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USB car cigarette lighter chargers

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 Otis 28 Oct 2014
Hi folks,

Does anyone know if Usb chargers that you plug into you car cigarette lighter socket all deliver the same outputs (voltage and current). I've got one for my TomTom sat nav and was wondering if I can use this to charge my phone and gopro? I've searched for the spec for my TomTom charger but couldn't find what I was looking for..... And obviously I'm keen not to frazzle some pricey electrical kit!

Cheers,

Mike
 jkarran 28 Oct 2014
In reply to Otis:

In short: There's no guarantee.

USB chargers generally deliver 5V, some only up to the 500mA norm for USB, some can deliver a lot more if required which isn't a problem unless what you're connecting is very badly designed indeed. Pin-outs are also standard but there's no guarantee the particular charger you're using will be right, just a reasonable to good chance.

I'd just plug it in and hope for the best personally.
jk
 gethin_allen 28 Oct 2014
In reply to Otis:

The output of the charger should be printed on the side of it. As said above, most put out anything from 0.5 amps up to around 2 amps.

in my experience, don't be tempted to buy a real cheap one off e-bay, I was and it toasted my old phone.
 icnoble 28 Oct 2014
In reply to Otis:

Works for me, I charge my iphone and ipad via the cigarette lighter socket.
 Dan Arkle 28 Oct 2014
My cheapo car charger gives out enough to charge my phone but not my tablet.

 wilkie14c 28 Oct 2014
In reply to Otis:

As already said, standard ones will be mili amps, perhaps 1A but you can get 2 amp ones that'll charge tablets which they need and charge phones really quickly. I got one off the popular auction site, has 2 slots a 1A and a 2A. Pretty sure I saw them at wilkinsons last week
 Martin W 28 Oct 2014
The important thing is the voltage, and all USB outlets should be at 5V. It's fairly easy to check this using multimeter if you have doubts. Excess voltage can definitely be harmful, but I'd expect a Tom Tom adaptor to be pretty much spot on.

The current rating (500mA, 1A or 2A are common values) is what the adaptor can supply. In practice they only deliver the amount of current the device wants draw. You can happily plug a device that only needs 500mA in to an outlet that can deliver 2A, in the same way that you can happily run a 100W light that draws less than half an amp from a 240V socket which can also run a 2kW kettle that draws nearly 10A.

Bear in mind that mobile phone manufacturers have standardised on charging from USB outlets at 5V for years now (albeit the physical input plug to the phone is micro USB, not the full sized USB A plug, but that's simply achieved using a cable with different plugs on each end) so basically anyone who puts more than 5V out of their USB-shaped socket is going to very unpopular very quickly.
 rj_townsend 28 Oct 2014
In reply to Otis:

I've never had any problem with charging iPhone, windows phone, sat nav, kindle etc via the lighter socket. Tablet doesn't charge as quickly, but is fine for a top-up.
 wilkie14c 29 Oct 2014
In reply to Martin W:

> so basically anyone who puts more than 5V out of their USB-shaped socket is going to very unpopular very quickly.

I'm not sure what you are saying here? Why would anyone put more than 5V through their USB socket? Unless they open the thing up and bypass the voltage reducer curcuit they couldn't anyway?
 marsbar 29 Oct 2014
In reply to Otis:
http://www.halfords.com/motoring/interior-accessories/multisockets/halfords...

I swapped my tomtom one for this so I can charge my phone at the same time. Seems fine. The phone doesn't charge if the satnav isn't in the cradle which is odd but I am used to it.
 marsbar 29 Oct 2014
In reply to wilkie14c:

If you read anyone as any manufacturer does that make sense? Thats what I assumed anyway.
 wilkie14c 29 Oct 2014
In reply to marsbar:

Strange quirk about yours, it must have something to do with the internal curcuit. although the spec isn't given on the halfords site it does say its a 2.5 amp one so I'm guessing it requires a minimum power drain requirement that switches it internally and your phone isn't attempting to draw the minimum required to turn on the internal switching, once the sat is drawing (in the cradle) it switch it on as sat navs generally draw power than a phone.

I have one similar to this:
http://www.amazon.co.uk/New-Trent-high-speed-Micro-USB-NT88C/dp/B009HD44US
The 1amp socket for phones and 2 amp for tablets etc

Whatever car charger you get though, inside that little lump of plastic there will be a voltage reducing curcuit that reduces the cars 12v down to 5v, thats why I couldn't understand what Martin said
 jkarran 29 Oct 2014
In reply to marsbar:

IIRC and it's a few years since I looked, the standard for USB chargers dictates there should be a resistance between the data lines looking into the charger, to determine whether you're connected to an unresponsive computer port which may only be able to source 150mA or a charger that should be capable of at least 500mA. Most chargers don't bother witht he resistor saving a fraction of a penny on the cost. Most devices don't look for it either since it's rarely there, they just assume power without data is a charger.

I've had two identical phones running different versions of firmware, one would charge from a Tom Tom power supply, the other wouldn't, both were happy on the USB compliant Motorola charger.

jk
 Reach>Talent 29 Oct 2014
In reply to Otis:

As others have said, in theory they should all be identical in practice they aren't. There are several different specifications for USB and all of them are 5 volts-ish however some cheap supplies are really noisy and I've seen big voltage discrepancies from some cheap usb chargers. The main difference between usb chargers is normally the current they will supply (how fast they can charge a device); I've got a supposedly ipad compatible car charger that claims to give out upto 2 amps, I doubt it manages 100mA. There are several reasons why the chargers may not give out the correct current, some are picky about the resistance across the data lines while others are just crap! I'd be a little reticent about plugging an uninsured phone into some of these cheap car chargers from fleabay or amazon having stuck a multimeter across a few of them, definitely don't turn the ignition key with one plugged in as generally the first place they save money is by removing the surge protection.


The current batch of TomTom chargers seem pretty good (I've got a Go500) and certainly charges my phone and tablet with no problems.
 wilkie14c 29 Oct 2014
In reply to jkarran:

Interseresting

I get quite a few tablets in for repair that need 'a new charging socket'. when tested these devices are perfectly fine its just that the owner has been using a phone charger instead of the proper, higher amperage one. Its a common mistake folk make and understandable but just because its a micro USB doesn't mean all chargers are the same. Its all in the output but they all fit the same socket physically so it becomes confusing. On a tablet that is on you'll often get the charging indication when a 500ma charger is put in but its delivering less power than the tablet is actually using. Not so bad if its on standby or switched off as the screen isn't taking any power let alone everything else, and the phone charger will trickle charge it, albeit slowly. Tablets also shut down down when battery level becomes critical and as charging is controlled by software, the phone charger isn't giving enough for the software to detect and initiate the charging circuit. Thats when they come to me and I just plug them in to a 2a socket and they charge up fine more often than not. In fact I have 2 or 3 2a wall chargers from wilkinsons (£6.99) to sell to frustrated tablet owners that all seem to lose the proper charger and use a phone charger instead because they think its the same. Did one Monday infact, nexus 7 - owner using wrong charger.

google 'blackberry playbook stack charging' to see how common the mistake is! People let the device slip below 20% charge and can't charge it unless they use a 2a charger or 'stack' it with a phone charger. What happens is you plug in phone charger, red light come on the tablet, 10 secs later the light goes out. what happened was the software sensed an amperage coming in but couldn't detect high enough increse of battery voltage to initiate the charging circuit so it reverted to 'dead battery' mode. Stacking is plugging in the charger and taking it out just before the red light goes out. you have to repeat this over and over again, 10 or 20 times but all those little 10 sec charge times you gave it are often enough to bring the battery back over the 20% threshold and normal charging can resume. They are a pain in the bloody arse!
 Martin W 29 Oct 2014
In reply to marsbar:
> (In reply to wilkie14c)
>
> If you read anyone as any manufacturer does that make sense? Thats what I assumed anyway.

That was what I meant, sorry if it wasn't clear.

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