A 4Ah battery at 5V would be a 20Wh battery, drop the kilo. Electronics draw power at idle, not energy. 2kWh is meaningless without an idle duration. What are you saying?

Wh may be better for determining total energy storage across differing cell chemistry. mAh is standard for electronics and makes more sense at the design level as the battery voltage is chemistry dependent and known to the designer.

[–] lime@feddit.nu 8 points 2 months ago (1 children)

i don't think any manufacturer publishes the voltage their devices run at, could be anywhere from 3.3 to 5V. so i don't know how an end-user is supposed to compare battery sizes between devices.

[–] untorquer@lemmy.world 5 points 2 months ago

They would also have to give current draw which isn't really possible since each end user has different apps and behavior. So you more often get standby time or video playback time which are based on an "ideal" (probably non-bloated) clean OS. That's more useful to an end user but also subject to marketing fudging the figures.

You can often look up the battery chemistry or use an app to access sensors btw.

At the end of the day battery capacity is only one factor of many in battery/charge life and is generally just marketing in the context of phones.

[–] Eiri@lemmy.ca 5 points 2 months ago (1 children)

What? They draw power, not energy?

Energy is just the product of power and time. And just like amperage, the power draw of a device varies.

And this should be obvious, but what makes more sense to an electronics engineer doesn't matter one bit to the end user. And the end user doesn't know anything about milli-amperes or volts (except maybe their wall outlet voltage).

[–] untorquer@lemmy.world -1 points 2 months ago (1 children)

Yes power is a rate. As you said energy is the time integral of power. So it's meaningless to state an "energy draw" without a duration implied or explicit. E.g. what does drawing 2kWh at idle even mean?

I agree about end user sentiment. I was trying to suggest as well. The only way to know which battery/phone is going to have a better battery life is to identify reviews with similar usage to your own or cross-compare metrics across devices you're familiar with. In general, phone A with a 4000mAh battery won't necessarily outlast phone B with a 4500mAh batt.

[–] Eiri@lemmy.ca 3 points 2 months ago (1 children)

Well you don't say it draws 2 kWh at idle. You say it draws 2 kW at idle. While that is incredibly inefficient, it means that for every hour the device is idle, it draws 2 kWh of energy.

Oh yeah battery size isn't sufficient to fully gauge battery life. You need to know power draw to calculate that. And it's good to get battery life ratings from reviews. Great. It helps a lot.

But it doesn't mean we shouldn't get good, comparable physical specs.

Kinda like processors. Gigahertz and core counts are far from telling you everything, but it doesn't mean it should be abstracted into some weird unit.

[–] untorquer@lemmy.world 0 points 2 months ago

Per the kW vs kWh, see top level reply.

Yeah a metric would be nice but it would need a standard test. That's why idle time and video playback time makes a good amount of sense. But it's not entirely clear how that would translate into usage for example in back country (where cell network drains power harder) or travel. So it's not perfect. But it is probably the best measure guven hardware and usage vatiation. In any case it's subject to marketing dudging the numbers in various ways.