Newbie - Battery Questions

I just received my first laptop today

First, I did read the Battery Guide posted on this forum... I have some basic n00b questions though...

Right now, I have the battery in and the laptop is also plugged into A/C power...

Question one, am I running off the battery or off A/C power? Like is the A/C power going directly to the laptop, or is it being routed through the battery to the laptop? Does the battery charge in this situation?

Question two, is it safe to disconnect the laptop from A/C power in this situation without turning it off?

Question three, I have a HP and it has a "battery light" next to the power light and "activity" light... What does it mean when this light is lit? I noticed that when I first turned on the laptop it was lit, and the battery was not at 100%... Now it is turned off and the battery is at 100%, so does that light show that the battery is charging?

Question four, does the laptop have to be on when I am charging the battery? Like say I want to charge up the battery overnight, do I leave the computer off with the battery in it and simply connect the A/C cord to the laptop?

 

1) You are running through A/C power. The battery will charge.
2) Yes
3) It means that the battery was charging
4) No. It will charge regardless of whether the computer is on or not.

 

I'll try to give some details I know (and I think are real, so..):

1. You'll be running off A/C power, although power gets to the battery regardless if it's full or not. Meaning: excess power becomes wasted heat. (detrimental to battery)

2. Everybody does this, and afaik it's safe.

3. In different brands these lights act differently. In Acers the light turns green (at least for my Acer) if the battery is full, but it's much better to remove the battpack when it's fully charged to not introduce heat to it.

4. Just like TevashSzat said. Although some (older) battery packs tend to heat up and get a shorter life if you get it overcharged.

 

Where does those excess power come from??? They magically appeared out of nowhere?

Just like a PC power supply, the laptop's power brick will only supply power that the computer needs. Excess power capability is simply unused instead of wasting it as heat.

The power from AC first reach the powersupply inside the laptop. Then the some of the power is used by the laptop itself. Some of the power is used by the battery controller (IC) which feeds the battery electricity.

 

IIRC the power that comes from the AC adaptor still feeds power to the battery controller which in turn still supplies power to the battery pack--that's why some battery packs, when fully charged already, heat up.

I'm not sure, though, so clarifications are welcome. I just posted out of my observations, and also my mom's notebook's battery didn't die, but lost some cells I think because of that exact thing.

Also IIRC in my Physics class about conservation of energy, and I remember that excess energy (in this case, electricity) gets transformed into another kind of energy (in this case heat.)

 

Unless the battery controller is broken, the battery pack when finished charging should not heat up by itself. Because the battery controller would cut the current off after fully charging the laptop, the heat on the battery pack should be from other sources.

 

Well, I don't know, in any case it's not just me (I think, at least) who removes his/her battery pack after it's done charging or if the laptop will be plugged in for a long period of time.

Oh, now that I remember, I think I could justify where the heat comes from. Remember that in a system, in this case the AC providing power to the laptop PSU, the 100% energy transfer is theoretical, since not 100% of the power from the AC would be conveyed to the PSU, hence the heat.

....but for the questions the OP posted, this wouldn't be necessary, right? (Apologies to OP, if the thread seemed to veer OT) but in any case, I think we could agree that the battery, once finished charging, is better removed from the laptop, right?

 

Most of the conversion and heatloss is at the powerbrick. Power brick, due to its MOSTF design, will only convert enough AC power to DC power in order for everything to function. These power adapters typically operate at 15-35% efficiency.

The actual thermal energy released by the internal PSU is very little. Also, charging the battery usually requires no conversion because most of the time, the the battery charging circuit bypass the internal laptop PSU. It gets its share of power directly from the source/powerbrick.

When a battery is done charging, it's converted to a UPS backup. The battery isn't really connected to the laptop after the battery is done charching. Thus there's no need to unplug the battery unless the computer is heating up the battery considerably.

 

Thanks guys... One last basic question... Is charging the battery while the laptop is on and in use the same as charging it when the laptop is off?

 

No. If you charge the battery when it's off, the battery will charge faster.