How many amp hours of aux battery to charge a phone? |
8 amp hours |
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6 amp hours |
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4 amp hours |
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2 amp hours |
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20% |
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1 amp hours |
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80% |
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Total Votes : 5 |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9936 Location: Orbiting San Diego
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Posted: Sat Jun 05, 2021 2:59 pm Post subject: How many amp hours of aux battery to charge a phone? |
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If my iPhone 11 battery runs very low, how many amp hours of my aux battery capacity are needed to full charge it? |
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kourt Samba Member
Joined: August 13, 2013 Posts: 1947 Location: Austin, TX
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Posted: Sat Jun 05, 2021 4:07 pm Post subject: Re: How many amp hours of aux battery to charge a phone? |
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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 |
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SSWesty Samba Member
Joined: August 20, 2008 Posts: 732 Location: Bellevue
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Posted: Sat Jun 05, 2021 4:21 pm Post subject: Re: How many amp hours of aux battery to charge a phone? |
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I think you're in the 2 amp hour range +/-1 |
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DanHoug Samba Member
Joined: December 05, 2016 Posts: 4791 Location: Bemidji, MN
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Posted: Sat Jun 05, 2021 4:31 pm Post subject: Re: How many amp hours of aux battery to charge a phone? |
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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. _________________ -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 |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9936 Location: Orbiting San Diego
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Posted: Sat Jun 05, 2021 5:01 pm Post subject: Re: How many amp hours of aux battery to charge a phone? |
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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
kourt wrote: |
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 |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9936 Location: Orbiting San Diego
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Posted: Sat Jun 05, 2021 6:43 pm Post subject: Re: How many amp hours of aux battery to charge a phone? |
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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
DanHoug wrote: |
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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kamzcab86 Samba Moderator
Joined: July 26, 2008 Posts: 7923 Location: Arizona
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Posted: Sat Jun 05, 2021 6:49 pm Post subject: Re: How many amp hours of aux battery to charge a phone? |
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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. _________________ ~Kamz
1986 Cabriolet: www.Cabby-Info.com
1990 Vanagon Westfalia: Old Blue's Blog
2016 Golf GTI S
"Real knowledge is to know the extent of one's ignorance." - 孔子 |
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Sodo Samba Member
Joined: July 06, 2007 Posts: 9613 Location: Western WA
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Posted: Sat Jun 05, 2021 7:58 pm Post subject: Re: How many amp hours of aux battery to charge a phone? |
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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. _________________
'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb |
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Abscate Samba Member
Joined: October 05, 2014 Posts: 22668 Location: NYC/Upstate/ROW
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Posted: Sun Jun 06, 2021 4:49 am Post subject: Re: How many amp hours of aux battery to charge a phone? |
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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! _________________ .ssS! |
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DanHoug Samba Member
Joined: December 05, 2016 Posts: 4791 Location: Bemidji, MN
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Posted: Sun Jun 06, 2021 6:51 am Post subject: Re: How many amp hours of aux battery to charge a phone? |
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crazyvwvanman wrote: |
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
DanHoug wrote: |
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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ack!! you're right!! need to equivalent everything to watt-hours, which accounts for the voltage diff. oops! _________________ -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 |
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jimf909 Samba Member
Joined: April 03, 2014 Posts: 7472 Location: WA/ID
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Posted: Sun Jun 06, 2021 7:09 am Post subject: Re: How many amp hours of aux battery to charge a phone? |
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crazyvwvanman wrote: |
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
DanHoug wrote: |
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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As best as I can tell, iPhone 11 batteries are 3.7 volts and 3100 mAH so charging one from zero will consume 11.5 watt hours or .9 amps from your aux battery assuming it's @ 12.7 volts. _________________ - Jim
Abscate wrote: |
Do not get killed, do not kill others.
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Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
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crazyvwvanman Samba Member
Joined: January 28, 2008 Posts: 9936 Location: Orbiting San Diego
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Posted: Sun Jun 06, 2021 3:03 pm Post subject: Re: How many amp hours of aux battery to charge a phone? |
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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
jimf909 wrote: |
As best as I can tell, iPhone 11 batteries are 3.7 volts and 3100 mAH so charging one from zero will consume 11.5 watt hours or .9 amps from your aux battery assuming it's @ 12.7 volts. |
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DanHoug Samba Member
Joined: December 05, 2016 Posts: 4791 Location: Bemidji, MN
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Posted: Sun Jun 06, 2021 4:30 pm Post subject: Re: How many amp hours of aux battery to charge a phone? |
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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 |
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