I've got 4 different batteries with 2 different G5s - Same issue... I really have to scrutinize all 4 batteries, but so far the ones my wife keeps using keeps dying while my son's is also behaving the same way. I think only 1 or 2 of them is not doing it.
phone shuts down when bat hits 20%
- Thread starter moldyeye
- Start date
tickerguy
Well-known member
The battery is dead.
It's also possible the charge-level sensor is out of calibration, but unlikely. To calibrate it wait until it shuts off on its own and then charge it fully with the PHONE OFF.
But if it happens again, and it probably will, the battery is toast.
What's going on is that there is a low-voltage safety cut-off for Lithium chemistry cells. The reason it's present is that over-discharge can result in an internal short in the battery, which will then cause the cell to overheat and explode when charged. There is a protocol to get around this risk (essentially you charge it at a VERY LOW current level until the voltage comes up; this detects the short if it exists and avoids the problem) but you don't want to short the cell as that ruins it permanently.
As cells age they cannot deliver current at the required level without the voltage collapsing. If the voltage collapses then the phone detects that as a low-voltage cutoff violation and shuts down. If it happens materially before the power level is at 0% (fully discharged) then the cell is junk. It may appear to charge and work ok but if you actually measure its capacity using an accurate means (I have a bench charger/discharging unit that can do so) you'll find it's pretty-materially deficient in its capacity.
The reason Accubattery (and others) recommend only charging to 80% is partly because fully-charging Lithium chemistry cells does do more cycle damage than not (and there's no "memory effect" to avoid with them) but also because cellphone manufacturers intentionally over-drive the charge rate to shorten charge times. The correct means to charge a Lithium chemistry cell requires 3 or 4 hours, and nobody wants to wait that long. You can get into the 60-80% range very rapidly (with careful calibration of the charge controller you can run your charge rate at 1C, which would mean at 3,000ma for this battery) but once you reach 4.2V you hold voltage constant until current drops to about 3% of rated capacity in ma/h (so in this case that would be about 100ma.)
The problem with doing this is that the saturation charge cycle is a couple of hours. Total charge time doesn't change much but the higher the rate you run the bulk charge at the lower the actual capacity when the threshold voltage is reached, so if you were to charge at 3,000ma you'd probably see threshold at 60-65% instead of 80% if you ran the charge at 1,500ma.
Manufacturers however want to sell you "fast charge time!" so they run their bulk phase up higher, in some cases in excess of 4.3V. Beyond 4.3V there is risk, in that plating of lithium can happen and if it does you can get plating of metallic lithium, gas production in the cell (which makes it bulge) and ultimately the potential for thermal runaway and fire. The cells are supposed to have both a temperature and pressure switch in them that permanently disconnects the output if this happens (but as we've seen with certain phones and laptops that doesn't always work.) The other issue, however, is that stuffing the charge rate like this stresses the battery severely and shortens its service life -- it will take what was a 500-cycle battery and turn it into a 200-cycle one.
The only defense against that -- and the manufacturer's decision to screw battery life in favor of "fast charging" -- since you can't reprogram the charge controller is to disconnect it at 80% or so and do not "float charge" (e.g. leave the phone plugged in overnight) at all.
BTW there are some manufacturers of laptops (specifically, Lenovo in their X220) that come with their chargers set to NOT do this (they only charge to 95% and use a proper taper with NO float charge, so it really does take 3 hours or so to fully charge their batteries!) and the difference in service life is very, very material. I have one of these and have had to replace the battery exactly once in seven years of ownership; the replacement is still well within manufacturing tolerance (about 90% of original capacity.)
It's also possible the charge-level sensor is out of calibration, but unlikely. To calibrate it wait until it shuts off on its own and then charge it fully with the PHONE OFF.
But if it happens again, and it probably will, the battery is toast.
What's going on is that there is a low-voltage safety cut-off for Lithium chemistry cells. The reason it's present is that over-discharge can result in an internal short in the battery, which will then cause the cell to overheat and explode when charged. There is a protocol to get around this risk (essentially you charge it at a VERY LOW current level until the voltage comes up; this detects the short if it exists and avoids the problem) but you don't want to short the cell as that ruins it permanently.
As cells age they cannot deliver current at the required level without the voltage collapsing. If the voltage collapses then the phone detects that as a low-voltage cutoff violation and shuts down. If it happens materially before the power level is at 0% (fully discharged) then the cell is junk. It may appear to charge and work ok but if you actually measure its capacity using an accurate means (I have a bench charger/discharging unit that can do so) you'll find it's pretty-materially deficient in its capacity.
The reason Accubattery (and others) recommend only charging to 80% is partly because fully-charging Lithium chemistry cells does do more cycle damage than not (and there's no "memory effect" to avoid with them) but also because cellphone manufacturers intentionally over-drive the charge rate to shorten charge times. The correct means to charge a Lithium chemistry cell requires 3 or 4 hours, and nobody wants to wait that long. You can get into the 60-80% range very rapidly (with careful calibration of the charge controller you can run your charge rate at 1C, which would mean at 3,000ma for this battery) but once you reach 4.2V you hold voltage constant until current drops to about 3% of rated capacity in ma/h (so in this case that would be about 100ma.)
The problem with doing this is that the saturation charge cycle is a couple of hours. Total charge time doesn't change much but the higher the rate you run the bulk charge at the lower the actual capacity when the threshold voltage is reached, so if you were to charge at 3,000ma you'd probably see threshold at 60-65% instead of 80% if you ran the charge at 1,500ma.
Manufacturers however want to sell you "fast charge time!" so they run their bulk phase up higher, in some cases in excess of 4.3V. Beyond 4.3V there is risk, in that plating of lithium can happen and if it does you can get plating of metallic lithium, gas production in the cell (which makes it bulge) and ultimately the potential for thermal runaway and fire. The cells are supposed to have both a temperature and pressure switch in them that permanently disconnects the output if this happens (but as we've seen with certain phones and laptops that doesn't always work.) The other issue, however, is that stuffing the charge rate like this stresses the battery severely and shortens its service life -- it will take what was a 500-cycle battery and turn it into a 200-cycle one.
The only defense against that -- and the manufacturer's decision to screw battery life in favor of "fast charging" -- since you can't reprogram the charge controller is to disconnect it at 80% or so and do not "float charge" (e.g. leave the phone plugged in overnight) at all.
BTW there are some manufacturers of laptops (specifically, Lenovo in their X220) that come with their chargers set to NOT do this (they only charge to 95% and use a proper taper with NO float charge, so it really does take 3 hours or so to fully charge their batteries!) and the difference in service life is very, very material. I have one of these and have had to replace the battery exactly once in seven years of ownership; the replacement is still well within manufacturing tolerance (about 90% of original capacity.)
Last edited:
Imrankhalit12
New member
I have the Huawei Honor 3c lite.....and the phone was 3 years old the battery started to make a problem....when I unplug my phone in 70%..when it goes down to a 20%..it just shutting off the phone without the warning message..
Imrankhalit12
New member
Is my charger broken?
I have the Lenovo tab 2 a7-30..I just bought a 3.0A plug adapter for my tablet..but it still slow.. is there any ways to fix this issues? ..
I have the Lenovo tab 2 a7-30..I just bought a 3.0A plug adapter for my tablet..but it still slow.. is there any ways to fix this issues? ..
utfan1963
New member
Re: Is my charger broken?
My wife and I both have the LG V20 and both of them just randomly shut off between 24% and 28% any day and every day. I just don't get it. Every Samsung we have had before this LG has gone down to almost 0% before turning off. It started about 6 months ago right after an LG major update was installed. It is so frustrating. Battery life on the LG V20 is horrible and I knew that from the reviews before purchasing them, but I didn't think it would be this bad. I love the quality of the sound for the V20. Which was my deciding factor when making this purchase. I have 7,500 songs on my memory card and I play music all day at work on my Bluetooth. I come home and my phone is sitting on my counter while eating dinner and talking with friends. It was at 78% when we started dinner, two hours later I open the phone and look at a few things and the next thing I know it's a black screen! I put the charging cable in and it shows the battery screen which is at 28%. I really wanted LG to give Samsung a run for their money, but it just isn't happening for me. If they don't improve things quickly, I am going back to Samsung.
My wife and I both have the LG V20 and both of them just randomly shut off between 24% and 28% any day and every day. I just don't get it. Every Samsung we have had before this LG has gone down to almost 0% before turning off. It started about 6 months ago right after an LG major update was installed. It is so frustrating. Battery life on the LG V20 is horrible and I knew that from the reviews before purchasing them, but I didn't think it would be this bad. I love the quality of the sound for the V20. Which was my deciding factor when making this purchase. I have 7,500 songs on my memory card and I play music all day at work on my Bluetooth. I come home and my phone is sitting on my counter while eating dinner and talking with friends. It was at 78% when we started dinner, two hours later I open the phone and look at a few things and the next thing I know it's a black screen! I put the charging cable in and it shows the battery screen which is at 28%. I really wanted LG to give Samsung a run for their money, but it just isn't happening for me. If they don't improve things quickly, I am going back to Samsung.
tickerguy
Well-known member
Replace the battery; it takes 30 seconds and you can get a new one for under $20.
Try that on a Samsung with a glued-on back!
Try that on a Samsung with a glued-on back!
Re: Is my charger broken?
i have the same problem with my v20, my friend v20 too. at first mine such down at 10% slowly increrase to 15 20 25 and now 32% im worried that it will increase more, i bring my phone to LG shop they test the battery say its okay, and want to test my phone too, but i have no space to back up my phone so didmt manage to do any testing. not going to buy lg anymore
i have the same problem with my v20, my friend v20 too. at first mine such down at 10% slowly increrase to 15 20 25 and now 32% im worried that it will increase more, i bring my phone to LG shop they test the battery say its okay, and want to test my phone too, but i have no space to back up my phone so didmt manage to do any testing. not going to buy lg anymore
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