Correct usage of "rated" and "specified"?

When writing about technical subjects, how do we use the adjectives rated and specified correctly?

As an example, suppose I am writing about a rechargeable battery, and I would like to express that its capacity is 2500 mAh. My problem is that I am not sure which word should be used after rated or specified:

• The battery is specified with 2500 mAh (might be the natural solution for German native speakers like me, but does not really sound correct)
• The battery is specified at 2500 mAh (didn't find such an example, but might be not completely wrong)
• The battery is rated as 2500 mAh (found such an example on Linguee, but still sounds slightly odd)
• The battery is rated at 2500 mAh (also used in an example I have read, eventually sounds correct to me)
• The battery is rated 2500 mAh (the solution I eventually would use after having read some dictionary entries)

What would be the correct wording?

Solution 1:

Specified means that something is named or stated explicitly or in detail. (see Webster)

Rated refers to a quantification, such as a quantity, amount, or degree of something, which may be measured per unit of something else, or a relative condition or quality. (see Webster)

A rating is a type of specification. Specifications refer to characteristics or requirements. Ratings refer to performance or classification on a relative scale (which are characteristics).

For something like a battery, the battery will be rated at 2500 mAh, which is a quantification of the battery's performance. The device that uses it will be specified to take a 2500 mAh battery, which is a requirement for the device; the device isn't being quantified. You could quantify the device's performance using the battery: the laptop run-time on a full battery charge is rated at 4 hours.

The battery being black in color would be referred to as a specification, not a rating, because black isn't a quantity. But if you were classifying black by gradation, you could say its color is rated "very black".

A laptop's measurements, say 10" x 13" x 1", are a quantification, but not of a performance type of measure, so that would be a specification. But if you were classifying laptops on a size scale, you could say the laptop is rated "mid-size".

"Rated" doesn't require a linking word; you can say "The battery is rated 2500 mAh". If you do use a linking work, "at" is usually appropriate: "The battery is rated at 2500 mAh".

"Specified" is sometimes used without a linking word, but is typically used with one, and "as" is usually appropriate: "The battery is specified as 2500 mAh"; although if the specification is a rating, "at" can be used.

Solution 2:

The two terms are not synonymous. They apply to entirely different ideas.

Specified is used when speaking about formal requirements. Rated is used when speaking about the performance with respect to some performance measurement standard. So a designer may have specified a 2500 mAh rated battery. Meaning the designer wants one that the supplier promises will perform at a 2500 mAh rating. Built in to the idea of a rating is the notion that a standard, formal method of determining that rating exists. In formal procurement documents, that standard will always be called out explicitly. Suppliers will often have to submit certifications from labs that the item meets the specified rating.

Use specified when you are referring to a formal requirement. You are referring back to the document that contains the specification.

Use rated when talking about performance within the context of a formal and mutually accepted standard for measuring/rating performance. Performance ratings are not always literal - gasoline octane rating, for example. Advertised battery ratings on small, cheap batteries are notorious for being pure fiction.

So if you are writing about some particular battery itself (mfg and part number), you would use rated; it may have a rating with respect to any number of things. If writing about some battery component in an assembly specification, use specified, which doesn't refer to any one battery in particular, but rather any battery which could potentially do the job.

The two don't overlap unless the specification calls out the battery mfg and part number explicitly.