Power consumption difference softOff vs off

[espruino-discuss2]

Posted at 2022-05-26 by d3nd3-o0

Does anyone have any estimate on the power consumption differences here? I'm curious.

[espruino-discuss2]

Posted at 2022-05-26 by @gfwilliams

Looks like around:

• 16uA off
• 25uA softOff

In reality they're so small it won't make much difference - that's around a year on the 200mA battery, so self-discharge is probably going to have a bigger effect

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Posted at 2022-05-26 by d3nd3-o0

Turned off - 0.08mA (0.6mA if turned off via Bootloader)

Quoted from https://www.espruino.com/Bangle.js
Is this 0.08mA on top of a baseline, or do you mean 0.08mA as the baseline when 'off'. Cos the other lines.

GPS on - 30mA

are implying extra power usage, not total? So if i use GPS + SCreen ON, I add them up?

Looks like around:
16uA off
25uA softOff

1000 uA = 1 mA
100uA = 0.1 mA
10 uA = 0.01 mA
1uA = 0.001 mA

So 0.08 mA = 80 uA.
I am aware the bangle2 has 0.04 mA written for off power instead of 0.08. So lets work with Bangle2 since its lower.
Are you saying power consumption has been improved somehow down to 16uA from 40 uA written on that page?

Lots of wrong math here, DELETED!

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Posted at 2022-05-26 by @gfwilliams

I gave the figures from Bangle.js 2

Are you saying power consumption has been improved somehow down to 16uA from 40 uA written on that page?

I'll update that page with the figures I measured, but:

It may have got better, but also I tend to round upwards quite heavily when giving power consumption figures, since power usage can vary device to device, and it's hard to measure values that small accurately (when the power usage fluctuates). I also probably gave softOff figures.

On 300mAh battery, 1 month=30*24=720 hours. So 2% = 6mA in 720 hours = 0.008 mA = 8uA of power draw all the time

... about the difference between 16 and 25uA

My math could be wrong too of course :)

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Posted at 2022-05-26 by d3nd3-o0

Ye my math is incorrect because mAh rating of battery is per hour.!

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Posted at 2022-05-26 by d3nd3-o0

Lets try again:
2,592,000 seconds in a month
730 hours to a month
0.016 mA * 2,592,000 sec = 41,472 mA monthly usage.
300mAh battery in a month gives total of = 300 * 730 = 219,000 mA
2% of 219000 = 4380 mA
self-discharge per month = 4380 mA
self-discharge per second = 4380 / 86400 = 0.0507 mA = 50uA
Fail Math

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Posted at 2022-05-26 by d3nd3-o0

I don't know how you got 0.008

So 2% = 6mA in 720 hours

I lost you after this.
I would think from here you have claimed 6mA per hour drain. So next is to turn into seconds, which is 6/3600 = 0.0017 mA (seconds obviously)
= 1.7 uA
lol so confused now :D
Fail Math

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Posted at 2022-05-26 by d3nd3-o0

Okay my bad, 86400 is seconds to day, not month, I will fix all the above! sorry!

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Posted at 2022-05-26 by d3nd3-o0

Okay forget months, forget hours, just SECONDS! mA = per second, mAh = per second.
300 mA/hour means it can provide 300 mA (per second) for an hour!
6 mA/hour over a month as a quantity.
ma/Month would be 730 times smaller than ma/hourly if total coulomb usage remains the same, because there are more seconds in a month. So. We have to make 6 smaller by 730, to get the correct ma/month value.
So lets convert 6mAh/month to hourly drain.
6 mAh / 730 = 0.0082 mA/month DRAIN.

Our usage is 0.016 mA. Which is 0.016/0.0082 = 1.95x larger than the drain.
0.025 - 0.016 = 0.009. I would argue the difference is almost the same as the discharge!
0.0082 mA vs 0.009 mA

So Ye you were spot on!
I'm done finally. This was harder than I anticipated.
Succeed Math?

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Posted at 2022-05-26 by d3nd3-o0

The confusion is because mAh means coulombs flowing per second, for an hour. So 6 mA per second , for an hour, is a large amount.
mAh is a rate for a duration, thus becoming a total after you multiply it by the duration?.
When we say 6mA per month, its still 6mA per second, for an hour, except spread over a month.
So instead of work with rates, we should get totals.
Converting 300 mAh to a total, would be 300 * 3600 = 1080000 milicoulombs
2%:
6 * 3600 = 21600 milicoulombs drain over a month.
21600/2,592,000 = 0.00833 mA
Same answer. different math.

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Posted at 2022-05-26 by d3nd3-o0

Calculating how many days/months you have with 0.00833 drain + 0.025 idle(off) current.
0.025 + 0.0083 = 0.0333
300mA for an hour = capacity.
300 / 0.0333 = 9009 hours.
9009 / 730 = 12.34 months.
12.5 months softOff with 25% drain because of self-discharge.
self-discharge is 33% of general power draw

With 0.016 + 0.0083 = 0.0243
300/0.0243 = 12345
12345/730 = 16.9 months
~17 months Off with 34% drain because of self-discharge
self-discharge is 52% of general power draw.