# CommercialHow much power would a smart phone drain fr a 12 volt 150 amp/h battery when charging

Discuss How much power would a smart phone drain fr a 12 volt 150 amp/h battery when charging in the Auto Electrician Forum area at ElectriciansForums.net

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#### David Hyde

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Hello
I wonder if you could help.. here is our problem/ question.

How much power would a modern smart phone drain from a 12volt,
for example a 150 amp hour battery. From flat phone battery to full phone battery.

If we wanted to charge 400+ phones
How would we work out how many batteries are required to safely charge 400+ mobile phones. Flat phone to full.
repeatedly.

How long would it take to recharge eg a 150 amp hour battery, using van alternator, wind, solar as back up.
any help would be amazing.

I know its a big ask, we have rough figures. but need summat more accurate.
ie flat iphone 4 uses 0.09 amp when flat to .01 when almost full on 12vlot supply

All the best
dave

#### telectrix

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Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

@ 0.09A per phone, 10 phones would take 0.9A, round that up to 1A, and a 150Ah battery would be dead in 150hours ( in practice it would be less, say 100 hours to the point when the output voltage was seriously dropping ).

Last edited:

#### Lucien Nunes

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Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

Got a bug in your abacus there Tel! 9A per 100 phones. Also, I think those current figures are too low. The charger or host can tell the device what maximum current is available, but typical iThings require 0.5A to 1A at 5V for normal charging, i.e. a minimum of 2.5W. Allowing for charger losses maybe 0.3A at 12V, so 30A per 100 phones. However, what we really need is total energy input during the charge cycle, which is the next thing to research...

#### telectrix

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Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

oops. was the 100 phones was wrong. must have put an extra zero in. meant to say 10. now corrected. cheers.

#### HandySparks

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Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

...typical iThings require 0.5A to 1A at 5V for normal charging, i.e. a minimum of 2.5W. Allowing for charger losses maybe 0.3A at 12V, so 30A per 100 phones. However, what we really need is total energy input during the charge cycle, which is the next thing to research...

So if it took typically one hour to charge a device (guess), you might get enough power out of a 150Ah battery to charge your 400 phones once each.

Assumes a fully charged 150Ah battery working at close to its rated capacity.

OP
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#### Lighthouse Phil

Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

Interesting Question.
I'm in the process of having a USB type charger installed into our solar control cabinets so that we can charge mobile phones and tablets in emergency situations.
We hope we never have to use them, but,,, you never know...

OP
D

#### David Hyde

Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

We already have a 240 volt system that has outlets and has been full with 250+ phones and battery's being charged at once
For this we buy a 16amp supply and have had no problems.
this is why we struggle with the maths. as even at .09 amps per phone, and with 250 plugged in plus lights, caravan, lap top etc.. no power problems at all.
The next system we really would like to go off grid. and use batterys and have a bigger phone charge capacity. ie more phones.....

any ideas?

Hello
I wonder if you could help.. here is our problem/ question.

How much power would a modern smart phone drain from a 12volt,
for example a 150 amp hour battery. From flat phone battery to full phone battery.

If we wanted to charge 400+ phones
How would we work out how many batteries are required to safely charge 400+ mobile phones. Flat phone to full.
repeatedly.

How long would it take to recharge eg a 150 amp hour battery, using van alternator, wind, solar as back up.
any help would be amazing.

I know its a big ask, we have rough figures. but need summat more accurate.
ie flat iphone 4 uses 0.09 amp when flat to .01 when almost full on 12vlot supply

All the best
dave

OP
G

#### Geordie Spark

Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

oops. was the 100 phones was wrong. must have put an extra zero in. meant to say 10. now corrected. cheers.

Have you thought about a change of career??

Maybe fitting wet UFH systems?

OP
D

#### David Hyde

Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

Have you thought about a change of career??

Maybe fitting wet UFH systems?

Nope nope

#### HandySparks

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Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

...this is why we struggle with the maths. as even at .09 amps per phone, and with 250 plugged in plus lights, caravan, lap top etc.. no power problems at all.
The next system we really would like to go off grid. and use batterys and have a bigger phone charge capacity. ie more phones.....

any ideas?

Yes. You've already given some charging current figures in your first post. You need to re-do the measurements with more detail and using a representative sample of phone types. If you know how long it takes to charge and the average charging current for a few different phones, then the maths is fairly straightforward.

#### Lucien Nunes

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Re: How much power would a smart phone drain fr a 12 volt 150 amp/h battery when char

Ball park figures only:
16A x 230V = 3680W available from your mains supply
12V x 150Ah = 1800Wh stored in your battery
1800 / 3680 x 60 = 29 mins
So, under ideal conditions, your 150Ah battery would supply the same amount of energy as the 16A supply gives you in 29 minutes before being totally flat. Of course you can't get it all out that fast - the Ah capacity is normally quoted at the 20 hour rate, so you can have 150/20 Ah = 7.5A for 20 hours. Any greater current will give you less total energy because the efficiency of the battery drops off. In practice, even at the 20h rate, you probably can't bank on more than 120Ah cyclic while averaging 12V and not killing the battery.
12 x 7.5 = 90W output at 20h discharge rate
3680/90 = 41, i.e. the maximum useful power output of your battery is about one fortieth (2.5%) of what you can draw from the 16A supply, and it will be flat after 20 hours.
If a phone requires 1 hour charging time at 5W input (or equivalent longer charge with tapering consumption) you can charge 20 batches of 18 phones, one batch per hour, for a total of 360 phones. If you want to charge more than 18 at a time, the total number charged will be less before the battery is flat. This seems optimistic, it does not include conversion losses or adverse battery conditions, and the figures are very rough. You must get exact energy input per charge, the whole thing depends on this data.

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