energy monitor favour please

QrizB

ariarnia said:

awesome. but i'm not sure how to read that... little bear brain again. can you give an example of how to work out one.

The phones in the chart all have batteries with similar capacities. They're quoted in mAh which is OK if you're comparing phones with one another but isn't quite what we need here.

Taking a 3300mAh battery as an example, that's 3.3Ah. The battery is likely to be a single lithium-iron cell with a nominal cell voltage of 3.7V, so the battery capacity is 3.3 x 3.7 = 12.2 watt-hours (Wh).

There's 1000Wh in a kWh so, on the face of it and ignoring losses, you could charge that battery from flat 1000 / 12.2 = 82 times (or charge 82 separate phones) with a single kWh of electricity.

But what if we don't ignore losses? Well, that gets more complicated.

Wired chargers are pretty good; in much bigger applications (grid-tied battery storage) you'd often assume a 90% charging efficiency so let's go with that. Your phone now needs 12.2 x 110% = 13.4Wh and you can charge it almost 75 times with a single kWh.

Wireless charging is much less efficient. The numbers in this article say it needs 40-50% more electricity than wired charging. Taking the lower estimate, 13.4 x 140% = 18.8Wh. You can now only charge 53 times with your kWh.

Edited for typos (including the one highlighted below, thanks Glum for pointing it out).

Glum

A very helpful explanation.

Minor typo:
1000 / 12.2 = 82

ariarnia

QrizB said:

ariarnia said:

awesome. but i'm not sure how to read that... little bear brain again. can you give an example of how to work out one.

The phones in the chart all have batteries with similar capacities. They're quoted in mAh which is OK if you're comparing phones with one another but isn't quite what we need here.

Taking a 3300mAh battery as an example, that's 3.3Ah. The battery is likely to be a single lithium-iron cell with a nominal cell voltage of 3.7V, so the battery capacity is 3.3 x 3.7 = 12.2 watt-hours (Wh).

There's 1000Wh in a kWh so, on the face of it and ignoring losses, you could charge that battery from flat 1000 / 12.2 = 82 times (or charge 82 separate phones) with a single kWh of electricity.

But what if we don't ignore losses? Well, that gets more complicated.

Wired chargers are pretty good; in much bigger applications (grid-tied battery storage) you'd often assume a 90% charging efficiency so let's go with that. Your phone now needs 12.2 x 110% = 13.4Wh and you can charge it almost 75 times with a single kWh.

Wireless charging is much less efficient. The numbers in this article say it needs 40-50% more electricity than wired charging. Taking the lower estimate, 13.4 x 140% = 18.8Wh. You can now only charge 53 times with your kWh.

Edited for typos (including the one highlighted below, thanks Glum for pointing it out).

so rough ball park we could say you would use 4.8kwhs (365/75) a year for wired charging and 6.8 (365/53) for wireless allowing for losses?

that's about 1.60 or 2.30 a year at domestic rates (and potentially much higher at comercial but obviously not all days are working days and not everyone would charge from flat and not every day but potentially times many more phones across a whole workforce)