The Reader

Great writeup Bruce. I appreciate you doing this.

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Roger R. Prokic
-=[ This email was sent from my iPhone 4. Please note my new email is rprokic@me.com ]=-

On Sep 13, 2010, at 4:44 PM, Bruce Carter <rbrucecarter@yahoo.com> wrote:

> I used to design circuitry to charge Lithium Ion batteries. So hopefully this will of some advice.
>
> Lithium Ion batteries have a cell voltage of somewhere around 3.7 to 3.8V, although there are several chemistries and I doubt Apple wants to give away the details. Anything from 2.7V (discharged) to 4.2V (charged) is normal. Damage occurs if the battery is discharged below 2.5V, which will probably happen only if you put away the phone and don't use it for weeks.
>
> So your job as an owner is to prevent cell voltage from ever getting below 2.5V - so charge OFTEN. Otherwise you kill the Li-Ion. This is counter intuitive for people that remember the days of Ni-Cads which had "memories". They tend to apply the same logic to all recharge-ables, and that advice is exactly wrong for Li-Ion batteries. It is even wrong for newer generations of NiCad and Ni-MH batteries, which no longer have memories. Most damage I have observed comes from the ridiculous process of welding straps to the battery. They last a lot longer with pressure connections. Unfortunately welding is popular and here to stay.
>
> The charging circuitry associated with Li-Ion is carefully designed to give optimum charge characteristics for the battery chemistry chosen. It will probably give you a bad battery notification if it detects a cell voltage under 2.5V, which means a trip to the Apple store / ATT - or a local / web based repair service that does batteries. There are also web sites devoted to "do it yourself" - but that Li-Ion battery is not easily replaceable for a reason - a shorted Li-Ion battery can reach 1500 degrees or more, in other words the temperature of molten lava! For that reason, most are internally fused to avoid shorts, but sometimes the fuse fails, too. I often tell people if their i____ or laptop or other device that contains a Li-Ion battery gets hot, find a cement floor and put it down, because there is a chance of a meltdown. A cement floor is usually about the only thing around that can withstand the temperature of Li-Ion in meltdown. Stand back several feet!!! So be warned
> - unless you know exactly what you are doing - it is extremely dangerous to replace a Li-Ion battery. We stored Li-Ion batteries in concrete bunkers with numerous safety protocols in place to avoid shorts.
>
> --- In apple-iphone@yahoogroups.com, "jiminmanjr" <jiminmanjr@...> wrote:
>>
>> I have an iPhone 3Gs, and I am wondering if I might be overcharging the phone... causing in a shortened battery life.
>>
>> I charge my phone overnight, and then leave it on a iRadio unit at work (playing the iPod). When I come home I usually leave it off the charge throughout the evening... and it may run down to 55-70%, depending on how much I am using it.
>>
>> Years ago when I worked for Cingular the rule was to let phones go down to 20% or less before charging. That would give the batteries the best longevity.
>>
>> Is this the same case today?
>>
>> FYI - I have my WiFi turned off, and email push set to every 30 minutes.
>>
>> Thanks!
>>
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