Electron Management for Digital Devices - Part 1

I hope I didn't scare you away with the title...maybe I should have called it something like Getting the Most Out of Your Smartphone Battery. This will be a two part series because of the amount of information that I'm going over here. Either way, here goes.

So before I get started with the practical stuff, I'd like to give a brief overview of the technical/theoretical aspect as well as dispel a few myths. I believe that knowing even the basics of the how will help you understand the why. Now, most of the information in this section are not my original thoughts and I like to give credit where credit is due (see footnote). I've tried to only pass on the information that I feel is relevant to this post. Also if you want to get even more technical than what I'm presenting here or you aren't sure of the terms that I'm using, feel free to head on over to Battery University for as much information as your little grey matter desires.
If you would like to skip all the technical jargon head on over to the practical tips and what-not-to-do sections in Part 2 (coming soon).

Batteries 101

First of all, what are the batteries that are used in most phones? Since batteries were invented about 2000 years ago (o yes, there were batteries back then...think clay pots), there has, and continues to be, demands placed on them by consumers. They need to have a greater capacity (how much energy can be stored), be lighter, and have a higher discharge rate (how much energy can be used in a set time). More recently, a technology called lithium ion has revolutionize the field of batteries. This is the battery that your phones use. They are used because they are extremely light weight for their capacity, can be shaped into almost any form (unlike traditional cylindrical or cube batteries), they have a relatively high discharge rate suitable for all modern-day electronics. They are also rechargeable to their original capacity up to 300 times (or cycles). Now all of these advantages do come with certain drawbacks. One of the biggest ones is that they are relatively dangerous compared to other battery technologies. This danger is still fairly low, but most people will remember the massive recall by a few major laptop manufacturers due to this danger.

Now a quick note for you environmentalist who are thinking how toxic the metal lithium can be. Unlike other battery technologies, Li-Ions are completely safe to throw in the trash can and are landfill friendly because there is little to no actual free lithium in the battery itself. It is also recommended that you discharge the battery before disposing if it's safe to do so. This is different from the NiCd/MH's that used to be prevalent years back and do contain hazardous materials that would make it into the soil.

Another comparison and myth to this older technology. Li-Ion's have ZERO "memory-effect". If anyone tells you differently, they are wrong. This is probably one of the biggest myths that I've heard over the years and has been carried over from NiCd's, and to a lesser degree NiMH's. You can charge a Li-Ion from 80%, 50% or 20% and it will be able to get the full capacity that it had before. This is an awesome improvement from the older NiCd's which had to be discharged first OR used with an expensive charger to monitor the battery during charging.

What Damages a Battery?

The simple answer is HEAT. Now you may read that over-charging, over-discharging, and not balancing the cells are also reasons, but those all boil down to HEAT (pun intended :-P). I won't go into details, but just know that those secondary issues cause the battery to overheat and therefore degrade or possibly destroy the cell(s). Note that in almost all cellphone batteries, there is only one cell, so balancing isn't an issue. Also with the advanced charging circuitry, over-(dis)charging isn't a huge issue as well. However, HEAT is still a problem.

The reason heat is generated in your phone is because no electrical process is 100% efficient (yet...see superconductors). The wasted energy is converted to heat. A perfect example of this waste is an incandescent bulb where over 80% of the electricity used is wasted as heat (that's why CFLs and LEDs use so much less electricity for the same light output, they have less waste in the form of heat).

Now that we know why the heat is caused, you may be asking where it comes from. The two main sources on a smart phone are the battery (big surprise give the topic of this article) and the processor (or CPU). Of the two, the CPU actually generates a lot more heat, but because of its close proximity to the battery, it's still a concern.

So what actually is causing the heat in my phone, you may be asking.

1. High-CPU/data usage (a lot of programs running or data being transferred through the antennas)
2. High discharge of the battery (see #1)
3. Charging
4. Environment (external temp.)

The first two causes can't really be helped (minus one exception, a hung process...more on that later) unless you want to scale back on whatever you are doing to cause these conditions. The second two are very much within your control. By themselves, any of these reasons aren't a problem, but combined they can cause enough heat that can and will damage your battery. Also note, that the battery doesn't need to be in use (i.e. your phone is off) to cause damage to the battery. Obviously, the heat in that case would be external, such as leaving it in your car on a sunny day. In any case, the important thing to remember is that IF you can reduce the heat being cause, you should.

Ok, so how much heat will damage your battery? There is no set temp that WILL damage your battery but there are a few recommendations to follow to avoid any damage. The easiest way (if you don't have an infrared thermometer like I do...I know I'm a geek) is that if you can't hold your battery tightly in your hand indefinitely, it is too hot. That threshold is actually around 60°C (140°F). Most people would agree that even that is too hot and a maximum of 50°C (about 125°F) is much safer.

So aside from powering down your phone or having a fancy gadget like me, how do you tell the temp. of your battery? Well I'm glad you asked. There are a ton of apps on the market that will allow you to see the temperature of the battery probe without ever having to take the cover off (if you even can). Some will even allow you to set a high temp alarm. I recommend something lower than the max to give you time to do something about it. The app that I use is called OS Monitor because it can also display other useful information. On some apps/phones there is also a CPU temperature probe so make sure you are looking at the right one.

Notice the Temp

So there is the technical information. Stay tuned for Part 2 where I will go over the practical of what drains your battery and what you can do. Also I'll cover things that don't actually work and could make things worse.

References:
RCHelicopterFun.com - This site is absolutely amazing for anything dealing with RC Helicopters and related (e.g. Li-Ion batteries). Check out his full site if it interests you or read his entire article for more details on batteries. There is a ton of information that I didn't cover here for the sake of space and some is beyond the scope of this topic.