How many amp hours of aux battery to charge a phone?

[crazyvwvanman]

If my iPhone 11 battery runs very low, how many amp hours of my aux battery capacity are needed to full charge it?

[kourt]

Too many variables. What amperage is your USB charging port? Or the charger itself? Are you disabling wifi and cellular while charging?

This question is useless without details.

kourt

[SSWesty]

I think you're in the 2 amp hour range +/-1

[DanHoug]

iPhone 11 batteries are ~3100mAH. so... figure a charge conversion efficiency of a conservative 60% therefore:

XmAH x .60 = 3100mAH
XmAH = 5100mAH or 5.1AH

that's for a fully discharged phone batt, which few let get that low but this is all armageddon scenario figuring a dead batt and poor charge efficiency.
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60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[crazyvwvanman]

I didn't ask how long it would take, just how much energy would be needed from the aux battery. The phone battery only holds a certain amount of energy and that is roughly how much must come from the aux battery. I realize there losses and some small variables.

Mark

[crazyvwvanman]

You missed a key aspect which is the relative voltages of the 2 batteries in question. That puts your 5.1ah number way off, too high.
I'd say your efficiency assumptions are off too, but don't know that for certain.

Mark

[kamzcab86]

I don't have an iPhone, but I do have a USB amp meter in my van. I think my Android is something like 1.3 amps... I'll double-check when I get home next week.
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~Kamz
1986 Cabriolet: www.Cabby-Info.com
1990 Vanagon Westfalia: Old Blue's Blog
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"Real knowledge is to know the extent of one's ignorance." - 孔子

[Sodo]

For $13 you can read how many mAh passed thru this device.
a "USB Meter" on Amazon

The USB outlet adds some losses but it's probably not much different than the power that departed your aux battery.
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'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
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[Abscate]

It took more energy to makes these posts than the energy in a phone.



Just looking at my battery meter, it charged from 2100-2300 to full cap last night ona 1 amp brick at 5 volts, that’s 10 watt hours

So fir your 12 volt battery, that’s less than 1 amp hour

It’s marginally on par with the self discharge rate of a flooded lead scid battery!
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.ssS!

[DanHoug]

[jimf909]

[crazyvwvanman]

I think you meant to say .9 amphours so I'll agree, plus a little more for efficiency losses.
What meager info I have found for car charger efficiency indicates a 5% to 10% loss, far less than many home wall chargers waste.

Mark

[DanHoug]

so, Mark.... what's the application for determining the rilly small demand? curiousity? running an array on the edge? off grid budget balance? inquiring minds and all that.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com