Excessive battery capacity loss?

I have a ~ 1-yr old 13” Dell Inspiron 7000 with an internal 43WHr 3-cell L-Ion battery. I mostly use it as “desktop replacement" – it is connected to an external monitor and plugged in via AC adapter 99% of the time. I’ve only logged about 90 hours of battery time in a little less than a year. However, I noticed the battery drained faster than usual the last few times I used the laptop in ‘battery-only’ mode. I ran the battery report in Windows 10 and it showed the battery capacity has decreased from 43WHr to 32WHr. I was shocked to see the new battery degraded by 25% in less than year, considering how rarely I use this laptop in ‘battery only’ mode.

I was thinking the battery might be defective but the Windows and BIOS battery diagnostics did not show any battery issues. I called Dell and their tech support guy told me the 25% decrease in capacity could have happened due to me not using the battery enough/keeping the laptop plugged into AC for too long; as well as having the display brightness set to 100% and my habit of putting the laptop in ‘sleep’ mode instead of shutting it down (I didn’t think it would impact the battery at all, as long as the laptop is plugged in!)

Does what he said make sense or is he full of it? 25% capacity loss in under a year still seems unreasonable to me under these circumstances but I am far from an expert. Can I request battery replacement as long as this laptop is still under warranty?

 

That's within expectations of the Li-ion technology. It degrades no matter what you do, but heat, leaving at full charge, and deep cycling all accelerate the rate of degradation.

A couple of full discharge/recharge cycles are needed every month to keep the readings accurate though, so first rule that out.

 

I wouldn't recommend twice a month but twice a year as full discharges aren't good for the battery chemistry. However, these full discharges are needed from time to time to ensure that the battery chip has accurate voltage-capacity data. The procedure for calibration is (i) fully charge the battery; (ii) fully discharge the battery (note that Windows shuts down the computer with several % charge remaining so you need to go to the BIOS screen to do the final discharge to empty); (iii) fully charge the battery. I recommend BatteryInfoView for checking the battery data.

John

 

See if disabling Dell's Battery optimiser (that charges battery to 50,75 or 80% based on your usage) helps you in any way.