Develop Bugs

High current car charger

Anybody come across a car charger that is high current like the HTC wall charger?

Most car chargers are classified as "rapid".

Anything designed to charge an iPad (2.1A versus the typical 1A) will give you plenty of juice. I use the Scosche reVIVE II with Pandora, Bluetooth, and GPS Navigation all on and still have enough power to positively charge my battery.
Fair warning, though, this will cause the phone to get real hot (I've had the overheating warning lights flash twice so far), so make sure you have plenty of ventilation around the phone, keep it out of the sun, etc etc.

Any charger that is at least 1 amp. will do. The phone 'pulls' a max of around 0.85 amps. No need for more then 1 amp.
If it has a replaceable cable, it must be the heaviest gauge, shortest cable, that you can use. I have seen long cheap thin cables that drop over a volt, and the Thunderbolt charges really slowly.
The charger or cable have to state that they for rapid charging. To rapid charge, you need to have the USB D- and D+ lines shorted. If that are not shorted, the Thunderbolt limits the charge current to around 0.35 amps. thinking it is connected to a PC. If they are shorted, letting the Thunderbolt know it can be rapid charged, you get up there around 0.85. You can easily modify the charger for high rate if it is good for at least an amp.
And in the end is heat. Heat and lots of it. It will damage the battery. So put it out of the sun and in cool air like near a vent.

Motorola Rapid Charger on Amazon is the best. I bought two.
http://www.amazon.com/Motorola-Vehi...Q9CA/ref=sr_1_1?ie=UTF8&qid=1309959388&sr=8-1
Review off Amazon
Genuine Motorola charger in retail packaging. 4.75-5.25V 950mA output, works w/ most micro-USB phones like Incredible, etc., June 11, 2010
By
David Pearlman "sound fanatic" (Arlington, MA) - See all my reviews
(TOP 500 REVIEWER) (VINE VOICE) (REAL NAME)
Amazon Verified Purchase(What's this?)
There are so many sketchy sellers selling phone chargers out there, that it can be a bit scary. The problem is that if the charger is poorly made, the output of the charger can be out of spec and can, in some cases, fry the phone you connect to it.
For that reason, when it comes to phone chargers, you should stick to name brands. (They are all made in China, but the name brand ones are usually subject to stricter QA).
When I found this charger on Amazon, SOLD BY AMAZON, I jumped on it. It's a MICRO USB car charger, made for Motorola and sold under the Motorola name, in retail packaging. The rated output is 4.75-5.25V and 950mA.
This charger should work fine with most any phone that uses the MICRO USB connector. The key number to pay attention to is the second one, the rated amperage. This is the MAXIMUM amount of current that the phone can request from the charger. A typical USB port on a PC provides as little as 100mA, and few provide more than 500mA. So this charger should charge your phone faster than when it's connected to a PC. A few phones out now can use up to 1000mA. But that just means they CAN use that amount. If 950mA is provided, they'll still charge, just a bit more slowly.
Note that the amperage (second number) merely tells you how much the charger CAN supply, if requested. The phone itself is responsible for asking for the current. That is to say, if this charger can provide 950mA, but your phone can only use 300mA--no problem. Your phone asks for 300mA and the charger provides all of what is requested. If, on the other hand, your phone can use 1000mA, this charger will provide all it can, which is 950mA--a wee bit less than the max asked for. That's also not a problem; it just means your phone will charge a little bit (not much in this case) more slowly. The rated voltage for this charger is presented in a range of 4.75-5.25V. The "ideal" voltage for a USB charger of any type if 5V. And most chargers for home use are rated right at 5V. But car chargers work in a noisier environment and thus you have the range. This is where a cheapo charger can really do damage, as some of them are poorly regulated and can provide voltages that are WAY out of spec. Again, when you can get a name brand charger from a seller you can trust (Amazon) for such a reasonable price, it's very foolish to consider the cheapo no-names.
This is an excellent quality name brand travel micro USB charger at a price that beats the no-name junk from third party sellers. What's not to like?
BE SURE TO ORDER IT FROM AMAZON AND NOT ONE OF THE THIRD PARTY SELLERS, as some of those have been known to make mistakes with respect to what they ship relative to the listing. I can confirm that Amazon is shipping the P513 /89143N charger, as pictured.
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ddgarcia05 said:
Motorola Rapid Charger on Amazon is the best. I bought two.
http://www.amazon.com/Motorola-Vehi...Q9CA/ref=sr_1_1?ie=UTF8&qid=1309959388&sr=8-1
Review off Amazon
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I've been contemplating buying this one, but I'd like to ask you if it charges your battery with navigation+music going? I have a usb charger in my truck, and with both of those going it just manages to keep my battery level where its at, sometimes losing a % or two.

kr0n1c said:
I've been contemplating buying this one, but I'd like to ask you if it charges your battery with navigation+music going? I have a usb charger in my truck, and with both of those going it just manages to keep my battery level where its at, sometimes losing a % or two.
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From what I've read in the past here on XDA and on the reviews for the charger (on amazon) you shouldn't have a problem. The second review for the charger on amazon states that the reviewer was looking for a charger which actually charged his phone will using GPS and that he found it. It's a very well built charger and cheap. It's made my Motorola and sold by Amazon so buy with confidence.

kr0n1c said:
I've been contemplating buying this one, but I'd like to ask you if it charges your battery with navigation+music going? I have a usb charger in my truck, and with both of those going it just manages to keep my battery level where its at, sometimes losing a % or two.
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It does indeed charge. I've had it since my original Droid and was concerned when I updated to the TB but it will charge the TB no matter what you're doing (I've had Nav running while on a phone call with BT and searching the internet and it still showed it was charging). Just be prepared for your phone to get HOT!! Great charger.

worwig said:
Any charger that is at least 1 amp. will do. The phone 'pulls' a max of around 0.85 amps. No need for more then 1 amp.
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Actually, the phone will pull more than 850 mA. You're probably basing that on using a battery monitor, which only shows the flow of current into/out of the battery. I've seen 800 mA into the battery at the same time I have display, GPS and a phone call going, which is definitely more than an additional 50 mA. It wouldn't surprise me if the phone can take advantage of something more than 1A, since I see a battery drain of more than 200 mA with all of that going when not on the charger.

kr0n1c said:
I've been contemplating buying this one, but I'd like to ask you if it charges your battery with navigation+music going? I have a usb charger in my truck, and with both of those going it just manages to keep my battery level where its at, sometimes losing a % or two.
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I have that Motorola charger and am a heavy GPS user. It charges the battery as if it were plugged into the wall. You'll be very satisfied.

mike.s said:
Actually, the phone will pull more than 850 mA. You're probably basing that on using a battery monitor, which only shows the flow of current into/out of the battery. I've seen 800 mA into the battery at the same time I have display, GPS and a phone call going, which is definitely more than an additional 50 mA. It wouldn't surprise me if the phone can take advantage of something more than 1A, since I see a battery drain of more than 200 mA with all of that going when not on the charger.
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No, that was measured at the 5 volt power supply, based upon a lab power supply. I did a lot of experimenting when I developed the charger and phone mount for my motorcycle. And to get the 850ma from the power supply, I used a very short, maybe 8 inch, USB cable, and a charge voltage close to 5.3 volts. With 5 volts at the power supply, it would only pull about 650ma from the power supply. That was due to the voltage drop in the USB cable. With the 5.3 volts at the power supply, I was getting close to an actual 5 volts at the Thunderbolt. I never measured the current at the battery, but I could see it being a bit more then the 850ma in, if there were a switch mode supply in there.
Though I like the Battery Monitor widget as a rough guide, I never tested to see if the battery current and the battery monitor are accurate.

Does anyone know if the included HTC ac adapter and cable will charge faster than using your pc with the included USB cable?

happimeal said:
Does anyone know if the included HTC ac adapter and cable will charge faster than using your pc with the included USB cable?
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Absolutely.
A PC USB port is limited to under 500ma. The Thunderbolt appears to to limit PC USB draw to about 350ma. I haven't measured the actual current in the HTC charger, but it is a high current charger, and charges my Thunderbolt very quickly. Battery Monitor widget shows high battery charge rates. I suspect it is getting near the max rate up near 1 amp.

worwig said:
Absolutely.
A PC USB port is limited to under 500ma. The Thunderbolt appears to to limit PC USB draw to about 350ma. I haven't measured the actual current in the HTC charger, but it is a high current charger, and charges my Thunderbolt very quickly. Battery Monitor widget shows high battery charge rates. I suspect it is getting near the max rate up near 1 amp.
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HTC charger states 5V/1A on the charger itself.

You can use the Palm car charger for $3.75+tax, free shipping. it is 5V/1A, same rating as the HTC wall charger.
Go here for 25% off
http://www.wireless.att.com/cell-ph...otion/accessories.jsp?source=EC0A0011600jtl10
Add product here, must add to cart to see 25% discount.
http://www.wireless.att.com/cell-ph...027&q_sku=sku4720234&q_manufacturer=&q_model=
Also, if so inclined, you can lop the top off of the charger so that you can use any usb cable (ipod, iphone, anything)

dpham00 said:
HTC charger states 5V/1A on the charger itself.
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That doesn't mean much. That is the MAX the charger can output. The amount that the Thunderbolt will pull varies. If it thinks it is plugged into a USB, it will be less then 500ma. even if the charger is capable of 10 amps.

worwig said:
That doesn't mean much. That is the MAX the charger can output. The amount that the Thunderbolt will pull varies. If it thinks it is plugged into a USB, it will be less then 500ma. even if the charger is capable of 10 amps.
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i have used the Palm car charger, checking with bmw, it shows around 850ma, same as on my htc charger.

worwig said:
Any charger that is at least 1 amp. will do. The phone 'pulls' a max of around 0.85 amps. No need for more then 1 amp.
If it has a replaceable cable, it must be the heaviest gauge, shortest cable, that you can use. I have seen long cheap thin cables that drop over a volt, and the Thunderbolt charges really slowly.
The charger or cable have to state that they for rapid charging. To rapid charge, you need to have the USB D- and D+ lines shorted. If that are not shorted, the Thunderbolt limits the charge current to around 0.35 amps. thinking it is connected to a PC. If they are shorted, letting the Thunderbolt know it can be rapid charged, you get up there around 0.85. You can easily modify the charger for high rate if it is good for at least an amp.
And in the end is heat. Heat and lots of it. It will damage the battery. So put it out of the sun and in cool air like near a vent.
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Click to collapse
um, i am aware that any charger that will do 1A will do. that was my question, what car charger will do 1A. Alot of times, they dont have that info listed on pages that are selling them.
and the whole thing about the D- and D+ shorted together, i do not believe. the HTC cable that came with the phone does rapid charging and i use it for data all the time too. if they D- and D+ was shorted, i would not be able to use it for data transfer. not unless the HTC charger shorts them internally inside the charger.

leoingle said:
unless the HTC charger shorts them internally inside the charger.
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Bingo!!

leoingle said:
um, i am aware that any charger that will do 1A will do. that was my question, what car charger will do 1A. Alot of times, they dont have that info listed on pages that are selling them.
and the whole thing about the D- and D+ shorted together, i do not believe. the HTC cable that came with the phone does rapid charging and i use it for data all the time too. if they D- and D+ was shorted, i would not be able to use it for data transfer. not unless the HTC charger shorts them internally inside the charger.
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Yes, it is hard to find the current info online or even on the package sometimes.
Yes, it is shorted in the charger. I have seen it done in the cable and the cable can't be used for data of course. Not sure why anyone would do that, but they do.

Compatibility with Nokia fast microUSB chargers

The Samsung charger adapter which comes in the box is very slow in nature. It take more than 2 hours to charge my phone. I was wondering if I can use the following Nokia brand chargers which are fast chargers?
Nokia Charger Adapter CA-146C
Nokia Fast Micro-USB Charger AC-10

It won't make any difference the phone decides what current it draws from the charger, so it'll take just as long to charge.

Are you really sure about this? Can you link me to some articles which confirm this.
Even I was thinking about purchasing AC-10 charger from Nokia.

How fast is the nokia charger?
0-10% -> 100% in an hour or less?

Joey2o11 said:
It won't make any difference the phone decides what current it draws from the charger, so it'll take just as long to charge.
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I'm not sure about this. I have a friend with a Blackberry Playbook and he reckons his phone charges much faster if he uses the charger from that.
The "stock" S2 charger is 700mA - it doesn't take a genius to work out that for a 1650mAh battery this will take about 2.5 hours to fully charge the battery under ideal conditions (phone off) or anything from 3-6 hours with the phone on, depending all what's running or if you're using the phone while it's charging.
Which is all pretty ridiculous - ok we're comparing apples and oranges when we compare a S2 to the likesw of a Nokia, but I do miss the days when I could charge my phone in an hour and have it last two or three days. I thought my Blackberry was bad but at least I can usually squeeze a full day out of it...
The only wall wart I had lying around that was more than 700mA was a 5V 2A supply. I've tried with that which works, but the phone chokes with a "battery overtemp" warning after about 10 minutes - which tells me I AM pumping more into the battery than it can handle. This would suggest that there IS a happy medium where we can optimize the battery charge time - I'm bust looking for a 1A supply...

I have TWO AC-10Xs, and am using it with the Ninphetamene kernel (which comes with increased charge input mods to 800ma) fine. Charges to full in about 2.5-3 hours.
I've never gotten overcharge errors either.

Hi,the usage of more powerful charger will eventually reduce lifespan of your battery. This comes from basic physics, materials and so... Higher mA means faster current, which wear the material of the capacitor - battery.

I have capdase 2 USB car charger that was used for my old iphone device.
It outputs 1A.
is it safe to use it?
I tried to charge with it for 10-15minutes or so, and didnt recognize any suspicious warmups...it reached 41~degrees while at the moment im charging and using it as a hotspot and its on 38 degrees.

DobermanS said:
Hi,the usage of more powerful charger will eventually reduce lifespan of your battery. This comes from basic physics, materials and so... Higher mA means faster current, which wear the material of the capacitor - battery.
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The phone (specifically, the kernel) limits charge coming in, and there MUST be hardware limiters on the batteries and the phone themselves (which, in some cheapo batteries DON'T WORK and results in them frying themselves and the phone in process) and the batteries are replaceable anyway.

eranyanay said:
I have capdase 2 USB car charger that was used for my old iphone device.
It outputs 1A.
is it safe to use it?
I tried to charge with it for 10-15minutes or so, and didnt recognize any suspicious warmups...it reached 41~degrees while at the moment im charging and using it as a hotspot and its on 38 degrees.
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i use htc wall charger rated at 1A and having no proplem with ,a pc USB port is capable of 1A and we all know there are no problem ,even so there are no visible improvement in charging time because as someone said the charging current is automatically regulated

ledavi said:
i use htc wall charger rated at 1A and having no proplem with ,a pc USB port is capable of 1A and we all know there are no problem ,even so there are no visible improvement in charging time because as someone said the charging current is automatically regulated
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That's good to know that the current is regulated by the device.
Is there a software to see what is the current taken by the phone?
As long ad the temperture isn't higher than 45degrees is it ok?
By the way, Im pretty sure that usb outputs 0.5A and not 1A
Sent from my GT-I9100 using XDA Premium App

battery monitor widget

It seems logical to be able to use all chargers as smartphones all have micro usb .
(I 'm not sute that's mean something in english, sorry)

Great widget! thanks.
I really like the data it gives!
Sadly, while charging with my .7A original charger & meanwhile giving a hotspot to my laptop, it shows that only 76mA comes in!
hehe, gonna take forever to charge the battery this way.

i doubt this. i'm still worried about the compatible problem~~~

After two days with the battery monitor widget Im affraid itself it drains the battery.
could it be it affects the battery?
settings are regular, it monitors changes every 60seconds

Let's see if I can help make things a bit clearer. Feel free to correct where I may be off.
The Nokia thing, it's not a charger. It's a power supply.
The "charger" is built into your phone, hardware-wise.
How can I prove it?
Take the Samsung supplied cable, plug it into your computer. You'll see that your phone is charging too. No, the cable is not a charger. Do you think your computer is a special built charger for your phone? Hardly.
The charging circuit is within the phone, and thus charging the battery when there's available power.
Ok, so we have the charger (i.e. the mobile phone), we have the battery, we need the power. Where do we get power from? The wall adapters (or computers). So what are the wall adapters? Ratings of 1000mah means that the wall adapter can provide up to 1000ma per hour.
However, your charging circuit will determine how much current to actually draw. For example, drawing 800mah for 10 min may raise the temperature to 55 degrees, so after 10 min the charging circuit drops the charging current to 500mah.
Of course, if you're using el cheapo cables, some cables may not be able to support the current draw and you may find that even with 20000000mah power supplies your phone can only draw 100mah.
The SGS2 heats up pretty easily, and it doesn't quite draw beyond 700mah. The circuit built into the phone doesn't allow it to, if i'm not wrong. If your phone is overheating while charging, you better change your case as it's going to cause your phone to overheat sooner or later.
Using a 20000000mah power supply isn't an issue, because the charging circuit within the phone will be able to draw only a certain amount.
Me, I plug my SGS2 into a 2Ah charger every night to charge, and yes it's perfectly fine. I'm only upset that after buying an expensive 2A charger, I realised that the phone is not able to draw high currents (phone even heats up to 55degree Celsius when charging).
Charging the phone on a ice pack (which lowered the phone temperature to 16 degrees while charging) didn't increase the amount of current drawn by the phone, even on a 2A power supply.
My humble advise is, stick with the stock power supply, or at most get a 1A version. No need to splash for a 2A power supply. If you really need faster charging, get a battery charging dock.

eranyanay said:
After two days with the battery monitor widget Im affraid itself it drains the battery.
could it be it affects the battery?
settings are regular, it monitors changes every 60seconds
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Click to collapse
yes of course it does. It consumes a certain amount of ma per hour, doesn't it?
Personally, there's a app called watchdog, look for it, IMHO it helps to catch rouge apps better, and manage battery better.

I thought the whole idea of having a universal micro USB charging connection across most good brands was so you could use other chargers!

moooxooom said:
yes of course it does. It consumes a certain amount of ma per hour, doesn't it?
Personally, there's a app called watchdog, look for it, IMHO it helps to catch rouge apps better, and manage battery better.
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Well I just like the widget, which shows me also the battery temperture
I hope it doesnt takes too much

1A or 2.1 A?

So, I have powerbank and I have 2 ways of charging: 1A and 2.1A. which one to use when charging my note 2?
Handwritten from my Note 2

Depends on the cable you'd use. Samsung cable will go near 2amp, generic ones do about 1 amp

kebabs said:
Depends on the cable you'd use. Samsung cable will go near 2amp, generic ones do about 1 amp
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I have samsung cable.. So is it smart to charge via 2.1 A ? Can it do some damage on the phone ?

I have a Momax external battery and have charged the phone with the 2.1A port. It didn't heat up, it didn't have any problems. I was planning on measuring the exact amperage that comes out of the samsung charger and the momax battery (iPower Pro), but I didn't get around to it, because I suspect the difference is actually smaller. There are many people who used more powerful chargers to charge their phones faster, and the only thing that degraded was the battery lifespan, but the difference in those cases was upwards of 0.5A between the original and the new charger. I find the 0.1A to be a small difference and I have no problem using the 2.1A port on the iPower.
So to answer your question, no, it won't damage your phone. Theoretically it damages your phone's battery, but it degrades anyway due to charging cycles, so you won't notice any damage caused by the extra 0.1A unless you plan on still using the note 2 10 years from now.

sandulea said:
I have a Momax external battery and have charged the phone with the 2.1A port. It didn't heat up, it didn't have any problems. I was planning on measuring the exact amperage that comes out of the samsung charger and the momax battery (iPower Pro), but I didn't get around to it, because I suspect the difference is actually smaller. There are many people who used more powerful chargers to charge their phones faster, and the only thing that degraded was the battery lifespan, but the difference in those cases was upwards of 0.5A between the original and the new charger. I find the 0.1A to be a small difference and I have no problem using the 2.1A port on the iPower.
So to answer your question, no, it won't damage your phone. Theoretically it damages your phone's battery, but it degrades anyway due to charging cycles, so you won't notice any damage caused by the extra 0.1A unless you plan on still using the note 2 10 years from now.
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Thanks for reply mate ! I was thinking the same, but i needed some sort of confirmation tho

Use the 2.1A one.
The phone should only draw 2A from it anyway, that just means the port is capable of supplying 2.1A.
Using the 1A port will just charge your phone slowly, the 2.1A port should charge it as quick as the official charger, depending on which cable you use.

It is a matter of supply and demand. All USB devices can safely be plugged into any USB charger. Given an unlimited amount of current available from the charger, each device will still only draw only as much current as it is designed to draw. If the charger is rated 2.1 Amps or 5 Amps or 10 Amps, a 1.5 Amp device will still only draw 1.5 Amps. The charge rate will be at maximum Think of it like your house wiring. The circuit may have a 20 Amp circuit breaker in the basement but we plug in 40 Watt bulbs and 100 Watt bulbs and TVs and electric shavers that all draw different amounts of current. The 100 Watt bulb uses less than an amp but is unharmed being plugged into a 20 Amp receptacle (charger). Now we come to the flip side. If the charger Is rated lower than the device it just charges slower than it would if the charger could supply at least as much as the device uses. To go back to our example, the 1.5 Amp device plugged into a 1 Amp charger will take longer to charge that it would with a charger rated 1.5 Amps or higher. My analogy has one hole. If the stuff plugged into the house receptacles exceeds 20 Amps the circuit breaker pops. This will not happen with USB chargers as they limit the current and will not try to supply more than they are rated for. Stick to chargers rated as high as the one that came with your device or higher and you will be fine

Can our phones charge safely from a 6V USB charger?

Like the title says, can the typical smartphone (I'm actually asking for Galaxy Nexus specifically) safely charge from a 6V USB charger?
I'm asking because I want to make an Altoids portable USB charger for my GNex during travels. I've Googled a few results with mixed results. Some people built such a charger with a 4-AA battery setup, which means there will be 6V in the circuitry. However, some people have added a 5V regulator to the setup, while some have not. Those that have added it, sometimes reported insufficient voltage to charge the phone.
Basically, do I need the 5V regulator to safely charge my phone in this particular setup?
I know I can buy such a charger that is mass produced, but I want the satisfaction of a DIY product and appear to be the coolest hipster geek with my Altoid charger

Use Ni-MH rechargeable battery. Their voltage is 1.2V each, resulting in 4.8V in total.
If you use 4 Ni-MH battery with 5V regulator, it won't work. Voltage regulators are only good for stepping down, otherwise there will be improper operation.

I never understood portable chargers...with no disrespect to the OP, why wouldnt you just buy another battery or two? They are smaller and easier to travel around with than a portable charger without the voltage risk of running out of spec.

tincbtrar said:
I never understood portable chargers...with no disrespect to the OP, why wouldnt you just buy another battery or two? They are smaller and easier to travel around with than a portable charger without the voltage risk of running out of spec.
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The spare battery idea is a good one but I think one of the drawbacks to that idea is how to recharge the spares once they are dead. Energizer, Duracell and a host of other battery makers sell rechargeable power packs for not a lot of money.
I would hate to see you build one and have it short and catch fire or damage your phone not to mention the acid leaks from discharged batteries.
Edit. Just saw this in another thread. I bet a lot of us have rechargeable AA's lying around or since the are fairly inexpensive it may be worth picking some up.
http://www.batteryspace.com/battery...ndbeltcliponoffpowerswitch-rohscompliant.aspx

tincbtrar said:
I never understood portable chargers...with no disrespect to the OP, why wouldnt you just buy another battery or two? They are smaller and easier to travel around with than a portable charger without the voltage risk of running out of spec.
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No disrespect taken. Like the ol' fried chicken guy said, where would I suddenly charge my batteries once they're out of juice? I could throw a portable charger in the car, and then go buy some cheap AA's during traveling. If I'm out of country, my charger simply won't even work (I think), due to plug incompatibilities.
Mind you, I have a Verizon Gnex, so I could use all the juice I can get my hands on. Especially during vacations, I'll likely be using the GPS, camera, and various other travel aid apps (Yelp, for one) that would likely drain my batteries a lot faster than I could imagine.
Back on topic: The NiMh idea is a good suggestion, but then I'd only be limited to using rechargables. I've seen the link to that commercially made portable charger before, but my ultimate goal is to go the DIY route. Also, the description of that item has the exact problem I'm trying to tackle, so that one is no better than something I throw together from radioshack and some Altoid tins.

mengsuan said:
Use Ni-MH rechargeable battery. Their voltage is 1.2V each, resulting in 4.8V in total.
If you use 4 Ni-MH battery with 5V regulator, it won't work. Voltage regulators are only good for stepping down, otherwise there will be improper operation.
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Some AAs are 1.2v, while most are 1.5v off the shelf now. It is possible to use a 5v regulator to make sure the voltage does not go higher than 5v to protect your device. If the voltage drops below 5v it will simply stop charging as you need at least 5v +/- 3% or so.
What would be better is if you bought a dc-dc step up converter. This way you can use a single lithium battery (3.7v) or about 3 AAs (4.5v). The step up converter will take that 3-4v and bring it up to 5v or higher (adjustable).
Here's a dc-dc step up converter (http://www.ebay.com/itm/1PCS-LM2577...682?pt=LH_DefaultDomain_0&hash=item3cca94d2ca)
These are what most portable chargers use anyway. They step up the voltage to probably 6-7v? then bring it back down to 5v with a regulator. The reason why they step up the voltage to around 6-7v is to maintain amperage.

http://m.samsung.com/us/mobile/cell-phones-accessories/ETC-CPK008GSTA
what about using one of these to charge the spare. Love mine.
Sent from my Galaxy Nexus using Tapatalk 2

I recently got this because I had a lot of spare eneloops lying around. In 90 mins I get about 20%. For whatever reason when the phone stops charging, I can plug it into my friend's One X and his phone will continue charging where as the Nexus will charge for maybe another minute and then stop, not sure whats going on there but otherwise its a very good product.
http://www.engadget.com/2009/11/12/eneloop-stick-booster-supplies-emergency-power-to-your-portable/

rptw said:
I recently got this because I had a lot of spare eneloops lying around. In 90 mins I get about 20%. For whatever reason when the phone stops charging, I can plug it into my friend's One X and his phone will continue charging where as the Nexus will charge for maybe another minute and then stop, not sure whats going on there but otherwise its a very good product.
http://www.engadget.com/2009/11/12/eneloop-stick-booster-supplies-emergency-power-to-your-portable/
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I was about ready to jump all over that until $40 gave me a slap in the face
I really liked what I read, but I don't think I can justify $40 on it.

rice923 said:
I was about ready to jump all over that until $40 gave me a slap in the face
I really liked what I read, but I don't think I can justify $40 on it.
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34$ and free shipping on ebay, but i actually got it as a gift straight from japan

6V batteries can't make a voltage regulator give out 5V, let alone if you use 4,8V batteries (4x1,2V).
A Voltage Regulator needs to have its input 2,5V minimum above the output voltage (5V+2,5V=7,5V).
You'd be better off (and more stable using either 6 1,5v batteries (or 7 1,2v NIMH) and a voltage regulator.
If you are "too near" of the desired output voltage as soon as the batteries discharge a little the voltage will drop (specially if you use 500mAh batteries) and the phone will no longer charge. Better off being above voltage on the batteries. 6x1.5v=9v, after a lot of discharge,6x1.25v=7,5V will still make the regulator output 5v. (Also don't be "too far" above the voltage or most will be dissipated by the regulator).
You'd be better off using a DC-DC converter which will convert power in any form to the form you wish. Example= 1,5vx500mA=0,75W=5vx100mA (well, allways with some efficiency loss, but way less of voltage regulator).
I've seen different devices, at 5V, charging at different currents. My Samsung will require a minimum of 500mA to charge. My Nexus, with a 1000mA (1A) charger will still discharge (although at a much slower rate than when not connect). Even with the device poweroff you wouldn't be able to charge it with AA batteries.
Or EVEN Better. An external LiON rechargable 7800mAH battery that, fully charged, will charge my Nexus 7 two times

6 Volt Charger

Recently bought a camping lantern that runs on a built in 6v 4.5 AH lead acid battery. It also has a USB connector which is for charging cell phones. I initially thought that the USB would be giving off a safe 5v but on testing it turns out that it is 6 volts straight from the battery.
Is this safe to use occasionally while camping? Will that extra 1 volt kill the battery or is there some mechanism inside the phone to regulate that voltage to a safe level?

Good question....hope someone has the answer for you.
Sent from my SCH-I535 using xda app-developers app

executionist said:
Recently bought a camping lantern that runs on a built in 6v 4.5 AH lead acid battery. It also has a USB connector which is for charging cell phones. I initially thought that the USB would be giving off a safe 5v but on testing it turns out that it is 6 volts straight from the battery.
Is this safe to use occasionally while camping? Will that extra 1 volt kill the battery or is there some mechanism inside the phone to regulate that voltage to a safe level?
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Of course there should be.You get more than 6v in a power socket around the house.

Gkikas said:
Of course there should be.You get more than 6v in a power socket around the house.
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No one plugs their phone directly to the wall socket :/ Thats what the charger is for, it only gives 5v to the phone. Just need to know if it can regulate that 6v to a safe level.
*edit. I think no one here would know about the hardware aspects of a phone. Can someone point me to a forum or anywhere where they may know the answer to a question like this?

May I asked how you measured this?
I'd love to check what output my 12v chargers are outputting

TieNN89 said:
May I asked how you measured this?
I'd love to check what output my 12v chargers are outputting
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A multimeter and a stripped usb cable

executionist said:
A multimeter and a stripped usb cable
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ah yeah
My brain has already flicked off for the day LOL

if you use IRC, try the freenode server in the ##electronics channel. they should help you out there. pretty nice ppl in general there.
Sent from my GT-I9300 using xda app-developers app

?
I'm interested as well. Will 6 volts @ 500mAh fry the phone?

Ok, I am an electronic engineer so a few comments.
I have no idea what kind of charging circuit is in our phones, could probably look it up but ..... in my opinion only 10% above 5V is to be considered safe.
Now you are talking about a 6V battery. That battery is not always 6V. A nice example is the 12V battery in your car which is 12.8V when fully charged. Another example are the cells inside our phones which have a nominal Voltage of 3.7V but are charged to 4.2V.
The Voltage they put on those things is the nominal Voltage.
I would check if there is no electronic circuit in that lamp since I would not connect anything directly to a battery at all.
If you go camping I would check this thing coolook pb-2000. Insert 4 x 18650 batts and you can do a couple of recharges. Very good box for the price and you can salvage 18650 from broken laptop batt packs ... but google and youtube a bit before you do that to make sure you do it the right way.

I'm also interested, any news?

You can see the specs of this type of batteries here. The 6V is nominal, as already mentioned above. The maximum noted is 6.9V and TBH, i would be rather reluctant to test is my SGS3 charging circuit likes the idea of being fed with 40% higher voltage than usual.
Are you sure there is nothing in the lantern that would limit the voltage under load? Could be something as simple as 2 diodes in series, in this case measuring the voltage on the open circuit, totally unloaded, with a DMM that barely draws microamps from it, would show the battery voltage. Try drawing some current from it (use a resistor, a USB LED lamp, etc) while measuring. I seriously doubt a self-respecting vendor would setup a USB port on that thing that would potentially output 40% more than specs, really.
PS: if the port is, indeed, fed straight from that battery, i would rather avoid hooking my SGS3 to it. Even though, it would probably survive.
---------- Post added at 07:08 PM ---------- Previous post was at 06:59 PM ----------
lukesan said:
I have no idea what kind of charging circuit is in our phones...
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MAX77686. Good luck finding the datasheet. And good luck trying to guess if there is anything else potentially fed straight from the USB connector. The bottom line is - i wouldn't dare

Solder this to red wire https://en.wikipedia.org/wiki/Zener_diode
OFC you need 5V model

GR0S said:
Solder this to red wire https://en.wikipedia.org/wiki/Zener_diode
OFC you need 5V model
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Not if it doesn't have a resistor in series. And wait. if the battery is at 6.8 Volt and you have a 5.1 Volt zener and it is charging at 1 Amp so you will need a power resistor. You will have a lot of loss of energy because it will go away in heat.
You could use a dc-dc convertor but believe me forget about it and get one of those charging banks where you can put in your own cells.

lukesan said:
Not if it doesn't have a resistor in series. And wait. if the battery is at 6.8 Volt and you have a 5.1 Volt zener and it is charging at 1 Amp so you will need a power resistor. You will have a lot of loss of energy because it will go away in heat.
You could use a dc-dc convertor but believe me forget about it and get one of those charging banks where you can put in your own cells.
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I'm not sure about how practical it would be to be cutting usb cables and wiring zener diodes just to use this lamp....
I think I had a charger that supplied too much voltage (I'm not positive I didn't measure the voltage output or anything), but I can say that the phone did not like it. It would eventually charge somewhat, but the touch screen wouldn't work and would go bezerk if touched lol.
Again I'm not sure how much V it supplied, but I would assume it was more than 6V. It didn't really damage the phones either, I would try it.

Here's your answer, definitively:
6v at the source (the lantern in this case) will probably be 5v or less at the phone because of the resistance in the USB cable itself. The longer the cable is the higher the resistance will be and thus the more voltage you lose to it. Also, the cheaper the cable (the thinner the wires) the more voltage you will lose per foot.
Here's some specs you can plug into THIS VOLTAGE CALCULATOR:
The USB definition specifies up to 5.3v.
Most USB cables will use 30awg wire or maybe 28awg for the better ones.
Depending on which of the sources I've read, some USB cables/chargers use one pair of wires for charging, and some will use two pairs. You can see that using two pairs of conductors drastically improves the voltage transmission but even still, at 28awg over a 6foot cable you're still losing .75v which puts you at 5.25v and well within the USB spec.
So the lantern is fine to use with your phone with your average 6-foot USB cord.
If you're like me and prefer 10-15 foot USB cords in some places you would actually benefit from a 6v or even 7v power supply at the wall. I've found that even on the OEM Samsung wall charger, when I use a 10-foot cable I don't get enough juice to actually charge my S4. With the screen on the battery charge level still drops. The Galaxy Charge Rate app shows something like 500ma charge rate and that's because there's not enough voltage / too much voltage-drop across the long cable. (Radio Shack sells a modular, adjustable voltage wall-wart power supply as well as USB and micro-USB adapters for it. I'm starting to experiment with it and the long cables.)

USB voltage vs charging current
This is an old thread, but I can confirm that my moto G charges at 6v. Apparently the original Motorola charger outputs 5.75v. I hooked up a variable power supply to my phone. The data lines are shorted together to indicate a high current power source is present. The moto G will test load the power supply before settling on a stable charging current. One that does not cause the voltage to sag excessively. When I applied 5v the charging current was approximately 600 mA. At 6v the charging current was approx 1200 mA. The charging current was measured directly on the phone using an app called ampere.
So I conclude that Motorola use this tactic to ensure their phones charge fastest with their chargers. On the up side, its fun watching my phone go from 40% to 100% in 45 minutes