I found some good reading about it below. Pretty much saying to keep it above 20% whenever possible. As well well do not leave at 100% for long. In other words, keep the charge above 20% and below 90% as much as possible.
Charging and recharging
So how do you make your lithium-ion battery last as long as possible? You may have heard you need to do a full charge and discharge when your device is right out of the box—but this doesn't really matter on modern batteries. What matters most is how you charge your phone or laptop after you've started using it.
Shallow discharges and recharges are better than full ones, because they put less stress on the battery, so it lasts longer. When your battery is discharging, Battery University recommends that you only let it reach 50 percent before topping it up again. While you're charging it back up, you should also avoid pushing a lithium-ion battery all the way to 100 percent.
If you do fill your battery all the way up, don't leave the device plugged in. Instead, follow the shallow discharge and recharge cycle we just mentioned. This isn't a safety issue: Lithium-ion batteries have built-in safeguards designed to stop them from exploding if they're left charging while at maximum capacity. But in the long term, electronics will age faster if they're constantly plugged in while already charged to 100 percent.
Although shallow charges and discharges hit the longevity sweet spot, there are exceptions to this rule. Once a month, let the battery undergo a full discharge to about 5 percent, just to recalibrate its self-assessment. This mechanism allows your laptop or smartphone to give you an "estimated battery time remaining" reading that's somewhat accurate. (Not needed for the PSM) Regular full discharges aren't a good idea though. In general, you should be keeping your battery above 20 percent, according to Samsung.
These are all guidelines, by the way: There's nothing dangerous about keeping your phone charged overnight, and modern phones and laptops include mechanisms for minimizing the strain on the battery if your device is plugged in all the time. Fortunately for users, small tweaks and improvements are made to the technology each year, so every time you upgrade your smartphone, you're getting a lithium-ion battery that should go further between charges and last longer overall.
Storage and general care
Something else lithium-ion batteries don't like is extreme temperatures. Whenever possible, you should avoid leaving phones and laptops in hot cars or in chilly rooms, because these temperature extremes won't do their batteries' lifespans any favors. You should particularly watch out for overheating during charging—though if your phone or laptop manufacturer has done its job, this shouldn't be an issue.
As another precaution, you should also make sure you're using the official charger that came bundled with your phone or tablet, or you should invest in an exact replacement. This will guarantee that the charger is safe to use with your device's battery, and optimized to charge it as efficiently as possible. The official charger will apply the best practices for your battery's general health.
If you're going to be storing your laptop or smartphone for an extended period of time, you should leave the gadget with a charge somewhere around 50 percent, as recommended by Apple and other sources. Switch your device off while you store it, and as we mentioned earlier, make sure to keep it in a Goldilocks spot: not too hot and not too cold.
Charging and recharging
So how do you make your lithium-ion battery last as long as possible? You may have heard you need to do a full charge and discharge when your device is right out of the box—but this doesn't really matter on modern batteries. What matters most is how you charge your phone or laptop after you've started using it.
Shallow discharges and recharges are better than full ones, because they put less stress on the battery, so it lasts longer. When your battery is discharging, Battery University recommends that you only let it reach 50 percent before topping it up again. While you're charging it back up, you should also avoid pushing a lithium-ion battery all the way to 100 percent.
If you do fill your battery all the way up, don't leave the device plugged in. Instead, follow the shallow discharge and recharge cycle we just mentioned. This isn't a safety issue: Lithium-ion batteries have built-in safeguards designed to stop them from exploding if they're left charging while at maximum capacity. But in the long term, electronics will age faster if they're constantly plugged in while already charged to 100 percent.
Although shallow charges and discharges hit the longevity sweet spot, there are exceptions to this rule. Once a month, let the battery undergo a full discharge to about 5 percent, just to recalibrate its self-assessment. This mechanism allows your laptop or smartphone to give you an "estimated battery time remaining" reading that's somewhat accurate. (Not needed for the PSM) Regular full discharges aren't a good idea though. In general, you should be keeping your battery above 20 percent, according to Samsung.
These are all guidelines, by the way: There's nothing dangerous about keeping your phone charged overnight, and modern phones and laptops include mechanisms for minimizing the strain on the battery if your device is plugged in all the time. Fortunately for users, small tweaks and improvements are made to the technology each year, so every time you upgrade your smartphone, you're getting a lithium-ion battery that should go further between charges and last longer overall.
Storage and general care
Something else lithium-ion batteries don't like is extreme temperatures. Whenever possible, you should avoid leaving phones and laptops in hot cars or in chilly rooms, because these temperature extremes won't do their batteries' lifespans any favors. You should particularly watch out for overheating during charging—though if your phone or laptop manufacturer has done its job, this shouldn't be an issue.
As another precaution, you should also make sure you're using the official charger that came bundled with your phone or tablet, or you should invest in an exact replacement. This will guarantee that the charger is safe to use with your device's battery, and optimized to charge it as efficiently as possible. The official charger will apply the best practices for your battery's general health.
If you're going to be storing your laptop or smartphone for an extended period of time, you should leave the gadget with a charge somewhere around 50 percent, as recommended by Apple and other sources. Switch your device off while you store it, and as we mentioned earlier, make sure to keep it in a Goldilocks spot: not too hot and not too cold.
Always a pleasure when 
