Mobile USB Chargers discussion (Buyer Beware: see post 1)

[stampeder]

I have a Nokia N900 and it requires more power than a USB port or a typical 12V car charger can provide, so I've blown out several of the above due to the little unit's big current draw. The N900 is a Linux computer after all, running lots of my neat apps, and I tend to run it with the CPU wide open. I could order the proper Nokia DC-10 car charger from Europe for it, or...

When I plug my Nokia N900's AC wall charger into my old Belkin 150W inverter I can't use the N900's FM transmitter to listen to my music over my truck's radio because of all the nasty RF and/or line noise coming from the inverter. When I run the phone on it's normal battery the FM sound is free of noise.

Edit - Buyer Beware:
Sigh... I bought one of the Scosche 1 amp USB chargers and it does not work on a Nokia N900. The reason is that the N900 adheres to the official USB spec requiring that chargers must have the D+ and D- pins shorted by a 200Ω resistor, as seen on pages 7 through 9 in this document:

http://www.usb.org/developers/devcla...arging_1_1.zip

So why do these common USB chargers not follow the spec? Probably because the vast majority of MP3 players, Blackberrys, iPhones, and other devices use their own non-standard pin assignments rather than the official USB ones.

[recneps77]

What current does it need?
I know 2A car chargers (USB port) exist, which is 4x the usual 500mA USB chargers out there.. should be enough to charge even the most power hungry devices.
If not, how much battery capacity does this thing have? :P

[stampeder]

The reason it uses so much power is because I run it hot with lots of stuff going on it (GPS, FM transmitter, 3.5G and/or WiFi, Bluetooth, HD movie & photo camera, flashlight, etc. etc.) and a full battery charge lasts about 12 hours. The AC wall adapter puts out 1.2A so that would be nice to find in a car charger device.

Regarding a high amps USB-enabled car charger can you tell me what brand name and model number to look for?

[recneps77]

Well I have a belkin USB charger (was a dell deal) and that's 1A
If your wall charger is 1.2 that should do it, provided your phone doesnt "know" its a usb plug vs wall charger - usually they dont if there's no data, but sometimes you have to have a cable with the pins shorted. (e.g. my nexus one knows its a 'usb' port, even though there's no data and defaults to 500mA. I have to get a charging-only cable with no data pins to fool it into charging at full, or to cover/short the pins on my regular usb cable)

Anyways, the charger I have is (box is still here, hah.. need to clean off my desk)
Model is (cant seem to find it on the box, this is what dell says it was):
F8Z446

Regular $20, I got it on sale for half, so decent deal. I just tossed the ipod cable in the junk bin for if someone i know with an apple product needs it.

If you think you'd need more than 1A, I know of Griffin's model (pretty much the same as belkin, designed for ipod, so just toss the cable :P)
GC23095

A bit more pricy (especially if you source it from canada - best buy.ca wants double what a US source wants!)

[i6s1]

Buy dot com has a 2.1 amp USB car charger for under $10. Any of the 1-2 amp car chargers are going to be cheaper than a new pure-sinewave inverter.

[stampeder]

The N900 is USB data/charge aware, btw, and comes with the appropriate USB cable. If it senses that choice it offers a screen option on whether to proceed with data or charging or both.

Regarding cheap no-name USB chargers, even the high amp ones blow out too easily due to poor construction, from what I've read. I'll check out the models you guys suggested.

Cheers

[stampeder]

I'll probably take a shuffle over to Walmart to get one of these car/home 1A USB charger combos then:

http://www.scosche.com/ecom/download/IP3IN1.pdf

Belkin and Scosche seem to carry the exact same product line these days.

[sailmaker]

And you are running all those things in a truck (while driving I assume) because ???? Just askin'.

[stampeder]

Because I can. I don't use the e-book reader while driving though...

[recneps77]

Let me know how it goes. I need to do something similar for my nexus one, so it will use the full 1A and not default to 500mA. You'd think someone would sell these cables prewired, but I guess when the main market is iProducts (which accessories can be sold for a premium), why bother with the other 80% of the market with a standard connection?

I doubt my phone ever draws more than 0.5A, even with everything on (gps, intensive programs, music, data connection, etc). It may not charge, but it can at least sustain the battery @ 500mA. So I'm fine with it for now. Better than no power at all for a road trip.

[stampeder]

I found a couple of 100Ω 1W resistors in my workshop so I'm going to solder them in series across the two pins and that should do the trick. Unfortunately USB ports don't give much room to do stuff so this is going to have to be a small man-in-the-middle device that the phone will plug into, which will then plug into the USB charger that plugs into the 12V socket.

[rpr]

If you still have issues after doing that, let me know. I have a Palm Pre that requires north of 1A as well, for my car I got a DC-DC voltage regulator and wired it into a USB plug and it works great. I can lookup the link if you are interested. I think I paid around $7 plus shipping for it on ebay. It was rated for I think 2A, and the voltage is adjustable from around 3V to 18V, roughly.

[Paolo]

thats why i always buy OEM chargers.. i know not many products follow the usb specification, but now handset manufacturers say using a non oem charger can "damage" your device too, or it wont charge it properly, you risk voiding your werranty.

[stampeder]

Agreed, warranty issues must always have the highest priority so OEM is wise. In my case the N900, never actually having been officially released in the North American market by Nokia, means having to rustle up an OEM charger from Europe, which is why I downloaded the USB specs so that I could hack together a simple, standards-compliant hardware solution instead. With the phone being 100% USB compliant, I'm satisfied there are no warranty concerns.

I found my son's Blackberry charger (from before he switched to an iPhone) and sure enough it is non-standard.

[JamesK]

you risk voiding your werranty

My Nexus One came with a charger and also a USB cable. The manual says USB will charge at a lower rate than the charger, but makes no other mention of using other than the included charger. Many phones these days are designed to charge from USB, so it'd be difficult for your warranty to be voided by going that route. Both the charger and USB cable connect to the same micro USB connector on the bottom of my phone. I also bought a 2 port USB power adapter for use in my car and keep a spare micro USB cable with it. I do not know if the reduced charge rate with USB is due to computer USB ports or detection of a power supply. I also have a USB power supply, that came with a camera, that can put out 1 amp, which is the same rating at the charger that came with the phone. I have no idea if I can get full charging rate with it. I believe someone mention a 200 ohm resistor across a pair of pins in the USB cable. I guess I'll have to get out my meter and do some checking.