Solar Battery Backup Calculator Pakistan

The default picks on this page (3 ceiling fans, 6 led bulbs, 1 led tv, 1 fridge, 1 laptop, 1 wi-fi router) draw about 614 W. For 8 hours that is 4,912 Wh. A lithium battery delivers roughly 86% of its nominal capacity after depth of discharge and losses, so you need about 5.7 kWh nominal, which is one 48V 100Ah lithium pack. On tubular batteries, which should only be drained to 50%, the same night needs about 12.3 kWh, or 8 × 200Ah tubular batteries at 48 V.

Yes, but it is the single biggest load. Adding one 1.5 ton inverter AC to the default picks for 8 hours takes the requirement to about 19.8 kWh nominal on lithium (4 × 48V 100Ah lithium, about PKR 940,000) or 42.3 kWh on tubular (20 × 12V 200Ah tubular, about PKR 1,100,000). An inverter AC draws much less once the room is cool, so real consumption is often lower than the rated figure we use, but size for the rated figure if you want the AC to run every night.

Per rupee of upfront cost, tubular is cheaper: for the default picks and 4 hours this page prices 4 × 12V 200Ah tubular at about PKR 220,000 against 1 × 48V 100Ah lithium at about PKR 235,000. Per usable kWh over the battery's life it is the other way round: a tubular battery gives roughly 50% of its capacity and lasts 2-4 years of daily cycling, while LiFePO4 gives 90% and is rated for several thousand cycles. If you discharge every day, lithium usually costs less per year.

It is the share of a battery's nominal capacity you can use without shortening its life. Tubular lead-acid batteries should not be drained below half, so a 200Ah tubular gives you about 100Ah. LiFePO4 can be taken to 90%. On top of that some energy is lost in charging and discharging, which is the round-trip efficiency: about 95% for lithium and 80% for tubular. This calculator divides your energy need by both, so the kWh it shows is the nominal capacity to buy, not the energy you will draw.

Because amp-hours only mean something at a voltage. The same 5 kWh is 104 Ah at 48 V, 208 Ah at 24 V and 417 Ah at 12 V. Energy in kWh is the figure to compare across systems. Most new hybrid inverters in Pakistan from 3 kW up are 48 V, which is why that is the default here; 24 V suits small 1-2 kW inverters and 12 V is for very small loads.