Work out what size UPS you need and how many batteries it takes to keep running for as long as you want. Battery capacity is corrected for discharge rate, temperature and ageing — the three things that make a UPS die years earlier than the brochure promised.
Tap the equipment you want on the UPS. Put only what truly matters on it — every extra watt costs battery, and batteries are most of the price.
This is the single biggest decision you will make here. Doubling the time roughly doubles the batteries — and the batteries are most of what you pay for.
The default suits most Iraqi sites, where the incoming voltage moves around a lot. If you are unsure, carry on.
This is the UPS and battery bank your list needs. Send it to us for a price, or go back and change the backup time to see how much the batteries move.
This calculator gives an indicative UPS and battery size for budgeting and comparing quotations. It is not a design document. Final selection must be confirmed by a qualified engineer against the UPS and battery manufacturers' own discharge curves, the real load characteristics including inrush, and the ventilation and safety rules for battery rooms. Mega Standard accepts no liability for decisions made on these figures alone.
Discharge-rate factors are typical VRLA values. Your battery manufacturer's own discharge tables take precedence, and should be used for the final selection.
A UPS has to satisfy two separate limits at the same time, and most undersized installations happen because only one of them was checked.
The first is power: can the UPS carry the load at all? The second is energy: can the batteries hold it up for as long as you need? These are independent. A UPS can be more than big enough to carry your load and still die after ninety seconds, because the battery bank behind it is too small.
A UPS carries two ratings and it is limited by whichever runs out first. A 10 kVA UPS with an output power factor of 0.8 can only deliver 8 kW. If your load is 9 kW, that 10 kVA UPS is too small no matter what the sticker says.
Modern units are usually rated at 0.9 or unity power factor, which is why a 10 kVA unity-rated UPS genuinely gives 10 kW. Always check which one you are being quoted — this is the most common way a UPS quotation looks cheaper than it really is.
A battery labelled 100 Ah gives 100 Ah only when discharged slowly, usually over ten or twenty hours. Pull the same battery flat in fifteen minutes and you will get roughly half of that. This is a physical property of lead-acid chemistry, not a manufacturing defect.
Sizing a UPS bank by dividing watt-hours by battery voltage therefore under-sizes it badly — often by half. This calculator applies a discharge-rate factor from the autonomy you chose, then adds the two corrections IEEE 485 requires:
DC power = load W ÷ inverter efficiency Energy = DC power × autonomy hours Ah at rate = Energy ÷ battery bus voltage Ah rated = Ah at rate ÷ (rate factor × depth of discharge × temperature factor) × ageing
The ageing factor is normally 1.25, because a battery is considered dead when it can no longer deliver 80 % of its original capacity — so the bank must still meet the duty at that point, not only when brand new.
This matters more in Iraq than anywhere in the specification sheet suggests. A sealed lead-acid battery is designed around an ambient temperature of 20 °C. Its life halves for every 10 °C above that.
The arithmetic is brutal. A battery rated for five years at 20 °C gives about two and a half years at 30 °C, and roughly fifteen months at 40 °C. An unconditioned battery cupboard in Basra or Kirkuk in August will be well above 40 °C.
The practical consequence: if you are choosing between a bigger battery bank and an air conditioner for the battery room, the air conditioner is usually the better investment. It costs less than one replacement set of batteries.
A UPS is an expensive way to store energy. Its job is to cover the seconds or minutes between the mains failing and something else taking over — not to power the site.
Beyond about thirty minutes of autonomy, the battery bank grows faster than most people expect, and it brings floor loading, ventilation and replacement costs with it. At that point a generator with a short-runtime UPS to cover the changeover is almost always cheaper to buy and much cheaper to keep.
The right question is rarely "how long can my UPS run?" It is "how long until my generator is carrying the load?"
Add up the watts of everything you want protected, then add roughly 25 % headroom so the UPS is not running flat out. Enter the list above and the calculator does this for you, including the kVA against kW check that catches most undersized quotations.
It depends on the load, the battery bus voltage and how hot the room is — but expect considerably more than a simple watt-hours calculation suggests, because a battery discharged in an hour delivers only about three quarters of its rated capacity. Enter your figures above for a realistic number.
On most Iraqi sites, online double conversion. It rebuilds the output waveform completely, so whatever the incoming supply does — sagging, surging, or coming from a generator — the load sees a clean, steady voltage. Line-interactive is cheaper and fine for an office on a stable supply, but it passes more of the input disturbance through to the load.
Almost always heat. Sealed lead-acid batteries lose about half their life for every 10 °C above 20 °C, so a battery cupboard sitting at 40 °C will give you a fraction of the rated life. Deep discharges and a badly set charger make it worse. Cooling the battery location is usually the cheapest fix available.
You can, but size it carefully. Motors draw several times their running current for the first seconds, and a UPS has very little overload capacity compared with a generator or the mains. Either choose a UPS rated well above the running load, or keep motor loads off the UPS entirely and put them on the generator.
No. It gives a defensible number for budgeting and for checking a quotation. Final selection needs the actual UPS and battery discharge curves, the real inrush behaviour of your load, and compliance with the ventilation and safety rules that apply to battery installations.
We supply and install UPS systems and battery banks across Iraq, and we will tell you honestly when a generator would serve you better than more batteries. Send us the result and we will come back with a specification, a price and a realistic battery life for your site conditions.