Battery problems, Is it bad to run the Nexus down all the way to zero?

[ExceptforKhloe]

I've heard after updates batteries sometimes get crappy for awhile, and one solution I've heard is to power cycle it, or let the battery run down all the way, charge, etc

But then I've seen threads implying that running the battery down to zero before you turn it off is baaad.

How far is safe?

Do you let it run down to one percent and turn it off?

Do you let it run down until turns itself off?

What is good, what is bad?

 

[ExceptforKhloe]

I'm curious because now my battery is worse than ever, and updates seem to just destroy it.

 

[Ultra50#WP]

I've heard bad things about letting it run down until it turns itself off. People have had problems getting their N7 to power back up.

Sent from my Nexus 7 using Tapatalk HD

 

[Al Dobler]

Don't run lithium batteries right down to zero. They don't like it at all.

It was once useful to cycle nickle cadmium batteries, but these are a whole different chemistry.

Lithium prefer to be topped up, like lead acid batteries.

 

[wunderbar]

That being said it isn't bad to let the battery discharge all the way once in a while. I know of a few companies that recommend doing a full battery cycle once a month on laptops with the lithium ion batteries.

I don't believe you should fully charge/discharge it every single time, but once in a while is good.

 

[ExceptforKhloe]

"Lithium prefer to be topped up, like lead acid batteries." I don't really know anything about different batteries, please explain?

 

[ExceptforKhloe]

Wunderbar: so if I'm "skating" near the edge of allowable/safe discharging, how low is good, how far is too far? 3%?

 

[Al Dobler]

That being said it isn't bad to let the battery discharge all the way once in a while. I know of a few companies that recommend doing a full battery cycle once a month on laptops with the lithium ion batteries.

I don't believe you should fully charge/discharge it every single time, but once in a while is good.

I believe laptop batteries need to be fully discharged in order for the battery monitor chip to calculate battery capacity. It's very hard on the battery, but the manufacturers don't care if you ruin your battery, they'll sell you another.

 

[Al Dobler]

"Lithium prefer to be topped up, like lead acid batteries." I don't really know anything about different batteries, please explain?

Think of a lithium battery like a car battery. They prefer shallow discharges, and topped back up as soon as possible. That's the way to get maximum life from them.

Also, lithium batteries lose capacity temporarily when they're cold, and their life is shortened with high temperature. Don't leave your lithium powered appliances in a hot car.

 

[Al Dobler]

Wunderbar: so if I'm "skating" near the edge of allowable/safe discharging, how low is good, how far is too far? 3%?

I try to never let my lithium batteries go below 20% before I recharge them. This will maximize their life.

 

[ExceptforKhloe]

Dobler: thank you for the explanation, and the info about the cold also.

 

[horseflesh]

I would be surprised if Google or anyone else designed a tablet that will suffer permanent battery damage from being used until it hits 0% battery. They probably set "0%" to be well above the level that actually harms the battery.

Most people don't know anything about battery chemistry, nor should they have to in order to use a gadget without harming it. I have never had a phone, laptop, tablet, or any other consumer device that reacted to how I chose to charge its Li-ion battery. I try to top off often so I have lots of use time available but if I run it down to 0% I don't sweat it. (That isn't true on stuff like model airplanes, where you DO need to be very careful not to over-discharge the battery--they have poor safeties!)

If someone wants to find out for sure, run a Nexus 7 until it shuts itself off, then take apart the battery and measure the voltage of each cell.

 

[ExceptforKhloe]

Well this is great. Earlier today I let it run down until 20%, then turned it off and plugged it in to charge for a little over two hours. That should've netted 50-70% of power. At least 60%. So I expected to be around 80-90% when I turned it back on. I did so just now and I was barely at 52%.

So in an amount of time where it would've charged 60% or more, it only charged 32%.

It might be easy to blame the charger, but I know it isn't. Since I accepted the update this weekend, the power goes down even when the charger is plugged, if I'm using it. Usually, sometimes it will slowly increase. I used it for slightly over an hour yesterday unplugged just browsing, and it burned through an uncharacteristic 20%. Ugh.



Edit: plugged in and surfing, it's actually charging now, but the "only 52%" charge is still disturbing.
I don't trust myself to perform the experiment with the battery.

 

[jpash549]

If you do take it apart and gain access to the LiPo battery be careful. They can be dangerous. Agree that it should not damage the battery to run down till the device shuts off. But don't let it stay that way too long for further loss will make it harder to recharge.

From my N7 or BBPB or HPTP or HP Laptop

 

[ExceptforKhloe]

After yesterday's crap, I plugged it in and it was still going down while charging. I unplugged it from the tablet for a moment and back in. It's climbing up again, albeit slowly.

 

[ExceptforKhloe]

Okay, so if it is good to top off the lithium battery, is it bad to leave it on the charger too long once you hit 100%? I assume it has a protection that kicks in, but sometimes devices are more vulnerable to this than they should be.

If I forget or am simply not sure if it's at 100% and it stays plugged on past 100%, will it hurt it?

What if I'm actively using it and leave it plugged in after it his 100%? Is that bad?

 

[Al Dobler]

Okay, so if it is good to top off the lithium battery, is it bad to leave it on the charger too long once you hit 100%? I assume it has a protection that kicks in, but sometimes devices are more vulnerable to this than they should be.

If I forget or am simply not sure if it's at 100% and it stays plugged on past 100%, will it hurt it?

What if I'm actively using it and leave it plugged in after it his 100%? Is that bad?

You are correct. Older batteries like Ni-Cd were damaged by leaving them charging for extended periods. They would continue to accept current, and turn this excess into heat. The heat damaged the battery. Lithium batteries are not damaged by leaving them on the charger after the charge cycle is completed. Once they are done charging, they will not accept any additional current. I probably wouldn't leave it plugged in for weeks/months, but a few hours or days won't hurt.

 

[idaute]

You are correct. Older batteries like Ni-Cd were damaged by leaving them charging for extended periods. They would continue to accept current, and turn this excess into heat. The heat damaged the battery. Lithium batteries are not damaged by leaving them on the charger after the charge cycle is completed. Once they are done charging, they will not accept any additional current. I probably wouldn't leave it plugged in for weeks/months, but a few hours or days won't hurt.

Al, you have it 90% correct. You are technically wrong when you say that lithium batteries will not accept any additional current once they have achieved full charge. The charging systems that are incorporated into your phones and tablets have circuitry that prevents impressing further current to the battery once the battery approaches its full charge. Do a google search for charging lithium batteries. If the protective circuitry is not provided for the charger, the batteries can continue to accept current. They then become very dangerous subject to fire and explosion. Thus, all chargers are provided with the protective circuitry to prevent this very dangerous condition. Because the protective circuitry could possibly fail to work, I would not recommend leaving the charger on for any extended time after the battery is fully charged.

Sent from my ASUS Transformer Pad TF700T using Tapatalk HD

 

[jpash549]

Here's a link to some great battery information.

http://batteryuniversity.com/

The N7 programmer has to balance the desire to give the customer long battery life on a single charge and to avoid overcharging which can be dangerous and depleting too far which can lead to difficulties in recharging. The decision is to stick to a range between about 3.45 and 4.2 volts. This is controlled by the operating system and a control circuit on the battery. The reported per cent charge and power usage for the battery is not a measured number but is calculated from reported voltages and currents probably with adjustments for temperature. There apparently is the need to make parameter adjustments for differences between individual batteries. Thus the reference to occasionally running the battery down until it shuts off. You should consider the reported battery percentage as an approximation.

It does help to maintain the battery between a narrower range than allowed above but you may wear out your USB port by the constant plugging and unplugging. The battery will be more quickly aged by higher temperatures anyhow. The battery on the N7 is easy to replace since it is easily accessed by taking off the back. Anybody got a replacement cost?

Agree that it is not good practise to leave it on the charger for extended periods of time when it is fully charged. But you don't have to get up in the middle of the night to unplug it. Also when you run it down to a low percent you should recharge as soon as possible. If that is going to be a while shut down programs and put in airplane mode or turn off altogether.

From my N7 or BBPB or HPTP or HP Laptop

 

[philba]

There is a lot of both correct and mis-information in this thread.

First, some confusion to clear up - the battery charger (AKA charge manager) is actually built into the tablet itself. The thing you plug into the USB connector is simply a power supply. The supply you use should be able to deliver 2 Amps. There are lots of different chargers out that that supply USB level voltage (5V) but can't supply enough current. Typical phone chargers can only give you 1 Amp. This leads to slower charging. A PC USB port can only give you a max of 1/2 Amp and MUCH slower charging. Use the stock wall wart that comes with the N7 or one that delivers 2 Amps or better for best results.

The charge manager in the N7 will not let the batter over charge and will prevent it from discharging lower than a safe level. LiPos will become damaged below a certain voltage level.

0 to 100% is basically a fabrication of the Android software.

LiPos have a limited lifetime. Calendar age is one factor. Heat and cold affect capacity and lifetime. Number of discharge/charge cycles is another factor and we do have some control over this. However, there isn't a simple formula you can use and every battery design is a little different. In it's simplest form, deep discharge cycles wear the LiPo out more quickly that shallow ones. This is the source of the "top it off" advice and it's a very good idea. Your battery will last a lot longer if you don't let it go below 80%. It won't kill your battery to discharge to 20% once in a while, but do it regularly and you will definitely shorten it's life. There's a chart on the internet (that I couldn't find in my quick look) that shows the relationship between depth of discharge and max number of cycles at that discharge level. Below 50% it starts to look pretty bad.

I don't believe that the battery manager needs to the see a low discharge to "calibrate" the battery capacity. For LiPos, most capacity estimates (which is really all you are getting) are based on LiPo voltage which follows a well understood discharge/charge curve. I don't know what the charge manager in the N7 is set to though I wouldn't be surprised if it is 3.45V to 4.2V (I also wouldn't be surprised if it was somewhat different - every battery design is slightly different). So going with above numbers, 3.45 is 0% and 4.2 is 100% and the software "linearizes" the non-linear discharge curve. This is why when charging, you may see the % stuck when in fact,the battery is just in a "flatter" part of it's charge/discharge curve. You don't see this when discharging because most people don't hope that it goes down (i.e you aren't really looking at it so closely).

Leaving the N7 plugged in for extended periods should not damage the battery if the circuit designers did their job (which, I am confident they did).

By the way, if you are using the N7 while charging, expect it to take longer. A running N7 will pull about 400 mA (.4 Amp) which DOESN'T go to the battery. Less so if it's sleeping, of course.

PS, good point on the USB plug/jack wearing out. They are probably spec'd for something like 10K lifetime insertions/removals but that assumes perfect alignment each time.