AC Operation w/o Battery

[w9cw]

Hello,

I've read a number of differing opinions on this, so I thought I would ask the group. If this has been covered before, I apologize. I searched the archieves and could not find a specific answer to this question. And, I would assume this would apply to not only ThinkPad notebooks, but notebooks in general using Li-ION batteries.

Some reference material suggests that you should not use a notebook on AC power without the battery installed, as the notebook's DC power supply and charging circuit is designed to always "see" a battery within the charging circuit. This reference material suggests that without the battery installed, possible damage could occur to the notebook's DC power supply.

On the other hand, I've read specifically with ThinkPads, if the charging light blinks, and the battery does not accept a charge, that continual use with a blinking light can cause damage to the DC power supply and circuit. In this case, it makes sense to remove the dead battery prior to use on AC power.

What is the "official" word on using a notebook on AC power - should the battery be removed, or left in the unit? Of course, it appears this would be affected by whether or not the battery was in good condition, and able to accept a charge.

I would imagine that in general use, many notebooks spend as much time, or more, connected to AC power than on battery operation. In researching the data from Li-ION battery manufacturers, it is an accepted fact that Li-ION batteries should be stored long term at cool temps (say in a fridge, but not the freezer!) at a 40% charge level. This 40% charge level for storage is referenced many times by a number of Li-ION battery manufacturers.

Thanks,
Don

[JHaislet]

I don't know the specific answer to your question, but for all practical purposes, when a battery reaches its full capacity (fully charged), no more energy can physically be displaced into the battery.

Therefore, the DC circuitry must be capable of adapting to a fully charged battery. Common sense would lead me to believe the charging circuits & DC adapter are in the exact same state for both a fully charged battery & a no battery present situation.

I could be wrong, but desktop PSU's draw only the power presently needed and I would assume laptops and almost any other electrical device works exactly the same way.

[sugo]

This is no official word but it works for me. With the two laptops I had, the battery retain over 95% capacity after about one year of ownership.

You don't need a battery to run a T4x thinkpad on AC.

If you stay on AC for weeks or months, store the battery at around 40% charged in a cool, dry place. There is no need to put it in fridge. Don't put it in freezer.

If your thinkpad is on the go all the time, don't worry about when to take the battery out. Just keep it in the thinkpad. It will stop charging after it's fully charged and before a threshold is hit.

[storage_man]

sugo is correct. If you plan a extended period of time where you will not be using your batteries, store them at around 40% charge. When u need to use them, Charge them up and they should retain 95% charge. I have a older thinkpad (R31) of which spends most of its life time on the brick. My batteries are almost 3 yrs old, and they still (when I need them) retain a 95% charge (After 3 years). As far as running on the AC Adaptor, there should be no problem.

Storage_man

[leoblob]

I think the original question is, can you run on AC when there's NO battery installed. FWIW, my TP360 has been running like this for almost 3 years. The battery developed some type of internal short, so I had to remove it... so it runs on the AC adapter with no battery in there. I just never got around to buying a new one. No problems yet... and no blinking light...

I believe this ancient machine is supposed to use a NiCAD battery, so perhaps my experience doesn't apply to newer machines...?

[Laurence Spiegel]

It's not that simple.
Heat affects the battery; if you use the machine all day on ac with the batt installed, the batt will be rather warm and will age faster.
BUT
Thinkpads (some at least) write to the cmos during startup. If the power blinks during that time, sorry!

Quote from http://www.ja.axxs.net/unlock/dont_try_this.htm
regarding what may happen if all power (you used ac with no batt + something jigglest the cord etc) is interrupted during boot.

running TP from AC adaptor with battery removed, and removing total power (by unplugging AC adaptor) at various stages after switching TP on

DON'T EVEN CONSIDER DOING THAT!

This will almost certainly SCRAMBLE the eeprom contents and cause BAD CRC1 or CRC2 ERROR

The eeprom is written to at various stages during boot, specifically the AT24RF08 is written to , to change block and page access to hide block containing passwords, the eeprom is also written to each time a password is rejected.

If you remove power during an eeprom write, the results are unpredictable

What is predictable is that the results are NOT helpful, you can recover even from this disaster without replacing the entire System Board by using my CRC Repair Kit.

bullet If you are using my KM interface and KM software, then;

[leoblob]

running TP from AC adaptor with battery removed, and removing total power (by unplugging AC adaptor) at various stages after switching TP on

DON'T EVEN CONSIDER DOING THAT!

I would agree with this. But if you power up with the AC adapter plugged in, and leave it plugged in the whole time the computer is on, and don't unplug the AC adapter until after the computer is off, I think you'd avoid this problem.

As for a momentary AC power problem which happens just during boot up, this hasn't happened to me (yet!)

[jack NYC]

I used A31p for over a year with just AC. The one thing you loose is clock speed on CPU. IBM lists as a "feature" that the CPU slows to half speed or so when on only Battery or AC power.
While like anyone I would never recommend pulling the plug on a booted up computer I have to confess that this happened MANY times to me. I have not seen or felt any byproduct from this type of activity..... yet. I now have a new battery so its not an issue for me unless there is some kind of cancer lurking in my machine that this could have unleashed. I'm planning on new HDD soon with clean XP install. Will this help any possible lingering effects or is the possible damage at the Bios level?

Jack

[bhtooefr]

As for the clock speed issue - if you're using the SpeedStep applet, you can drop the speed on AC - I do it all of the time, because folding during the day gets my temps too high at full speed.

[JohnDrake]

I've run an R series with no battery for nearly two years on AC...no issues...