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CALCULATOR Free · indicativeKnow your backup time and battery size
Work out how long a battery bank will last, how many Ah you need for a target backup, how to wire it, and how long it takes to charge.
You’ll get
- Backup time from your Ah
- Bank size and layout
- Charging time and charger size
Your inputs
Advanced assumptions
Result
-hours
Battery needed for target-
Bank layout-
Charging time-
Suggested charger-
Capacity used (Ah)-
Usable energy-
Usable energy vs what your target needs
Indicative estimate only. Real results depend on your equipment, site conditions and applicable standards. This is not a design or an offer.
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Send us your result and we’ll review it and prepare a recommendation and quotation.
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Method & assumptions
- Depth of discharge50% for lead-acid / VRLA, 80% for lithium (LFP).
- Backup timeAh × V × DoD × inverter efficiency ÷ ageing margin ÷ load.
- Charging timeAh used ÷ (charger A × charge efficiency), plus an absorption allowance (15% lead-acid, 5% lithium).
- Charger sizeAbout 10% of Ah for lead-acid, 30% for lithium.
- Real-worldTemperature, discharge rate (Peukert effect) and battery age change results; confirm with the battery datasheet.
FAQ
About this calculator
Why only 50% depth of discharge for lead-acid?
Regularly discharging lead-acid deeper shortens its life. 50% is a common design value; your battery maker may allow more.
What is the ageing margin?
Batteries lose capacity over time; sizing with a margin keeps the backup adequate at end of life.
Can I mix battery brands or ages?
It is not advised. Use identical batteries in a bank.
Do you supply batteries and chargers?
Yes - industrial and solar batteries and charger options are in our catalogue; send an enquiry for a quotation.
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