CALCULATOR for Battery Size

How much backup time is needed
to keep the business going?

Short Backup Time approx 10-20 mins

Emergency power is suitable for PC and router needing short backup time to close programs or shut down the system.

Long Backup Time approx 1-6 hrs

Back up power suitable for TV/DSTV combination, PCs, Routers, etc… for continuous power during an outage.

Use the Battery Calculator provided below
Appliance Watts   Amp Hour
Hours backup time required
We’ve catered for a 90% efficiency in charger, inverter and battery
UPS needs a
Amp Hour battery
How to use the CALCULATOR –
1) Type in Watts Appliance tag estimated wattage.
2) Type in HoursHours backup time you require.
3) Click on>> Calculate power usage <<

For the engineering mind!

How to Calculate Battery Size?


Battery capacity is expressed by how many Amps it can deliver for how many hours a battery will last – Amp-Hour (A.H.) capacity

Battery AH rating is based on a 20-hour total discharge.
Calculated as follows: 100AH / 20 hours = 5 Amps (DC) per hour
This goes to say 100AH battery will discharge at
5 Amps-per-hour over 20 hrs.

Battery Run Time?

For most applications this formula will give you the battery run time before reaching complete discharged:

For 12V Battery Inverter UPS system run time fixed factor 10
10 (Fixed Factor) x Battery AH / Load Watts = Hours run time
Example: 10 x 60AH / 100W = 6 hours run time (90% discharge time)
OR after 3 hours run time battery will have reached 50% discharge time.

For 24V Battery Inverter UPS system run time fixed factor 20
(2 x 12v Batteries connected in series = 24v)
20 (Fixed Factor) x Battery AH / Load Watts = Hours run time
Example: 20 x 60AH / 100W = 12 hours run time (90% discharge time) OR after 3 hours run time battery will have reached 50% discharge time.

Equipment Power Usage

The power drawn by computing equipment is expressed in
Watts or Volt-Amps (VA).
Power in Watts is the actual power drawn by the equipment.
The VA is called the “apparent power” – is the product of the voltage applied to the equipment and current drawn by the equipment.

Both Watt and VA ratings have a use and purpose.
Watt ratings determine the actual power purchased from your utility company and the heat-load generated by the equipment.

The VA rating is used for sizing circuit breakers and circuit wire.

For some types of electrical loads the VA and Watt ratings, are identical, as are the old incandescent light bulbs.
However, for computer equipment, the Watt and VA ratings are most times significantly different, with the VA rating always being equal to or larger than the Watt rating.

This ratio between Watt to VA rating is known as the “Power Factor”
and expressed either as a percentage (i.e. 70%). or a number (i.e. 0.7)

For the engineering mind!

Calculating UPS size

“the safest approach is to keep the sum of the load nameplate ratings below 60% of the UPS VA rating”

Example: Consider the case of a 1000VA UPS. The user wants to power a 900VA file server with the UPS.
The file server has a Power Factor Corrected power supply.
Therefore has a Watt rating of 900W and a VA rating of 900VA.
Although the VA rating of the load is 900VA is within the VA rating of the UPS, the UPS will not power this load!
That is because the 900W rating of the load exceeds the Watt rating
of the UPS – which is 60% of 1000VA or around 600W.

Ensure correct loading of your UPS.
Equipment nameplate ratings are often in VA, which makes it difficult to know the Watt ratings. If using equipment nameplate ratings for sizing, a user might configure a system, which appears to be correctly sized based on VA ratings but actually exceeds the UPS Watt rating.

By sizing the VA rating of a load to be no greater than 60% of the VA rating of the UPS – It is impossible to draw more power out of the UPS than the UPS stipulated Watt rating.
Therefore, unless you have an accurate Watt rating of the loads, the safest approach is to keep the sum of the load nameplate ratings below 60% of the UPS VA rating.

Note that this conservative sizing approach will typically give rise to an oversized UPS and larger run time than expected.
If an accurate runtime of the system is required, call our power experts who have the ability to accurately size your UPS.

To calculate the power usage (Watts) from battery capacity (VA)
Use the following formula:
Factor 0,7 x VA = Watts
To convert VA to Watts
E.g. 0.7 x 500VA Power Supply = 350 Watts max load
If UPS specs quote 500VA can run for 3-4hrs
i.e. UPS can deliver 350 watts for 3-4hrs or 175 Watts for 4-6hrs

To see Amps usage in Watts

Watts = Amps x Volts
E.g. If a power supply draws 5 Amps
= 5A x 220VAC
= 1100 Watts

Watts to VA – To convert 1100 watts to VA (VA power supply rating)
1100 / 0.7 = 1571VA (1.57KVA)
i.e. (UPS) Power supply needs to be 1.6KVA – 2KVA

Power back UPS will supply you with power when you need it most. 
We are striving to create ideals for work and leisure during power outages.
Power for your Servers, Desktop Computers, Laptops, PABX’s…
and all other power needing sources –