I only ever charge my phones and tablets to 80% and don't go below 20% in the 3-4 years i have had them, apart from the 5-6 full charges after updating the software or recalibrating the battery gauge.
I use to do this with my notebooks when they had the option in the power settings.
Though i have not seen a flashlight or battery charger with an 80% charge option, Maybe the SkyRC MC3000 can be programmed to do this?
John.
Hi there,
Yes such thing does exists: http://www.mateksys.com/?portfolio=upm
You can get it from Aliexpress or something, its not cheap, around 8 to 10 USD.
But I do have a personal experience with them, this method is a bit fidgety. For example, the current drawn by the device is never the same all the time, due to differing loads (when the screen is on, or when wifi is switched on, or when you receive SMS, etc). Hence there is always some level of uncertainty. Not to mention that the charger and the USB cable also plays a role.
Next, the preset values of END LEVEL of 10, 20, 30, 40, 60, OFF, might not be suited to your device to cut it off at a certain level, ie 80% exactly. Also, until now, I have no idea what END LEVEL refers to, is it the residual current (mA) or what, no explanation on that. I have tried setting on various levels before, but all end time seem very erratic , resulting in different charge level most of the time.
So going with the other forumer’s suggest is better, ie setting timer for a charge.
If you have better luck with this thing, do let me know by PM ya. Or, if you find a better device which allows you to program the residual current instead of a fixed value of 10, 20. 30. 40 or 60.
PS: I did give the suggestion to the manufacturer, they did not respond.
Hi and thanks for your reply. 
I am not expert enough to say you are wrong so I am always eager to hear from others.
Would you please tell me how you disagree?
What is the flaw in my thoughts here?
Thanks
Hi,
I’m getting an error when I try to see this?
Tesla does this with their cars IIRC, so you only charge to 100% when planning to do a long road trip.
Helps extend the life of the battery.
This isn’t really good in phones since people go through an entire battery in a day so charging it to 80% would only make people either think they have less battery life or be inconvenienced to charge to 100% all the time.
This charge limiting technology needs to be implemented into the device itself, not the charger.
The charger is just supplying power to the device, it is the device which determines when to limit or stop the charging.
Please correct me if I’m wrong because it’s very possible……
But I “thought” you could pretty much get the battery voltage from a USB port such as a cellphone USB port?
AFAIK, there is a positive (+) pin in the USB port and a negative(-) pin. If you were to take a USB to USB-micro cable and plug the USB micro plug into a cell phone you would then have 4 wires….Red, Black, Green & White. Red being positive to the battery, black being negative or ground and the white and green being data transmission wires.
For example, let’s say you had two identical phones with identical batteries in an identical state of health. One battery was at 100% charge and one at 10% charge. I believe that if you had a USB cable with Micro-USB male ports on both ends, you could connect these two phones together and the higher charged phone would charge the lesser charged phone until such point as both phones had the same charge and were charge balanced.
Of course the USB port in the phone might have additional connections (not just 4), that route ground, power or some data to other channels inside the phone but the cord only has 4 wires AFAIK. And, I also believe all cell phones have voltage sensing capability and protect the battery from over charge and overly deep discharge. But they are allowed (I believe) to reach 4.2v (I have used a multitester to test a fully charged Cellphone LiIo)
So, theoretically, couldn’t this USB device have a circuit that first detected the battery voltage of the phone, then charge it (taking the voltage again every second or so (or every minute or so etc), until it reached a voltage preset in the USB controller device?
I’m speculating a bunch here so please forgive if I’m way off track 
Understood. Allow me to attempt to clarify my (possibly faulty) reasoning here. My phone (for example) can run for several days (about 3) on one full charge. My old Samsung Galaxy 3 in contrast would barely go 5 or 6 hours.
So, on a daily basis my usual routine is to charge it to 70% at night or when I get up, then let it run all day or unit it reaches about 30% charge.
This way I avoid a full saturation charge……and “hopefully” prolong the battery life.
There’s no way we’re ever going to get a cell phone manufacturer to implement a charge limit feature, so an external device would be the only possible way.
All this said….I’m not really 100% sure it’s worth all the trouble. I have no idea how much longer (if at all) my cell phone batteries might last if I rarely ever charge it to full 100% charge. I’m only doing this because I;ve read over and over that Lithium Ion batteries last longer if they are not pushed to their voltage limits often. If that is false, then this whole thread is an exercise in futility.
If that was possible then you would be able to use your phone as a power bank and charge other devices with it.
I’ve never seen anyone do that…
Ok…thanks. good points.
I feel so dumb sometimes :confounded:
That’s good, means u learning 
Not a bad thing at all.
now you see
K, but I’ve never seen that phone before either, so it’s probably a special feature and I highly doubt regular cell phones can do this.
Like the kind of cell phone normal people use, a galaxy, iphone, lg, etc…
Of course there is always some special case, like the cell phones with heat cameras, cell phones with washing machines, etc…
No, almost everyphone nowaday can do this, as long as it has OTG( which even 100$ phone can have)
As mrheosuper says, OTG (On The Go) is the way to get power out of your device. If your phone or tablet supports USB OTG, you can buy an OTG adaptor (cheap, $1-$2) and plug in anything you like that requires power, as long as it doesn’t overload the phone or tablet.
Warning: the maximum available current could be 100mA or less, depending on your phone or tablet. This is very device-dependent.
Tiny adaptor from Gearbest: link
Harder to lose adaptor from Amazon UK: link
This is actually meant for things like USB memory sticks that require external power to work, but can work as a low-power charging source if you need that device more than your phone or (especially) your tablet.
You can also make it work with power-hungry devices like external hard disks, as long as they get their power from something other than the USB connection.
Let the debate about not using your phone as a powerbank or a flashlight commence
I don’t know if it is worth all the trouble of watching and switching or plugging the plug. We have 2 same brand slightly different laptops. Bought within 6 months of each other. The first will charge to 100% when plugged in; no choice that is the way it was built. The second, slightly newer one has software that can set the charge limit. They both use the same battery, a flat pouch lithium type similar to, but larger than smartphone batteries. They both are mainly used at home and are plugged in most of the time, but both do see a biweekly road trip when they are used for 4 or 5 hours
When the laptop that was set to only charge to 83% was two years old the battery died. That was 18 months ago. The battery that was “abused” by being held at 100% still performs well on the original battery when it is taken off to the boonies. That may just prove that every so often you get a dud.
But my 3 year old smartphone still gives me all the daily use I need and it starts every day at 100% running down to about 20% most days before I plug it in for the evening.
That’s interesting MtnDon. Makes you wonder if one battery was just a better battery of if the limited charging scheme caused the early demise :question:
Maybe it might be a good idea to go ahead and fully charge a battery to 100% every so often?
I’m sure a battery expert or a chemist could give the actual answer.
Well….I did find a solution to the OP.
Like Enderman said in post 10, it had to be implemented in the device….so poking around in GooglePlay I found quite a few Apps that you can install that have alarms you can set at various charge levels to let you know to unplug the phone when it reaches the charge level you want.
Here is one for example that lets you set an alarm at ANY charge level……(I usually charge my battery to 80%)
But there are many. None that I found would actually STOP the charging at the level you choose, just alert you when the battery reaches the level you set and then it’s up to you to unplug the charger at that point. Still, good enough for my purposes.
I prefer gSam monitor as you can set battery above alarm, battery below alarm and temperature above and battery overheated and battery over voltage.
I have used this app for over 5 years on all my android devices with captive battery`s, check in settings/alarm to set alarm levels, I use 80% high 20% low.
John.
Awesome John…I like your app even better
Uninstalled mine and installed GSam
Thanks
Have your batteries lasted any longer than they would have if you had not used it?
(If you’ve compared battery life before installing it for example)
Devices with LiPo batteries like phones, laptops, and tablets actually never charge to 100% of the possible battery capacity. The manufacturers test and set the highest charge level to provide the best balance between use-time and battery life. When the device says 100%, that means you’ve reached the upper limit they have set, not that the battery can hold no more power at all It also bears remembering that a LiPo batteries lifespan is also related to the number of charging cycles it goes through- the fewer charge cycles the better for it’s lifetime. So if your undercharging results in more charge cycles you’re not likely to gain anything.
These folks have their entire business staked on how well their products perform for the average user and they’ve got top-notch engineers figuring this stuff out, so you’ll be hard-pressed to beat them at their own game. If you’re a non-typical user it may be worth trying.
Phil
