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Wikidata:Property proposal/electric charge capacity

< Wikidata:Property proposal

electric charge capacity

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Originally proposed at Wikidata:Property proposal/Natural science

   Not done
Descriptionelectric charge a battery can store
Representscharge capacity (Q18021646)
Data typeQuantity
Domainbattery (Q267298), electronic device model (Q62008942)
Allowed unitsampere hour (Q212120), milliampere hour (Q3858002), coulomb (Q25406)
Example 1Fairphone 3 (Q67174340) → 3040 milliampere hour (Q3858002)
Example 2INR18650-MJ1 (Q120766894) → 3500 milliampere hour (Q3858002)
Example 3INR18650-P28B (Q120767033) → 2800 milliampere hour (Q3858002)
See alsoenergy storage capacity (P4140)

Motivation

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I mainly came across the need by noticing that energy storage capacity (P4140), originally proposed for energy capacity, is now being used for electric charge capacity, too. Those represent different, dimensionally incompatible physical quantities. The goal is to migrate statements using electric charge units. The overall motivation is to allow only compatible units for a given property. Toni 001 (talk) 08:37, 1 June 2022 (UTC)[reply]

Discussion

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  • @Toni 001: Hmm, aren't these implicitly energy storage units, under a specific assumption of the voltage that will be supplied from the battery? Yes they are nominally units of charge, but in practice that's not why they're used. And batteries are not capacitors so it's not literally a unit of charge being stored, right? ArthurPSmith (talk) 14:22, 2 June 2022 (UTC)[reply]
    Correct, given a voltage the electric charge (current times time) can be translated to energy. This relationship is analogous to that between volume and mass, given a density.
    From the IEV: "capacity, <for cells or batteries>: electric charge which a cell or battery can deliver under specified discharge conditions". Toni 001 (talk) 08:02, 3 June 2022 (UTC)[reply]
    Regarding the "overall motivation", there are two kinds of conversion:
    a) unit conversion
    b) conversions between different quantities, given a third quantity
    We should strive to allow unit conversions (a) between all values of a given property. For other conversions (b) we should create distinct properties, just as we have volume as quantity (P2234) and mass (P2067). Toni 001 (talk) 08:08, 3 June 2022 (UTC)[reply]
      • Should we have qualifiers to describe the "specified discharge conditions" then? It just seems a bit misleading if we are stating that batteries are storing a quantity of electric charge. ArthurPSmith (talk) 16:13, 3 June 2022 (UTC)[reply]
        I don't think it's easy to model exactly the relationship between electric charge and energy: Those might be temperature, electric current drawn, but also the history of the battery. (Note that the simply relation given above, "energy = charge times voltage", is problematic in that batteries supply a different voltage depending on their charge and current.)
        So I suggest we content ourselves with what's given on the label of a battery (if some document lists conditions then of course we could try to model those).
        Regarding the proposed property label: I'm open for other suggestions. My main concern is to distinguish "energy capacity" and "charge capacity". Toni 001 (talk) 09:28, 5 June 2022 (UTC)[reply]
  • Maybe we can specify that this should be the "nameplate" capacity of the battery as specified by the manufacturer? BrokenSegue (talk) 04:48, 14 September 2022 (UTC)[reply]
    I think that's what I had in mind: When I see chargeable batteries in a store they state something like 2200 mA h, typically without further explanation. So that's what this property is meant for. Toni 001 (talk) 07:40, 14 September 2022 (UTC)[reply]
  • @Toni 001: I am a battery developer and can confirm that your proposal to distinguish "capacity" from "energy" is correct and necessary. Battery manufacturers usually report some nominal properties for capacity (in Ah or mAh) and energy (in Wh or mWh) that are measured under a specific set of conditions (set by ISO). A typical datasheet will report these nominal values. This term for capacity should be the same as IEV 482-03-15. The term for energy storage capacity (P4140) should correspond to IEV 482-03-21. --DrSimonClark (talk) 22:01, 20 July 2023 (UTC)[reply]
  •   Not done, no consensus of proposed property at this time based on the above discussion. Regards, ZI Jony (Talk) 10:38, 2 June 2023 (UTC)[reply]
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