Battery Backup Runtime

How long will this automatic-door or access-control system operate on battery backup under realistic use?

More than amp-hours divided by amps

Continuous mode is for loads that stay on. Automatic-door mode weights standby current against total current while the door is moving, using openings per hour and seconds per cycle. Adjusted runtime applies the usable-capacity factor you enter.

Load model

Use this when the door sits in standby and draws more current only while it is moving.

Battery voltageCapacity per batteryAmp-hours of one battery, not the whole bankQuantity

Wiring

Series adds voltage. Parallel adds Ah. Do not add Ah in series.

Usable capacityReserve / usable percentage. Adjusted runtime uses this factor.Standby currentTotal current while door is operatingTotal current during motion — not the extra current above standbyOpenings per hourOperating duration per cycleSeconds the door is moving in one open/close cycle

Field result

Battery bank24.0 V · 7.00 Ah

Usable capacity5.60 Ah (80.0%)

Standby current0.20 A

Operating current2.00 A

Openings / hour60

Duty cycle10.0%

Average load0.38 A

Theoretical runtime18 h 25 min

Adjusted runtime14 h 44 min

Estimated door cycles884

Series versus parallel

Two 12 V 7 Ah batteries in series make a 24 V 7 Ah bank. The same two in parallel make a 12 V 14 Ah bank. Amp-hours are not added in series.

FAQ

Is operating current extra current above standby?: No. Enter the total current while the door is moving. The average-current model already weights standby time and operating time so standby is not counted twice.
Does this prove emergency-egress runtime?: No. It is a field estimate. Age, temperature, chemistry, and actual motor load change runtime.

More than amp-hours divided by amps

Field result

Series versus parallel

FAQ

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