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Battery & DC System Sizing Calculator

IEEE 485 duty-cycle section method for vented/VRLA lead-acid batteries. Enter your battery manufacturer's own published capacity-rating (Kt) table — IEEE 485 defines the calculation method, not the table itself. Random/intermittent loads, cell count & voltage window checks, and charger sizing (IEEE 946-style) are subscriber features.

AAJappsEngineering Calculation Report

Battery & DC System Sizing Calculator

IEEE 485, IEEE 1188, IEEE 946

Generated

For preliminary engineering use only — always verify results against project-specific standards and a qualified engineer's review before use in a real design.

Duty cycle (periods)

Break the discharge into sequential periods, each with its own constant net current. Periods run back-to-back in the order listed. The prefilled values are an illustrative example — replace with your own load profile.

1A formin (cum. 15)

2A formin (cum. 25)

3A formin (cum. 100)

4A formin (cum. 110)

Capacity rating table (Kt)

From your battery's data sheet: the capacity-rating factor at each discharge time, to your required end-of- discharge voltage. The values below are a placeholder, not real product data — replace them with your manufacturer's published Kt table before using this for a real design.

Time (min)Kt factor

Correction factors

Temperature correction factor(1.00 at 25°C reference)

Aging factor(IEEE 1188: ~1.25 typical)

Design margin(growth / cell variation)

Random / intermittent loads

Subscriber

Preview only — random load entries are not added to the free-tier result.

Cell count & voltage window

Subscriber

System DC voltage

Nominal voltage / cell

Equalize voltage / cell

Min voltage / cell at EOD

Equipment max allowable V

Equipment min allowable V

Charger sizing

Subscriber

Continuous steady-state DC load

Target recharge time

Recharge efficiency factor(charging losses)

Section-by-section capacity (IEEE 485)

Section	I (A)	Cumulative T (min)	Kt(T)	Required Aⱼ
1	5	15	1.7500	8.750
2	35	25	2.1500	75.250
3	15	100	4.1000	61.500
4	45	110	4.3500	195.750 ← governs

Required battery capacity

Largest section (uncorrected)195.750 (section 4)

+ Random/intermittent loadsnone entered

Required rated capacity269.156

In whatever units your Kt table used (Ah, positive-plate number, etc.).

Cell count & voltage window

Number of cells

String voltage at equalize

135.1 V

Equalize check

✅ PASS

String voltage at EOD

101.5 V

EOD voltage check

❌ FAIL

Charger sizing

Recharge current

25.79 A

Required charger rating

30.79 A