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LITHIUM BATTERY TRICKS AND MYTHS

 


• Battery capacity: replacement batteries and the battd file

Batteries from places like eBay often don't report their real capacity to your phone.

If the capacity reported by your battery is equal or less than what's in the battd file then your battery will charge to the max without changing the file.
But if the reported capacity is less than the real capacity your battery will seem to drain too fast, and then spend hours running at 1%. In that case changing battd may fix your erratic battery indicator.

If the reported capacity is higher than what's written in battd you need to change it, or else your battery won't charge to its full capacity.

Editing battd is not easy, and can take a lot of trial and error to get the callibration right. See if you can find a tweaked battd file for your device on the xda forums.



• Battery life: make your smartphone last longer without dumbing it down

Click to read how to make your battery last through the day.



• Callibration: wiping the battery stats doesn't make it last longer

The battery stats file just logs how the battery is used. It's got nothing to do with the percentage reported by your phone, and it doesn't affect charging and discharging at all.



• Charge time: charge to 80% does NOT make your battery last longer

Charging stops automatically when the battery voltage reaches about 4.2 V and the charge current drops to about 3% of the maximum.

Your battery never charges to 100%, so there's no need to babysit your phone to pull the plug.

• Charge time: charging beyond 100% doesn't make much sense

When your phone or tablet says "100% charged," you can feed it some extra juice by keeping it plugged in longer.

But don't wait for it, because the law of diminishing returns kicks in really hard.
When you plug your phone in, it starts charging real fast, but as it gets closer to maximum capacity the charging rate drops real quick. The tiny amount of extra battery power from long charges is barely noticable, and definitely not worth waiting for.



• Charge time: overcharging doesn't exist

Did anyone ever tell you to pull the plug when your battery indicator reaches 100% so that it doesn't overcharge? Don't believe it!

Lithium batteries have a self-protection circuit that won't let that won't let them overcharge, no matter how long you keep 'em plugged in.



• Dead battery: put it in the freezer to kick it back to life

Sometimes a dead battery will wake from the dead at low temperature. If it's voltage dropped too low then two or three days in the freezer can put it back to life.

Just make sure your freezer isn't too cold. At -40 C the electrolyte freezes, and that shortens the life of your battery. A typical household freezer doesn't go below -20 C, so it won't freeze your battery to death. Just make sure you've sealed your battery to keep moisture out. Water will condense from the air trapped with your battery. This corrodes the metal contacts, so seal it real tight with saran wrap, then put it in a ziplock bag with the air squeezed out. Let your battery warm up to room temperature before unwrapping it.



• Draining your battery doesn't kill it

If you let your battery run dry, it will self-discharge beyond repair. Yes, this can happen in theory, but in real life you don't need to worry about it.
When your Android screams "0%" and switches itself off, your battery isn't empty yet. Not even close.

Your battery says that it's empty when the voltage drops to a little over 3 V (more as it gets older and the internal resistance goes up). By then you can store it over a year at room temperature (and twice as long in the fridge) before the protection circuit makes it commit suicide. By then your battery is so old that you need to replace it anyway, because lithium batteries lose capacity over the years at any charge and there's no way to stop this.



• Memory effect: it doesn't exist for lithium batteries

Some people claim you should always charge your batteries to 100%, and then drain them completely to 0% to avoid the dreaded memory effect. They're wrong.

There was a memory effect ages ago with really old batteries. There's not a single Android device with such outdated batteries in it.
Android phones have lithium batteries, and they don't have any memory effect.



• Storage: freezing your battery is not worth the trouble

Freezing the electrolytes kills your battery. That doesn't mean freezers are bad for your battery. The electrolyte freezes at about -40 C, and most consumer freezers won't go below -20 C.

If you really want to freeze your battery, make sure to keep it dry. Water will condense from the air trapped with your battery. This corrodes the metal contacts, so seal it real tight with saran wrap, then put it in a ziplock bag with the air squeezed out. Let your battery warm up to room temperature before unwrapping it.

Don't expect miracles from freezing. Storing lithium batteries in the fridge instead of at room temperature prolongs their life a lot, cooling them down further only has a modest (often insignificant) effect.



• Storage: storing your battery in the fridge at 40% makes it live longer (yes, really)

Battery charge and capacity go down over time, even if it sits on a shelf doing nothing. But at a 40% charge its capacity goes down at less than half the rate compared to 100%, and at 4 C it deteriorates less than half as fast than at room temperature.

Half full and cold reduces degradation a lot (from up to 20% per year down to 2% per year), so storing unused batteries in the fridge is a good idea. Just make sure you've sealed your battery to keep moisture out. Water will condense from the air trapped with your battery. This corrodes the metal contacts, so seal it real tight with saran wrap, then put it in a ziplock bag with the air squeezed out. Let your battery warm up to room temperature before unwrapping it.



• Voltage and battery charge

Voltage is a rough measure for how full your battery is, but no more than that.

Voltage vs. capacity isn't linear. When you connect your charger the voltage goes up fast, but the amount of juice (usually expressed in mAh) rises much slower. When the voltage reaches 4.2V (this goes quickly) your battery is not fully charged yet. It keeps charging for a while, but really slow. When you unplug your phone the voltage drops quick first, then it slows down a lot, and then it slows some more.

A typical phone battery is "full" at 4.2 V and "empty at 3.2 V, but that doesn't mean that it's half full at 3.7 V.



• Voltage: undervolting usually makes sense

Undervolting my CPU won't improve battery life by more than 2%. Someone on a forum said so.

Yes, and he's wrong.

Some phones run at close-to-optimal voltage/clock speed combos out of the box, but other phones are severely overvolted. The biggest gain from undervolting is increased standby time, because your phone spends most of its time not doing very much.

The guy who made the 2%-claim tested it on a Nexus at 50% display brightness with the processor working its ass off. Your phone spends most of its time doing low power jobs, and if you drop the voltage on that your standby time goes up. If you value battery life you'll turn the brightness of your display way below 50% (it's way too bright for most real world conditions) which tips the scale towards undervolting even more.





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