What does this picture have to do with…… Battery Charger Sizing?

What does this picture What does this picture have to do with……have to do with……

Battery Charger Sizing?Battery Charger Sizing?

Half Half Full?Full?

Half Half Empty?Empty?

Neither,Neither,

Wrong Size Glass!Wrong Size Glass!

Would you charge Would you charge this battery…this battery…

……using this using this charger?charger?

Wrong Size!Wrong Size!

Battery charging is Battery charging is definitely a matter of size.definitely a matter of size.

Properly sized Properly sized chargers will result in;chargers will result in;

•Properly charged batteries.Properly charged batteries.

•Properly maintained loads.Properly maintained loads.

•More efficient operation More efficient operation than if the charger is than if the charger is oversized.oversized.

•Lower cost at inception.Lower cost at inception.

•Lower cost over the life of Lower cost over the life of the system.the system.

Standards that Standards that describe battery describe battery charger sizing;charger sizing;

•IEEE Std 446-1987, also IEEE Std 446-1987, also known as the known as the “Orange “Orange Book”Book”

•IEEE Std 946-2004IEEE Std 946-2004

Constant Potential Constant Potential ChargingCharging

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


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

…….Today constant .Today constant potential charging is used potential charging is used for just about for just about everything………..everything………..UtilityUtility

StationaryStationary

CommunicatiCommunicationsons

Oil & GasOil & Gas

Petro Petro Chemical Chemical

ChemicalChemical

TransportatiTransportationon

Important Important terms………..terms………..

Float ChargeFloat Charge – maintains the – maintains the battery voltage and prevents self battery voltage and prevents self discharge from occurring.discharge from occurring.

Basics we must all understand about battery charging.Basics we must all understand about battery charging.

Important Important terms………..terms………..

Float ChargeFloat Charge – Float charge voltage – Float charge voltage ranges are determined by the ranges are determined by the battery manufacturer.battery manufacturer.

Basics we must all understand about battery charging.Basics we must all understand about battery charging.

Important Important terms………..terms………..Basics we must all understand about battery charging.Basics we must all understand about battery charging.

Equalize ChargeEqualize Charge – – used to cause a used to cause a battery’s cells to battery’s cells to become more become more equivalent in their equivalent in their voltages.voltages.

Equalize charge Equalize charge voltages are also voltages are also determined by the determined by the battery manufacturer.battery manufacturer.


Constant LoadsConstant Loads – – defined as those defined as those loads which remain loads which remain steady and present.steady and present.


Transient LoadsTransient Loads – – defined as those defined as those loads which are loads which are fleeting.fleeting.

The FormulaThe 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.




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




T = Recharge time desired, usually a number between 8 hours and 24 hours, typically 8 to 12 hours.




L = Constant Loads, not transient loads as those are handled by the battery.




Amperes Charger – the output current determined to be adequate for the application.




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




Let’s give it a try………………………………………………..


(AH removed x R)






Let’s give it a try………………………………………………..


(150AH x 1.15)






Let’s give it a try………………………………………………..


(150AH x 1.15)


8 Hours




Let’s give it a try………………………………………………..


(150AH x 1.15)

---------------------------------- + 25 Amps = Amperes Charger

8 Hours




Let’s give it a try………………………………………………..


(150AH x 1.15)

---------------------------------- + 25 Amps = 46.563A use 50Amps

8 Hours

Other Other Considerations…..Considerations…..

TemperatTemperatureure

Other Considerations…..

TemperatTemperatureure


AltitudeAltitude

Other Other Considerations…..Considerations…..Temperature and Altitude are interrelated.Temperature and Altitude are interrelated.

•As altitude increases the ambient temperature As altitude increases the ambient temperature usually decreases.usually decreases.

•Also as altitude increases the molecules Also as altitude increases the molecules available to heat sink decrease.available to heat sink decrease.

•As ambient temperature increases, the As ambient temperature increases, the charger’s ability to operate at full rating will charger’s ability to operate at full rating will therefore decrease.therefore decrease.

Other Other Considerations…..Considerations…..Temperature and Altitude are interrelated.Temperature and Altitude are interrelated.

•Check the manufacture's suggestions. Usually Check the manufacture's suggestions. Usually they have a chart that shows the relationship they have a chart that shows the relationship between altitude and temperature.between altitude and temperature.

•Note the relationships between temperature Note the relationships between temperature and altitude it may be acceptable to operate and altitude it may be acceptable to operate without de-rating by just adjusting the useful without de-rating by just adjusting the useful ambient temperature allowance.ambient temperature allowance.


Design Margin Design Margin – –

Big enough to Big enough to do the job?do the job?


Design Margin Design Margin – –

Big enough to Big enough to do the job?do the job?•It is important to It is important to have enough capacity have enough capacity without over sizing.without over sizing.

•Also, use current Also, use current limit values as long as limit values as long as you can get full you can get full capacity from the capacity from the charger.charger.


Anticipated Growth – Anticipated Growth –

Did I plan for the future?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?


•Was the battery sized for future growth such that the charger Was the battery sized for future growth such that the charger calculation already takes this growth into account?calculation already takes this growth into account?

•Finally, just adding capacity is not good “insurance” if you Finally, just adding capacity is not good “insurance” if you really do not need it! Good engineering is the best insurance.really do not need it! Good engineering is the best insurance.

In conclusion…..In conclusion…..•If I plan my application carefully and realistically my If I plan my application carefully and realistically my charger, battery, and all associated equipment will be charger, battery, and all associated equipment will be properly sized.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 Separate your transient loads from your constant loads – the charger does not accommodate the transient – the charger does not accommodate the transient loads.loads.

•Use the formula! Don’t assume or use a “standard rule Use the formula! Don’t assume or use a “standard rule of thumb”, use engineering practices.of thumb”, use engineering practices.

•Doing a thorough job of application engineering will Doing a thorough job of application engineering will result in a properly sized application that will work result in a properly sized application that will work correctly and as efficiently as possible.correctly and as efficiently as possible.

•This means…………….This means…………….

In conclusion…..In conclusion…..

Correct size Correct size glass!glass!

What does this picture have to do with…… Battery Charger Sizing?

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