.

Rgds

Navin

 

[nightfox1925]

I just got back from site...

We normally use 10% Service Factor = 1.1, 15% to account for battery inefficiency = 1.15, A recharge time of 8 hours (or as per your requirement), A temperature rating factor Kt = 1 for temperatures equal or below 25 Deg. C. and 1.2 for above 25 Deg. C.

By the way, the Ah is equal to the rated ampere-hour rating selected for the battery for a 8 hour duty cycle time (C8). In this regard, you have to size your batteries and select a standard Ah rating of the battery. Since you have a variable DC loading with respectto time, you may have to develop a battery cycle and use the IEEE battery sizing sheet (IEEE 1115).

Please be noted that this is only for DC charger applications. In addition, ensure that the charger you will purchase later shall also consist of a battery disconnect switch with auxiliary contacts and a DC Undervoltage Unit to be used for alarm pusposes. If the system is for very critical applications and DCS is available, you may consider a stand-alone solid state batterym monitoring system (BMS).

The formula I used is an empirical formula based from our company engineering standard. I will check that out for you.



GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata