Forums

car 12v phone chargers

Started by Ivan Vegvary May 7, 2014
Why do they take longer to charge than mt wall charger.  The output of my wall charger is 5v.  Seems like my car should be able to imitate that level. ??
Thanks
Ivan Vegvary
On Wednesday, May 7, 2014 11:37:57 AM UTC-4, Ivan Vegvary wrote:
> Why do they take longer to charge than mt wall charger. The output of my wall charger is 5v. Seems like my car should be able to imitate that level. ?? > > Thanks > > Ivan Vegvary
Charging time will depend on the current and not the voltage. I'll guess that the 12V auto charger just has a linear regulator.. (not a switcher) and so to do (say) 1 amp at 5 Volts it would need to dissipate 7 or 8 watts... that's too much so they cut dwon the current. Just a guess, George H.

"George Herold" <gherold@teachspin.com> wrote in message 
news:9f005aaf-1576-4c0f-a057-a4a709ad4a1f@googlegroups.com...
> On Wednesday, May 7, 2014 11:37:57 AM UTC-4, Ivan Vegvary wrote: >> Why do they take longer to charge than mt wall charger. The output of my >> wall charger is 5v. Seems like my car should be able to imitate that >> level. ?? >> >> Thanks >> >> Ivan Vegvary > > Charging time will depend on the current and not the voltage. > I'll guess that the 12V auto charger just has a linear regulator.. > (not a switcher) and so to do (say) 1 amp at 5 Volts it would need to > dissipate 7 or 8 watts... that's too much so they cut dwon the current.
They probably have a switcher these days - the really cheap crappy plastic case would deform with the heat from a dropper resistor inside. There's a discussion on another group whether the ones from the &#2013266083; shop are even safe to use - I was going to pick one up to crack open to see what's in it, but they were out of stock and I don't go into town that often.
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On Wed, 7 May 2014, Ian Field wrote:

> > > "George Herold" <gherold@teachspin.com> wrote in message=20 > news:9f005aaf-1576-4c0f-a057-a4a709ad4a1f@googlegroups.com... >> On Wednesday, May 7, 2014 11:37:57 AM UTC-4, Ivan Vegvary wrote: >>> Why do they take longer to charge than mt wall charger. The output of =
my=20
>>> wall charger is 5v. Seems like my car should be able to imitate that=
=20
>>> level. ?? >>>=20 >>> Thanks >>>=20 >>> Ivan Vegvary >>=20 >> Charging time will depend on the current and not the voltage. >> I'll guess that the 12V auto charger just has a linear regulator.. >> (not a switcher) and so to do (say) 1 amp at 5 Volts it would need to >> dissipate 7 or 8 watts... that's too much so they cut dwon the current. > > They probably have a switcher these days - the really cheap crappy plasti=
c=20
> case would deform with the heat from a dropper resistor inside. > > There's a discussion on another group whether the ones from the =A3 shop =
are=20
> even safe to use - I was going to pick one up to crack open to see what's=
in=20
> it, but they were out of stock and I don't go into town that often.=20 >
I needed a USB charger recently, and thought of buying one of those cheap= =20 small cubes. And I decided I wouldn't trust it (not the cheap kind)=20 unless I did open it, and then I decided I wasn't so curious that I'd want= =20 to buy the thing twice, one for looking and then another for actual use if= =20 it looked safe. I admit they were cute and compact, but I just used a 5v AC adapter=20 (switching kind) that I'd pulled from somewhere, and wired on a USB jack I= =20 desoldered from a scrap motherboard. Not as neat, but I trust it. Michael --8323328-564184301-1399502800=:9304--
On 2014-05-07, Ian Field <gangprobing.alien@ntlworld.com> wrote:
> They probably have a switcher these days - the really cheap crappy plastic > case would deform with the heat from a dropper resistor inside.
> There's a discussion on another group whether the ones from the &pound; shop are > even safe to use - I was going to pick one up to crack open to see what's in > it, but they were out of stock and I don't go into town that often.
The ones I've looked inside have some sort of DIP8 based switcher... I've not tested the max output current, -- umop apisdn --- news://freenews.netfront.net/ - complaints: news@netfront.net ---

"Michael Black" <et472@ncf.ca> wrote in message 
news:alpine.LNX.2.02.1405071844550.9304@darkstar.example.org...
> On Wed, 7 May 2014, Ian Field wrote: > >> >> >> "George Herold" <gherold@teachspin.com> wrote in message >> news:9f005aaf-1576-4c0f-a057-a4a709ad4a1f@googlegroups.com... >>> On Wednesday, May 7, 2014 11:37:57 AM UTC-4, Ivan Vegvary wrote: >>>> Why do they take longer to charge than mt wall charger. The output of >>>> my >>>> wall charger is 5v. Seems like my car should be able to imitate that >>>> level. ?? >>>> >>>> Thanks >>>> >>>> Ivan Vegvary >>> >>> Charging time will depend on the current and not the voltage. >>> I'll guess that the 12V auto charger just has a linear regulator.. >>> (not a switcher) and so to do (say) 1 amp at 5 Volts it would need to >>> dissipate 7 or 8 watts... that's too much so they cut dwon the current. >> >> They probably have a switcher these days - the really cheap crappy >> plastic >> case would deform with the heat from a dropper resistor inside. >> >> There's a discussion on another group whether the ones from the &#2013266083; shop >> are >> even safe to use - I was going to pick one up to crack open to see what's >> in >> it, but they were out of stock and I don't go into town that often. >> > I needed a USB charger recently, and thought of buying one of those cheap > small cubes. And I decided I wouldn't trust it (not the cheap kind)
If you're that wary, build a breakout box to contain a SCR crowbar protection.

"Jasen Betts" <jasen@xnet.co.nz> wrote in message 
news:lkf9ed$mvc$1@gonzo.reversiblemaps.ath.cx...
> On 2014-05-07, Ian Field <gangprobing.alien@ntlworld.com> wrote: >> They probably have a switcher these days - the really cheap crappy >> plastic >> case would deform with the heat from a dropper resistor inside. > >> There's a discussion on another group whether the ones from the &pound; shop >> are >> even safe to use - I was going to pick one up to crack open to see what's >> in >> it, but they were out of stock and I don't go into town that often. > > The ones I've looked inside have some sort of DIP8 based switcher... > I've not tested the max output current,
A common type is the MC34063 - its actually hard to find versatile switcher chips that don't have UVLO at a lower voltage than you want to run it from. Although I missed out at the &pound; store - I've just been in Lidl, among their weekly offers was a &pound;3.99 car to 5V adaptor with loads of pluggable phone charging connectors. I'll crack it open for a look inside later.