What does this picture have to do with……

Battery Charger Sizing?

Half Full? Half Empty? Neither, Wrong Size Glass!

Would you charge this battery… …using this charger? Wrong Size!

Battery charging is definitely a matter of size.

Properly sized chargers will result in; Properly charged batteries.Properly charged batteries. Properly maintained loads.Properly maintained loads. More efficient operation than if the charger is oversized.More efficient operation than if the charger is oversized. Lower cost at inception.Lower cost at inception. Lower cost over the life of the system.Lower cost over the life of the system.

Standards that describe battery charger sizing; IEEE Std , also known as the “Orange Book”IEEE Std , also known as the “Orange Book” IEEE Std IEEE Std

Constant Potential Charging One of the oldest methods of battery charging – first used for aircraft…….

Constant Potential Charging Provides a means to keep the battery charged without overcharging by maintaining a constant voltage while limiting charger output current.

….Today constant potential charging is used for just about everything……….. Utility Utility Stationary Stationary Communications Communications Oil Oil & Gas Petro Petro Chemical Chemical Chemical Transportation Transportation

Constant Potential Charging

Important terms……….. Float Charge – maintains the battery voltage and prevents self discharge from occurring. Basics we must all understand about battery charging.

Important terms……….. Float Charge – Float charge voltage ranges are determined by the battery manufacturer. Basics we must all understand about battery charging.

Important terms……….. Basics we must all understand about battery charging. Equalize Charge – used to cause a battery’s cells to become more equivalent in their voltages. Equalize charge voltages are also determined by the battery manufacturer.

Important terms……….. Basics we must all understand about battery charging. Constant Loads – defined as those loads which remain steady and present.

Important terms……….. Basics we must all understand about battery charging. Transient Loads – defined as those loads which are fleeting.

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time)

(AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) AH removed – AH removed from the battery as part of the load profile.

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) AH removed – AH removed from the battery as part of the load profile. R = Recharge Factor Wet Vented Lead Acid – 1.1, 1.15 Valve Regulated Lead Acid – 1.15 Wet vented Nickel Cadmium – 1.3, 1.35, 1.4 Valve Regulated Nickel Cadmium – 1.4

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) T = Recharge time desired, usually a number between 8 hours and 24 hours, typically 8 to 12 hours.

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) L = Constant Loads, not transient loads as those are handled by the battery.

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) Amperes Charger – the output current determined to be adequate for the application.

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) Let’s give it a try……………………………………………….. Assume 200AH wet vented lead acid battery with 150AH removed recharge in 8 hours and a constant load of 25Amps

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) Let’s give it a try……………………………………………….. Assume 200AH wet vented lead acid battery with 150AH removed recharge in 8 hours and a constant load of 25Amps (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time)

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) Let’s give it a try……………………………………………….. Assume 200AH wet vented lead acid battery with 150AH removed recharge in 8 hours and a constant load of 25Amps (150AH x 1.15) L (constant loads) = Amperes Charger T (desired recharge time)

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) Let’s give it a try……………………………………………….. Assume 200AH wet vented lead acid battery with 150AH removed recharge in 8 hours and a constant load of 25Amps (150AH x 1.15) L (constant loads) = Amperes Charger 8 Hours

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) Let’s give it a try……………………………………………….. Assume 200AH wet vented lead acid battery with 150AH removed recharge in 8 hours and a constant load of 25Amps (150AH x 1.15) Amps = Amperes Charger 8 Hours

The Formula (AH removed x R) L (constant loads) = Amperes Charger T (desired recharge time) Let’s give it a try……………………………………………….. Assume 200AH wet vented lead acid battery with 150AH removed recharge in 8 hours and a constant load of 25Amps (150AH x 1.15) Amps = A use  50Amps 8 Hours

Other Considerations….. Temperature

Temperature

Altitude

Temperature and Altitude are interrelated. As altitude increases the ambient temperature usually decreases. Also as altitude increases the molecules available to heat sink decrease. As ambient temperature increases, the charger’s ability to operate at full rating will therefore decrease.

Temperature and Altitude are interrelated. Check the manufacture's suggestions. Usually they have a chart that shows the relationship between altitude and temperature. Note the relationships between temperature and altitude it may be acceptable to operate without de-rating by just adjusting the useful ambient temperature allowance.

Design Margin – Big enough to do the job?

Design Margin – Big enough to do the job? It is important to have enough capacity without over sizing.It is important to have enough capacity without over sizing. Also, use current limit values as long as you can get full capacity from the charger.Also, use current limit values as long as you can get full capacity from the charger.

Other Considerations….. Anticipated Growth – Did I plan for the future?

Should I use a larger charger now or plan for redundancy later?Should I use a larger charger now or plan for redundancy later? Perhaps a complete parallel system would make sense?Perhaps a complete parallel system would make sense? Is growth budgeted or assumed?Is growth budgeted or assumed?

Other Considerations….. Was the battery sized for future growth such that the charger calculation already takes this growth into account?Was the battery sized for future growth such that the charger calculation already takes this growth into account? Finally, just adding capacity is not good “insurance” if you really do not need it! Good engineering is the best insurance.Finally, just adding capacity is not good “insurance” if you really do not need it! Good engineering is the best insurance.

In conclusion….. If I plan my application carefully and realistically my charger, battery, and all associated equipment will be properly sized.If I plan my application carefully and realistically my charger, battery, and all associated equipment will be properly sized. Insist on getting the facts before sizing the application.Insist on getting the facts before sizing the application. Separate your transient loads from your constant loads – the charger does not accommodate the transient loads.Separate your transient loads from your constant loads – the charger does not accommodate the transient loads. Use the formula! Don’t assume or use a “standard rule of thumb”, use engineering practices.Use the formula! Don’t assume or use a “standard rule of thumb”, use engineering practices. Doing a thorough job of application engineering will result in a properly sized application that will work correctly and as efficiently as possible.Doing a thorough job of application engineering will result in a properly sized application that will work correctly and as efficiently as possible. This means…………….This means…………….

In conclusion….. Correct size glass!