Max safe amps for car charger in us?

[jaltman]

I am surprised no one has piped up a little basic electricity here. A device draws the power its can use. The power is regulated to the battery to control the charge. The regulator is in the battery. But a laptop USB port with a power capacity of 2.5w can never provide more than what its capable of. 5 volts at .5 Amps = 2.5 watts. Your wall wart (car plug) is capable of more than that. I have wall warts rated from 10 watts (5V. x 2A) to 5 watts. (5V x 1A).

There must be some sort of use of the data lines to signal to the phone the limits so it can indicate USB or AC. I guess the regulator could be smart enough to conclude which it is based on the initial charge rate which would be the time of highest draw.

So, the maximum capacity of the power source will affect how fast a charge it is capable of, but the regulator of battery will control and limit the power consumed to what it decides is the right level. I have a 12v. 50A power supply to power my 100 watt radio transmitter. I could slap a big 5 volt regulator on it to control the voltage and use some car battery jumper cables to my phone (nice image, eh?) and the phone would be just fine.

 

[Tkbredx]

I am also getting really dumb lol. Ever'm after all the explanations. Here is the question I want to know...

Assuming this phone has a max of charging at 1 amps then if I bought a 1.8 amp charger it would only charge at 1 amps?

 

[jaltman]

The answer to your question is yes. If the maximum draw of your device is 1 Amp and you connect it to a 1.8 Amp charger it will draw 1 Amp.

It will charge at the maximum safe rate determined by the regulator in the phone. The current is referred to as current DRAW. That is, the unit being powered will draw current from the charger at the rate it consumes it. Until you hit the max of the supply, when it will not go up any further.

Think of this like a household light bulb. The voltage is 110v. Let me make the math easier to do and lets pretend its 100v. Your house has a master fuse of 100 Amps. The max power you can draw before the fuse blows is 100x100=10000 watts. Your 100 watt light bulb does not blow because 100 amps is available, it draws what it needs. 1 Amp. 100v x 1A = 100 watts. Remove the bulb and replace it with a 50 watt bulb. The current draw drops to .5 Amp because thats what it needs. 100v x .5 Amps = 50 watts. But if the electric company is having a bad day and only 45 watts is available to your house, the 50 watt bulb will dim because its draw exceeds the max available. Your light bulb is not harmed by the fact 100 Amps is available to it.

The battery in your phone is not like a light bulb. Its a smart device. It is capable of controlling its rate of charge and, as the battery fills, it reduces the charge until it is full and stops charging altogether. An automobile battery charger does the same thing, hard charge at first, taper off as it fills, trickle when its full. So, if your charger is capable of 1.8, but your phone is limited to 1.0 there is excess capacity available at the charger. Get a Y connector and plug in another phone. If your charger is capable of 50 A. get 50 Y connectors and plug in 50 phones. There is no harm in having more capacity than any single device requires.

Now all this applies to current capacity, but not voltage. Plug your phone directly into 100v and watch your teeny lil regulator cook itself to death in but a tiny little instant. All USB chargers are always 5 volts.

A moment, if I may on the cables to connect to the charger. Every piece of wire has resistance. The resistance of the wire consumes power by turning it into heat. The resistance of a given piece of wire is a matter of its diameter and length. For our purposes the length is short enough that the amount of heat generated is negligible. What do you get in a "charging cable" ? Maybe a lil larger diameter wires on the charging lines. I bet not. I bet its a marketing scam. I have never felt a USB cable get warm while in use charging. I got one of these lil cables on a retractor that winds it up when not in use. The wire bundle is really thin. I have never felt it get warm even when used to charge my tablets. I have never noted a slower charge when using it over one of my larger cables.

I do note that my little Sedio charging stand charges my phone slower that directly connecting the phone to the cable. Why? It has some electronics in it that deals with and lights some led's. That consumes power leaving less available for the phone. If I connect it to a 2A charger instead of the one that came with my phone I bet the charging rate goes back up to the full rate. Will I harm anything by doing so? Nope, not a chance.

Sent from my cm_tenderloin using Android Central Forums

 

[pcguys]

Excellent explanation JaltMan, very informative!

So, my only remaining question before I buy them is CaMiller's point about proprietary signaling for car chargers designated as ipad/iphone.

Is there one that will charge an ipad AND an android at full speed using a charging cable?

Thanks All,

Mike

 

[camiller]

The answer to your question is yes. If the maximum draw of your device is 1 Amp and you connect it to a 1.8 Amp charger it will draw 1 Amp.

It will charge at the maximum safe rate determined by the regulator in the phone. The current is referred to as current DRAW. That is, the unit being powered will draw current from the charger at the rate it consumes it. Until you hit the max of the supply, when it will not go up any further.

Think of this like a household light bulb. The voltage is 110v. Let me make the math easier to do and lets pretend its 100v. Your house has a master fuse of 100 Amps. The max power you can draw before the fuse blows is 100x100=10000 watts. Your 100 watt light bulb does not blow because 100 amps is available, it draws what it needs. 1 Amp. 100v x 1A = 100 watts. Remove the bulb and replace it with a 50 watt bulb. The current draw drops to .5 Amp because thats what it needs. 100v x .5 Amps = 50 watts. But if the electric company is having a bad day and only 45 watts is available to your house, the 50 watt bulb will dim because its draw exceeds the max available. Your light bulb is not harmed by the fact 100 Amps is available to it.

The battery in your phone is not like a light bulb. Its a smart device. It is capable of controlling its rate of charge and, as the battery fills, it reduces the charge until it is full and stops charging altogether. An automobile battery charger does the same thing, hard charge at first, taper off as it fills, trickle when its full. So, if your charger is capable of 1.8, but your phone is limited to 1.0 there is excess capacity available at the charger. Get a Y connector and plug in another phone. If your charger is capable of 50 A. get 50 Y connectors and plug in 50 phones. There is no harm in having more capacity than any single device requires.

Now all this applies to current capacity, but not voltage. Plug your phone directly into 100v and watch your teeny lil regulator cook itself to death in but a tiny little instant. All USB chargers are always 5 volts.

A moment, if I may on the cables to connect to the charger. Every piece of wire has resistance. The resistance of the wire consumes power by turning it into heat. The resistance of a given piece of wire is a matter of its diameter and length. For our purposes the length is short enough that the amount of heat generated is negligible. What do you get in a "charging cable" ? Maybe a lil larger diameter wires on the charging lines. I bet not. I bet its a marketing scam. I have never felt a USB cable get warm while in use charging. I got one of these lil cables on a retractor that winds it up when not in use. The wire bundle is really thin. I have never felt it get warm even when used to charge my tablets. I have never noted a slower charge when using it over one of my larger cables.

I do note that my little Sedio charging stand charges my phone slower that directly connecting the phone to the cable. Why? It has some electronics in it that deals with and lights some led's. That consumes power leaving less available for the phone. If I connect it to a 2A charger instead of the one that came with my phone I bet the charging rate goes back up to the full rate. Will I harm anything by doing so? Nope, not a chance.

Sent from my cm_tenderloin using Android Central Forums

The way the USB battery charging spec of 2007 is written (http://en.wikipedia.org/wiki/Universal_Serial_Bus#Power sorry I don't have a link to the spec handy), the device knows it can draw up to 1.5A if the two data lines are shorted together. A "charging cable" does this internally, probably at one end or the other. A AC to USB adapter or car charger can do this internally as well by shorting the data pins together.

Apples 10W/2A charger puts 2.8v on one of the data lines and 2v on the other (I forget which is which) to tell an iPad that it can pull up to 2A. Earlier iphone/ipod wall chargers put 2v on each data line which will limit the device draw to 500mA. MintyBoost - The mysteries of Apple device charging

This is why you need to use a "charging cable" with wall/car chargers made for apple products. The Apple oriented chargers do not internally short the data lines so most android phones will treat it like a 500mA source. The charger that ships with your android phone has the data lines shorted internally so it doesn't matter what cable you use.

 

[pcguys]

Excellent clarification. I now feel much smarter on this topic then I've ever imagined.

I've shared your knowledge with some coworkers - very interesting!!!

I'm off to buy an ipad car charger and some dedicated charging only cables.

I feel soo versatile now!

Thanks again,
Mike

 

[Tkbredx]

Thanks so much. I feel a lot better about this subject now that you've enlightened me.

I think this is my last question...

What's the max charging for the gs3? I've heard some people say the charger is 700 but the phone is capable of 1000. Is this true? (I just want to charge my phone at the fastest rate possible. So after this I will buy the needed charger)

 

[Jodie Schuman]

I don't know what everybody's been talking about the S3 charger only having .7 amps. I just got one and the charger is rated at 1 amp.

 

[PWhy]

Hi, I notice the confusion about the .7 or 1 amp charger for the S3 and wanted to post my findings.

The wall charger that came with my phone is 1 amp, but I recently bought one off of ebay and it is rated at .7 amp. I was under the assumption that these "oblong" shaped chargers were all rated the same, but I guess not. Posted pictures of the two below.

 

[PWhy]

Edit: Sorry, dup post.

 

[winmod21]

This thread seems to have a mind for duplicate posts! lol

Moreover, this is a very interesting thread read if you read this thread from it's OP. Thanks to all the contributor's. I'm feeling considerably less dumb too !
My stock 'Samsung Travel Adapter' / wall charger ? that shipped w/ my AT&T GS3 ? is identical to PWhy's 'Came with GS3' in the photos above;
5.0v ~ 1.0a (1 Amp).

So, here's my less dumb, but still pretty dumb question . . . .

Well, first the preamble . . .we have a car charger we purchased at our local AT&T store, approx. 3 years back ? if that matters, when we did our 2nd iPhone upgrades. The charger has always worked great ? but of course has the 30-pin male end ? which fits into the iPhones/iPods. The car charger also has one USB port on the back end of the charger/converter? that pushes into the vehicles cigarette lighter outlet. The charger is: 12~24V w/ 2A. No brand name, but sold by AT&T store.

Ok, question: Should or would it be safe to use our USB-to-microUSB data/charging cables that shipped with our android phones [a GS3 & Note], in our vehicles, by plugging them into the USB port on the back of said vehicle charger?again, meant for an Apple iPhone/iPod w/ 30-pin male end?but that also has an open USB port on the plugs' lighter outlet end? Or would it be safer/better to use a 'charging only' USB-to-microUSB cable?

 

[worwig]

WHAT YOU GET:
The S3 uses the defined Micro USB charging standard. If the charger or cable has the data lines shorted, it thinks it is a AC charger. If they are not shorted, it thinks it is plugged into a USB port on a PC.
When the phone thinks it is plugged into an AC charger, the phone pulls a maximum amount of current of about 800ma. If the charger is 1 amp, it pulls 800ma. if the charger is 2000 amps, it pulls 800ma. Now if the charger is LESS then 800ma. the phone may fall back to the lower current of a USB port. But, it makes no difference if the charger is 1 amp or more, the phone limits the current. Just make sure it is a 5 volt charger.
When the phone is plugged into a USB port (the data lines are not shorted), the it pulls a miximum current of between 300 and 400ma. Even if you have a 2 amp charger, if it doesn't have shorted data lines, the phone will only pull around 300ma. If the charger DOES have shorted data lines, but it can't handle the 800ma. AC charger setting, the phone falls back to the lower USB port rate of about 300ma. Again, just make sure it is 5 volts.
I use a low speed charger (that does not have shorted data lines) for overnight charging. The battery stays cooler at the lower rate, so should last longer. It takes 4 or 5 hours for a full charge, but I don't care. I keep a fast rate charger handy during the day in case I need a quick charge.

 

[pcguys]

Nicely stated, thank you!

 

[PWhy]

Thanks for that information.

If I use the .7 amp ac wall charger, will the phone assume it is a 1 amp? I'm concerned that the battery stats will get messed up if this is true. Or will the phone recognize that it is only drawing .7 amps? I like your idea of using a lower amp charger for overnight, I may use the .7 amp charger for overnight if it is "safe". Thank you.

 

[worwig]

Thanks for that information.
If I use the .7 amp ac wall charger, will the phone assume it is a 1 amp? I'm concerned that the battery stats will get messed up if this is true. Or will the phone recognize that it is only drawing .7 amps? I like your idea of using a lower amp charger for overnight, I may use the .7 amp charger for overnight if it is "safe". Thank you.

If it is 5 volts, it is safe.
It doesn't matter what the current rating is. If it is 5 volts, it is safe.
Also, if it is 5 volts, it is safe.
Hopefully that is clear. 5 volts=safe. The end.


Now as for the charge RATE, that depends on if the data lines are shorted and if the charger has a current ability of 800ma or so. I know that you can install the app 'Battery Monitor' and it will let you know if your charger is a USB (low rate) or AC (high rate with shorted data lines) and what the current is.

Just to note:
I use my smartphone as a GPS on the handlebars of my motorcycle. I designed a charger to charge the phone, at maximum brightness, while the GPS and software are running. I ended up using a 5.25 volt charge voltage, had the data lines shorted, and the phone pulled close to 1 amp (but still less then 1 amp). That ran the phone at max brightness, and charged the battery faster, while pulling closer to 1 amp. All was well. Except the phone would get VERY hot. So I ended up dropping back to 5 volts, which is about 800ma. Everything is still fine, and it runs much cooler, but the battery charges at a slower rate since so much current is going to driving the display at max brightness in the sunlight.

 

[winmod21]

Thanks worwig.

Well, after 7 weeks with no vehicle charger for our androids (and, actually wondering if we really need one; but probably will), I decided to order a 'charging only' cable?that's basically just like the USB-to-microUSB cables that shipped w/ the phones?but for charging only w/ no data.
And also, an: Apple ipad Iphone docking 30pin female to Micro usb 5p male data charge adapter?to plug onto the [30-pin end] of our iPhone [12~24V w/ 2A] vehicle charger?that has always charged our iPhones really well. Just didn't want to have to throw-away or try to sell the good working iPhone charger.

Hope I understood your helpful posts worwig , and everything works well. :-\

 

[meyerweb#CB]

I took a look and using the Amazon dual-port 2.1A charger I referenced above, my S3 battery status says Charging (AC). Using the same cord but plugging into a laptop USB port, it says Charging (USB).

Dave

Every AC and Car USB charger I have is recognized as an "AC" charger, rather than USB. As long as it's not a charger aimed specifically at Apple products, I think this will be true. Only when I charge from and actual USB port on a computer does the phone recognize it as a lower current USB device.

 

[winmod21]

UPDATE:
Received this: Apple ipad Iphone docking 30pin female to Micro usb 5p male data charge adapter?today . . AND IT DOESN'T WORK !

The iPhone 30-pin male plug on the end of the vehicle charger ? plugs into the adapter fine ? the adapter microUSB plugs into the GS3 fine . . . but zero, nothing, none, naught, nil, nada, nix, null, zero, zilch, zip, zippo, aught, goose egg . . .and a big fat 'O' current. No charge detected at phone.

Not that anyone else was gonna try this hair-brained idea. lol

 

[winmod21]

However, this PureGear Charge Only Cable for Universal Micro USB ? is a great charging cable, imo!
First, because it's a 'charging only' cable, it charges at full (AC) current? off the vehicles (DC) converter? not (USB) current (which, if I've got this straight, USB charges at either 300mAh's or 500mAh's less than AC?).
Charges our android phones in our vehicles practically as fast as the stock AC USB-to-microUSB charging/data cable; it seems very well made with what appears to be high quality materials; cable doesn't heat up, and so far either has our GS3 or Galaxy Note; fits snugly into the GS3 & Note microUSB charging/data ports (in fact, just as good or better than the stock AC charging/data cable).

Would highly recommend this cable to anyone who wants a: 'charging only' cable. Both thumbs way up!

[ UPDATE ]: When I ordered a few of these 'charging only' (no data) cables last week, they were selling for only $4.36 /ea. However, now I see that they've jacked the price up to $9.99 I wonder what's up with that? Do Amazon Seller's?routinely jack-up the selling prices for their items? as sales of the item(s) increase?

 

[mllyou]

This is an informative thread. Thanks to all.
So my understanding is that as long as a charger (AC, car charger, or whatever) has the same voltage as the original charger, you can plug it into a phone, a tablet, etc. (with the right plug, USB, or one of those barrel connectors). If the amperage of the charger is higher than required, it will do no harm to the charger or the battery/device: it will charge at a suitable rate determined by the battery and regulator. If the amperage of the charger is less than required, it will not charge at a maximum rate, but a lower rate, or not at all if there is not enough juice, so to speak; and again, there is no harm to the charger or the battery/device.

I have one of the newer tablet pc, the Cube U30GT2 (a very nice Android tablet for the price of $300, more or less), but the 12V 2A charger was DOA. I have a Seven Star SS105 18Watt power supply that can be set to output 12V with the right plug and polarity for the Cube. The SS105 is rated at max 1A (1000 mA). However, if I measure the open load voltage at 12V setting with a multimeter, I get 18 to 19V. I can also set it at 9 V and the measurement would then be about 12V (I haven't actually checked this, but this is just for .easier computation). At 9V, the power supply should be able to source 2A.
Questions: (1) Is there a difference between what we normally call an AC charger or AC adapter (as supplied by phone and tablet manufacturers), and an AC-DC power converter (which the SS105 is)?
(2) Is it safe to use the SS105 as a "charger" to the Cube?
(3) If it is safe, which setting should I use, the 9V or 12V?
Note that because the Cube has a barrel connector (2.5mm OD/0.8mm pin), there is no need for a USB charging cable.

If it is not safe, instead of buying a new original charger, I plan to buy a LiPo balance charger (for all rechargeable battery types) which not only have the regulation for charging, but also an LED screen to display the charging (or even discharging) progress. Another question:
(3) Is it okay to charge the Cube from such a balance charger? My concern is the duplication of regulators, one from the balance charger, and one from the battery itself.

If that is not okay, then I have a third proposition: Use a regulated switched mode power supply from an old PC that supplies a steady 12V at up to at least 10A, and connect the molex connectors to the right plug, observing polarity.
(4) Would that be safe to charge the Li-Ion or Li Polymer batteries in an Android tablet?

I am a newbie. There have been a lot of reported problems with charging (even with manufacturer's charger) on Android tablets due to upgrade to Android 4.2 (for example, Nexus 7) and some solutions have to do with bypassing the battery built-in control circuits. That's what brings me to this forum.

Many thanks.
Mllyou