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

Nothing is measured in just mAh, that’s just an abbreviation.

A battery’s capacity is listed as #V###Ah. Like a 3.7V-2400mAh phone battery, or a 12V-7Ah car battery.

Since all phone batteries operate at the same voltage (3.7V for Li-Po), people just leave that part out.

They could do the same for car batteries, since 99.9% of cars use 12V batteries. But I have never seen any car batteries labeled in just mAh (or Wh for that matter).

For house batteries it would normally once again be V x Ah. For example, we had 2 x 12V200Ah batteries in our house, or 24V200Ah total. I have no idea what the actual voltage specs for tesla powerwalls are. In case of a house it makes sense to convert the V x Ah to kWh, since your house runs at 110V or 220V, and the 24V number will be meaningless, and your AC devices will list their power consumption as watts anyway.

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