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Watts Should Replace MAh as Essential Spec for Mobile Devices

8 points by m463 2y ago

johndoe0815 2y ago
"With watts, you can tell how much literal power is under the hood — how much energy is provided by your battery [...]". Ouch.
- deleted 2y ago
  [deleted]
JohnFen 2y ago
Yep, this has been a pet peeve of mine for a very long time.
- Numerlor 2y ago
  While more informative on its own, it's still kind of useless with the wide variance of power usage across models. Laptops use Wh but you still need to do the same research as you would have if it was in mAh (ignoring the 100Wh max for planes that you'd have to calculate yourself)
  - crote 2y ago
    The problem is that mAh tells you absolutely nothing about battery capacity. An mAh rating is useful if you're comparing two single-cell batteries using the same chemistry - but that's not what we are doing in practice. For example, a 100Wh battery could be built using a single li-ion cell, which means it would be 27,000mAh. Same battery using an LFP cell? 31.250mAh. But wait, it's a laptop - it's far more efficient to put multiple cells in series. Four li-ion cells in series would mean a capacity of 675mAh, or 540mAh if you use five cells. The five-cell one is probably more efficient, but if you blindly look at the mAh rating it looks like it has a significantly smaller capacity. Nobody is going to buy that, so the marketing team will convert it back to "single-cell equivalent" and put 27,000mAh on the box while still keeping an 18.5V rating, and people who passed a highschool physics class are going to think it's a 500Wh battery. It gets even worse with LFP, because now the marketing team is asking you to convert it to "single-sell li-ion equivalent" and the figure is now completely unrelated to what's actually happening! That 520mAh 6-cell LFP battery? Just put a 27,000mAh label on it: who cares, bigger is better.
perilunar 2y ago
> "At its most basic, the watt is a measure of work. It’s the amount of energy it takes to do something at a particular speed." Oh dear. This article is full of confusion between energy and power. But I agree that batteries should list total energy. Just list the voltage, energy (in Wh or J) and the max power output (W).
- VogonPoetry 2y ago
  Yes, totally agree. Also a paragraph on the relationship between energy, heat, cooling and that computers effectively turn all energy into heat might have been useful. The April 1st date on the article is telling. Shout out to "Technology Connections" YouTube channel for recently publishing "Power is not energy" - <https://www.youtube.com/watch?v=OOK5xkFijPc https://www.youtube.com/watch?v=OOK5xkFijPc>.

8 points by m463 2y ago

"With watts, you can tell how much literal power is under the hood — how much energy is provided by your battery [...]". Ouch.

deleted 2y ago
[deleted]

JohnFen 2y ago

Yep, this has been a pet peeve of mine for a very long time.

Numerlor 2y ago
While more informative on its own, it's still kind of useless with the wide variance of power usage across models. Laptops use Wh but you still need to do the same research as you would have if it was in mAh (ignoring the 100Wh max for planes that you'd have to calculate yourself)
- crote 2y ago
  The problem is that mAh tells you absolutely nothing about battery capacity. An mAh rating is useful if you're comparing two single-cell batteries using the same chemistry - but that's not what we are doing in practice. For example, a 100Wh battery could be built using a single li-ion cell, which means it would be 27,000mAh. Same battery using an LFP cell? 31.250mAh. But wait, it's a laptop - it's far more efficient to put multiple cells in series. Four li-ion cells in series would mean a capacity of 675mAh, or 540mAh if you use five cells. The five-cell one is probably more efficient, but if you blindly look at the mAh rating it looks like it has a significantly smaller capacity. Nobody is going to buy that, so the marketing team will convert it back to "single-cell equivalent" and put 27,000mAh on the box while still keeping an 18.5V rating, and people who passed a highschool physics class are going to think it's a 500Wh battery. It gets even worse with LFP, because now the marketing team is asking you to convert it to "single-sell li-ion equivalent" and the figure is now completely unrelated to what's actually happening! That 520mAh 6-cell LFP battery? Just put a 27,000mAh label on it: who cares, bigger is better.

perilunar 2y ago

> "At its most basic, the watt is a measure of work. It’s the amount of energy it takes to do something at a particular speed." Oh dear. This article is full of confusion between energy and power. But I agree that batteries should list total energy. Just list the voltage, energy (in Wh or J) and the max power output (W).

VogonPoetry 2y ago
Yes, totally agree. Also a paragraph on the relationship between energy, heat, cooling and that computers effectively turn all energy into heat might have been useful. The April 1st date on the article is telling. Shout out to "Technology Connections" YouTube channel for recently publishing "Power is not energy" - <https://www.youtube.com/watch?v=OOK5xkFijPc https://www.youtube.com/watch?v=OOK5xkFijPc>.