Decoding Backup Time: Lithium Batteries vs. Tubular Batteries in 10 KVA Inverter Applications

 When we need to run heavy loads like Air conditioners, motors, Microwave ovens, treadmills, Power tools, Deep Frezeers, Heating Systems geysers, etc.

We need to choose the high Capacity or heavy-duty Duty Inverter/UPS. So, when choosing the heavy-duty inverter/UPS, we must choose the right battery bank to give us the desired backup time. So, in this article, we have tried to analyse the backup time and price of the Tubular lead Acid battery Vs lithium-ion battery bank.

Can a 10 KVA Inverter run an 8 KW load on 150 Tubular Lead Acid batteries? To understand this question, we need to understand the characteristics of Tubular lead Acid batteries.

The Tubular lead acid batteries come in the C20 capacity, which is meant to draw a current of 5% of its total Capacity. If we try to draw more current than the 5% value, then the Capacity of the C20 Tubular battery will start reducing. Now the question is how much Capacity it will reduce, and are there any general formulae by which it will fall? The answer is no,

as the different manufacturers make Tubular batteries, they do not provide any data on the discharge rate and Capacity, which can be drawn from the C20 battery.

So we did the actual test on the 10KVA inverter having IGBT-based Double Conversion Technology, and the results are astonishing. Any other person can repeat it by taking an Inverter from the Indian market and testing it on the Isolation Inverter, which has an efficiency of 85 to 88%.


So when we tried to run the Resistive load on this Inverter having eight batteries of 150 Ah of tubular batteries of the reputed brand, the results were the following:

The time taken to charge the batteries with a 15Amp charging current was around 16 hours.

The load is 8KW, the Discharge Current from the batteries is 96 Amps from the DC side, the Output Voltage is 225Volts, and we received a backup of 16 minutes only. So, the next step is to run the same Inverter on a 6KW Resistive Load, in which case the Inverter Output Current on AC voltage of 224 Volts and the discharge current from the battery side DC came to 79 Amps, and the backup time we got was 32 minutes only.

Now, in the last step, we run the Lithium Inverter on a 4KW load, which is half of its capacity, so the Output current is 18.7 Amps at the voltage of 224.7V, and the discharge current on the battery side is 50 Amps DC, and we got 1-hour backup only on 4KW resistive Load. In comparison, on a 9.6 KW Lithium-ion battery, we got a backup time of 2 hours and 20 minutes. 

We can well imagine the life of the batteries having C20 capacity on these loads as the current drawn from these batteries is very high, so the life of the batteries and the water topping will be very high.

The charging of the Lithium battery bank of 9.6KW took 4 hours at the current charging current of 30 Amps as the Lithium battery can take 50% of its capacity, but we charged it with 30% of its Capacity only.

So, we try to do the same thing with a single bank’s lithium-ion battery bank of LifePO4 chemistry. The Capacity of the Lithium-ion bank was 9.6 KW of 96Volt DC. Since the lithium battery is of C1 capacity and the results are so different, we got the same discharge current of 96 Amps, and the Inverter’s output voltage was 225 Volts. We received the backup of 1 hour and 5 minutes.

When we tried to discharge the lithium-ion battery bank of the same Capacity on a 6 KW load of 79 Amps, the backup we received was 1 hour and 40 minutes.

Now we can compare the price in terms of wattage as the LTubular battery costs approximately Indian Rs 12,000/ and eight batteries cost around Rs.96,000/.

A Lithium-ion battery costs around Rs 16,000 to 18,000, and the 9.6 KW battery price will be around  1,55,000-1,75,000/ approximately.

Now let us see which is a cheaper battery in absolute terms as the Lithium battery gives a 1-hour 5-minute backup compared to the tubular battery bank of 8 batteries. So the Lithium bank gives four times the backup time, so the cost difference is only 1.5 times or 1.6 times the Tubular battery price. The life of the Tubular battery will also be three to 4 times of the Tubular battery.

So, the obvious result here is that a Lithium-ion battery is cheaper than a tubular battery bank.

So we can compare the Tubular Lead Acid battery in terms of these points:

The Capacity of the battery we get in Lithium-ion vs. tubular battery: this is the mind-boggling parameter which will be understood by people soon that the Tubular battery comes in C20 Capacity sticker or the Solar battery comes in C10 capacity sticker. The Lithium battery comes in a C1 capacity package. How do we understand this factor?

2. Clean technology vs Polluted technology: People using Tubular batteries in their homes and offices are breathing Lead fumes because the Tubular deep discharge batteries emit lead-based fumes, which are very harmful to the people consuming them. The lungs are affected by these lead fumes, and children and older people are the most affected. The lithium-ion battery is a clean technology with no fumes or emissions of any gasses. So, health hazards are the major challenge in Tubular batteries.

3. Depth of Discharge in Tubular Vs Lithium battery LifePO4: The depth of discharge we can take out from a tubular deep discharge battery is 50%, whereas, from the lithium battery, the DOD can be 98% as this is C1 Battery compared to the tubular battery, which is C20 battery capacity.

4. The power bill for Charging comparison of Lithium-ion battery: As already described, the Tubular Deep discharge battery has 4-stage or 6-stage charging as the charging of a Tubular battery is quite complicated, even needing to do the Temperature Compensation. Making the proper gravity into the battery is not easy. So, the backup time will also change on different temperatures if not used with the ATC technology. Lithium battery charging is straightforward and charges in the Bulk Charging stage and a little bit of the Absorption stage for 5 to 10 minutes, and the battery is charged in 2 to 3 hours. In the tubular battery, all these stages waste a lot of energy. On top of it, the trickle charge keeps happening even after the battery is completely charged, which is not required in a Lithium battery. The self-discharge of lithium batteries is very low compared to that of tubular batteries.

5. Space and weight of Tubular vs lithium-ion battery: The comparison between Tubular and lithium batteries is shocking as a 150 Ah tubular battery is 62 Kgs in weight. Hence, the eight batteries become 496 Kgs. The 9.8 KW battery bank is of 75Kgs. So one needs a rack to keep the eight batteries at 150 Ah, which takes a lot of space, whereas the Lithium battery can be mounted on the wall, takes hardly any space or can be kept on the top of the Lithium Inverter by making a small rack.


6. Maintenance Of Tubular Vs Lithium battery: the water topping in the Tubular deep discharge battery is a headache for anyone maintaining those batteries. Eight batteries of Tubular need watering every 5 to 6 months. After filling the water, there may be a chance that acid water oozes out from one of the batteries and destroys the floor, which happens in most installation sites. Lithium bank doesn’t require any maintenance at all. A lithium-ion battery bank is sealed and doesn’t emit fumes, etc.

7. Cost: The cost of a Lithium-ion battery is cheaper than that of a Tubular battery as we have compared the backup time on the different capacities.

8. Life: The life of the tubular lead acid battery will be 2 to 3 years, and the life of the lithium-ion will be between 7 and 10 years.

At Su-vastika, we have installed more than 200 units with Lithium battery banks, and we can see the different types of installations and their usage.

Suppose we try to compare the Diesel Generator cost Vs features. In that case, we also realise that a 10 KVA lithium Inverter is cheaper than the Diesel generator cost as the upfront cost of a DG set of 10 KVA is nearly Rs.2,50,000/ approximately, which requires diesel to run daily. The size of the Diesel Generator Vs Lithium Inverte is one-fourth, and it’s a clean and green product.


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