What's the highest Amp USB car charger available?

EverythingApple

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#1
I have an old Griffin PowerJolt 2.1 Amp single USB car charger. I want a more powerful one. The Apple wall charger charges fast, while this one is so slow. I saw the Scosche ReVolt at 4.8 Amps but that's 2.4 Amps per USB.

Any suggestions?
 

Europa

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#2
2.1 amps is the highest the phone will accept. Are you using a 12-volt input in your car? That's what's slowing it down. Upgrading to a stereo with a built-in USB port will speed it up and eliminate the need for an adapter. All you'll need is a Lightning cable.
 

EverythingApple

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#3
2.1 amps is the highest the phone will accept. Are you using a 12-volt input in your car? That's what's slowing it down. Upgrading to a stereo with a built-in USB port will speed it up and eliminate the need for an adapter. All you'll need is a Lightning cable.
So a 2.4 amp charger will only put out 2.1 amps to the iPhone?
 

Europa

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#6
So my Griffin PowerJolt at 2.1 amp is fine. Better than the USB port on my car, which I read is only 1 amp.
You said it's slow. It might be charging at the same rate or lower than the USB port, in which case you might as well switch to the USB and simplify things. You didn't answer my other question so I'm not sure what your source is, but I'm assuming it's the 12-volt input in your car. Have you tried comparing charge speeds to the USB port?
 

EverythingApple

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#7
You said it's slow. It might be charging at the same rate or lower than the USB port, in which case you might as well switch to the USB and simplify things. You didn't answer my other question so I'm not sure what your source is, but I'm assuming it's the 12-volt input in your car. Have you tried comparing charge speeds to the USB port?
My source is my cigarette lighter. There's also an accessory port for a car charge that I haven't tried. The USB port is in another car that I don't drive anymore.
 
#9
2.1 amps is the highest the phone will accept. Are you using a 12-volt input in your car? That's what's slowing it down. Upgrading to a stereo with a built-in USB port will speed it up and eliminate the need for an adapter. All you'll need is a Lightning cable.
I don't think the 12 v car input voltage is what is slowing down the charge rate. All chargers put out 5v because that is the standard for USB. The 'flow' in the charge is related to the Amperage, and as you indicated, the iPhone only accepts up to 2.1 Amps. Regardless of the source voltage (12v for car, 120v for house) it is reduced to 5v by the charging device. A charger with a rated output of 5v at 2.4 Amps should charge at the same rate regardless of whether it is plugged into a wall, car, or other source. It gets more confusing than just looking for Amp ratings since many devices are rated on Power (watts) instead. Fortunately the conversion is simple, watts are simply Amps x Volts.
Code:
Source           Voltage    Current      Power
PC USB           5 volts    0.5 amps     2.5 Watts
iPhone Charger   5 volts    1.0 amps     5 Watts
iPad Charger     5.1 volts  2.1 amps     12 watts
The OP's device should provide the fastest charging possible, and if it isn't doing as well as his Apple wall charger (the 12 watt for iPad) then something is wrong with it.

While I'm not an electrician or EE, I believe the above is accurate. Comments or corrections are welcome.
 

EverythingApple

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#10
Maybe it's also because I use it while in the car to play music, listen to 5-0 Radio or use Google Maps navi. I should put it in the car charger and not use it and see how much % it changes over a set amount of time. Than do the same with the wall charger.
 

Europa

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#12
Maybe it's also because I use it while in the car to play music, listen to 5-0 Radio or use Google Maps navi. I should put it in the car charger and not use it and see how much % it changes over a set amount of time. Than do the same with the wall charger.
Yeah, that would have been helpful to know. I almost asked if you were using navigation, but then I thought the odds of you using it every time you drove were low and you would notice the difference and mention that it's only charging slowly with maps running. Maps draw a lot of power. I haven't really paid attention to this lately, but I remember my phone would charge to 100% fairly fast via USB in my car with music playing. But when I had a navigation app running and music playing, it could only keep up with the current charge. So if I left at 80% charge, it would end up around 80% when I arrived.

Test is without navigation and post back. I think you're find that it's quite a bit faster.
 

EverythingApple

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Yeah, that would have been helpful to know. I almost asked if you were using navigation, but then I thought the odds of you using it every time you drove were low and you would notice the difference and mention that it's only charging slowly with maps running. Maps draw a lot of power. I haven't really paid attention to this lately, but I remember my phone would charge to 100% fairly fast via USB in my car with music playing. But when I had a navigation app running and music playing, it could only keep up with the current charge. So if I left at 80% charge, it would end up around 80% when I arrived.

Test is without navigation and post back. I think you're find that it's quite a bit faster.
See my post above yours. But, I don't use the navi that much. I got my warranty replacement lightening cable from the Genius Bar. He looked at my phone for clicking and didn't hear anything. Than told me not to bring it in modified by third party apps as that voids the warranty. But he still looked at it.

Than I looked at car chargers there. They have ones by incase with maximum charge of 2.4 amps. I spoke to the sales rep there and told him if my current charger. It's probably not charging at proper amps as I've had it since the iPhone 3G or 4. So could that really be the problem?
 

TudorJ

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#14
The charger has a 2 amp fuse, you say. This is on the 12v input, not the 5v output. Look up Ohms Law to work out the current.
Also chargers do not, in lay man's terms, push the current to the device. The device pulls, draws, the current from the charger and Apple devices will only pull up to their rated current. You therefore cannot 'push' too much current to an Apple device. If the charger cannot support the full amount of current required by the device, the device will only pull up to the chargers maximum rating.
 

EverythingApple

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#15
The charger has a 2 amp fuse, you say. This is on the 12v input, not the 5v output. Look up Ohms Law to work out the current.
Also chargers do not, in lay man's terms, push the current to the device. The device pulls, draws, the current from the charger and Apple devices will only pull up to their rated current. You therefore cannot 'push' too much current to an Apple device. If the charger cannot support the full amount of current required by the device, the device will only pull up to the chargers maximum rating.
I understand this, but 2.1 amps can't be the maximum of the charger. Fuses are set using a safety factor. 75% of the fuse at ambient temperature is the safety factor. That being said, this charger is incapable of drawing more that 1.5 amps.
 
#16
I understand this, but 2.1 amps can't be the maximum of the charger. Fuses are set using a safety factor. 75% of the fuse at ambient temperature is the safety factor. That being said, this charger is incapable of drawing more that 1.5 amps.
A 2 amp fuse on a charger means it can only draw 2 amps at 12 volts (the feed or input side). That is equivalent to 24 watts of power (2a X 12v). The output side is only going to be 5v so the same 24 watts of power can support 4.8 amps (24w / 5v). This is why car chargers usually max out at having two 2.1 amp ports. Even using your suggested 1.5 amp max on the input side it would produce 18 watts (1.5a X 12v) and the output side maximum would then be 18w / 5v = 3.6 amps.
 
#18
So my 15-20 min ride home and in my car charger, with only checking this thread once through the app, my phone went from 14% to 23%.
That sounds pretty good to me. The only real way to test is to discharge to a specific percentage (anything except really high) and charge for 30 min in car with no use. Then discharge again to the same or close percentage and charge for 30 min with no use at home.
 

EverythingApple

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#19
That sounds pretty good to me. The only real way to test is to discharge to a specific percentage (anything except really high) and charge for 30 min in car with no use. Then discharge again to the same or close percentage and charge for 30 min with no use at home.
I'll try this. Thank you. Although, I also got a new lightening cable that was frayed at the end. Maybe that was the problem, but I'll try what you suggested.
 

Europa

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#20
I'll try this. Thank you. Although, I also got a new lightening cable that was frayed at the end. Maybe that was the problem, but I'll try what you suggested.
I argee with up10ad that your charging rate sounds pretty good.

Apple cables should be all-or-nothing. It's not going to charge slower if it's frayed. Most frayed Apple cables work fine. I still get them replaced because it's only a matter of time before they quit working altogher.