Are cell phone batteries different somehow?

[judson]

I have been reading in ES for a month or two now in preparation for my first ebike conversion. I feel like I have a ton more to learn but one thing I thought I knew was that, with respect to Lithium batteries, one should not deplete them completely. Shallow cycles = better. Then I pop the case of my extended battery on my cell phone. These instructions, printed directly onto the battery, seem to go against a lot of what I have read (most recently here http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries).

What am I missing?

Thanks!

 

[neptronix]

I doubt they're different.
I've seen many smart phone manufacturers charging them to full voltage and then LVCing them at their rated capacity in order to maximize battery life, but the battery does not last long when you do that.

NASA did some study that found out that shallow cycling lithium batteries extended the cycle life insanely. The more you gimped the cell out, the better it was. I wish i could find the paper.

 

[Alan B]

The people who write the label on the battery may not always give good advice. Much of that advice is more applicable to NiCads than Lithium. Are you sure it is a lithium battery? Perhaps they made a lot of labels in the past before lithium and they want to use them up, or they just used the old copy over again. Or perhaps they want to sell more batteries and don't want you to get longer life.

 

[Alan B]

The people who write the label on the battery may not always give good advice. Much of that advice is more applicable to NiCads than Lithium. Are you sure it is a lithium battery? Perhaps they made a lot of labels in the past before lithium and they want to use them up, or they just used the old copy over again. Or perhaps they want to sell more batteries and don't want you to get longer life.

 

[Tamaz]

Like people here say, the manufacturer probably want you to have a good experience in the beginning, thinking "Wow, this battery can really hold a charge!" if it starts to deteriate efter a couple of months is no problem. It will happen a little at a time and you will probably not notice untill it's really bad and at that point way to late to claim a refound and you need to buy a new one. Consumers buy looking at capacity at best, no one looks into how long lifetime the battery itself has, so better make the poduct perform as good as posible in the area people who buy cares about.

 

[neptronix]

Like people here say, the manufacturer probably want you to have a good experience in the beginning, thinking "Wow, this battery can really hold a charge!" if it starts to deteriate efter a couple of months is no problem. It will happen a little at a time and you will probably not notice untill it's really bad and at that point way to late to claim a refound and you need to buy a new one. Consumers buy looking at capacity at best, no one looks into how long lifetime the battery itself has, so better make the poduct perform as good as posible in the area people who buy cares about.

^-- yup.
It's all about designing the battery to meet the demand of the 1-2 year contract agreement, then throwing it into an e-waste pile and shipping it off to a dump in Africa where it will be picked apart by children for it's precious metals.

Why engineer it to last.. typical battery designs for this application run 100% SOC on cells that aren't designed to last a thousand cycles.

 

[Ykick]

I believe most cellphone batteries are fairly similar parameters to RC Lipo and I’ve even ripped away many 1S BMS’ to fabricate a simple single cell charger. See here - http://endless-sphere.com/forums/viewtopic.php?f=14&t=60953&hilit=+cell+phone+bms
Use any 5V source like USB, wall wart, etc. Very handy for touching up low cells.

Or, as I recently suffered BMS balance resistor turned ON and drained an RC Lipo bike pack cell down to LVC. Luckily ‘had one of those in my bag and after several hours from USB charger the cell was close enough in balance to get my ass back home.

The other thing to remember with this chemistry is temperature of operation. Warmer, the better. Cold operation (laying/hanging by AC vent) or simply cold ambient temps can create some very interesting discharge curves.

But after 1-2 years, the C rate will begin to noticeably suffer. But even then, I’ve got many repurposed Li-ion/Lipoly still in mild service after 5 years or more.

 

[dogman dan]

This is the catch 22

If your cell phone, battery, and charger stop the charge at 4.2v or less, then charge it as often as possible. Shallow cycles will definitely make it last longer.

But I had a battery eating cell phone once, and for that phone, running it down till empty, then charging worked best. Why was that? Later on, as I learned more about batteries, I put the voltmeter on it. That thing charged to 5v every time you charged it.!!!

Dammmn. A wonder I got six months from batteries charging .8v too high every cycle, let alone that it never set my house on fire.