Regarding battery/AC question

I have heard from a friend that using the AC while the battery is still plugged in greatly shortens battery life. He believes that the computer constantly draws power from the battery, while the AC continually recharges it. I think that while the AC is plugged in and the battery is at 100%, the notebook should know to draw straight from the AC rather than through the battery. I felt that based on the sole fact that the laptop even runs straight on AC w/o a battery, the laptop should have the ability to utilize the AC directly rather than through the battery. However, there's still the whole idea that all batteries "leak" and when the battery leaks, the AC recharges... so his theory fits too. Anyone care to shed some light on this matter?

This is for the M1530, but I think it's pretty universal for all notebooks.

 

The M1530 Battery is a Li-ion battery. Leaving the battery plugged in does not shorten the battery life. My office leaves the batteries in our plugged in laptops all the time for the last 12 months. Most of them only show a 2-3% battery wear level. What will shorten the life on a Li-ion battery though is letting it discharge to far.

For example, I have a 9 cell battery for a Dell E1405. For 18 months I let the battery alarm settings force hibernation of the laptop when power got down to a 10% level. Well, 5 weeks ago I loaded a battery monitoring software that tells me my battery wear level is 52%. That week, the laptop forced hibernation again at 10% of battery life. A day later the wear level is now 55%. The next week, I'm at a meeting & the laptop hibernates again at 10%. I find out that afternoon after fully charging the battery that the wear level is now 57%. So I tested a theory, for the last 3 weeks I have set the laptop to force hibernation at 20%. The wear level has not moved at all even though the laptop has forced hibernation once a day.

As far as battery leak,...my new 9 cell replacement battery has been out of the laptop at 100% charge for 4 weeks & still shows as 100%.

Based on the above, my opinion is that leaving the battery in while plugged in does a lot less damage.

 

When plugged in, your laptop will draw power from the adapter, not the battery. This applies to pretty much all laptops.

From my understanding, batteries, however, tend to lose their charge whilst sitting idle inside a notebook; it's a slow loss, but ultimately a perceivable one. This generally applies to all laptops as well.

Thus what your computer will try to do is "top off" when the charge falls below a certain threshold whilst the battery is installed.

In general, you're right and he's wrong about laptops drawing power from the battery.

 

As a follow up, do you recommend that the battery be removed while using AC power, or should I just leave it in?

 

Battery Guide.

 

Ok, while that is semi true chances are he will never get it to that point with all of the features on laptops.

If you run your battery so low that one of the cells reaches a voltage of less than 3.7 volts then that cell will never charge again, so then if he runs his battery, say its a 9 cell but one cell got below 3.7 volts then now he's only got 8 functioning cells, dropping his voltage, and reducing time. But this should not be able to happen with the voltage cutoffs and features on laptops, so it shouldn't be an issue...but yes, you do need to be careful about discharging them.

lithium ion batteries can be discharged to any random point along their reasonable voltage, and be charged up no problem. Just don't run your laptop until the battery dies and it shuts off then turn it back on again to see if you can boot up and check the weather...those are the people who kill batteries.

The types of batteries that you had to let them die before you recharged were nickel cadmium and nickel metal hydride....these batteries have a "memory" if you drain them to where theyre still 90% charged and then charge it again and do this a few times then it will think that 90% charge is the lowest it can go and it will no longer discharge beyond that point. lithium-ion and lithium-ion polymer do not have this problem