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Solar Battery Calculator

Sizes an off-grid battery bank in Ah from daily energy use, days of autonomy and battery chemistry.

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Enter your figures and press Calculate.
In short Solar Battery Calculator is a free online tool on inputtesthub.com that sizes an off-grid battery bank in Ah from daily energy use, days of autonomy and battery chemistry. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the Solar Battery Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the Solar Battery Calculator

The Solar Battery Calculator sizes an off-grid battery bank in Ah from daily energy use, days of autonomy and battery chemistry. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Sizing a battery bank for an off-grid cabin.
  • Comparing lead-acid against lithium for the same job.
  • Seeing what a higher system voltage would save in cable.

Details

Lead-acid usable50%
LiFePO₄ usable85%
Lithium bank is≈ 40% smaller on paper
48 V vs 12 VA quarter of the current

The maths behind it

This tool uses Bank Wh = daily Wh × days ÷ (depth of discharge × inverter efficiency). Ah = bank Wh ÷ system voltage. Every intermediate value is shown on screen, so the result can be checked by hand.

Chemistry moves this more than anything else. Note also the last rows: running the bank at 24 or 48 V halves or quarters the current for the same energy, which means far thinner cable and much lower losses on anything above a few hundred watts.

Frequently asked questions

Is the Solar Battery Calculator free?
It is free, with no account, no trial and no daily cap. Every calculators tool on inputtesthub.com works the same way: open the page and use it.
Can you see what I put into this page?
No. The Solar Battery Calculator runs entirely in your browser using JavaScript. Because the work happens locally, the page also keeps working if your connection drops, and closing the tab is all it takes to discard everything.
What is the equation behind the Solar Battery Calculator?
It uses Bank Wh = daily Wh × days ÷ (depth of discharge × inverter efficiency). Ah = bank Wh ÷ system voltage. The full working is printed under the result, so you can follow every step rather than trusting a black box.
What is the Solar Battery Calculator used for?
The most common reasons people reach for it: sizing a battery bank for an off-grid cabin. Comparing lead-acid against lithium for the same job. Seeing what a higher system voltage would save in cable. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
What do people usually get wrong here?
Chemistry moves this more than anything else. Note also the last rows: running the bank at 24 or 48 V halves or quarters the current for the same energy, which means far thinner cable and much lower losses on anything above a few hundred watts.
What are the key numbers for the Solar Battery Calculator?
Lead-acid usable is 50%. LiFePO₄ usable is 85%. Lithium bank is is ≈ 40% smaller on paper. These are printed on the page itself, so you do not have to take them on trust.
How precise is the result?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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