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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> rated in watts (especially if it’s USB-C), so why are the batteries specified in amp hours
Those are different units completely.
Watts is a unit for POWER, Amp Hour (or watt hour) is a unit of CAPACITY. See the difference as how much water a hose can deliver vs how much water a bucket can hold.
The main ‘feature’ of a battery is how much capacity they can hold so while it is relevant to know what kind of power it can deliver its still more important to know how much capacity fits in there.
> rated in watts (especially if it’s USB-C), so why are the batteries specified in amp hours
Those are different units completely.
Watts is a unit for POWER, Amp Hour (or watt hour) is a unit of CAPACITY. See the difference as how much water a hose can deliver vs how much water a bucket can hold.
The main ‘feature’ of a battery is how much capacity they can hold so while it is relevant to know what kind of power it can deliver its still more important to know how much capacity fits in there.
mAh doesn’t properly indicate capacity, since it doesn’t tell you the voltage, and therefore not the power. However, almost every phone and powerbank uses a 3.7V battery. Since the voltage is the same, you can use mAh to compare. However, large batteries often have different voltages, so they use kWh or Wh.
I guess the use of mAh is just a habit and no-one sees a need to change. And to the uninitiated, 5000 mAh probably sounds better than 18.5 Wh, even though it’s the same at 3.7V.
mAh as a unit for capacity is just a scam, because you don’t know the voltage and therefore not the batterie’s real capacity. But 3000 mAh sounds much better than 9 Wh. That’s why.
Short answer is, small devices all tend to have the same battery voltage, while bigger batteries don’t.
In phones, using mAh is mostly acceptable as *most phones* are using a battery that’s around the same voltage, usually 3.7-3.8 volts. That’s the standard voltage of a single lithium battery “cell”, just as AA or AAA batteries are always around 1.5 volts. If the voltage of the batteries is the same, you can compare their mAh ratings directly. There’s nothing stopping you from defining this in Wh, but we don’t typically do that.
With bigger batteries, there’s a lot more variation in how the individual cells inside the battery pack are configured, so voltage can be anything from the single cell voltage of 3.8ish volts, to an 800v pack you’d find in a new electric car, or maybe even higher. When you can’t compare packs of the same voltage, you can multiply it by the Ah rating to get the Wh rating, and that will let you compare their *capacities* more directly.
A 6 cell pack where each cell is 2.5Ah will always have around ~57Wh of capacity, but depending on how those cells are connected, you could have a lot of combinations, 22.8V @ 2.5Ah and 11.4V @ 5Ah being just 2 of them.
mAh doesn’t properly indicate capacity, since it doesn’t tell you the voltage, and therefore not the power. However, almost every phone and powerbank uses a 3.7V battery. Since the voltage is the same, you can use mAh to compare. However, large batteries often have different voltages, so they use kWh or Wh.
I guess the use of mAh is just a habit and no-one sees a need to change. And to the uninitiated, 5000 mAh probably sounds better than 18.5 Wh, even though it’s the same at 3.7V.
mAh doesn’t properly indicate capacity, since it doesn’t tell you the voltage, and therefore not the power. However, almost every phone and powerbank uses a 3.7V battery. Since the voltage is the same, you can use mAh to compare. However, large batteries often have different voltages, so they use kWh or Wh.
I guess the use of mAh is just a habit and no-one sees a need to change. And to the uninitiated, 5000 mAh probably sounds better than 18.5 Wh, even though it’s the same at 3.7V.
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).
Short answer is, small devices all tend to have the same battery voltage, while bigger batteries don’t.
In phones, using mAh is mostly acceptable as *most phones* are using a battery that’s around the same voltage, usually 3.7-3.8 volts. That’s the standard voltage of a single lithium battery “cell”, just as AA or AAA batteries are always around 1.5 volts. If the voltage of the batteries is the same, you can compare their mAh ratings directly. There’s nothing stopping you from defining this in Wh, but we don’t typically do that.
With bigger batteries, there’s a lot more variation in how the individual cells inside the battery pack are configured, so voltage can be anything from the single cell voltage of 3.8ish volts, to an 800v pack you’d find in a new electric car, or maybe even higher. When you can’t compare packs of the same voltage, you can multiply it by the Ah rating to get the Wh rating, and that will let you compare their *capacities* more directly.
A 6 cell pack where each cell is 2.5Ah will always have around ~57Wh of capacity, but depending on how those cells are connected, you could have a lot of combinations, 22.8V @ 2.5Ah and 11.4V @ 5Ah being just 2 of them.
Short answer is, small devices all tend to have the same battery voltage, while bigger batteries don’t.
In phones, using mAh is mostly acceptable as *most phones* are using a battery that’s around the same voltage, usually 3.7-3.8 volts. That’s the standard voltage of a single lithium battery “cell”, just as AA or AAA batteries are always around 1.5 volts. If the voltage of the batteries is the same, you can compare their mAh ratings directly. There’s nothing stopping you from defining this in Wh, but we don’t typically do that.
With bigger batteries, there’s a lot more variation in how the individual cells inside the battery pack are configured, so voltage can be anything from the single cell voltage of 3.8ish volts, to an 800v pack you’d find in a new electric car, or maybe even higher. When you can’t compare packs of the same voltage, you can multiply it by the Ah rating to get the Wh rating, and that will let you compare their *capacities* more directly.
A 6 cell pack where each cell is 2.5Ah will always have around ~57Wh of capacity, but depending on how those cells are connected, you could have a lot of combinations, 22.8V @ 2.5Ah and 11.4V @ 5Ah being just 2 of them.
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