# What is rated capacity of battery?

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Nuno on 3 Oct 2011
Answered: Mike Sasena on 25 May 2022
Hi... In battery block in Simulink, what is rated capacity? In battery's datasheet's appears the capacity, for example, 3100 Ah. But who i calculated the rated capacity that i have introduce in battery block?
Walter Roberson on 3 Oct 2011
This present question contains no more information than your previous version of it. Was there a particular reason to have deleted the earlier question and re-post it?

Fangjun Jiang on 3 Oct 2011
The rated capacity is a parameter of the battery. Usually it is not to be calculated by your model. When you create the model for the battery, you need to know and specify some basic parameters of the battery, right? Like the voltage, it could be 1.5 volt, or it could be 120 volt.
The rated capacity of the battery is simply the energy capacity of the battery under normal condition. 3100Ah means if the battery is fully charged, it can provide a sustained current of 100 Amps for 31 hours before it is completely discharged. It will take 62 hours to fully charge it up if the charging current is 50 Amps constant. All these are ideal theoretical numbers.
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Walter Roberson on 3 Oct 2011
A good example of this is in UPS (Uninterruptable Power Supplies). Such devices must deliver a constant voltage and current as long as they last. Once you get out of the consumer-level UPS market, UPS almost always have an option to add additional power modules for additional duration, thereby increasing the amp-hours.
If you have a non-rechargable battery, you should always be asking, in any circuit, not just "How much current can it provide" but also "How long do we need it to provide that load?"
The situation is, of course, more complex in real life, when you take in to account heat (environmental, or generated by having to deliver heavy current loads), rate of degradation of the battery due to natural chemical decomposition, whether a particular rechargeable battery type has "memory effects", and so on.

Mike Sasena on 25 May 2022
This question was posted in 2011. Since that time, MathWorks has created a wide variety of battery models in our products (Simscape, Powertrain Blockset, etc.). You can do a doc search to see blocks available and determine which ones are best suited for your needs.

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