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Old 01-19-2011, 08:08 PM   #1
BMaloney
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Concern about charging the battery via USB

Hello everyone. Because the Sony Reader PRS-650 does not have a wireless connection you must plug it in to the computer via USB in order to transfer files. This, at the same time, is what charges the battery.

Now I don't know if I'm just being paranoid, but am I the only one who has wondered: isn't this bad for the battery?

There is no doubt that you have to fully charge the battery before using it for the first time. Isn't it also true that you should avoid over-charging a battery? Or using using it just a little bit, and re-charging it too soon? Doesn't this reduce the life of the battery cell?

I hope you can see where I'm going here. Should I try to transfer files as quickly as possible, to avoid over-charging? Or worse: should I wait until my battery is low before transferring new books?

Thanks for your attention. What you you think?
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Old 01-19-2011, 08:13 PM   #2
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The type of battery in the Reader doesn't suffer from the "memory effect" you are describing - at least I think so!
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Old 01-19-2011, 08:41 PM   #3
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Thanks for the swift reply, Halk. And thanks for the term "memory effect." I hadn't heard it before.

With that new information, my now extensive knowledge (ie. Google) tells me that there are no known memory effect problems with Lithium ion cells, but there are with Nickel Metal Hydride batteries (found on older laptops).

The PRS-650 User Manual says it has a "Built-in rechargeable battery: 3.7 V DC, 940 mA."

Anyone?
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Old 01-19-2011, 09:15 PM   #4
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Virtually nothing uses Nickel Metal Hydride batteries now (except the rechargeable batteries usually sold with cheap chargers in camera shops)... eReaders, mobile phones, cameras, laptops, notebooks etc... all Lithium ion cells... manufacturers say perfectly happy with incremental top-ups, not recommended to fully discharge, if stored and not used then set at around 50% charge before switching off... also when charging, charge lights normally go out at around 80% charge so leave on for full charge and the technology stops charging at full power...
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Old 01-19-2011, 09:32 PM   #5
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Well, that settles it. Thanks elcreative!
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Old 01-20-2011, 06:07 AM   #6
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Yep, it's not one of those... it's a real Li-ion battery.
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Old 01-20-2011, 06:27 AM   #7
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The wall charger uses the same usb socket, I use my Kindle's adapter from time to time, and there is little difference (you can read while using the wall charger).
Anyway, the red charging led next to the power button should go off when the reader is fullly charged.
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Old 01-20-2011, 11:38 AM   #8
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I like that you can read with the wall charger plugged in. I'm going to have to get one of those.
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Old 01-20-2011, 12:51 PM   #9
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BMaloney, do you have a cell phone charger that has the same usb port as the Sony?

Most have found that newer phones have chargers that the Sony can use as well.

My Droid Incredible charger works perfectly for both devices.
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Old 01-21-2011, 12:53 AM   #10
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My cell phone is a creaking dinosaur and it's plug is from another time! The good news is that I am due for a change-up. I'll have to look into that before choosing a new model. Thanks a mil, grooks!
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Old 01-21-2011, 01:01 AM   #11
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That's what happened to me -- my old antique mobile phone was lost/stolen(?) not too long after I got my ereader and my new LG one's charger works great for my Sony, too.
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Old 01-23-2011, 09:18 AM   #12
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The "memory effect" was seen in early NiCd (nickel cadmium) rechargeable batteries. Where, if you recharged them repeatedly, from a partially charged state, they should seem to lose capacity, "remembering" the partially charged level as discharged. The fix was to occasionally "cycle" them, which was to discharge them and then fully recharge them.

NiMH (nickel metal hydride) batteries do not exhibit "memory."

Virtually everything these days uses some form of lithium ion/lithium polymer battery. And these also have no memory effects. And the way they are charged, they cannot be overcharged. They charge via a Constant Current/Constant Voltage cycle. For the intial part of the charge cycle, the charging circuit limits the voltage to give a certain charge current (normally about 1x the battery capacity, so a 1000 mAH batter, would be charged at 1000 mA). When the voltage gets to the max voltage for the battery, the charging circuit switches to constant voltage, and just holds that voltage and the charge current ramps down as the battery fully charges. For long live, many devices stop charging at the changeover point (which is about 90% of a FULL charge). This gives MANY more charge cycles before the battery dies.

And with lithium based batteries, you will KNOW if the battery gets overcharged. The battery will, as the manufacturers state, "Vent with flame." Or they basically explode in a fire ball.

Slightly overcharged, they get VERY hot (think the Dell and Sony laptop recalls).

I have noticed that my 650 charges strangely. I use an iGO system (www.igo.com). With that, if I charge until the red light goes out, the 650 shows 4 bars, full charge, but it drops to 3 bars more quickly. If I charge via USB, it takes longer to drop the first bar.

And lastly, I did notice that the last computer I built, using a Gigabyte motherboard, had a utility to leave the USB ports powered, when the computer is sleeping or off.

Last edited by Pinecone; 01-23-2011 at 09:20 AM.
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Old 01-23-2011, 09:29 AM   #13
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Red light off after charging = 80% charge. Full charge = +2 hours... see endless notes in threads about manufacturers' specifications for Lithium ion/polymer batteries...
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Old 01-24-2011, 07:09 PM   #14
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Thanks for all the info, Pinecone! If I ever have a spare lithium ion battery, I'm going to have to connect it to my car's battery via jumper cables and see what happens!

Actually, I know what you mean about overheating. I bought a Packard Bell portable that has a sticker on the bottom: "NOT a laptop." I guess it's that kind of battery that makes the difference between a "portable" and a "laptop."

I have just been talking about the battery for my Sony in this other thread. It started about something else, but it led me to discover that the battery has an impressively long life. I'm on three days and counting, and the battery indicator has not gone down one notch (minimal charging - just enough to pass a few files).

I'm going mobile phone shopping tomorrow. Wish me luck finding one with the right power plug!
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Old 01-25-2011, 05:14 AM   #15
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There are videos online of lithium type batteries exploding. They are commonly used in electric model aircraft (mainly the lithium polymer type, which is used in cell phones, and I am sure ereaders due to the form factor). And there have been a few fires that have destroyed cars and houses due to improper charging (normally using the wrong type of charger).
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