Check my maths please?

**Andrew_van_Zyl** · 07-Feb-23, 03:22 PM

Gents,
Getting my head around how to calculate backup battery requirements for an inverter. No PV - just battery backup.

Attached is a simple example for calculating battery storage requirement for a stand alone CCTV system.

Please could you check if I have done this correctly?

Thanks in advance,

Click image for larger version.

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**Justloadit** · 09-Feb-23, 06:56 AM

Sounds about right, however you are doubling the storage supplied figure by multiplying the number of batteries as well as batteries in series.
Remember that Ampere hour is the same in any series string, whilst voltage goes up with every battery in the series.

**Andrew_van_Zyl** · 10-Feb-23, 02:18 PM

Originally Posted by Justloadit

Sounds about right, however you are doubling the storage supplied figure by multiplying the number of batteries as well as batteries in series.
Remember that Ampere hour is the same in any series string, whilst voltage goes up with every battery in the series.

Ah yes, of course. Thank you for pointing that out. Have amended my spreadsheet