CHOOSING A CHARGER
(TL;DR - buy and use only 1000mA/1A up, strictly 5V-5.3V only)
When buying a third-party charger, it is always recommended to never go below the output A rating of the stock charger, which is 1.35A, or 1350mA. Lower mA chargers will still charge the phone slowly, but chargers lower than 1A or 1000mA may be unable to deliver sufficient current to satisfy power requirements. In that case, the phone will have to resort to draining the battery to satisfy the power requirement.
Regarding charger voltage, a 5V charger will charge slower than, say, the stock 5.2V charger, but it will be more efficient during saturation charge. The 5.3V charger will charge faster, but less efficient during saturation charge.
CHARGING VIA USB PORT
(TL;DR - no heavy usage when on USB 2.0 (regular/yellow port), USB 3.0 (blue port) has enough current)
Standard USB 2.0 (yellow) USB ports have rated output of 500mA, or 0.5A. That is less than half the current that the stock charger can output. Same precautions to low mA chargers apply to USB ports. If you have a USB 3.0 (blue) port, it should supply sufficient current for heavy use.
CHOOSING A POWER BANK
(TL;DR - [mAh capacity x 4.2V] / 5.2V = effective capacity in mAh, result must be larger than 2110mAh)
The first things you need are your phone's battery capacity (2110mAh) and the input voltage of the stock charger (5.2V). You then need to multiply the mAh capacity of the power bank (ex. 4000mAh) to Li-Poly's maximum charged voltage (4.2V), then divide by the charger's input voltage to get the effective capacity of the power bank, like so: (4000mAh x 4.2V) / 5.2V = 3230mAh. The result must be equal or larger than your phone's battery capacity to achieve a full charge (assuming you are charging with the phone turned off). This is simple ratio and proportion, by the way.
You need to do this because the power bank needs to convert it's output voltage to 4.2V to match the maximum voltage of the battery, and that consumes quite a lot of the power bank's charge. This is also why we'll never see 100% efficient power banks (2000mAh charges 2000mAh, etc.), and we must always buy power banks with much larger capacities than the batteries we need to charge.
PROPER CHARGING TIPS
(TL;DR - Do not let it stay at 100% for an extended period, you can use the phone lightly while charging, this also applies to power banks)
Just plug it in. It does not matter what % you charge, or what % you unplug. But do avoid obscene levels of discharge, such as fast, frequent full discharges, as this will quickly degrade your battery. All Zenfones have a dedicated charging IC that regulates voltage and current. Whether your charger is fast, stock or slow, the IC will manage. However, do not let a battery stay plugged in at 100% for an extended period of time, as this may degrade the battery capacity due to excess heat.
You can use the phone while charging, however, always limit your use to light tasks such as texting, and take into account the precautions regarding low mA chargers and USB ports. Power banks should also be treated as regular chargers, so proper charging tips also apply to them.
CHARGE CYCLES
(TL;DR - cycles are consumed by %; typical battery has 500 cycles)
Each Li-on battery has a limited amount of charge cycles. One charge cycle is consumed when you drain a battery from 100% to 0% then recharge back to 100%. Typically, a smartphone battery is rated above 500 full charge cycles.
You can consume charge cycles by %. If you drain your phone to 50% and recharge, you still have half a charge cycle (50%) left. Likewise, if you drain it to 80%, you have one-fifths of a charge cycle (20%) left.
"DRAIN BEFORE YOU CHARGE" MYTH
(TL;DR - not true)
The "drain completely before charging" procedure is only for old NiCD and NiMH batteries. This is because they develop a "memory effect" wherein you can only use them up to the point where they were last drained,unless completely reconditioned.
Recharging a partially charged Lithium-ion battery does not cause harm because there is no "memory effect". Several partial discharges with frequent recharges are better for lithium-ion batteries than one deep discharge, because there is a stress factor that can degrade the battery capacity when it is frequently discharged.
LONG-TERM STORAGE
(TL;DR - Store at 40% charge level)
Li-on battery packs are best stored at 40% charge, because of Lithium-ion chemistry. If you want to know exactly why, just use Google Search. It'll probably take too long to read or type the entire thing.
USING BATTERY SAVER APPS
(TL;DR - not everything works)
Watch what you use. Most battery saver apps are a waste of CPU, RAM, and, ironically, battery life, because they only do what you already do (manage brightness, WiFi, BT, running apps, etc.).
BEST AUTOMATED APPS - Greenify, Battery Doctor (Battery Saver), Shutapp
BEST CONFIGURABLE APP - JuiceDefender Ultimate
USING BATTERY SAVER FLASHABLE TWEAKS
(TL;DR - not everything works)
These are often more effective than apps, but some might be placebo. Also, some flashable tweaks that are meant to be for a particular model will not work on Zenfone 5 and might cause the phone to bootloop.
UNDERCLOCKING
(TL;DR - quite effective for intensive users, but decreases performance significantly)
This is one of the most effective ways to save battery life, next to reducing display brightness and turning off mobile data. The processor is one of the most power-hungry components. Underclocking will make the processor run on a slower clock speed, therefore reducing power requirements. However, this has a significant performance trade-off, so be reasonable when you underclock.
BEST APPS - SetCPU, No-frills CPU Control
(TL;DR - buy and use only 1000mA/1A up, strictly 5V-5.3V only)
When buying a third-party charger, it is always recommended to never go below the output A rating of the stock charger, which is 1.35A, or 1350mA. Lower mA chargers will still charge the phone slowly, but chargers lower than 1A or 1000mA may be unable to deliver sufficient current to satisfy power requirements. In that case, the phone will have to resort to draining the battery to satisfy the power requirement.
Regarding charger voltage, a 5V charger will charge slower than, say, the stock 5.2V charger, but it will be more efficient during saturation charge. The 5.3V charger will charge faster, but less efficient during saturation charge.
CHARGING VIA USB PORT
(TL;DR - no heavy usage when on USB 2.0 (regular/yellow port), USB 3.0 (blue port) has enough current)
Standard USB 2.0 (yellow) USB ports have rated output of 500mA, or 0.5A. That is less than half the current that the stock charger can output. Same precautions to low mA chargers apply to USB ports. If you have a USB 3.0 (blue) port, it should supply sufficient current for heavy use.
CHOOSING A POWER BANK
(TL;DR - [mAh capacity x 4.2V] / 5.2V = effective capacity in mAh, result must be larger than 2110mAh)
The first things you need are your phone's battery capacity (2110mAh) and the input voltage of the stock charger (5.2V). You then need to multiply the mAh capacity of the power bank (ex. 4000mAh) to Li-Poly's maximum charged voltage (4.2V), then divide by the charger's input voltage to get the effective capacity of the power bank, like so: (4000mAh x 4.2V) / 5.2V = 3230mAh. The result must be equal or larger than your phone's battery capacity to achieve a full charge (assuming you are charging with the phone turned off). This is simple ratio and proportion, by the way.
You need to do this because the power bank needs to convert it's output voltage to 4.2V to match the maximum voltage of the battery, and that consumes quite a lot of the power bank's charge. This is also why we'll never see 100% efficient power banks (2000mAh charges 2000mAh, etc.), and we must always buy power banks with much larger capacities than the batteries we need to charge.
PROPER CHARGING TIPS
(TL;DR - Do not let it stay at 100% for an extended period, you can use the phone lightly while charging, this also applies to power banks)
Just plug it in. It does not matter what % you charge, or what % you unplug. But do avoid obscene levels of discharge, such as fast, frequent full discharges, as this will quickly degrade your battery. All Zenfones have a dedicated charging IC that regulates voltage and current. Whether your charger is fast, stock or slow, the IC will manage. However, do not let a battery stay plugged in at 100% for an extended period of time, as this may degrade the battery capacity due to excess heat.
You can use the phone while charging, however, always limit your use to light tasks such as texting, and take into account the precautions regarding low mA chargers and USB ports. Power banks should also be treated as regular chargers, so proper charging tips also apply to them.
CHARGE CYCLES
(TL;DR - cycles are consumed by %; typical battery has 500 cycles)
Each Li-on battery has a limited amount of charge cycles. One charge cycle is consumed when you drain a battery from 100% to 0% then recharge back to 100%. Typically, a smartphone battery is rated above 500 full charge cycles.
You can consume charge cycles by %. If you drain your phone to 50% and recharge, you still have half a charge cycle (50%) left. Likewise, if you drain it to 80%, you have one-fifths of a charge cycle (20%) left.
"DRAIN BEFORE YOU CHARGE" MYTH
(TL;DR - not true)
The "drain completely before charging" procedure is only for old NiCD and NiMH batteries. This is because they develop a "memory effect" wherein you can only use them up to the point where they were last drained,unless completely reconditioned.
Recharging a partially charged Lithium-ion battery does not cause harm because there is no "memory effect". Several partial discharges with frequent recharges are better for lithium-ion batteries than one deep discharge, because there is a stress factor that can degrade the battery capacity when it is frequently discharged.
LONG-TERM STORAGE
(TL;DR - Store at 40% charge level)
Li-on battery packs are best stored at 40% charge, because of Lithium-ion chemistry. If you want to know exactly why, just use Google Search. It'll probably take too long to read or type the entire thing.
USING BATTERY SAVER APPS
(TL;DR - not everything works)
Watch what you use. Most battery saver apps are a waste of CPU, RAM, and, ironically, battery life, because they only do what you already do (manage brightness, WiFi, BT, running apps, etc.).
BEST AUTOMATED APPS - Greenify, Battery Doctor (Battery Saver), Shutapp
BEST CONFIGURABLE APP - JuiceDefender Ultimate
USING BATTERY SAVER FLASHABLE TWEAKS
(TL;DR - not everything works)
These are often more effective than apps, but some might be placebo. Also, some flashable tweaks that are meant to be for a particular model will not work on Zenfone 5 and might cause the phone to bootloop.
UNDERCLOCKING
(TL;DR - quite effective for intensive users, but decreases performance significantly)
This is one of the most effective ways to save battery life, next to reducing display brightness and turning off mobile data. The processor is one of the most power-hungry components. Underclocking will make the processor run on a slower clock speed, therefore reducing power requirements. However, this has a significant performance trade-off, so be reasonable when you underclock.
BEST APPS - SetCPU, No-frills CPU Control