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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An 18650 cell might be 3400-mAh, which is the same as 3.4-Ah.
When a house battery has 300,000-mAh, it gets easier to compare mentally when you call it 300-Ah
An 18650 cell might be 3400-mAh, which is the same as 3.4-Ah.
When a house battery has 300,000-mAh, it gets easier to compare mentally when you call it 300-Ah
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.
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.
Measuring it in ampere-hours works fine as long as the batteries (as a complete unit) are roughly of the same voltage, which is the case for most phones, as the vast majority use one single lithium-ion battery cell, and lithium ion based chemistries have very similar voltage levels.
It doesn’t work when you compare batteries of wildly different configurations, such as 100 Li-ion cells in parallel, or 10 sets of 10 cells in parallel which again are connected to form a serial battery that outputs 10x the voltage. Or batteries consisting of cells with entirely different chemistries such as lead acid (2.1V per cell) or NiMH (1.2V per cell).
To compare these, you need to use watt-hours instead to get a useful number.
Measuring it in ampere-hours works fine as long as the batteries (as a complete unit) are roughly of the same voltage, which is the case for most phones, as the vast majority use one single lithium-ion battery cell, and lithium ion based chemistries have very similar voltage levels.
It doesn’t work when you compare batteries of wildly different configurations, such as 100 Li-ion cells in parallel, or 10 sets of 10 cells in parallel which again are connected to form a serial battery that outputs 10x the voltage. Or batteries consisting of cells with entirely different chemistries such as lead acid (2.1V per cell) or NiMH (1.2V per cell).
To compare these, you need to use watt-hours instead to get a useful number.
mA is a measure of charge, or approximately how long a battery can last.
kW is a measure of power, or how much energy the battery provides.
The phone industry has pushed the agenda more mAh is better, but this isn’t necessarily true.
There are more factors to consider when purchasing a phone, and energy should be a huge factor.
If the phone can’t store more energy (bigger battery, better power management), all the mAh won’t matter as the phone will drain quickly.
mA is a measure of charge, or approximately how long a battery can last.
kW is a measure of power, or how much energy the battery provides.
The phone industry has pushed the agenda more mAh is better, but this isn’t necessarily true.
There are more factors to consider when purchasing a phone, and energy should be a huge factor.
If the phone can’t store more energy (bigger battery, better power management), all the mAh won’t matter as the phone will drain quickly.
In RC hobbies like quadcopters or whatever, we care about voltage (directly or indirectly, like 4S = 4 LiPo cells = ~16-17V) and can use mAh to directly compare between batteries of same cell count.
People intuitively (if not explicitely) understand a 6S 1000mAh battery has a lot more capacity than a 4S 1000mAh.
Yeah we could use watt-hours instead but since we also always care about battery voltage (more than overall battery capacity) it doesn’t matter. It is implicit in the specification (4S 1000mAh, 4S 750mAh, 6S 1200mAh, 1s 300mAh, etc).
In RC hobbies like quadcopters or whatever, we care about voltage (directly or indirectly, like 4S = 4 LiPo cells = ~16-17V) and can use mAh to directly compare between batteries of same cell count.
People intuitively (if not explicitely) understand a 6S 1000mAh battery has a lot more capacity than a 4S 1000mAh.
Yeah we could use watt-hours instead but since we also always care about battery voltage (more than overall battery capacity) it doesn’t matter. It is implicit in the specification (4S 1000mAh, 4S 750mAh, 6S 1200mAh, 1s 300mAh, etc).
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