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Old 08-12-2010, 01:12 PM
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Charging Batteries Using USB Power

Battery Charging issues: SOLUTION (not directly related to how long your battery lasts or why it goes to 85% after xxx minutes)
Pick up the A/C charger that came with the TP2, pick it up & look on the back, you’ll see Output 5v 1amp. Simply put you need to have a car charger that says “Output 1amp” (1amp=1000ma)
And if using an old phones USB charger at work (as a second charger), that one may not have enough amps.... all A/C chargers should say Output 1amp also!

I’ve seen a bunch of questions about this lately in a couple ROM forums. Pay no attention to discussions about PCs & laptops able to put out 5v! USB specs are ALL 5 volts!! U=Universal… all the same! (+- a little)

Best Buy has A/C & car (D/C) chargers that produce an amp. Get a charger that is a mini USB & says on the back: Output: 5v 1amp (or at least 800 ma)

The key is the amperage/amps/ or ma (milliamps) or mah (milliamp hours)
On full brightness that may suck up 350 ma just by itself not running anything!

Charging Batteries Using USB Power
All host USB host devices like PCs and notebooks can source at least 500mA, or five "unit loads" per USB socket. In USB terminology, "one unit load" is 100mA. Self-powered USB hubs can also supply five unit loads. Bus-powered USB hubs are guaranteed to supply only 1 unit load (100mA).

……So, if your phone is sucking down 600 miliamps running wifirouter & GPS & other apps.. your battery will not only ‘not charge’ while plugged into your laptop/pc, it’ll eventually die!

“Besides a data link, USB provides 5 +/- 0.25 volts to power an otherwise unpowered device or charge a battery in a self powered device. A USB controller or hub is required to power one unit load (100 mA, a low power load). It can optionally power up to 5 unit loads (500 mA, a high power load). The spec is silent about intermediate loads, so I assume that the sources deal with just the two cases. Either a load is low power (like a keyboard or a mouse) or high power (like an iPod or PDA).”

Why does that matter? Most big box stores (wal, k, target) will sell a “universal” mini USB charger (what a TP2 is), but have NO amp info… most are 350 ma. So, obviously if your battery is almost gone & your sucking down 700 ma, your using 2 times as much as your getting in & your battery will die. Same goes for plugging into a laptop or PC, an old mini USB A/C (house) charger from an old phone, or just about any D/C (car) charger.

Q: “but it sometimes works”… “I plugged it into my car & it didn’t die for the whole trip last time…” etc.. etc..
A: If your phone battery was full as opposed to almost out & one trip you ran GPS the whole time, it makes a difference.

Q: Sometimes the charger may say only how many watts it produces…
A: Power P = I × V = (Watts = Amps x V) : Amps=Watts/V : So if the charger at the store says it’ll do 2 watts… Amps = 2/5v, = .4 amps or 400 ma, not enough!

Q: Can I use a 500 ma charger?
A: Sure, should be enough 80% of the time! But, there is a reason HTC sends a 1amp charger when you buy the phone.. it’s possible if you have the screen on full & the program (GPS map) is using a lot of bright colors & the gps chip is running & you’ve got another couple programs in the background and your talking on the phone and your battery was at 2 % when you started… you may be drawing 700 milli amps.. then logically it’s only a matter of time until your battery dies & the charger isn’t putting out enough to keep the phone running & it shuts off. And if the charger it is putting out just barely enough to charge the phone, it will take forever to charge the battery!

Q: I’m using a USB charger from my old phone & it works some of the time…
A: Sure, a 350 ma (output) charger will charge your phone fully if it’s left overnight (it usually goes into sleep mode & is drawing almost no power).

~~~~~~~~~~~~~ BEST BUY SUCKS RANT ~~~~~~~~~
Called the 800 # because the web site sucks.
1. Web site sucks, Product info gives no actual info, no place for specs…
2. 800 bestbuy, didn’t give number so I had to search for the letters b, e, s, .. no biggy, but it was early & I was already cranky.
3. I had to press 1 for 'Marshen'… #$@#$&(_*(
4. wait forever to speak with someone & then had to wait forever again… since dialed it’s been 10 min

A rep finally comes on the line & I read him the first 4 items & then I ask is this:
Now I have a question for you, whether or not you can answer my question, do you think I’m likely to purchase anything from best buy today?

5. rep couldn’t tell me which USB car chargers produced 1 amp
6. had to be placed on a long hold while rep consulted supervisor which charger would work even after I gave him my phone model, HTC TP2
7. I was on the phone a total of over 20 min, most of it spent listening to adds over the excessive blaring music over maxing my speakers.
8. when cust serv finally came back, the guy (although he said he could ONLY find a charger if I gave him a model number) couldn’t find ANY charger for my HTC TP2!!

This is inexcusable given the fact that Best Buy IS an electronics store AND the fact that I was speaking with a mobile representative specifically trained in this area.

Asked for supervisor, another 5 min… read him the above 8 issues.. & asked:
So, I’m going to ask you the same question I asked your rep… Do you think I’m likely to purchase anything from Best Buy today?... how about tomorrow?

Over 35 min. got nothing done. I WAS going to post a link to the cheapest BestBuy charger you guys could go pick up, but you’ll have to hunt and peck at the store. I found 3 of them at best buy a year ago, & ended up getting one for under $20. I’d even tell you not to go to Best Buy, but I’m not sure where else you’d find one. Look online for one if you can wait…

FYI: I did tell the rep. it wasn’t his fault & not to take this personally, but he does work for them & is their representative to me… the potential customer…

Hope that helps...

Last edited by teradog; 09-23-2011 at 12:24 PM. Reason: deleted white screen info
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