Why are larger (house, car) rechargeable batteries specified in (k)Wh but smaller batteries (laptop, smartphone) are specified in (m)Ah?

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I get that, for a house/solar battery, it sort of makes sense as your typical energy usage would be measured in kWh on your bills. For the smaller devices, though, the chargers are usually rated in watts (especially if it’s USB-C), so why are the batteries specified in amp hours by the manufacturers?

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Anonymous 0 Comments

Ah is the capacity of a battery, Wh is also the capacity of a battery. Both are giving you an estimate of how big the capacity is of a battery.

A battery with 10 Ah, running with 24 V will have a capacity of 240 Wh.

A battery with 240 Wh running with 24V will have a capacity of 10 Ah.

The 10 Ah will be able to give you 10 A for an hour, or 1 A per hour for 10 hours.

The 240Wh will be able to give you 240W for 1 hour or 24W for 10 hours.

How long your battery hold depends on the voltage and the item you are using the electricity for (how many watt it draws).

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