I have a dell inspiron laptop. Since I got it the time remaining has been extremely erratic. Sometimes I will have 800 hrs remaining, other times I will have 1 minute. All while staying at 98% (or whatever the percentage is). There is absolutely no correlation between battery percentage and time remaining, but the percentage does seem correct.
I am running windows 10 with all latest updates and drivers installed. Battery has been charged to 100%, then discharged to 0% and then recharged to condition it. I have done everything I can think of.
I know it does not really matter in the long run, but every time I see it say I have 8% and 600 hrs it irks me.
1. Completely drain the battery (Don't do this too often, because it will damage the battery if done repetitively)
2. Disconnect the battery
3. Plug the laptop back in
4. Restart without the battery
5. When Windows loads, reattach the battery
6. Let the laptop charge completely without interacting with it. (Do not unplug it, or you will need to start over)
After you do this, Windows can accurately measure your battery.
Contrary to popular belief, you laptop battery should be drained and recharged every 30 "cycles". The don't let it get to zero mindset comes from technology that is 20 years old. Some lappies have built in software which tell you when to do this, if you don't have it, your can download BatteryCare utility.
It is very important to do this every 30 cycles because of they way battery charging works .... a stronger charge is applied at the start which as your battery gets closer and closer to being fully charged, that charge is tapered more and more to just a trickle. If you to not "Calibrate" your battery monitoring system, you can wind up damaging the battery and / or wind up with the conditions you have observed which may not be reversable.
So yes, you do want to avoid repeatedly discharging you battery to 0 every day ... but it **is** necessary to do it occasionally to keep it properly calibrated.
First of all it's necessary to unfold a myth that persists in many peoples head. The battery memory effect.
In lithium-based batteries this is in fact a myth, it only applies to older Nickle-based batteries. So fully discharging and charging the battery is completely useless and even harmful as we will see below. Read what BatteryCare has to say...
The modern lithium battery can be charged regardless of its current percentage, given that it has absolutely no negative effect in its performance.
A "cycle" is defined as taking your battery from 100% to 0%, tho not necessarily all at once. let's say you draw the battery down as follows:
That adds up to 100% so that's one full cycle. If you use 20% a day for a week, then that's 1 full cycle.
Full battery discharges (until laptop power shutdown, 0%) should be avoided, because this stresses the battery a lot and can even damage it. It's recommended to perform partial discharges to capacity levels of 20~30% and frequent charges, instead of performing a full discharging followed by a full charging.
Laptop batteries contain a capacity gauge that allows us to know the exact amount of energy stored. However, due to the charging/discharging cycles, this sensor tends to be inaccurate overtime. Some laptops include in their BIOS, tools to recalibrate this battery gauge, which is nothing more than a full discharge followed by a full charge.
So to calibrate the gauge, it should be performed, in every 30 discharge cycles, a full discharge non-stop , followed by a also, non-stop, full charge.
An inaccurate gauge can lead to the fact that the the battery capacity values are are wrong. The battery may report that it still has 10% of capacity when in fact it has a much lower value, and this causes the computer to shutdown unexpectedly.
In short, how often you need to calibrate depends on your usage. If you get down to 67% battery life every day, then every 3 days would be a cycle and you should do a full discharge / calibration every 90 days or so.
If you install the utility, it automatically keeps track of this for you and tells you when to do a calibration.