I have a new Thinkpad R40 with a lithium Ion battery. From what I understand it does not suffer from the memory effect. Even though I hear that, I still like to drain it down almost all the way and let it charge fully before unplugging it. First question…Is this pointless? Am I truly safe plugging it in and unplugging it whenever I feel like it? Second…Am I doing it any harm to leave it plugged in much longer then neccesary? For example. I get home from work at 7 plug it in, by 10 or 11 it’s fully charged, but I don’t unplug it until the next morning when I leave. Is that bad? Lastly, I’m planning to buy another power cord. One for home, one for work, IBM offers both a 56* and a 72 watt charger. Assuming I have the time to let it charge, would I be better off with a slower charge. I’ve heard that the slower the charge, the better it is for the battery, but I’m not sure if that’s true for lion batteries
*not sure if it works for my system though.
The one that I can definitely answer is that you can leave the laptop plugged in as long as you want, it’s designed to run off of the AC power when available even if the battery is fully charged, so it knows full well when to stop charging.
-lv
There seems to be some evidence that even old Ni-Cad batteries didn’t actually have the memory effects that people claimed to experience. With Li-ion batteries, as you say, that’s not an issue, so I think, as Lord Vor says, you can just leave it plugged in and charging all the time. That’s what I do with my Dell notebook, and I’ve seen no ill effects. (Although to be completely frank, I haven’t had the computer that long.)
However, I think that draining the battery all the way could cause problems, or at least not do any good. Don’t go out of your way to run the battery all the way down.
Don’t drain the battery just for the sake of draining. LiIons have notoriously short lifetimes and this just shortens them.
Letting the battery trickle charge while running on AC is also Not Good (but not quite as bad). It will heat up the batteries, shorten their lifetime, and things like that.
If an AC plug is nearby, run off that first and foremost. Leave the battery in only if it really needs charging (or your bridge battery is non-existent/unrealiable).
Are you suggesting that the batteries be removed when running the laptop on AC power? That’s a serious inconvenience, and I’m not convinced it’s worth the trouble. Surely laptops are designed to run indefinitely on AC power with the battery installed?
I do agree that running the battery down before recharging is not only pointless, but damaging. Batteries have a finite lifetime measured in charge/discharge cycles. If you use half the charge in the battery and recharge it, you’ve only used up half a cycle. If you continue using it and then plug it in, you’ve used a whole cycle.
The choice of AC adapter doesn’t make a difference. The AC adapter is simply a constant voltage source. The charging circuit inside the laptop regulats battery charging current.
What’s a bridge battery?
So from what I’m understanding here, It would be a good idea to buy a seperate charger and always keep it plugged in, only running off the battery when neccesary (but I’m not going to remove the battery). Am I understanding everyone correctly?
Okay, now I’m confused again. For the last few days my laptop has been plugged in almost all the time it’s in use. The only time it’s not plugged in, is during transport during which it’s in hibernation. I’ve noticed something else odd, the battery never reaches 100%, right now it’s been at 96% for quite a while, yesterday it stop at either 97% or 99%. I assume even though it says that it’s fully charged, I have a feeling I’m just confusing the meter, since it’s not all that accurate anyways. (I know that because right out of the box, it came with TWO meters running for some reason and they were always slightly different. I think the percentage was the same but the time left on the battery would very from a few minutes to almost an hour off. But I suppose one was based on a constant assumption or X mins per percent and the other took more into consideration (whether the hard drive is spinning, monitor brightness, CPU usage)…but I digress.
Thats normal, it’s not good for the battery to coninually trickler charge so what happens is that the laptop lets it drop to say 95% then charges it to 100%.
Also, I’ve found that the battery meter becomes a lot more accurate after a full discharge. Over about 2 months of use, I can get about 10 extra minutes after the battery has displayed 0% before the computer shuts off. The battery meter can then re-calibrate itself.
There’s a lot of variance in laptop design, even when talking about a particular “era”.
A bridge battery is a small battery that allows you to remove the main battery and swap in a charged spare without losing the state of your machine. Most require that you enter “suspend” mode first. Many can help you thru an “oops” experience of knocking the adapter plug loose when running on AC.
Bridge batteries can be of various types. NiCads, whatever, regardless of the main battery type. I have a really old Toshiba that has a really weird one that looks sort of like a skinny yellow flourescent tube.
Next.
Laptops usually have some method of “learning” the status of the battery. Not just its (pun alert!) current voltage, but also how much charge is can hold, how close it is to being discharged beyond use, etc. Different laptops learn this different ways. Some just require you go thru a “full” (very incorrect!) discharge every so often. One system I know needs it done once a year. My current plaything laptop uses a sep. software program, run it from a bootdisk overnight, to do battery learning.
Since battery learning usually needs at least one full charge cycle, it should be done sparingly on LiIons. For the other types, there’s usually no big harm in doing it (it can in fact be good for the batteries) if you really need to run off the battery for a while anyway.
Ideally, a laptop will note that a battery has been fully topped off and will stop trying to trickle charge it. But this is consumer electronics, and computer gear in particular, we are talking about. Pennies are squeezed tight. Such “frills” are usually omitted. Plus, there is a big side benefit for the maker: They get to sell you a new $ battery even more frequently! Wow, aren’t we lucky!
In short, do as little as possible to the battery. Either charging or discharging.